Systems and methods for electrical monitoring and pre-charging of connected battery packs

Abstract

The present disclosure relates generally to methods for pre-charge control, including a. method comprising: receiving a first selection of a first or second battery pack to pre-charge circuitry of a first and second battery pack by a first battery management unit associated with the first battery pack, receiving a second selection of the first or second battery pack to pre-charge the circuitry of the first and second battery packs by a second battery management unit associated with the second battery pack, selecting one of the first and second battery packs to pre-charge the circuitry of the first and second battery packs based on the received battery pack selections, and controlling circuitry of the selected battery pack to perform the pre-charge.

Description

SYSTEMS AND METHODS FOR ELECTRICAL MONITORING AND PRECHARGING OF CONNECTED BATTERY PACKSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 616,316, titled “BATTERY MANAGEMENT SYSTEM,” filed December 29, 2023. The entire contents of the aforementioned application are incorporated by reference herein for all purposes.TECHNICAL FIELD

[0002] This disclosure relates generally to the field of powered aerial vehicles. More particularly, and without limitation, the present disclosure relates to innovations in an aircraft’s high voltage system. Certain aspects of the present disclosure generally relate to innovations in pre-charging, fault monitoring, and associated circuitry.BACKGROUND

[0003] The present disclosure generally relates to monitoring and pre-charging battery packs, including associated circuitry layouts. A large inrush of current or undetected faults may damage circuitry components and / or components of connected loads. Many aircraft, however, have complex systems with many interconnected components, some of which are fragile and potentially susceptible to damage or malfunction from an inrush of current that can result in the absence of pre-charging. Given these complex systems, however, conventional pre-charging arrangements are not sufficiently tailored to meet the needs of the aircraft, particularly for systems that have redundant components.SUMMARY

[0004] The present disclosure generally relates to pre-charge control, fault monitoring, and circuitry layouts. More particularly, and without limitation, the present disclosure provides control and circuitry that allows for one battery pack to pre-charge another and allows for separate pre-charge of different portions of high voltage circuitry. Pre-charging control and circuitry layouts allow for pre-charging electrical aircraft components with and without a low voltage battery, greater control of power distribution within circuits and associated energy efficiency, coordination between battery packs to provide a better energy balance and monitoring capabilities, redundancy in the pre-charging process, and / or savings in the mass of components by reducing the number and / or size of pre-charging components. In systems with redundant components, the disclosed embodiments can also perform intelligent control of electrical processes to efficiently perform system operations without performingconflicting and potentially hazardous actions. Further, components of the pre-charge circuitry (e.g., fuses, resistors etc.) are selected and arranged to provide savings in the overall mass of components, which can allow an associated vehicle to travel further with the same amount of energy, due to a reduced load.

[0005] The present disclosure also allows for monitoring the status of high voltage circuitry and connected components to detect faulty or diminished conditions and respond accordingly. Further, in some embodiments, the present disclosure may perform this monitoring without a separate high-voltage interlock loop (HVIL) to monitor the integrity of the high voltage wiring, reducing the need to oversize components and thereby providing mass savings for the aircraft.

[0006] One aspect of the present disclosure is directed to a computer-implemented method for pre-charge control, comprising: receiving a first selection of a first or second battery pack to pre-charge circuitry of a first and second battery pack by a first battery management unit associated with the first battery pack; receiving a second selection of a first or second battery pack to pre-charge the circuitry of the first and second battery packs by a second battery management unit associated with the second battery pack; based on the received first selection and second selection, selecting the first battery pack to pre-charge the circuitry of the first and second battery packs and refraining from using the second battery pack to precharge the circuitry of the first and second battery packs; and controlling circuitry of the selected first battery pack to perform the pre-charge.

[0007] Another aspect of the present disclosure is directed to an electrical system for an aircraft, the system comprising: a first switching device configured to electrically connect a first pre-charge circuit to pre-charge a bus powering a non-propulsion load; a second switching device configured to electrically connect a second pre-charge circuit to pre-charge a bus powering at least one electric propulsion unit; and at least one battery management unit configured to control the first and second switching devices based on a mode selection made by an input device communicably connected to the system.

[0008] Another aspect of the present disclosure is directed to a system for an aircraft, the system comprising: a switching device configured to electrically connect a pre-charge circuit to pre-charge a bus powering a propulsion load; a bidirectional DC / DC converter configured to pre-charge a bus powering a non-propulsion load; and at least one battery management unit configured to control the switching device and the bidirectional DC / DC converter based on a mode selection made by an input device communicably connected to the system.

[0009] An additional aspect of the present disclosure is directed to a system for an aircraft, the system comprising: a first switching device configured to electrically connect a first precharge circuit to pre-charge a bus powering a non-propulsion load; a second switching device configured to electrically connect a second pre-charge circuit to pre-charge a bus powering at least one electric propulsion unit; and at least one battery management unit configured to control the first and second switching devices based on a mode selection made by an input device communicably connected to the system.

[0010] An additional aspect of the present disclosure is directed to a system for an aircraft, the system comprising: a switching device configured to electrically connect a pre-charge circuit to pre-charge a bus powering a propulsion load; a bidirectional DC / DC converter configured to pre-charge a bus powering a non-propulsion load; and at least one battery management unit configured to control the switching device and the bidirectional DC / DC converter based on a mode selection made by an input device communicably connected to the system.

[0011] An additional aspect of the present disclosure is directed to a system for an aircraft, the system comprising: a first bidirectional DC / DC converter configured to pre-charge a bus powering a non-propulsion load and provide current to at least one second bidirectional DC / DC converter, and at least one battery management unit configured to control, based on a mode selection made by an input device communicably connected to the system, the first bidirectional DC / DC converter and the at least one second bidirectional DC / DC converter.

[0012] In accordance with additional embodiments, the at least one second bidirectional DC / DC converter is configured to receive the current from the first bidirectional DC / DC converter and pre-charge a bus powering a propulsion load.

[0013] Another aspect of the present disclosure is directed to a computer-implemented method for high voltage power control, comprising: toggling a first switching device on a pre-charge circuit to raise a voltage on a bus powering at least one electric propulsion unit; determining whether the bus voltage exceeds a voltage threshold within a time threshold; and pre-charging the bus in response to determining the bus voltage exceeds the voltage threshold within the time threshold.

[0014] Yet another aspect of the present disclosure is directed to a computer-implemented method comprising: receiving a signal that a battery pack is to be disconnected from a common bus; detecting a level of each of multiple cells within the battery pack; detecting a level of each battery pack configured to be connected to the common bus; determining an adjustment for each of the multiple cells, wherein the adjustment: balances each of themultiple cells to have an a first electrical state within a first threshold level of other cells within the battery pack, and balances the battery pack to have a second electrical state within a second threshold level of each battery pack connected to the common bus; and controlling, for each of the multiple cells, a balancing resistor circuit according to the respective adjustment.BRIEF DESCRIPTION OF THE DRAWINGS

[0001] Figures 1A and IB illustrate exemplary wiring connections for an aircraft, consistent with disclosed embodiments.

[0002] Figure 1C illustrates an exemplary wiring diagram of circuitry to manage power distribution, consistent with disclosed embodiments.

[0003] Figures 2A-2E illustrate a first exemplary set of pre-charge circuitry and modes, consistent with disclosed embodiments.

[0004] Figures 3A-3E illustrate a second exemplary set of pre-charge circuitry and modes, consistent with disclosed embodiments.

[0005] Figures 4A-4E illustrate a third exemplary set of pre-charge circuitry and modes, consistent with disclosed embodiments.

[0006] Figures 5A-5E illustrate a fourth exemplary set of pre-charge circuitry and modes, consistent with disclosed embodiments.

[0007] Figure 6 illustrates exemplary aircraft power circuitry, consistent with disclosed embodiments.

[0008] Figures 7A, 7B, 7C, and 7D illustrate exemplary control sequences for paired pack pre-charge control, consistent with disclosed embodiments.

[0009] Figure 8A illustrates an exemplary control sequence for performing checks prior to energizing an electrical circuit, consistent with disclosed embodiments.

[0010] Figure 8B illustrates exemplary voltage control results when performing checks prior to energizing an electrical circuit, consistent with disclosed embodiments.

[0011] Figure 8C illustrates exemplary voltage control when performing checks prior to energizing an electrical circuit, consistent with disclosed embodiments.

[0012] Figure 9 illustrates an exemplary control sequence for battery pack balancing, consistent with disclosed embodiments.

[0013] Figure 10 illustrates a flowchart for an exemplary battery pack pre-charge selection process.

[0014] Figure 11 illustrates a flowchart for an exemplary battery pack pre-charge process.

[0015] Figure 12 illustrates a flowchart for an exemplary battery balancing process.DETAILED DESCRIPTION

[0015] The present disclosure provides a system to ensure safe, reliable, and efficient high voltage pre-charge and power-on sequence for an electric or hybrid-electric aircraft. The aircraft may be an aircraft with a pilot, an aircraft without a pilot (e.g., a UAV), a drone, a helicopter, and / or an airplane. An aircraft includes a physical body and one or more components (e.g., a wing, a tail, a propeller) configured to allow the aircraft to fly. In some embodiments, the aircraft is driven by one or more electrical propulsion units (hereinafter referred to in the singular as “EPU” and in the plural as “EPUs”), which may include at least one engine, at least one rotor, at least one propeller, or any combination thereof. The EPUs may be powered by an aircraft energy source (e.g., one or more battery packs). Improper monitoring and / or control of high voltage power may result in damage to circuitry components and / or components of connected loads (e.g., EPUs). High voltage (HV) may be voltage that is above a predetermined threshold and / or is higher than another voltage used by another system or subsystem. Additionally or alternatively, high voltage may be at least 50 volts (V) or higher, at least 100V, at least 120V, at least 200V, or at least 400V. Additionally or alternatively, low voltage (LV) may be 100V or lower, 50V or lower, or 12V or lower. For example, a high voltage battery may supply a higher voltage than a low voltage battery. For example a high voltage battery may supply 50-500V, and a low voltage battery may supply 1- 49V. By way of further example, a high voltage load may be configured to use 50-500V, and a low voltage load may be configured to use 1-49V. The disclosed embodiments provide circuitry layouts and control processes that improve safety, reliability, and / or energy efficiency of an aircraft.

[0016] For example, the disclosed embodiments allow separate pre-charge of circuitry feeding high voltage and low voltage loads. This provides for greater power control and associated energy savings. In some of the disclosed embodiments, pre-charge of the aircraft circuitry (e.g., electric engine circuitry, tilt actuator circuitry, and / or a direct-current-to- direct-current converter circuitry) is through high voltage battery packs, avoiding the cost and weight of one or more additional low voltage batteries to perform the pre-charge. Further, pre-charge circuitry components are selected and arranged to reduce a weight of the aircraft while still providing reliable pre-charge.

[0017] Further, the disclosed embodiments allow for one battery pack to pre-charge circuitry connected to another battery pack. In a configuration where both battery packs include pre-charge circuitry, this configuration allows for redundancy in case of failure of one of the precharge circuits. In some configurations, the weight of the aircraft may be reduced by including only one pre-charge circuit for at least one group of multiple battery packs. The disclosed embodiments allow communication between battery packs to allow one battery pack to pre-charge the circuitry of another battery pack. This provides for better balancing of battery pack loads and better monitoring of the pre-charge process.

[0018] The disclosed embodiments also include a process whereby the status of high voltage wiring and connections may be reliably checked by controlling a voltage provided to a propulsion bus and / or electric propulsion unit(s). In some embodiments, this process may be performed without a separate HVIL to monitor the integrity of the high voltage wiring. In other embodiments, this process may be performed in addition to HVIL monitoring, providing redundancy and / or increasing reliability of the high voltage circuitry monitoring.

[0019] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the subject matter recited in the appended claims.

[0020] Figures 1A and IB illustrate exemplary wiring connections for an aircraft, consistent with disclosed embodiments. As shown in Figure 1 A, in some embodiments, the distributed electrical propulsion system of the aircraft 100 may include twelve EPUs 110 (e.g., electric engines, fans, turbines etc.), which may be mounted on booms forward (e.g., closer to a front edge) and aft (e.g., closer to a rear edge) of the main wings of the aircraft 100. Any or each of the forward EPUs 110 may be tiltable (e.g., during flight) between a horizontally oriented position (e.g., to generate forward thrust) and a vertically oriented position (e.g., to generate vertical thrust). Any or each of the forward EPUs 110 may be of a clockwise type or counterclockwise type in terms of direction of propeller rotation. The aft EPUs 110 may be fixed in a vertically oriented position (e.g., to generate vertical thrust), and may also be of a clockwise type or counterclockwise type in terms of direction of propeller rotation. As used herein, the term “electric aircraft” may refer to an aircraft that uses at least one electric-based energy source and may include fully electric aircraft as well as hybrid aircraft that uses electricity in addition to another fuel source.

[0021] The aircraft 100 may possess various combinations of forward and aft EPUs 110. For example, in some embodiments, the aircraft 100 may possess six forward EPUs 110 and six aft EPUs 110. In some other embodiments, the aircraft 100 may include four forward EPUs and four aft EPUs, or any other combination of forward and aft EPUs 110. In some other embodiments, the number of forward EPUs 110 and aft EPUs 110 are not equivalent.

[0022] In some embodiments, for a vertical takeoff and landing (VTOL) mission, the forward EPUs 110 as well as aft EPUs 110 may provide vertical thrust during takeoff and landing. During flight phases where the aircraft 100 is in forward flight, the forward EPUs 110 may provide forward thrust (e.g., in a horizontal direction), while the propellers of the aft EPUs 110 may be stowed at a fixed position (e.g., with their propeller blades orientated parallel or near parallel to a front-back axis of the aircraft) in order to minimize drag. The aft EPUs may be actively stowed with position monitoring.

[0023] In some embodiments, in a conventional takeoff and landing (CTOL) mission, the forward EPUs 110 may provide forward thrust for wing-borne take-off, cruise, and landing. In some embodiments, the aft EPUs 110 may not be used for generating thrust during a CTOL mission and the aft propellers may be stowed in place.

[0024] Transition from vertical flight to forward flight and vice-versa may be accomplished via a tilt propeller subsystem. The tilt propeller subsystem may redirect thrust between a primarily vertical direction during vertical flight phase to a mostly horizontal direction during forward-flight phase. A variable pitch mechanism may change the forward electric engine’s propeller-hub assembly blade collective angles for operation during the hover-phase, transition phase, and cruise-phase.

[0025] As shown in Figure 1A, a high voltage power system (HVPS) of the aircraft 100 may include a power source, such as battery packs 120, which supply high voltage power to be converted into, among other possible uses, mechanical shaft power to rotate rotors and / or propellers of the EPUs 110. The amount of thrust each electric propulsion unit 110 generates may be governed by a torque command from a Flight Control System (FCS) over a digital communication interface to each electric propulsion unit 110.

[0026] In some embodiments, the aircraft includes six battery packs 120 (further differentiated as Pl, P2, P3, P4, P5, and P6), which may be installed within the battery bays in the wing of the aircraft 100. In some embodiments, the six battery packs 120 may have an identical design to simplify design, manufacturing, and logistics, although battery packs 120 having different designs are also contemplated. Battery packs 120 may power one or more EPUs 110. While six battery packs 120 are shown, the aircraft 100 may have any number ofbattery packs 120. In some embodiments, battery packs 120 may comprise sensors, such as current, voltage, and / or temperature sensors. The sensors may be configured to measure a state of one or more battery pack cells, circuitry of the battery pack(s) 120 (e.g., configured to received power from the battery pack(s) 120), as described below. In some embodiments, battery packs 120 may include one or more of contactor(s), relay(s), transistor(s), controller(s), and / or any other device(s) capable of controlling flow of (e.g., switching on and off) electricity from battery pack(s) 120, as described below. In some embodiments, battery packs 120 may comprise processor(s), controller(s), logic circuitry, logic devices, and / or communication wiring to monitor and / or control the battery pack(s) 120, as described below. Unless otherwise indicated, “(s)” indicates that the associated word may be either a singular one of the associated component or thing or multiple instances of the associated component or thing.

[0027] In some embodiments, battery packs 120 may comprise battery packs cells (e.g., a cell stack configured to power EPUs 110). A battery pack cell may include at least one of a cathode, an anode, an electrolyte, or any component or material configured to store and / or permit flow of electrical energy.

[0028] In some embodiments, a single battery pack 120 may be electrically connected to, and power, multiple EPUs. For example, in some embodiments, a battery pack 120 may power an electric propulsion unit 110 on either side of a longitudinal axis running through the center of the aircraft fuselage. In some embodiments a battery pack 120 may power an electric propulsion unit 110 on either side of a horizontal axis running through the wing. In some embodiments, as shown in Figure 1A (as shown in the different dashed lines between battery packs and EPUs), a battery pack 120 may power two diagonally opposing EPUs. Therefore, upon a loss of a battery pack 120, the impact to roll or pitch moments on the aircraft can be reduced because the loss of lift is balanced. In some embodiments, battery packs 120 may power different arrangements of EPUs to reduce roll, pitch, or yaw moments that may be caused by a loss of the battery pack 120. For example, in some embodiments, battery packs 120 may be connected to EPUs in any manner that balances lift and / or forward thrust across the longitudinal and horizontal axis of the aircraft.

[0029] Further, the exemplary HVPS system includes a cross-link 130 (three of which are depicted between the open dots) possessing at least one fuse allowing for pairing of two or more battery packs 120. Through the cross-link, power for the EPUs can be shared among the paired battery packs 120. While in the example of Figure 1A, battery packs 120 are connected in pairs using three separate cross-links 130, it is appreciated that any number ofbattery packs (e.g., pairs, triplets, quadruplets, or a combination thereof) may be connected using cross-links and / or that some or even all batteries may not be connected using any crosslink. Thus, in some embodiments, multiple battery packs 120 may simultaneously power multiple EPUs. This arrangement provides for redundancy and avoids a single point of failure because each paired battery 120 may act as a backup for the other(s). Based on failure of a battery pack 120, one or more connected battery packs 120 may continue powering the failed battery pack’s connected EPUs.

[0030] Figure IB illustrates an exemplary embodiment whereby the battery packs may also power a tilt propeller system of the EPUs. For example, the battery packs may power linear and / or rotary actuators to change the orientation of a propulsion system during operation. In some embodiments, the pitch of the propulsion system may be changed as a function of the orientation of the propulsion system. In some embodiments, a rotary actuator may include a motor, inverter, and gearbox. In some embodiments, as shown, each battery pack 120 powers a tilt propeller system (e.g., T1-T6) that corresponds to an electric propulsion unit being powered by the battery pack. As described above, the aircraft may include a different number and / or combination of battery pack and propulsion system arrangements (with corresponding tilt propeller systems). In some embodiments, each of the arrangements described with reference to Figure 1 A may further include a tilt actuator being powered by the battery pack powering the electric propulsion unit whose tilt is controlled. While in the example shown in Figure IB only the forward EPUs 110 are tiltable, in other embodiments the aft EPUs 110 are also tiltable and high voltage power similarly runs from the battery packs 120 to the aft EPUs 110.

[0031] Figure 1C illustrates a diagram of circuitry to manage power distribution, consistent with disclosed embodiments. A person (e.g., pilot, technician) may select a desired mode through an input device such as mode switch 116. An input device may be or include a user input device, such as a user interface, handheld device, touchscreen, console, pilot control, a manual switch, knob, button, lever, and / or any mechanical part configured to be moved by a user, or any combination thereof. An input device may be communicably connected to the aircraft (e.g., to one or more systems or devices of the aircraft, such as a BMU, pre-charge circuitry system, controller, FCC, etc. A mode (which may be considered an electrical connection mode, charging mode, and / or pre-charging mode) may include a combination of components to be powered and an amount of power to provide to those components. Additionally, a mode may include a sequence of combinations of components to be powered and an amount of power to provide to those components. For example, a mode may include acombination of open or closed switch states to apply to one or more switches (e.g., by transmitting at least one signal and / or instruction to the one or more switches). A mode switch may be considered any software, hardware, and / or non-electrical mechanism configured to cause a change in electrical circuitry configuration of the aircraft. For example, a mode switch may be physical switch or a selectable user interface element that may be rendered on a display. For example, a mode switch may be a turnable knob that may select and / or initiate one of a plurality of different modes, consistent with disclosed embodiments. In some embodiments, the mode switch 116 is located on a pilot dashboard and / or panel. In some embodiments, mode switch 116 may be a user interface element provided on a pilot’s display screen or control panel. In some embodiments, the selected mode may be sent to battery management unit 102, including one or more controllers 102(a). In some embodiments, the selected mode may be sent to one or more other components (e.g., flight control system 118, charge control unit(s), switch(es), power distribution box(es), and / or system control unit(s)). In some embodiments, battery management unit 102 may receive the selected mode from one or more other components, such as a flight control computer (FCC) or controller. An FCC may be a computer associated with controlling multiple different aircraft functions, including communicating with BMUs, pilot interfaces, aircraft effectors (e.g., actuators, EPUs), or any aircraft system.

[0032] High voltage distribution 103 may power a variety of loads 104 (e.g., EPUs, tilt actuators, heating and cooling equipment, low voltage systems, equipment etc.) and may provide power to one or more paired battery packs 120 (e.g., through a cross-link 130 shown above in Figures 1 A-1B). Further, high voltage distribution 103 may include main contactors, electric propulsion unit contactors, charge contactors, pre-charge switching devices, resistors, pyro-fuses, thermal fuses, and / or any other circuitry components described below.

[0033] Battery Management Unit (BMU) 102 may be implemented by at least one processor (e.g., at least one microprocessor-based controller) configured to execute software code stored in a storage medium (e.g., a computer-readable medium, a non-transitory computer- readable medium) to implement any combination of the functions described herein. In some embodiments, BMU 102 may include multiple controllers (e.g., controller 102(a)) and / or associated logic devices. BMU 102 may monitor the conditions of one or more battery packs 120 and may communicate with various systems within and outside the battery pack 120. Monitoring may include accessing, detecting, receiving, and / or determining circuitry information (e.g., measurements, such as current, voltage, power, and / or temperature measurements), comparing circuitry information (e.g., to one or more thresholds), analyzingcircuitry information (e.g., determining temporal circuitry information, such as by integrating current measurements over time), and / or performing a responsive operation (e.g., changing at least one switch state and / or blowing at least one fuse), consistent with disclosed embodiments. In some embodiments, the BMU 102 may be integrated into a battery pack (e.g., its associated battery pack, an “instant” battery pack from the perspective of the BMU, a battery pack over which it has direct control) and / or considered to be part of a battery pack.

[0034] For example, the BMU 102 may receive voltage, current, resistance, and temperature sensing signals from the battery cell stack and / or HV Distribution 103. BMU 102 may receive the sensing signals from the battery cell stack, for example, via cell management unit (CMU) 105, which may include at least one a chip, microchip, and / or processor configured to measure characteristics indicative of a state of one or more battery pack cells within a battery pack and, in some embodiments, generate corresponding data describing the measured characteristics.

[0035] BMU 102 may receive the sensing signals from HV Distribution 103, for example, via sensors monitoring the HV distribution wiring configured to receive power from one or more battery pack(s) 120. In some embodiments, the BMU 102 performs computation of one or more battery states, such as a state of battery temperature (also referred to as an “SOT” of the battery), a state of battery charge (also referred to as an “SOC” of the battery), a state of battery energy (also referred to as an “SOE” of the battery), a state of battery health (also referred to as an “SOH” of the battery), a state of battery power (also referred to as an “SOP” of the battery), or a charging connection state of a battery.

[0036] As used herein, information described as “pack-level” or “pack level” means that the information is expressed with respect to one or more battery packs. For example, a pack-level temperature may be a temperature of, or a temperature representation of, one or more battery packs. Additionally, as used herein, information described as “cell-level” or “cell level” means that the information is expressed with respect to one or more battery cells, such as a single battery cell or group of battery cells forming a subset of the battery cells in a battery pack. For example, a cell-level voltage may be a voltage of, or a voltage representation of, one or more battery packs.

[0037] A state of temperature (SOT) may include or indicate a temperature of at least a portion of a battery cell (e.g., at least one active material of the battery cell, the battery cell itself, multiple battery cells, a battery pack, etc.). For example, an SOT may indicate a core or inner temperature of a battery cell, a temperature of the top of the battery cell, a temperature of the middle of the battery cell, and / or the temperature of the bottom of the battery cell. Insome embodiments, an SOT may be based on a measured temperature value (e.g., measured by a temperature sensor adjacent to or on a battery cell). In some embodiments, an SOT may be based on a measured temperature value (e.g., measured by a temperature sensor adjacent to or on a battery cell). An SOT may be estimated using temperature measurements, which may be associated with the at least a portion of a battery cell, such as individual battery cells. For example, an SOT may be estimated using the measured temperature value (e.g., using a model relating an outer measured temperature to an inner temperature).

[0038] As another example, an SOT may be a pack-level temperature based on (e.g., calculated using) multiple battery cell SOTs. In some embodiments, an SOT may be based on a measurement (e.g., direct measurement), an estimation (e.g., based on a direct measurement), or a combination of both. An SOT may be expressed as an absolute value of degrees (e.g., in Fahrenheit, Celsius, or Kelvin) and / or a ratio (e.g., with respect to rated limit, safety limit, etc.). In some embodiments, an SOT may be based on an SOH, as discussed further herein. In some embodiments, an SOT may be used to determine an SOC, as discussed further herein. Measurements used for SOT may be taken at a battery cell level and / or derived from measurements taken for multiple cells, such as pack-level measurements. Additionally or alternatively, the SOT of the battery pack may be equal to a combination (e.g., average, weighted average) of SOT of one or more (e.g., each) battery cells.Additionally, or alternatively, SOT of cells in a battery pack may be extrapolated from the SOT of the battery pack. For example, by applying the rationale that SOT of the battery pack estimated using pack-level measurements should be equal approximately the average of SOT of cells in the battery pack, SOT of cells in the battery pack can be estimated.

[0039] In some embodiments, an SOC may indicate an ability of at least a battery cell (e.g., the battery cell itself, multiple battery cells, a battery pack, multiple battery packs, etc.) at a particular instant of time to store (or provide) charge. State of charge may be expressed as an absolute number (e.g., Coulombs or Amp-hrs Ah) or as a ratio or percentage relative to a maximum ability of the at least a battery cell to store (or provide) charge. In some embodiments, a state of charge may refer to an available battery pack capacity relative to the battery pack’s rated capacity. Additionally or alternatively, in some embodiments, state of charge may refer to an available battery cell capacity relative to the battery cell’s rated capacity.

[0040] In some embodiments, an SOC may be based on a measured charge or voltage value (e.g., measured by a temperature sensor adjacent to or on a battery cell). An SOC may be estimated using charge or voltage measurements, which may be associated with the at least aportion of a battery cell, such as individual battery cells. Measurements used for SOC may be taken at a battery cell level and / or derived from measurements taken for multiple cells, such as pack-level measurements. Further, in some embodiments, a state of charge of a battery pack may be based on one or more states of charge of one or more battery cells. For example, a battery pack SOC may be a combination (e.g., summation, weighted summation) of each battery cell SOC. Additionally or alternatively, the SOC of the battery pack may be equal to a combination (e.g., average, weighted average) of states of charge of one or more (e.g., each) battery cells. Additionally, or alternatively, SOC of cells in a battery pack may be extrapolated from the SOC of the battery pack. For example, by applying the rationale that SOC of the battery pack estimated using pack-level measurements should be equal approximately the average of SOC of cells in the battery pack, SOC of cells in the battery pack can be estimated.

[0041] A state of energy (SOE) may indicate a predicted amount of energy remaining in at least one battery cell (e.g., a single battery cell, multiple battery cells, a battery pack, multiple battery packs, etc.) at a particular time. In some embodiments, an SOE may be based on (e.g., calculated using) an expected future power demand from the at least one battery cell (e.g., demanded by a system, such as a vehicle or aircraft). Additionally or alternatively, an SOE may include or may be based on one or more of an estimated range (e.g., flight range of an aircraft), an amount of useful energy, or an amount of usable energy. In some embodiments, a state of energy may be based on past use of the at least one battery cell (e.g., based on past flights). Additionally or alternatively, an SOE may include or be based on a total energy in a cell, which may be calculated by determining an area under an open circuit voltage-SOC curve. Additionally or alternatively, an SOE may include or be based on the expression of Vnom * Q, where the Vnom is the nominal voltage of a cell or battery, and Q is a charge capacity (e.g., expressed in Ah). In some embodiments, an SOE may include available discharge energy in a battery cell such that when an assumed power demand is realized, a system constraint is reached at the conclusion of the demand. For example, a system constraint may include a minimum cell voltage, a maximum cell temperature, and / or a minimum voltage of one or more connected loads (e.g., EPU). In some embodiments, an SOE may be based on a measured charge, temperature, voltage, impedance, and / or other value(s) of battery cell characteristic (physical, electrical, and / or chemical) (e.g., measured by a sensor adjacent to or on a battery cell, such as a voltage sensor). An SOE may be estimated using charge, temperature, and / or voltage measurements, which may be associated with the at least a portion of a battery cell, such as individual battery cells. Measurements used for SOE maybe taken at a battery cell level and / or derived from measurements taken for multiple cells, such as pack-level measurements. Additionally or alternatively, the SOE of the battery pack may be equal to a combination (e.g., average, weighted average) of states of energy of one or more (e.g., each) battery cells. Additionally, or alternatively, SOE of cells in a battery pack may be extrapolated from the SOE of the battery pack. For example, by applying the rationale that SOE of the battery pack estimated using pack-level measurements should be equal approximately the average of SOE of cells in the battery pack, SOE of cells in the battery pack can be estimated.

[0042] A state of health (SOH) may indicate a performance capability and / or performance loss of at least a battery cell (e.g., the battery cell itself, multiple battery cells, a battery pack, multiple battery packs, etc.). For example, the SOH may indicate an amount of degradation experienced by, or performance capability of, the battery cell, which may be expressed relative to an initial (e.g., original) capability of the battery cell. The performance of the battery cell may be based on or relate to one or more of: charge capacity, energy storage, energy output, power storage, power output, a cell state, a battery state, an electrical component state, or a system state. In some embodiments, an SOH may be based on one or more of a power fade (e.g., impedance growth) or a capacity fade of the at least one battery cell.

[0043] In some embodiments, a SOH of a battery pack may be defined by the SOH of one or more battery cells of the battery pack. For example, the SOH of the battery pack may be equal to the worst SOH of a battery cell (e.g., highest impedance growth, largest capacity fade). In some embodiments, at least one processor may determine an SOH of a battery cell or a battery pack based on measurements from one or more corresponding sensors. For example, an SOH of a battery pack may be determined based on battery pack-level signals acquired by one or more pack-level sensors. Further, an SOH of a battery cell may be determined based on battery cell-level signals acquired by one or more cell-level sensors. In some embodiments, an SOH may be based on a measured charge, temperature, and / or voltage value (e.g., measured by a voltage sensor adjacent to or on a battery cell). In some embodiments, an SOH may be based on a measured charge, temperature, voltage, impedance, or other value(s) of battery cell characteristics (physical, electrical, and / or chemical) (e.g., measured by a sensor adjacent to or on a battery cell, such as a voltage sensor). An SOH may be estimated using charge, temperature and / or voltage measurements, which may be associated with the at least a portion of a battery cell, such as individual battery cells. Measurements used for SOH may be taken at a battery cell level and / or derived frommeasurements taken for multiple cells, such as pack-level measurements. Additionally or alternatively, the SOH of the battery pack may be equal to a combination (e.g., average, weighted average) of states of health of one or more (e.g., each) battery cells. Additionally, or alternatively, SOH of cells in a battery pack may be extrapolated from the SOH of the battery pack. For example, by applying the rationale that SOH of the battery pack estimated using pack-level measurements should be equal approximately the average of SOH of cells in the battery pack, SOH of cells in the battery pack can be estimated.

[0044] In some embodiments, state of power (SOP) may indicate an available power that can be provided by the battery pack over a time horizon, e.g., without exceeding at least one system constraint (such as a battery pack voltage constraint, battery cell temperature constraint, HV wiring current carrying constraint, etc.). SOP may be expressed as an absolute number (e.g., kW, W) or as a ratio or percentage relative to a maximum rated power (e.g., a maximum rated system power).

[0045] In some embodiments, an SOP may be based on a measured charge, temperature, voltage, power, impedance, and / or other value(s) of battery cell characteristic (physical, electrical, and / or chemical) (e.g., measured by a sensor adjacent to or on a battery cell, such as a voltage sensor). An SOP may be estimated using charge or voltage measurements, which may be associated with the at least a portion of a battery cell, such as individual battery cells. Measurements used for SOP may be taken at a battery cell level and / or derived from measurements taken for multiple cells, such as pack-level measurements. Further, in some embodiments, an SOP of a battery pack may be based on one or more SOPs of one or more battery cells. For example, a battery pack SOP may be a combination (e.g., summation, weighted summation) of each battery cell SOP. Additionally or alternatively, the SOP of the battery pack may be equal to a combination (e.g., average, weighted average) of states of charge of one or more (e.g., each) battery cells. Additionally, or alternatively, SOP of cells in a battery pack may be extrapolated from the SOP of the battery pack. For example, by applying the rationale that SOP of the battery pack estimated using pack-level measurements should be equal approximately the average of SOP of cells in the battery pack, SOC of cells in the battery pack can be estimated.

[0046] BMU 102 may also control and monitor bus pre-charging, provide fuse and contactor commands, and communicate with various systems within and outside the battery pack. In some embodiments, BMU 102 may communicate with a flight control system (e.g., FCS 118 and / or one or more flight control computers), charge a charge control unit, and / or other components of the battery pack. In some embodiments, BMU 102 may receive power from alow voltage battery and / or a high voltage battery pack. Additionally or alternatively, BMU 102 or another electrical component may receive power through a direct-current-to-direct- current convertor, also called a DC / DC converter or a “DC / DC.” In some embodiments, a DC / DC may be bidirectional, which may refer to the fact that it is a converter that is configured to both step up or step down voltage from either side of the converter to the other side, which it may accomplish by using a controller and / or gate-signal generator.

[0047] As further described below, in some embodiments a mode selection (e.g., on mode switch 116) may indicate to BMU 102 that one or more buses need to be powered. For example, a mode selection may indicate that one or more of a bus powering EPUs and tilt actuators, a bus powering a DC / DC for low voltage systems, and / or a bus powering environmental controls needs to be pre-charged and powered.

[0048] Figures 2A-2E illustrate exemplary circuitry and modes, consistent with disclosed embodiments. While certain aspects of these figures and subsequent figures (e.g., Figures BASE, 4A-4E, 5A-5E, 6, 7, 8A-8C, and 9) may describe pairs of battery packs, it is appreciated that the circuitry layouts and processes described may apply to more than two paired battery packs. For example, three, four, five, or any number of battery packs may be connected to a common bus (e.g., cross-link 130) and therefore connected or connectable to each other (e.g., paired), may include the shown circuitry layouts (e.g., pre-charge circuits, DC / DC converters, low voltage battery etc.), and / or may perform any of the processes described in the figures of this disclosure. A common bus may be considered to be common to different components if those components can receive (e.g., based on a switch and / or fuse configuration) or are receiving, according to a circuitry path, power from that same bus. Figures 2A-2E each depict a circuitry system, which may be used according to any number of the processes discussed below, which may involve mode selection-related and / or pre-charging-related operations.

[0049] As shown in Figure 2A, 6, and others, each battery pack may include a high voltage junction box (HVJB) which is electrically connected to the HV loads to provide high voltage power (e.g., voltage exceeding 270V, such as 400V). Specifically, the power storage element BT1 (e.g., the battery cells connected in parallel and in series) can be used to provide the high voltage power. The power storage element BT1 is connected to each of the HV loads through pre-charge resistor(s) (e.g., resistor R1 and R7, which may be positive-temperature- coefficient (PTC) resistors) or current sensing resistor(s) (e.g., resistors R2-R6), switching devices K1-K5, and a combination of active and / or passive fuses (e.g., F1-F7) to protect against various failure conditions (e.g., overcurrent, short-circuit etc.). In some embodiments,at least one switching device and / or at least one fuse may be controllable by at least one processing device (e.g., a battery management unit, or BMU, a flight control computer, or FCC, or a combination thereof). For example, a BMU may transmit a command signal to cause a switching device to open (which may be referred to as “to open” or “opening”) or close (which may be referred to as “to close” or “closing”). Additionally or alternatively, a BMU may transmit a command signal to cause a fuse to blow.

[0050] In some embodiments, a different configuration of active and passive fuses may protect against failure conditions. For example, a single active fuse (e.g., F6) may be included on the cross-link between battery packs. As another example, a circuitry system may include a fuse configured to disconnect at least one of a first pre-charge circuit or second pre-charge circuit from a power source, a load, and / or another pre-charge circuit. For example, a circuitry system may include one or more active and / or passive fuses (e.g., F1-F7), which may be triggered to blow (e.g., by a BMU) in order to disconnect a battery pack from multiple loads (e.g. Fl) and / or a single load (e.g., F2, F3, F7).

[0051] By way of further example, the circuitry system may include a fuse configured to disconnect the first pre-charge circuit from the second pre-charge circuit (e.g., F6).

[0052] As another non-exclusive example, the circuitry system may include a fuse configured to disconnect the battery management unit from a power source. For example, the circuitry system may include a fuse between the BMU and a battery pack (e.g., F8).

[0053] While certain elements are shown within the HVJB, it is appreciated that elements depicted in the HVJB may exist outside of an HVJB (e.g., no HVJB may be present) and that a different combination of elements, including all or a subset of the elements in Figure 2A, may be included as part of an HVJB.

[0054] Switching device(s) K1-K7 may include one or more of contactor(s), relay(s), transistor(s), controller(s), and / or any other device capable of controlling flow of (e.g., switching on and off) electricity. In some embodiments, switching devices K6-K7 may control whether battery pack(s) receive a charge from a charging bus. Switching devices Kl- K5 may control whether high voltage power flows to the electric propulsion unit(s) (e.g., electric engines), tilt actuator(s), direct to direct current (DC / DC) converter(s), and / or environmental conditioning system (ECS) equipment (pumps, fans, condensers etc.). In some embodiments, K1-K7 are all contactors, while in other embodiments K3 and K5 are semiconductor devices (e.g., MOSFET devices) and the remaining switching devices are contactors. In some embodiments, one or more of the fuses F1-F8 may be pyrofuses (e.g., all of fuses F1-F8 are pyrofuses).

[0055] As shown, circuitry to a DC / DC converter and / or environmental conditioning system (ECS) equipment (e.g., a main bus) may be pre-charged through, at least in part, closing precharge switching device K3 to enable current to flow through pre-charge resistor R1 (e.g., a resistor connected in series) to pre-charge circuitry to non-propulsion loads. A nonpropulsion load may include a low power load and / or a load that is part of ECS equipment. Additionally or alternatively, a non-propulsion load may include a load that is not an EPU or a tilt actuator, which may be considered propulsion loads. For example, the non-propulsion load may include at least one of: environmental conditioning system (ECS) equipment, avionics, a flight control computer, or a flight control surface. In some embodiments, a precharge resistor may be configured to increase resistance based on a temperature increase. For example, R1 and / or R7 may be PTC resistors (e.g., thermistors) whose resistance increases with an increase in temperature.

[0056] As shown in Figure 2A, 6, and others, circuitry to EPUs (e.g., propulsion bus) and / or tilt actuators may be pre-charged through closing pre-charge switching device K5 (e.g., in response to a signal received, such as from a BMU) to enable current to flow through precharge resistor R7 (e.g., a resistor connected in series). Further, as shown, R1 and K3 (e.g., constituting all or part of a first pre-charge circuit) may be connected in parallel with R7 and K5 (e.g., constituting all or part of a second pre-charge circuit).

[0057] In some embodiments, a “main bus” may refer to a bus that is configured to power one or more systems and / or subsystems, for example one or more of: a low voltage system, one or more other battery packs, or environmental conditioning system (ECS) equipment. In some embodiments, the “main bus” may also be configured to power a propulsion bus (e.g., through closing one or more switching devices, such as K4). In some embodiments a “propulsion bus” may refer to a bus configured to power one or more electric propulsion units or tilt actuators. In some embodiments, a propulsion bus may be configured to receive power from a main bus.

[0058] In some embodiments, a system may include a first switching device, which may be configured to electrically connect a first pre-charge circuit to pre-charge a bus powering a non-propulsion load. As explained further herein, the first switching device may include switching device K3, which may be controlled according to one or more modes and / or instructions from a BMU or other processing device, as discussed further below.

[0059] The system may also include a bidirectional DC / DC converter, which may be configured to pre-charge the bus powering a non-propulsion load. The bidirectional DC / DC converter may also be controlled according to one or more modes and / or instructions from aBMU or other processing device. Controlling the bidirectional DC / DC converter may include instructing or causing the bidirectional DC / DC converter to step up voltage or step down voltage on a side of the converter. Controlling the bidirectional DC / DC converter may also include transmitting an instruction to the bidirectional DC / DC converter that indicates a side of the converter to step up or step down voltage, an amount of voltage to step up or step down to, and / or an amount of time for the step up or step down of voltage to occur. In some embodiments, one or more unidirectional DC / DC converters may be used in place of a single bidirectional DC / DC convertor.

[0060] In some embodiments, the system may also include multiple DC / DC convertors, such as a first bidirectional DC / DC convertor and at least one second bidirectional DC / DC convertor. In some embodiments, the first bidirectional DC / DC converter may be configured to pre-charge a bus powering a non-propulsion load, consistent with disclosed embodiments. Additionally or alternatively, the first bidirectional DC / DC converter may be configured to provide current to at least one second bidirectional DC / DC converter. The at least one second bidirectional DC / DC convertor may be configured to receive the current from the first bidirectional DC / DC converter and pre-charge a bus powering a propulsion load using the received current.

[0061] In some embodiments, a system may include a second switching device, which may be configured to electrically connect a second pre-charge circuit to pre-charge a bus powering at least one electric propulsion unit (EPU). As explained further herein, the second switching device may include switching device K4 or K5, either or both of which may be controlled according to one or more modes and / or instructions from a BMU or other processing device, as discussed further below.

[0062] Some embodiments may involve selecting and / or switching between modes, as discussed further herein. In some embodiments, a system may include at least one battery management unit (BMU), which may be configured to control, for example based on a mode selection made by an input device, the first and second switching devices, as discussed further below.

[0063] For example, in a first mode (e.g., selectable by mode switch 116) shown in Figure 2A, a battery pack (e.g., battery pack 120) may only supply power to BMU 102 (e.g., through a DC / DC). In some embodiments, the battery pack may provide no HV power to loads other than BMU 102 (e.g., when operating in the first mode). In some embodiments, at least one battery management unit of the system may be configured to control, based on a mode selection made by an input device, the first bidirectional DC / DC converter and the at leastone second bidirectional DC / DC converter. As discussed above, controlling the bidirectional DC / DC converter may include instructing or causing the bidirectional DC / DC converter to step up voltage or step down voltage on a side of the converter.

[0064] In a second mode (e.g., selectable by mode switch 116) shown in Figures 2B-2C, BMU 102 may command a switching device on a negative side (e.g., K2) closed and then command switching device K3 closed to allow for pre-charging circuitry feeding the DC / DC converter(s), environmental control system (ECS) equipment, and / or paired battery pack(s) 120 (e.g., pre-charging a main bus). Once BMU 102 determines that pre-charging is complete (e.g. through determining, such as by using one or more voltage sensors, a voltage difference between the battery pack and pre-charged bus is below a threshold), as shown in Figure 2C, BMU 102 may command a switching device on a positive side (e.g., KI) closed and subsequently open switching device K3, allowing high voltage power from the battery pack 120 to feed the DC / DC converter, ECS equipment, and / or paired battery pack(s) 120. In some embodiments, the DC / DC converter may power low voltage systems of the aircraft. Low voltage systems may include avionics, one or more flight control computers (FCCs), aircraft flight control surfaces, motors controllers, battery management systems for the battery packs, environmental conditioning system (ECS) equipment, sensors, medical equipment, cabin lights, and / or any other system on the aircraft requiring low voltage power.

[0065] Further, in a third mode (e.g., selectable by mode switch 116) shown in Figures 2D- 2E, BMU 102 may command switching device K5 closed (e.g., Figure 2D), allowing for precharging of the electric propulsion unit(s) and / or tilt actuator(s) (e.g., propulsion bus). As shown in Figure 2E, once BMU 102 determines that pre-charging is complete, the BMU 102 may, in response, close K4 and subsequently open switching device K5, allowing high voltage power from the battery pack to feed the EPUs and / or tilt actuators.

[0066] As further detailed below, in some embodiments, one battery pack 120 may precharge part or all of the circuitry associated with another battery pack (e.g., configured to receive power from the another battery pack 120). For example, as shown, pre-charging circuitry (e.g., R1 and K3, R7, and K5) configured to pre-charge circuitry that powers the DC / DC and / or ECS of a first battery pack (e.g., main bus of first battery pack) may also precharge the cross-link (e.g., cross-link 130) and circuitry configured to power a DC / DC and ECS of another battery pack (e.g., main bus of another battery pack). In some embodiments, a paired battery pack may not include pre-charge circuitry (e.g., R1 and K3). In other embodiments, both battery packs may include pre-charge circuitry. In some embodiments, BMU(s) of paired battery packs can communicate to determine which battery pack willperform the pre-charging, as further detailed below. Unless specified otherwise, as used herein, performing pre-charging may include supplying power to pre-charge one or more components, such as by closing one or more switches (e.g., MOSFETs, contactors, etc.).

[0067] Figures 3A-3E illustrate exemplary circuitry and modes, consistent with disclosed embodiments. In some embodiments, pre-charging the HV circuitry may be performed in the manner shown in any or all of Figures 3A-3E with only one pre-charge circuit configured to pre-charge circuitry that powers the EPUs and / or tilt actuators (e.g., a propulsion bus) and a separate low voltage battery for pre-charging other circuitry (e.g., a main bus). While several modes are described below, it is appreciated that the associated circuits or variants thereof may be configured to operate according to any or all of the described modes.

[0068] For example, in a first mode (e.g., an electrical connection mode selectable by mode switch 116) shown in Figure 3A, a battery pack (e.g., battery pack 120) may only supply power to BMU 102 (e.g., through a DC / DC). For example, with switching devices KI, K2, K5, K6, and K7, in open states, current from the battery pack (BT1) may flow only in a circuit between BT1 and the BMU. In some embodiments, the battery pack may provide no HV power to loads other than BMU 102 (e.g., when in the first mode).

[0069] In a second mode (e.g., an electrical connection mode selectable by mode switch 116) shown in Figure 3B, BMU 102 may control circuitry (e.g., switching devices, such as contactors, relays, MOSFET devices etc.) associated with (e.g., controlling electrical connectivity to and / or electrically connected to) a low voltage (LV) battery to provide power to a DC / DC converter and may control the DC / DC converter to pre-charge circuitry feeding a DC / DC converter associated with low voltage (LV) systems (e.g., systems configured to power devices configured for low power, such as lights, avionics equipment, FCCs, control surface actuators, media devices, Heating Ventilation and Air Conditioning actuators, or other electrical components separate from the EPUs, environmental conditioning system (ECS) equipment, HV DC / DC convertors, and tilt actuators), ECS, and / or paired battery pack 120 (e.g., a main bus). In some embodiments, as shown, the DC / DC converter used for precharge via the LV battery may also be used to step down power to feed low voltage equipment. For example, a bidirectional DC / DC may be controlled to step down an HV battery voltage to feed low voltage equipment and stepping up low voltage battery voltage to pre-charge the circuit as described above.

[0070] In a continuation (e.g., second stage) of the second mode, shown in Figure 3C, once BMU 102 determines that pre-charging is complete (e.g. through determining voltage difference between the battery pack and pre-charged bus is below a threshold), BMU 102may close KI and K2, allowing high voltage power to feed the DC / DC converter, ECS equipment, and / or paired battery pack (e.g., a main bus).

[0071] Further, in a third mode (e.g., selectable by mode switch 116), as depicted shown in Figure 3D, BMU 102 may command switch K5 closed, allowing for pre-charging of the circuitry feeding electric propulsion unit(s) and / or tilt actuator(s) (e.g., a propulsion bus).

[0072] In a continuation (e.g., second stage) of the third mode, shown in Figure 3E, once BMU 102 determines that pre-charging is complete (e.g. determining voltage difference between the battery pack and pre-charged bus is below a threshold), BMU 102 will close switching device K4 and subsequently open switching device K5, allowing high voltage power from the battery pack 120 to feed the electric engines and / or tilt actuators.

[0073] As further detailed below, in some embodiments, one battery pack 120 may precharge part or all of the circuitry associated with another battery pack (e.g., circuitry that is also configured to be powered by the another battery pack, and for which the another battery pack may be designated as a primary charging source). For example, as shown through the “battery pack pair” connection), an LV battery and DC / DC responsible for pre-charging circuitry configured to power the DC / DC and / or ECS of a first battery pack (e.g., main bus of first battery pack) may also pre-charge the cross-link (e.g., cross-link 130) and circuitry configured to power a DC / DC and / or ECS of another battery pack (e.g., main bus of another battery pack). In some embodiments, a paired battery pack may not include a connection to an LV battery and / or a bidirectional DC / DC. In other words, there may be two instances of the system in Figures 3 A (i.e., the version shown in these figures, and a mirror version), which may be connected through the “battery pack pair” connection. In other embodiments, both battery packs may include the connection to an LV battery and a bidirectional DC / DC. In some embodiments, BMU(s) of paired battery packs can communicate to determine which battery pack will perform the pre-charging, as described below.

[0074] Figures 4A-4E illustrate exemplary circuitry and modes, consistent with disclosed embodiments. In some embodiments, pre-charging the high voltage circuitry may be performed in the manner (e.g., switching device opening / closing sequence) shown in Figures 4A-4E with no pre-charge circuit.

[0075] For example, in a first mode (e.g., an electrical connection mode selectable by mode switch 116) shown in Figure 4A, a battery pack (e.g., battery pack 120) may only supply power to BMU 102 (e.g., through a DC / DC). In some embodiments, the battery pack may provide no HV power to loads other than BMU 102 (e.g., when the first mode is active).

[0076] In a second mode (e.g., an electrical connection mode selectable by mode switch 116) shown in Figures 4B and 4C, BMU 102 may control circuitry associated with a low voltage battery (e.g., switching devices, such as contactors, relays, MOSFET devices etc. influencing or controlling power to and / or from the low voltage battery) to provide power to a first DC / DC converter (e.g., 2.8 kW DC / DC shown on the right side of the circuit) and may control the first DC / DC converter to pre-charge circuitry feeding a DC / DC converter configured to power LV systems, ECS, and / or paired battery pack (e.g. a main bus). In some embodiments, as shown, the DC / DC converter used for pre-charge is also used to step down power to feed low voltage equipment. For example, a bidirectional DC / DC may allow for stepping down HV battery voltage to feed low voltage equipment and stepping up low voltage battery voltage to pre-charge the circuit as described above.

[0077] In a continuation (e.g., second stage) of the second mode, shown in Figure 4C, once BMU 102 determines that pre-charging is complete (e.g. through determining voltage difference between the battery pack and pre-charged bus is below a threshold), BMU 102 will close KI and K2, allowing high voltage power to feed the DC / DC converter, ECS equipment, and / or paired battery pack.

[0078] In a third mode (e.g., an electrical connection mode electable by mode switch 116) shown in Figures 4D and 4E, BMU 102 may control circuitry of low voltage battery (e.g., switching devices, such as contactors, relays, MOSFET devices etc.) and the first DC / DC to step down the high voltage power from the battery to feed one or more second DC / DC converters (e.g., DC / DC converters shown adjacent to the electric engines, which may be wired in parallel with engine components). In some embodiments, the second DC / DC converters may step up the low voltage power to pre-charge circuitry feeding the electric engines and / or tilt actuators (e.g., a propulsion bus).

[0079] In a continuation (e.g., second stage) of the third mode, shown in Figure 4E, in response to determining that the voltage difference between the battery pack and the precharged bus is below a threshold (e.g., via voltage sensors), BMU 102 may close K4 (e.g., transmit a command), thereby allowing high voltage power from the battery pack to feed the electric propulsion unit(s) and / or tilt actuator(s) (e.g., propulsion bus).

[0080] As further detailed below, in some embodiments, one battery pack may pre-charge part or all of the circuitry associated with another battery pack (e.g., configured to receive power from the another battery pack). For example, as shown, an LV battery and DC / DC (e.g., as shown on the right side of the circuit) responsible for pre-charging circuitry configured to provide power to a DC / DC and / or ECS of a first battery pack (e.g., a main busof a first battery pack, such as wiring connecting the pack, such as Fl, to a DC / DC and / or ECS, as well as potentially other components, such as R2, K2, KI, R5, and / or F5) may also pre-charge the cross-link (e.g., cross-link 130) and circuitry configured to power a DC / DC and / or ECS of another battery pack (e.g., a main bus of a second battery pack). In some embodiments, a paired battery pack may not include each of the bidirectional DC / DCs and / or the LV battery connection shown in Figures 4A-4E. For example, the paired battery pack may only include DC / DC(s) on circuitry configured to power the EPU(s) and / or tilt actuator(s). In other embodiments, both battery packs may include the same layout of DC / DC(s) and LV battery connection(s). In some embodiments, BMU(s) of paired battery packs can communicate to determine which battery pack will perform the pre-charging, as described below.

[0081] Figures 5A-5E illustrate exemplary circuitry and modes, consistent with disclosed embodiments. In some embodiments, pre-charging the HV circuitry may be performed in the manner shown in Figures 5A-5E with only one pre-charge circuit configured to pre-charge circuitry feeding a DC / DC converter and / or ECS (e.g., a main bus).

[0082] For example, in a first mode (e.g., an electrical connection mode selectable by mode switch 116) shown in Figure 5A, a battery pack (e.g., battery pack 120) may only supply power to BMU 102 (e.g., through a DC / DC). In some embodiments, the battery pack may provide no HV power to loads other than BMU 102 (e.g., when operating with the first mode active).

[0083] In a second mode (e.g., an electrical connection mode selectable by mode switch 116) shown in Figure 5B, BMU 102 may command a switching device on a negative side (e.g., K2) closed and then command switching device K3 closed to allow for pre-charging circuitry feeding the DC / DC converters, ECS equipment, and / or paired battery pack(s) 120 (e.g., a main bus).

[0084] In a continuation (e.g., second stage) of the second mode, shown in Figure 5C, once BMU 102 determines that pre-charging is complete (e.g. through determining, such as by using a voltage sensor, that the voltage difference between the battery pack and pre-charged bus is below threshold), BMU 102 may command a switching device on a positive side (e.g., KI) closed and subsequently open switching device K3, allowing high voltage power to feed the DC / DC converter and / or ECS equipment.

[0085] In a third mode (e.g., an electrical connection mode selectable by mode switch 116) shown in Figure 5D, BMU 102 may control a first DC / DC converter and / or associated circuitry (e.g., circuitry configured to power the first DC / DC, such as switching devices, suchas contactors, relays, MOSFET devices etc.) to step down the high voltage power from the battery to feed one or more second DC / DC converters configured to energize circuitry feeding electric propulsion unit(s) and / or tilt actuator(s). In some embodiments, the second DC / DC converters (e.g., as shown adjacent to the electric engines) may step up the low voltage power to pre-charge circuitry feeding the electric propulsion unit(s) and / or tilt actuator(s).

[0086] In a continuation (e.g., second stage) of the third mode, shown in Figure 5E, in response to determining that the voltage difference between the battery pack and the precharged bus is below a threshold (e.g., via voltage sensors), BMU 102 may close K4 (e.g., transmit a command to K4 instructing it to close), thereby allowing high voltage power from the battery pack to feed the electric propulsion unit(s) and / or tilt actuator(s) (e.g., propulsion bus).

[0087] As further detailed below, in some embodiments, one battery pack may pre-charge part or all of the circuitry associated with another battery pack (e.g., configured to receive power from the another battery pack). For example, as shown, pre-charging circuitry configured to pre-charge circuitry powering the DC / DC and / or ECS of a first battery pack (e.g., main bus of a first battery pack) may also pre-charge the cross-link (e.g., cross-link 130) and circuitry configured to power the DC / DC and / or ECS of another battery pack (e.g., main bus of another battery pack). In some embodiments, a paired battery pack may not include pre-charge circuitry (e.g., R1 and K3). In other embodiments, both battery packs may include pre-charge circuitry. In some embodiments, BMU(s) of parallel battery packs can communicate to determine which battery pack will perform the pre-charging.

[0088] By pre-charging using bidirectional DC / DC converters as described in the figures above, additional weight from pre-charge circuitry can be reduced. Further, the voltage value set by the DC / DC converter can ensure that pre-charge can be performed at an optimized value in both single and / or parallel pack pre-charging. For example, the voltage value may bet set to ensure that components aren’t receiving too high of a voltage which may risk or cause damage. It may further be set to ensure components that wake on receiving a voltage above a threshold aren’t accidentally turned on.

[0089] Figure 6 illustrates exemplary circuitry, consistent with disclosed embodiments. In some embodiments, as shown, a fuse (e.g., Fuse F8A) may be associated with both a battery management unit (e.g., BMU 201) circuitry powering the BMU (e.g., circuitry connecting the BMU to battery BT1, including all or path of the shortest path through BT1, Fl, F8A, BMU 201, and R2) and pre-charge circuitry that is configured to pre-charge one or more portions ofthe high voltage circuitry (e.g., circuitry connecting battery BT1 to components other than BMU 201). Therefore, based on detection of an electrical issue (e.g., fault, short circuit, overcurrent condition, and / or another operating condition that does not meet a performance metric), a fuse (e.g., fuse F8A) may be blown (e.g., based on at least one command from the BMU) to disconnect power to both the pre-charge circuitry and the battery management unit to ensure no damage to associated components. Sharing of fuse (e.g., F8A), as shown, allows for weight savings on the aircraft (potentially as much as a pound per battery pack or more).

[0090] In some embodiments, a resistor RIA may be shared between multiple pre-charge circuits. For example, in some embodiments, a resistivity of RIA may be sized to accommodate pre-charge of both circuitry feeding the electric propulsion unit(s) and / or actuator(s) (e.g. propulsion bus) and circuitry feeding the DC / DC and / or ECS (e.g., main bus). For example, in some embodiments, the resistivity of RIA will be oversized (e.g., a resistivity of RIA will be selected that is greater than is needed) for one of the circuits to ensure current is appropriately limited for another circuit. In some embodiments, an additional resistor(s) may be included on one or both of pre-charge circuitry configured to pre-charge circuitry powering the electric propulsion unit(s) and / or actuator(s) (e.g., propulsion bus) and pre-charge circuitry configured to pre-charge circuitry powering the DC / DC and / or ECS (e.g., main bus). Sharing of resistor RIA, as shown, allows for weight savings on the aircraft. In some embodiments, RIA may be a PTC resistor whose resistance increases with temperature. Therefore, a lighter resistor may be used while still ensuring current is appropriately limited to protect components.

[0091] In some embodiments, diode(s) (e.g., DI and D2) may be included on one or both of the circuitry feeding the electric propulsion unit(s) and / or actuator(s) (e.g., propulsion bus) and circuitry feeding the DC / DC and / or ECS (e.g., main bus). Therefore, current back-flow between the separate circuits may be prevented.

[0092] In some embodiments, one or more of the components and / or layouts described with respect to Figure 6 may be included in the circuitry control sequences shown in Figures 2A- 5E. For example, the circuitry layout shown in Figure 6 may be controlled in the same manner as that described with respect to Figures 2A-2D.

[0093] Figure 7A illustrates an exemplary control sequence process 700a for multi-pack (e.g., paired pack) pre-charge control, consistent with disclosed embodiments. In some embodiments, the process 700a is performed by a BMU 102 (which includes at least one processor), which may include at least one processor configured to execute instructions (e.g., instructions corresponding to the steps of process 700a) stored in a memory. In someembodiments, each BMU 102 of the aircraft may perform the process with respect to the battery pack (e.g., battery BT1) it is associated with (e.g., an “instant battery pack”).

[0094] An “instant battery pack,” or “instant pack,” as used throughout, may be considered from the perspective of the components that it is configured to directly (e.g., not across a cross-link, as may be the case for a paired battery pack) supply power to. Unless otherwise noted, an “instant battery pack,” or “instant pack,” may also be referred to as and / or considered to be a “first pack.” Similarly, a BMU communicably connected to, electrically connected to, and / or configured to control the instant pack may be referred to as and / or considered to be a “first battery management unit” or “first BMU.”

[0095] A “paired” pack, as used throughout, may be considered a pack to which the instant pack is paired, one of two paired battery packs, a secondary pack, and / or a pack whose BMU or other associated processing component is not performing process 700a. Unless otherwise noted, an “paired battery pack,” or “paired pack,” may also be referred to as and / or considered to be a “second pack.” Similarly, a BMU communicably connected to, electrically connected to, and / or configured to control the paired pack may be referred to as and / or considered to be a “second battery management unit” or “second BMU.”

[0096] Additionally or alternatively, the process 700a and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component, such as an FCC, controller, or any non-BMU processing device. In some embodiments, steps (e.g., decisions, checks, operations) from process 700b and / or 700c may be used in process 700a. Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs.

[0097] While one or more actions or operations described with respect to Figures 7A-7C, 8A, 9, 10, 11, and 12 may be described with respect to a battery pack or the process itself (e.g., “process 1000 may. . .”, “the instant battery pack may. . .”), it is appreciated that the step may be operated by at least one processor, such as a BMU or an FCC, which may use information from a battery package, such as a voltage measurement, switch status, or any other battery pack related information discussed herein.

[0098] At step 701, process 700a may initiate itself (e.g., by at least one processor).

[0099] At step 702, process 700a may determine a selection completion status. If the selection completion status is true, then the process may end. If the selection completion status is false, then the process may proceed to step 703.

[0100] At step 703, process 700a may set a pack selection variable to a value, such as 0, “unknown,” or any placeholder or default value.

[0101] Additionally or alternatively, process 700a may, at step 701 for example, receive a mode selection (e.g., a selection made through mode switch 116) and / or another indication that a portion of high voltage circuitry is to be pre-charged and powered. For example, the at least one processor may determine, that a propulsion bus (e.g., a bus feeding one or more electric propulsion unit(s) and / or tilt actuator(s)) of each paired battery pack is to be powered based on a first mode being selected. For example, the at least one processor may determine, based on the selection or indication, that a bus (e.g., a main bus feeding a DC / DC for low voltage systems, ECS equipment, and / or paired battery pack(s)) of each paired battery pack is to be pre-charged and powered based on a second mode being selected.

[0102] At step 704, process 700a may determine whether a battery pack is in a paired state (e.g., an electrically connected state). For example, a battery pack (e.g., using its BMU) may determine that it is connected to cross-link 130 and / or is otherwise configured to provide power to another battery pack (e.g., whether F4.1, F4.2, and / or F6 have blown and / or whether a stored status indicates a single pack testing state).

[0103] Based on determining that the battery pack is not in a paired state, process 700a may proceed to step 705, where it may automatically select or designate itself as the default to perform pre-charge (indicated by “Pack select = 1 (PRIMARY) in Figure 7A). For example, based on process 700a determining there is an electrical issue with the paired battery pack, that the paired battery pack or associated circuitry is not in a state to perform pre-charge, that a BMU 102 of a paired battery pack is not powered, and / or that a BMU 102 of a paired battery pack has not completed a start-up check, process 700a may select the instant battery pack (e.g., the battery pack whose associated BMU is performing process 700a, also referred to as a “current pack”) to perform pre-charge. Process 700a may control circuitry components (e.g., as described with respect to Figures 2A-5E) to perform pre-charge of the instant battery pack.

[0104] Then, process 700A may proceed to step 706.

[0105] At step 706, process 700a may determine, based on step 705 for example, that the selection completion status is true, and the process may end (step 707). At step 707, process 700a may proceed to, for example, process 700b, 700c, 800, or 900.

[0106] At step 708, process 700a may determine whether the paired battery pack is capable of pre-charging (e.g., receiving a pre-charge voltage or current). For example, process 700a may determine if there is an electrical issue with the paired battery pack. An electrical issue may include any malfunction or misperformance by an electrical component. For example, an electrical issue may include an overcurrent condition, short circuit, overheat condition, fault,software bug, software glitch, and / or another operating condition of the paired battery pack and / or circuitry configured to be powered by the paired battery pack does not meet a performance metric. In some embodiments, the at least one processor may determine whether it has received any notifications from a BMU 102 of a paired battery pack, such as a notification indicating an electrical issue with the paired battery pack. For example, the at least one processor may receive a notification indicating at least one electrical issue, such as one or more of those mentioned in this paragraph above. In some embodiments, the at least one processor may evaluate sensor measurements (e.g., current or voltage measurements) to determine whether there is an electrical issue with the paired battery pack and / or circuitry configured to be powered by the paired battery pack. In some embodiments, process 700a may determine if the paired battery pack is capable of pre-charging based on determining the instant battery pack is in a paired state.

[0107] In some embodiments, process 700a may receive a notification (e.g., from a BMU of the paired battery pack and / or a flight control system) indicating whether the current state of the paired battery pack is meets one or more criteria for pre-charging the battery pack. For example, in some embodiments, a notification may indicate whether the paired battery pack and / or associated circuitry is powering up or powered down (and thereby not available for pre-charging). In some embodiments, a notification may indicate whether a paired battery pack BMU 102 is powered and / or has performed additional start-up checks (e.g., power and checks required for pre-charging). In some embodiments, process 700a may proceed to step 709 based on step 708. For example, if process 700a determines that the paired battery pack is not capable of pre-charging, it may proceed to step 709. In some embodiments, process 700a may proceed to step 710 based on step 708. For example, if process 700a determines that the paired battery pack is capable of pre-charging, it may proceed to step 710.

[0108] At step 709, process 700a may select the instant battery pack to charge the bus, which may include designating the instant battery pack with a primary status.

[0109] At step 710, process 700a may determine if a paired pack is charging a bus, which may be shared between it and the instant pack. For example, process 700a may receive a notification indicating whether the paired battery pack is in a pre-charge state (e.g., from a BMU or a paired battery pack) and / or may directly detect whether the paired battery pack is in a pre-charge state. For example, a BMU 102 of the paired battery pack may determine whether one or more pre-charge switching devices (e.g., K3 and / or K5) of the paired battery pack are closed to allow for pre-charging. Additionally, or alternatively, the BMU 102 of the paired battery pack may determine whether voltage or current measurements are consistentwith a pre-charge state (e.g., by comparing measurements to one or more thresholds, where consistency with a pre-charge state may be achieved when at least one current and / or at least one voltage exceed a threshold and / or are between two thresholds). The BMU 102 of the paired battery pack may provide a notification to the at least one processor based on its determination. In some embodiments, the at least one processor may directly determine whether the paired battery pack is in a pre-charging state, such as through evaluating the state of pre-charge switching devices, current, and / or voltage measurements.

[0110] At step 712, process 700a may determine if a paired pack is energizing or has energized a bus, which may be shared between it and the instant pack. For example, process 700a may determine if the paired pack has energized the bus, such as by providing charge or voltage from its associated battery to the bus. By way of further example, process 700a may determine if the bus has reached a voltage level threshold associated with a fully or nearly fully pre-charged bus.

[0111] At step 713, process 700a may determine whether voltage measurements are being received and / or have been received for each of the instant battery pack (e.g., through voltage sensor measurements) and the paired battery pack (e.g., through voltage sensor measurements and / or notifications from a BMU 102 of the paired battery pack). For example, voltage measurements may indicate a voltage of the respective battery pack and / or circuitry being pre-charged. If process 700a determines that voltage measurements are being received and / or have been received for each of the instant battery pack and the paired battery pack, it may proceed to step 716. If process 700a determines that voltage measurements are not being received and / or have not been received for each of the instant battery pack and the paired battery pack, it may proceed to step 714.

[0112] At step 714, process 700a may determine a default pack, which it may designate as having the primary role. Process 700 may also instruct the default pack to begin pre-charge operations. A default pack may be pre-designated between a pair of electrically connected battery packs. For example, a BMU associated with each battery pack may store and / or have access to a stored variable in memory that pre-designates the associated battery pack with a primary role as default or a secondary role as default.

[0113] In some embodiments, process 700a, may, optionally based on determining that each battery pack selected the other to perform pre-charging, reference at least one default battery pack criterion to determine the battery pack to perform the pre-charging, such as by performing step 714. In some embodiments, a default battery pack identifier (e.g., location number) may be established to determine which battery pack of paired battery packs may(e.g., should) perform the pre-charging. The at least one processor may determine whether the instant battery pack is to perform pre-charging by comparing its battery pack identifier to the default identifiers. In some embodiments, a user may pre-select a default battery pack to perform the pre-charging. For example, a user interface (e.g., a display associated with a flight control system or maintenance panel) may allow a user to select battery pack identifiers to perform pre-charging. In some embodiments, a centralized computer (e.g., a flight control computer), charge control unit, or a battery management unit may automatically determine which battery packs to set as the default battery packs based on one or more criteria, such as an age of the battery pack, a state of the battery pack, and / or a location of the battery pack (e.g., a battery pack on an outer portion of an aircraft wing may be prioritized).

[0114] In some embodiments, process 700a may, optionally based on determining that the at least one default criterion matches that of the instant battery pack, control the instant battery pack circuitry to perform pre-charge.

[0115] At step 716, process 700a may determine whether the instant battery pack’s voltage is higher than that of a paired battery pack, such that the battery pack with the highest voltage (between the two) may be selected. For example, process 700a may compare a first voltage value received by a BMU of the instant battery pack and a second voltage value received by a BMU of the paired battery pack and determine which value is higher. The first voltage value and / or second voltage value may be measured by one or more voltage sensors, consistent with disclosed embodiments. If process 700a determines that the instant battery pack’s voltage is higher than that of a paired battery pack, it may proceed to step 715. If process 700a determines that the instant battery pack’s voltage is lower than that of a paired battery pack, it may proceed to step 717.

[0116] At step 715, process 700a may select the instant battery pack to perform (e.g., supply power for) the pre-charge (e.g., first selection is instant battery pack 1). For example, process 700a may select the instant battery pack to perform the pre-charge based on determining the instant battery pack’s voltage is greater than the paired battery pack.

[0117] At step 717, process 700a may select the paired battery pack to perform (e.g., supply power for) the pre-charge (e.g., first selection is paired battery pack 2). For example, process 700a may select the paired battery pack to perform the pre-charge based on determining the instant battery pack’s voltage is less than that of a paired battery pack.

[0118] In some embodiments, process 700a may include performing checking or confirmation steps to determine if the instant battery pack and the paired battery pack in agreement on their respective pre-charge roles. For example, at step 718, process 700a mayreceive an indication of which battery pack the paired battery pack (e.g., another BMU, associated with the battery pack paired with the instant battery pack) selected to perform the pre-charge (e.g., a second selection). In some embodiments, a BMU 102 associated with (e.g., configured to monitor and / or control) the paired battery pack may provide the selection. In some embodiments, the paired battery pack may select a battery pack to perform precharge by comparing respective battery pack states, as described above with reference to steps 708-717. In some embodiments, the at least one processor may check whether both battery packs selected themselves to perform the pre-charge.

[0119] At step 719, process 700a may determine if the selection by the paired pack is a secondary role (e.g., the paired pack is not designated, by the paired pack, to pre-charge a bus associated with the instant pack). If the selection by the paired pack is a secondary role, the respective selections made by the battery packs may be compatible (e.g., the instant battery pack will pre-charge the bus and the paired battery pack will not), and process 700a may proceed to step 720. If the selection by the paired pack is a primary role, the respective selections made by the battery packs may not be compatible, and process 700a may proceed to step 723. In some embodiments, process 700a may proceed to step 719 after performing step 709 and / or 715.

[0120] At step 721, process 700a may determine if the selection by the paired pack is a primary role (e.g., the paired pack is designated, by the paired pack, to pre-charge a bus associated with the instant pack). In some embodiments, process 700a may proceed to step 721 after performing step 711 and / or 717. If the selection by the paired pack is a primary role, the respective selections made by the battery packs may be compatible (e.g., the paired battery pack will pre-charge the bus and the instant battery pack will not), and process 700a may proceed to step 720. If the selection by the paired pack is a secondary role, the respective selections made by the battery packs may not be the same, and process 700a may proceed to step 723.

[0121] At step 722, process 700a may complete, at least temporarily. In some embodiments, step 722 may involve additional steps or operations, such as those described below. In some embodiments, process 700a may, after step 722, proceed to, for example, process 700b, 700c, 800, or 900.

[0122] In some embodiments, process 700a may, optionally based on determining that the battery packs have selected the same battery pack for pre-charging (e.g., did not meet the criteria) or the paired battery pack is in a pre-charging state, may determine a difference in voltage between the battery packs. In some embodiments, the instant battery pack (e.g.,through an associated BMU) may determine whether the difference in voltage is below a threshold. The threshold may be set to avoid an in-rush of current that may damage circuitry components. Otherwise, a high difference may indicate that circuitry has not been sufficiently pre-charged to withstand risks from a potential in-rush. For example, the difference in battery pack voltages may be set to a threshold with a value in a range of 5-30V (e.g., 10V).

[0123] In some embodiments, if the at least one processor determined that the paired battery pack is in the pre-charge state, and the voltage difference criterion is satisfied, the at least one processor may select the paired battery pack to perform the pre-charge.

[0124] In some embodiments, if the at least one processor determines that difference between the voltages is not below the threshold, the at least one processor may perform a battery balancing process (e.g., the balancing process described in Figure 9, below). Based on completion of the battery balancing process, the at least one processor may re-determine whether the battery pack voltages are within the threshold.

[0125] In some embodiments, at least one processor (e.g., executing process 700a), based on determining that the battery pack voltages are not within a threshold of each other, will not allow one battery pack to pre-charge another. In some embodiments, the at least one processor may send a notification indicating an imbalance fault to a user device (e.g., flight control system display and / or maintenance panel). In some embodiments, the notification may indicate the battery pack(s) associated with imbalance (e.g., experiencing the imbalance between them) and / or further details about the imbalance (e.g., a magnitude of voltage imbalance, corrective steps to be taken (such as charge the lower voltage battery pack) etc.). In some embodiments, the at least one processor may initiate a balancing process to get the battery packs within the threshold voltage of each other. In some embodiments, the precharging selection process may continue based on determining the voltages have been brought within the threshold range.

[0126] In some embodiments, at least one processor (e.g., executing process 700a), based on determining that the battery pack voltages are within a threshold of each other, will allow the agreed upon battery pack to perform pre-charging. For example, at least one processor associated with the agreed upon battery pack (e.g., a processor of the BMU of the agreed upon pack) will command pre-charge switching device(s), DC / DC converters, and / or other devices to pre-charge both battery packs (e.g., as detailed above with respect to Figures 2A- 5E).

[0127] In some embodiments, at least one processor (e.g., executing process 700a) may monitor (e.g., check, compare values to determine) whether pre-charging of the parallelbattery packs is complete. In some embodiments, the at least one processor may monitor whether the voltage of a pre-charged bus is within a threshold of the instant battery pack voltage (e.g., voltage on pack side of main contactors). In some embodiments, the threshold may be set within a range of 2-30V (e.g., 15V). In some embodiments, the instant battery pack may monitor whether a voltage on each side of the main contactor(s) (e.g., KI) on a paired battery pack is within the threshold and / or may receive a notification from a BMU of a paired battery pack indicating whether pre-charging of the paired battery pack is complete.

[0128] In some embodiments, monitoring whether pre-charging is complete may include monitoring for an electrical issue (e.g., non-responsive pre-charge switching device(s), fault, short circuit, overcurrent condition, and / or another operating condition that does not meet a performance metric etc.). If an electrical issue is detected and / or an indication of an electrical issue is received from a paired battery pack, the pre-charging process may be stopped. In some embodiments, monitoring whether pre-charging is complete may include monitoring whether a time has exceeded a threshold. For example, a time threshold may be established and may correspond to an expected amount of time to pre-charge the battery packs.

[0129] In some embodiments, at least one processor (e.g., executing process 700a) may provide a notification to indicate a detected electrical issue. For example, the at least one processor may send a notification indicating the electrical issue to a flight control system and / or maintenance panel of an aircraft, such as by controlling display screen(s), speaker(s), and / or lights. In some embodiments, the notification may detail the type of electrical issue, the battery pack and / or circuitry causing the electrical issue, and / or the battery pack(s) effected. In some embodiments, the pre-charging selection process may repeat from the beginning (e.g., step 701a or step 701b) based on (e.g., upon, in response to) detection of an electrical issue.

[0130] In some embodiments, at least one processor (e.g., executing process 700a), based on determining that pre-charging of the battery packs is complete, may enable current flow from the instant battery pack through a bus of the instant battery pack (e.g., a main bus feeding a DC / DC for low voltage systems, ECS equipment, and / or paired battery pack(s)). In some embodiments, the battery pack may command one or more main switching devices (e.g., KI and K2) closed, open pre-charging switching device(s) and / or control DC / DC converter(s) to stop pre-charging, as described above with reference to Figures 2A-6. In some embodiments, the at least one processor may enable current flow from the paired battery pack through a bus of the paired battery pack (e.g., a main bus feeding a DC / DC for low voltage systems, ECS equipment, and / or paired battery pack(s)).

[0131] In some embodiments, at least one processor (e.g., executing process 700a) may monitor whether current on the bus (e.g., main bus) is successfully enabled. For example, the at least one processor may monitor current, voltage, and / or state(s) of switching device state (e.g., state of switching devices KI and / or K2) and may monitor for electrical issues (e.g., non-responsive pre-charge switching device(s), fault, short circuit, overcurrent condition etc.). If an electrical issue is detected and / or an indication of an electrical issue is received from a paired battery pack, one or more main switching devices (e.g., KI and / or K2) may be controlled open and a notification may be provided to indicate the electrical issue.

[0132] For example, the at least one processor may send a notification indicating the electrical issue to a flight control system and / or maintenance panel of an aircraft, such as through controlling display screen(s), speaker(s), and / or light(s). In some embodiments, the notification may detail the type of electrical issue, the battery pack and / or circuitry causing the electrical issue, and / or the battery pack(s) effected. In some embodiments, the process may repeat from the beginning (e.g., from step 701a or 702b) based on (e.g., upon, in response to) detection of an electrical issue.

[0133] At step 716, the at least one processor, based on determining current from the battery pack(s) through the bus(es) (e.g., main buses) is successfully enabled, may send a notification to one or more flight components (e.g., flight control system 118 and / or a charge control unit) indicating the bus (e.g., main bus) is powered, the state of the main contactor(s), and / or the new mode of the aircraft (e.g., a successfully transition to a mode selected on mode switch 116).

[0134] In some embodiments, the at least one processor may increase a counter each time the process repeats due to an electrical issue at steps 714 and / or 715. In some embodiments, the process may only be allowed to repeat if the counter has not exceeded a threshold number of pre-charge attempts. If a threshold number of attempts has been exceeded, a notification may be provided indicating no further pre-charge attempts will be performed.

[0135] Figure 7B illustrates another exemplary control sequence for multi-pack (e.g., paired pack) pre-charge control, consistent with disclosed embodiments. In some embodiments, the process 700b is performed by a BMU 102, which may include at least one processor to execute instructions (e.g., instructions corresponding to the steps of process 700b) stored in a memory. In some embodiments, each BMU 102 of the aircraft may perform the process with respect to the battery pack it is associated with (e.g., an “instant battery pack”). Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs.Additionally or alternatively, the process 700b and / or one or more steps are performed by atleast one processor and memory associated with a different aircraft component (e.g., a non- BMU processing device, such as an FCC or controller). As detailed below, the “primary” battery pack has its pre-charge circuitry controlled (e.g., by at least one processor) to perform pre-charge. The “secondary” battery pack is not controlled to perform pre-charge and joins a bus after being pre-charged by the primary battery pack (though it may still have the same capability as the “primary” battery pack of performing pre-charging operations). In some embodiments, steps (e.g., decisions, checks, operations) from process 700a and / or process 700c may be used in process 700b. Additionally, some steps of process 700b may be the same as or similar to steps from process 700a and / or process 700c, as noted below.

[0136] At step 730a, process 700b may receive a mode selection (e.g., a selection made through mode switch 116) and / or another indication that a portion of high voltage circuitry is to be pre-charged and powered. For example, process 700b may determine that a propulsion bus and / or a main bus, as described above with respect to steps 701-703, needs to be precharged and powered based on the mode selection. In some embodiments, process 700b may confirm that the paired battery packs have not been assigned a role for pre-charging (e.g., primary or secondary) prior to proceeding.

[0137] At step 730b, process 700b may determine whether the instant battery pack is in a paired state (e.g., an electrically connected state). For example, process 700b may determine whether the instant battery pack (e.g., using its BMU) is connected to cross-link 130 and / or is otherwise configured to provide power to another battery pack (e.g., whether F4.1, F4.2, and / or F6 have blown and / or whether a stored status indicates a single pack testing state).

[0138] At step 731, process 700b may select the instant battery pack to pre-charge itself (e.g., set role as “primary”) based on determining it is not in a paired state. In some embodiments, process 700b may, after step 731, proceed to, for example, process 700b, 700c, 800, or 900.

[0139] At step 732, process 700b may check whether the paired battery pack is unable to perform the pre-charge. For example, process 700b may determine whether there is the paired battery pack has failed to satisfy at least one performance criterion (e.g., has a voltage below a threshold, has charge below a threshold, has loads above a threshold). In some embodiments, process 700b may determine whether it has received any notifications from a BMU 102 of the paired battery pack, such as a notification indicating an electrical issue with the paired battery pack. For example, process 700b may receive a notification indicating an overcurrent condition, short circuit, fault, and / or another operating condition of the paired battery pack and / or circuitry configured to be powered by the paired battery pack (e.g., precharge circuitry) that does not meet a performance metric. In some embodiments, process700b may evaluate sensor measurements (e.g., current or voltage measurements) to determine whether there is an electrical issue with the paired battery pack and / or circuitry configured to be powered by the paired battery pack.

[0140] In some embodiments, process 700b may further confirm (e.g., through information received from the paired battery pack BMU 102 and / or sensor measurements) whether the paired battery pack is able to be pre-charged. For example, process 700b may confirm whether a detected electrical issue is limited to the pre-charge circuitry associated with the instant battery pack and / or does not otherwise prevent the paired battery pack from being precharged.

[0141] At step 733, process 700b may select the instant battery pack to pre-charge itself (e.g., set role as “primary”) based on determining the paired battery pack is unable to perform precharge. In some embodiments (not shown), process 700b may further select the paired battery to receive a pre-charge from the instant battery pack (e.g., set role as “secondary”) based on determining the paired battery pack is not prevented from receiving a pre-charge and confirming the paired battery pack is in a “standby” state (e.g., as described below with reference to step 734). In some embodiments, the at least one processor may control circuitry of the instant battery pack to pre-charge circuitry of the instant battery pack but not circuitry of the paired battery pack based on determining one selection (e.g., by the first battery pack) selects the first battery pack back and the another selection (e.g., by the second battery pack) selects the second battery pack. For example, at least one processor may control circuitry of the instant battery pack (e.g., a first battery pack) to pre-charge circuitry of the instant battery pack but not circuitry of the paired battery pack (e.g., a second battery pack), such as based on determining a selection (e.g., by the instant battery pack) that the instant battery pack as selected itself and the another selection (e.g., by the paired battery back) selecting itself. In some embodiments, process 700b may, after step 733, proceed to, for example, process 700b, 700c, 800, or 900.

[0142] At step 734, process 700b determine whether the paired battery pack is in a “standby” state, indicating it is ready to pre-charge and / or be pre-charged by the instant battery pack. For example, process 700b may confirm whether one or more switching devices are open (e.g., KI, K2, and / or K4) to confirm a bus to be pre-charged is not already sourcing power from the paired battery pack.

[0143] At step 735, process 700b may select a default battery pack (e.g., determine which battery pack, between the instant battery pack and another pack paired with it) to assign precharging roles based on determining the paired battery pack is able to perform pre-charge andis in a stand-by state. For example, a default battery pack identifier (e.g., location number) may be established to determine which battery pack of paired battery packs may (e.g., should) set the primary and secondary roles for the battery packs. Process 700b may compare the instant battery pack identifier to the default identifiers to determine whether it is the default battery pack to assign pre-charging roles.

[0144] At step 736, process 700b may receive the role for the instant battery pack over a communication line, such as a CAN bus based on determining the instant battery pack is not the default pack to assign pre-charging roles. For example, process 700b may receive the role for the instant battery pack from a BMU 102 of the paired battery pack or another processing device. In some embodiments, process 700b may, after step 736, proceed to, for example, process 700b, 700c, 800, or 900.

[0145] At step 737, process 700b may compare a voltage of the instant battery pack to the voltage of the paired battery pack based on determining the instant battery pack is the default pack to assign pre-charging roles. For example, at least one processor may receive voltage measurements from the instant battery pack (e.g., through voltage measurement sensors) and the paired battery pack (e.g., through voltage sensor measurements and / or notifications from a BMU 102 of the paired battery pack) and determine whether the instant battery pack voltage is greater than that of the paired battery pack.

[0146] At step 738, process 700b may select the paired battery pack to perform pre-charge (e.g., set status to secondary) based on determining the instant battery pack has a smaller voltage than the paired battery pack. In some embodiments, at least one processor may communicate with a BMU 102 (and / or another processor) of a paired battery pack to indicate it will be performing the pre-charge of the battery packs (e.g., set status as primary). In some embodiments, process 700b may, after step 738, proceed to, for example, process 700b, 700c, 800, or 900.

[0147] At step 739, process 700b may select the instant battery pack to perform pre-charge (e.g., set status to primary) based on determining the instant battery pack has a larger voltage than the paired battery pack. In some embodiments, at least one processor may communicate with a BMU 102 (and / or another processor) of a paired battery pack to indicate it will receive a pre-charge from the instant battery pack (e.g., set status as secondary). In some embodiments, process 700b may, after step 739, proceed to, for example, process 700b, 700c, 800, or 900.

[0148] In some embodiments, after selecting the battery pack to perform pre-charge, process 700b proceed to pre-charge the battery packs using the primary battery pack, as describedabove. In some embodiments, process 700b may monitor pre-charge and, based on determining that pre-charge is complete (e.g., by determining if one or more measured voltages and / or currents have reached a threshold and / or are within a range), control switching devices (e.g., KI, K2, and / or K4) closed, open pre-charging switching device(s) and / or control DC / DC converter(s) to stop pre-charging, as described above with reference to Figures 2A-6. Further, process 700b may enable current flow from the secondary battery pack through a bus of the secondary battery pack (e.g., KI, K2, and / or K4 may be controlled closed).

[0149] Figure 7C illustrates another exemplary control sequence for multi-pack (e.g., paired pack) pre-charge control, consistent with disclosed embodiments. In some embodiments, process 700c is performed by a BMU 102, which may include at least one processor configured to execute instructions (e.g., instructions corresponding to the steps of process 700c) stored in a memory. In some embodiments, each BMU 102 of the aircraft may perform the process with respect to the battery pack it is associated with (e.g., an “instant battery pack”). Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs. Additionally or alternatively, the process 700c and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component (e.g., a non-BMU processing device, such as an FCC or controller). As detailed below, the “primary” battery pack has its pre-charge circuitry controlled (e.g., by at least one processor) to perform pre-charge. The “secondary” battery pack is not controlled to perform pre-charge and joins a bus after being pre-charged by the primary battery pack.

[0150] Steps 730a-734 are detailed above in reference to Figure 7B. In some embodiments, additional steps (e.g., decisions, checks, operations) from process 700a and / or process 700b may be used in process 700c. Additionally, some steps of process 700c may be the same as or similar to steps from process 700a and / or process 700b, as noted below.

[0151] At step 740, process 700c may determine whether the paired battery pack voltages are within a threshold of each other. For example, the at least one processor may receive voltage measurements from the instant battery pack (e.g., through voltage measurement sensors) and the paired battery pack (e.g., through voltage sensor measurements and / or notifications from a BMU 102 of the paired battery pack) and determine whether a voltage of the instant battery pack is within a threshold voltage of the paired battery pack. In some embodiments, the threshold may be based on a determined voltage measurement uncertainty that causes fluctuations in battery packs with equal and / or nearly equal voltages. In some embodiments,process 700c may determine if a difference between the instant battery pack and the paired battery pack are within a threshold value of each other.

[0152] At step 741, process 700c may determine whether the instant battery pack voltage is greater than that of the paired battery pack based on determining the battery packs are not within a threshold voltage of each other. If the instant battery pack has a larger voltage than the paired battery pack, the instant battery pack is selected to perform the pre-charge (e.g., set status to primary), as shown at step 743. If the instant battery pack has a smaller voltage than the paired battery pack, the paired battery pack is selected to perform the pre-charge (e.g., set status to secondary), as shown at step 744.

[0153] At step 742, process 700c may determine whether the instant battery pack is the default pack based on determining the battery packs are not within a threshold voltage of each other. For example, a default battery pack identifier (e.g., location number) may be established to determine which battery pack should perform the pre-charge. Process 700c may compare the instant battery pack identifier to the default identifiers to determine whether it is the default battery pack to perform the pre-charge. If the instant battery pack is the default battery pack, process 700c may select it to perform the pre-charge (e.g., set status to primary), which may cause the instant battery pack to pre-charge the bus and the paired battery pack to refrain from pre-charging the bus. If the instant battery pack is not the default battery pack, process 700c may select the paired battery pack to perform the pre-charge (e.g., set status to secondary), which may cause the paired battery pack to pre-charge the bus and the instant battery pack to refrain from pre-charging the bus.

[0154] At step 746, process 700c may determine whether the instant battery pack selected itself as the battery pack to perform pre-charge (e.g., set status to primary) and the paired battery pack selected itself to receive the pre-charge from the instant battery pack (e.g., set status to secondary). In some embodiments, process 700c may receive one or more selections (e.g., a set primary and / or secondary battery pack) from a BMU 102 of the paired battery pack to make this determination. In some embodiments, process 700c may receive one or more selections from the instant battery pack and one or more selections from the paired battery pack and determine if they agree. For example, process 700c may determine that selections from two battery packs agree if one or more selections from the instant battery pack have a same result at steps 746 and 747 (e.g., yes at step 746, no at step 746 and yes at step 747).

[0155] At step 747, process 700c may determine whether the instant battery pack selected itself to receive the pre-charge (e.g., set status to secondary) and selected the paired batterypack to perform the pre-charge (e.g., set status to primary). In some embodiments, process 700c may receive one or more selections (e.g., a set primary and / or secondary battery pack) from a BMU 102 of the paired battery pack to make this determination.

[0156] In some embodiments, such as when process 700c determines that neither of the battery packs has selected the other one or itself as having the primary or secondary role, process 700c may set the pre-charge role as unknown and return to step 734 if there is no agreement between the instant battery pack and the paired battery pack at steps 746 and / or 747. In some embodiments (not shown), process 700c may set the pre-charge role as unknown and return to step 724 if there is no agreement between the instant battery pack and the paired battery pack for a threshold number of samples (e.g., as further described below with respect to step 748). Subsequently, the process may return to steps 743 and / or 744, as depicted, such that process 700c may determine (e.g., by comparing) that a selection between the instant pack and a paired back (e.g., received over a CAN bus) are the same (e.g., for a number of repeated samples, as discussed regarding step 745).

[0157] For example, the instant pack may have only allocated a role for itself “prechgRole.” At the same time, the paired pack may have assigned its own “prechgRole” which relative to the instant pack is “pairPrechgRole.” Accordingly, steps 743 and 744 may perform a comparison to confirm that the role chosen by the instant pack “prechgRole” and received on CAN from its paired pack that it designates “pairPrechgRole” are compatible.

[0158] At step 748, process 700c may determine whether the first selection and the second selection match (also referred to herein as “agree”). A match may be considered the same determination of charging roles (e.g., for an instant battery pack and a paired battery pack) made by an instant battery pack and a paired battery pack. For example, a combination of role selections that are compatible may be considered a match. A compatible role selection may be considered one that causes only a single battery pack to pre-charge a bus that is shared by and / or electrically connected to multiple battery packs. In some embodiments, a threshold number (e.g., at least two, at least five, at least 10, at least 100) of repeated the same selection determinations may be needed before a match is determined. For example, process 700c may determine whether there is an agreement between the selections made by the instant battery pack and the paired battery pack. For example, at least one processor (e.g., of a BMU of the instant battery pack) may determine if both the instant battery and the paired battery pack determined that the instant battery pack should be designated with the primary role (e.g., designated for pre-charging circuitry that is directly connected to the instant battery pack) and the paired battery pack should be designated with the secondary role (e.g., designated to notpre-charge circuitry that is directly connected to the instant battery pack). Alternatively, at least one processor (e.g., of a BMU of the instant battery pack) may determine if both the instant battery and the paired battery pack determined that the paired battery pack should be designated with the primary role (e.g., designated for pre-charging circuitry that is directly connected to the instant battery pack) and the instant battery pack should be designated with the secondary role (e.g., designated to not pre-charge circuitry that is directly connected to the instant battery pack). In some embodiments, a number of samples (e.g., instances) of battery pack selections (e.g., multiple repeated selections for confirmation, potentially received from both the instant and paired battery packs) may be reviewed from the instant battery pack and the paired battery pack. An agreement may be considered reached when a consecutive number of samples in which the battery packs agree reaches and / or exceeds a threshold. In some embodiments, process 700c may repeat steps 743 and / or 744 based on determining the battery packs did not agree for the consecutive threshold number of samples. By using a threshold number of samples, agreement between the battery packs (e.g., by their respective BMUs) regarding the charging selections for the battery packs (e.g., a primary precharge role or a secondary pre-charge role) may be reached in environments where the battery packs and / or associated respective BMUs operate asynchronously.

[0159] At step 749, process 700c may proceed to pre-charge the battery packs using the agreed upon primary battery pack, as described above. For example, process 700c may select a battery pack that matches both battery pack selections (e.g., made by the instant battery pack and the paired battery pack) to pre-charge the circuitry of a first and second battery pack (e.g., instant and paired battery pack) based on determining that the selections match. In some embodiments, process 700c may monitor pre-charge and, based on determining that precharge is complete, control one or more switching devices (e.g., KI, K2, and / or K4) closed, open pre-charging switching device(s) and / or control DC / DC converter(s) to stop precharging, as described above with reference to Figures 2A-6. Further, process 700c may enable current flow from the secondary battery pack through a bus of the secondary battery pack (e.g., KI, K2, and / or K4 may be controlled closed). In some embodiments, process 700c may, after step 749, proceed to, for example, process 700b, 700c, 800, or 900.

[0160] Figures 8A and 8B illustrates an exemplary control sequence for performing checks prior to energizing an electrical circuit, consistent with disclosed embodiments. In some embodiments, process 800 is performed by a BMU 102, including at least one processor executing instructions stored in a memory. In some embodiments, one or more BMUs (e.g., each BMU 102) of the aircraft may be configured to perform the process with respect to thebattery pack it is associated with (an “instant battery pack,” as described above). In some embodiments, the process and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component (e.g., a non-BMU processing device, such as an FCC or controller).

[0161] In some embodiments, process 800 may be initiated and / or carried out by at least one processor receiving a mode selection (e.g., a selection made through mode switch 116) and / or another indication that high voltage circuitry state is to be changed. For example, the at least one processor may determine, based on the selection or indication, that a bus (e.g., main bus feeding a DC / DC for low voltage systems, ECS equipment, and / or paired battery pack(s)) is to be pre-charged and powered.

[0162] At step 801, process 800 may start, potentially based in response to a mode selection and / or input received.

[0163] At step 802, process 800 may command a switching device on a negative side (e.g., K2) of a bus (e.g., main bus) to close.

[0164] At step 803, process 800 may start a timer (e.g., for a first time threshold). A set time on the timer may be (or correspond to) an expected time for a voltage on the bus (e.g., main bus) to reach a threshold. For example, the set time may be determined based on experimental data and / or modeling that establishes an amount of time required to raise a bus voltage to the threshold level when increasing the voltage at a rate that maintains the integrity of the circuitry and / or associated components. In some embodiments, the set time may be in a range of 100ms-800ms (e.g., 400ms). In some embodiments, the threshold voltage may be set to a value (e.g., 10V) which is less than an eventual bus voltage once a main switching device (e.g., KI and K4) is closed. In some embodiments the threshold voltage may be set within a range, such as 5-60V, inclusive, for example.

[0165] At step 804, process 800 may determine whether the set time has been exceeded (e.g. which will not occur on the first iteration of the process).

[0166] At step 805, if the set time has been exceeded, process 800 may determine existence of a short circuit condition. In some embodiments, process 800 may, at step 805 open switching device(s) (e.g., K2, K3, and / or K5) to de-energize the bus. Process 800 may, at step 806, also abort based on detecting that the set time is exceeded. Additionally or alternatively, process 800 may send a notification or alert to a flight control system and / or maintenance panel of an aircraft. The notification or alert may be provided to a user via a display screen, speaker, lights, and / or haptic feedback. In some embodiments, the notification or alert maydetail the battery pack and / or circuitry causing the short circuit and / or the battery packs effected.

[0167] At step 807, process 800 may enable a pre-charge pulse, which may raise a voltage on the bus. In some embodiments, process 800 may initiate raising the voltage on the bus at the same time (and / or within a threshold time) as starting a timer. In some embodiments, process 800 may control a switching device on a positive side (e.g., K5) to slowly raise a voltage on the bus. For example, the BMU may toggle a switching device on a positive side (e.g., K3 or K5) open and closed to raise the bus voltage. In some embodiments, the switching device may be toggled open and closed such that it allows current flow through the switching device for a set portion of the duty cycle. For example, toggling the switching device may include closing the switching device to allow current flow through the switching device during an amount of time that is between 0.5-10% of a duty cycle (or other range), before opening the first switching device. For example, the set portion may be a percentage of the duty cycle in a range, such as 0.1-10% of the duty cycle, for example. In some embodiments, a switching device may be toggled closed for a set time (e.g., 10 microseconds).

[0168] At step 808, if the set time has not been exceeded, process 800 may determine whether the threshold voltage (e.g., zero volts, 0.001V, 0.01V, 0.1V, IV, 5V, 120V) has been exceeded. If the threshold voltage has not been exceeded, process 800 may continue to raise the voltage on the bus (e.g., as detailed in step 803). If the threshold voltage has been exceeded, process 800 may initiate a connection check process for one or more EPUs powered by the instant battery pack. For example, after the pre-charge pulse is commanded at step 803, the process may return to step 804 and determine how long the voltage has been below a threshold. In circumstances where the bus is not shorted, the voltage on the bus may rise with successive pre-charge pulses (e.g., until the timer exceeds the set time), and may reach the reference voltage before the timer exceeds the set time (e.g., reaches “yes” at step 805). If, however, the timer exceeds the set time and the bus voltage has not exceeded the reference voltage (e.g., after a repeated number of pre-charge pulses), the bus may be determined to be shorted (e.g., step 806).

[0169] At step 809, based on determining the propulsion bus has exceeded the threshold voltage within the set time, process 800 may start a second timer (e.g., set a timer for a second time threshold) for confirming that the one or more EPUs are appropriately connected (e.g., do not have at least one operation condition violating an operation criterion, such as an open circuit, a short circuit, and / or fault condition impacting flow of electricity through the EPUs etc.). A set time (e.g., a second set time corresponding to a second time threshold) onthe second timer may be (or correspond to) an expected time for determining connections to electric propulsion unit(s) are appropriate. For example, the set time may be determined based on experimental data and / or modeling that establishes an amount of time required to determine the electric propulsion unit(s) are appropriately connected when the at least one processor (e.g., of a BMU) and the high voltage circuitry are not experiencing issues (e.g., software or electrical issues, such as a short circuit, overcurrent condition, measurable electrical value exceeding a threshold, etc.). In some embodiments, the time set at step 809 may be longer than the time set at step 803. In some embodiments, the set time may be in the range of 2-20 seconds, inclusive (e.g., 10 seconds).

[0170] At step 810, process 800 may determine if the time (e.g., started at step 809) has been exceeded. If it has, process 800 may proceed to step 811. If it has not, process 800 may proceed to step 813.

[0171] At step 811, process 800 may open a main negative contactor, as discussed with respect to step 805, for example. In some embodiments, after step 811, process 800 may proceed to step 812, where it may abort (e.g., stop at least one processor from running process 800).

[0172] At step 813, process 800 may determine if a de-energize command (e.g., a command to de-energize one or more EPUs) has been received (e.g., from an FCS). If it has, process 800 may proceed to step 811. If it has not, process 800 may proceed to step 814.

[0173] At step 814, process 800 may determine, and / or receive a determination of, whether an EPU (e.g., propeller) bus voltage exceeds a reference value. For example, process 800 may request that a flight control system compare a voltage level read at the electric propulsion unit(s) to a threshold voltage. In other embodiments, process 800 may not send a request to the flight control system. Instead, process 800 may directly measure the voltage level at the electric propulsion unit(s) (e.g., via one or more sensors) and perform the comparison to the threshold voltage (e.g., if a there is a setting of CompareCmd = TRUE). In other embodiments, process 800 may receive the voltage level read by one or more controllers of the electric propulsion unit(s) and perform the comparison to the threshold voltage.

[0174] Additionally or alternatively, process 800 may control switching devices (e.g., K5) to hold the voltage above threshold voltage while the voltage level at the electric propulsion unit(s) is being analyzed (e.g., in step 814 or step 820).

[0175] At step 814, process 800 may determine whether the bus voltage is still above the threshold level (e.g., 10V). If process 800 determines that the EPU (e.g., propeller) busvoltage does not exceed a reference value, it may proceed to step 815 (e.g., from step 814). If process 800 determines that the EPU (e.g., propeller) bus voltage exceeds the reference value, it may proceed to step 816 (e.g., from step 814).

[0176] At step 815, based on determining the bus voltage is not above the threshold level, process 800 may enable a pre-charge pulse. For example, process 800 may control a switching device on a positive side (e.g., K5) to slowly raise a voltage on the bus. For example, the BMU may toggle a switching device on a positive side (e.g., K5) open and closed to raise the bus voltage. In some embodiments, the switching device may be toggled open and closed such that it allows current flow through the switching device for a set portion of the duty cycle. For example, the set portion may be a percentage of the duty cycle in a range, such as 0.1-10% of the duty cycle, for example. In some embodiments, a switching device may be toggled close for a set time (e.g., 10 microseconds).

[0177] At step 816, process 800 may disable a pre-charge pulse (e.g., disable operations described with respect to steps 807 and 815). Disabling a pre-charge pulse may include ceasing an active pre-charge pulse and / or preventing a pre-charge pulse from occurring (e.g., for at least a predetermined amount of time).

[0178] At step 818, process 800 may start (e.g., prompt) and / or run an engine connection check. An engine connection check may include determining and / or receiving engine information, such as a temperature, voltage, connection status (e.g., that the engine connections are healthy). For example, an engine connection check may include determining and / or receiving information indicating that one or more EPUs are connected to at least one bus (e.g., HV bus), are receiving power, and / or are ready to receive power or perform an operation.

[0179] In some embodiments, step 818 may include determining if an engine is disconnected or should be disconnected. For example, if process 800 determines the second set time has been exceeded without a confirmation that the voltage at the EPUs exceeds the threshold voltage, process 800 may disconnect the EPUs from high voltage circuitry and / or a battery pack. Similarly, if process 800 determines it has a received a disconnect command from the flight control system or another component of the aircraft, process 800 may disconnect the electric propulsion unit(s). In some embodiments, disconnecting the electric propulsion unit(s) may involve process 800 commanding the flight control system and / or a controller of the electric propulsion unit(s) to disconnect the electric propulsion unit(s) from power. In some embodiments, process 800 may open a switching device (e.g., K5, K2) to remove power to the electric engines.

[0180] At step 820, process 800 (e.g., the flight control system, the at least one processor, and / or a controller of the electric propulsion unit(s)) may determine whether the voltage at the electric propulsion unit(s) exceeds the threshold voltage. In some embodiments, at least one processor may directly monitor the voltage at the electric engines (e.g., via one or more current and / or voltage sensors) and perform the comparison. Additionally or alternatively, at least one processor may receive information from a flight control system indicating whether the voltage at the electric propulsion unit(s) exceeds the threshold voltage. Additionally or alternatively, a controller of one or more of the electric propulsion unit(s) may provide a voltage measurement to the at least one processor and / or the flight control system. At step 819, process 800 may request to abort one or more pre-charging operations (e.g., closing of one or more switches). For example, if the voltage at the electric propulsion unit(s) does not exceed the threshold voltage (e.g., within the set time), then the pre-charge process may be aborted and the EPUs may be de-energized and / or disconnected. For example, in some embodiments, the flight control system may send a command to the at least one processor to de-energize a bus (e.g., open K5, K2) while in other embodiments the at least one processor may directly determine to de-energize the bus. Therefore, the BMU and / or flight control system may determine there is a disconnect at one or more of the EPUs. In some embodiments, the at least one processor and / or flight control system may determine which electric propulsion unit did not meet the threshold voltage. In some embodiments, the at least one processor and / or flight control system may provide a notification to a user (e.g., pilot) based on determining that the electric propulsion unit did not exceed the threshold voltage. For example, the notification may be provided to a user via display screen(s), speaker(s), and / or light(s). In some embodiments, the notification may indicate which electric propulsion unit and / or connection is faulty or diminished.

[0181] At step 821, process 800 may generate, transmit, and / or receive a notification that precharging should proceed. For example, if the voltage at the electric propulsion unit(s) does exceed the threshold voltage (e.g., within the set time), then the pre-charge process may commence. For example, in some embodiments, the flight control system may send a command to the at least one processor to pre-charge the bus, while in other embodiments the at least one processor may directly determine to pre-charge the bus. At step 817, process 800 may determine if a command to energize (e.g., pre-charge) at least one component (e.g., a bus) has been received. For example, the at least one processor (e.g., of a BMU) may monitor whether it has received a command from the flight control system and / or another component of the aircraft to de-energize the electric propulsion unit(s).

[0182] In some embodiments, at step 817, process 800 may monitor whether it has received an energize command from the flight control system and / or the at least one processor has made a determination that pre-charge should begin. If not, the process may be repeated (e.g., starting at 809). If an energize command is received and / or the at least one processor determines pre-charge should begin, the at least one processor proceeds to the pre-charge process.

[0183] Continuing to Figure 8B, at step 822, process 800 may start a may start a timer (e.g., a third timer). A set time on the timer may be (or correspond to) an expected time for a voltage on the bus to reach a second threshold. As described above with reference to Figures 2A-7, the second threshold voltage may be a voltage level that allows main contactor(s) (e.g., KI) to close without risking damage to circuitry components. For example, in some embodiments, the second threshold may be within 10-20V (e.g., 15 V) of a voltage expected with the main switching devices closed (e.g, with KI and K4 closed).

[0184] At step 823, process 800 may command pre-charge to begin, which may include closing at least one pre-charge switching device (e.g., relay). For example, process 800 may close a pre-charge switching device (e.g., K4, K5) to allow the respective bus to be precharged.

[0185] At step 824, process 800 may determine whether the time has exceeded the third set time.

[0186] If the time has exceeded the third set time, process 800 may proceed to step 825, e.g., to stop the pre-charge. At step 825, process 800 may open a negative contactor (e.g., a main negative contactor, such as switching device K5).

[0187] Process 800 may also include step 826, which may be performed after step 825. At step 826, process 800 may open a pre-charge switching device (e.g., K4), which may be a relay.

[0188] Process 800 may also include step 827, which may be performed after step 826. At step 827, process 800 may abort one or more pre-charging operations (e.g., process 800 itself).

[0189] It is therefore appreciated that, if an electrical issue arises, high voltage power may be disconnected to avoid damage to circuitry components. A component (e.g., at least one processor) may send a notification to one or more flight components (e.g., flight control system 118) indicating the pre-charge process has failed (e.g., as described above in reference to Figure 7).

[0190] If the time has exceeded the third set time, process 800 may proceed to step 828 (e.g., from step 824). At step 828, process 800 may determine if a de-energize command (e.g., a command to de-energize one or more EPUs) has been received (e.g., from an FCS). If it has, process 800 may proceed to step 825. If it has not, process 800 may proceed to step 829.

[0191] At step 829, process 800 may monitor and / or determine a voltage on a bus to determine whether it exceeds the second threshold. For example, process 800 may receive and / or compare one or more measured voltage values to the second threshold to determine if one or more of the values exceed the second threshold.

[0192] At step 830, process 800 may close a main switching devices (e.g., K4) to fully charge the respective bus. In some embodiments, process 800 may, based on determining that the voltage exceeds the second threshold, close a main switching devices (e.g., K4) to fully charge the respective bus.

[0193] At step 824, process 800 may open one or more pre-charge switching devices (e.g., K5), such as a pre-charge relay, which may end the pre-charge process. For example, process 800 may open, based on determining the main switching devices are successfully closed (e.g., by measuring a current or voltage), a pre-charge switching device (e.g., K4, K5), which may be a relay.

[0194] At step 832, the pre-charge process may finish, and process 800 may confirm the completion of the process and / or take other actions. For example, based on determining the pre-charge switching devices are open and / or the current and voltage measurements on the bus are as expected, process 800 may send a notification to one or more flight components (e.g., flight control system 118 and / or a charge control unit) indicating the bus (e.g., main bus) is powered, the state of the main switching device(s), and / or the new mode of the aircraft.

[0195] Figure 8B illustrates exemplary voltage control when performing checks prior to energizing an electrical circuit, consistent with disclosed embodiments. In some embodiments, the pattern of voltage control shown in Figure 8B may be attained by performing the control sequence process shown in Figure 8A. In some embodiments, this voltage control process is performed by a BMU 102, which may include at least one processor executing instructions stored in a memory. In some embodiments, one or more BMUs (e.g., each BMU 102) of the aircraft may be configured to perform the process with respect to the battery pack it is associated with (an “instant battery pack”). In some embodiments, the process and / or one or more steps are performed by at least one processorand memory associated with a different aircraft component (e.g., a non-BMU processing device, such as an FCC or controller).

[0196] In a first region 833a representing the bus short check, continuous voltage pulses may be applied at a set interval. For example, continuous voltage pulses may be applied by toggling a switching device open and closed at a set interval. The voltage on the bus (e.g., propulsion bus) may be monitored to determine whether it exceeds a threshold voltage within a set time. If the voltage on the bus does not exceed the threshold voltage within a set time, a short circuit condition may be determined and the pre-charge process will not continue. As depicted in the example of Figure 8A, first region 833a may be present from around 0.2s to 0.5s.

[0197] In a second region 833b representing the electric propulsion unit check (e.g., electric engine check), intermittent voltage pulses may be applied to hold the voltage above the voltage threshold. For example, intermittent voltage pulses may be applied by closing a switching device based on detecting a drop in voltage below the threshold. The voltage at the EPUs may be measured to determine whether the EPUs are appropriately connected. If the voltage measured at the EPUs does not exceed the threshold voltage within a set time, an issue with the electric propulsion unit connection may be determined and the pre-charge process will not continue. As depicted in the example of Figure 8 A, second region 833b may be present from around 0.5s to 1.0s.

[0198] In a third region 833c representing pre-charge, pre-charge may be performed and the voltage may be raised to within a threshold of the battery pack voltage. Once the bus voltage meets the threshold criteria, main switching devices (e.g., K4) may be closed and pre-charge switching devices (e.g., K5) may be opened. As depicted in the example of Figure 8 A, third region 833c may be present from around 1.0 or 1.1s to 1.5s.

[0199] In a fourth region 833d representing main power enabled, once the main switching devices are closed, the bus may be fully powered off the battery pack. As depicted in the example of Figure 8 A, fourth region 833 d may be present from around 1.5 s onward.

[0200] Figure 8C illustrates exemplary voltage control when performing checks prior to energizing an electrical circuit, consistent with disclosed embodiments. In some embodiments, in addition to the control sequence process shown in Figure 8A, additional voltage control may be performed to detect whether there is an open bus condition. For example, in some embodiments, BMU 102, including at least one processor executing instructions stored in a memory may perform voltage control to detect whether there is an open bus condition. In some embodiments, each BMU 102 of the aircraft may perform theprocess with respect to the battery pack it is associated with. Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs. Additionally or alternatively, the process and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component (e.g., a non-BMU processing device, such as an FCC or controller).

[0201] Detecting whether there is an open bus condition may include providing a single short-duration voltage pulse (e.g., 835) on a bus and then collecting one or more measurements of the bus voltage. For example, detecting whether there is an open bus condition may include providing a single voltage pulse by closing and then opening a switching device. The magnitude and duration of the voltage pulse may be designed (e.g., through simulation and / or experimentation) such that a voltage on a closed bus would not raise (and / or would not raise beyond a threshold) within the duration of the pulse. Therefore, the at least one processor may detect an open bus condition if the measured voltage on the bus is greater than zero or is greater than another threshold value. As shown in Figure 8B, an open-circuit condition may result in measuring one or more voltage spikes (e.g., 824a-834d) that exceed zero and / or another threshold value indicative of a closed-circuit condition, based on detecting an open bus, the at least one processor and / or a flight control system may provide a notification to a user (e.g., pilot). For example, the notification may be provided to a user via display screen(s), speaker(s), and / or light(s) associated with a flight control system and / or maintenance panel of the aircraft.

[0202] Figure 9 illustrates an exemplary control sequency for battery pack balancing, consistent with disclosed embodiments. In some embodiments, the process 900 is performed by at least one BMU 102, which may include at least one processor configured to execute instructions stored in a memory. In some embodiments, each BMU 102 of the aircraft may perform the process with respect to the battery pack it is associated with (an “instant battery pack”). Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs. Additionally or alternatively, the process and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component (e.g., a non-BMU processing device, such as an FCC or controller).

[0203] At step 901, process 900 may detect a power-off condition (e.g., instruction, command, etc.) for at least one battery pack (e.g., battery pack 120). In some embodiments, process 900 may receive a user selection indicating the at least one battery pack will not be supplying power (e.g., should not be supplying power) to one or more buses. For example, process 900 may receive a selection (e.g., selected on mode switch 116 shown in Figure 1Cand / or another input device), indicating at least one battery pack may only supply power to BMU 102 (e.g., through a DC / DC) or may not supply power to any aircraft components. For example, the process 900 may detect a user selection indicating the at least one battery pack will be disconnected (or is disconnected) from a common bus shared with another battery pack (e.g., disconnection at cross-link 130). In some embodiments, instead of receiving a user selection, process 900 may directly detect (e.g., through current measurement s) and / or voltage measurement s) dropping below a threshold, status of switching device(s) indicating open etc.) that the at least one battery pack is disconnected from one or more buses. In some embodiments, in addition to a power-off condition, process 900 may detect that the at least one battery pack is fully charged prior to performing balancing (e.g., based on communications from a charge control unit and / or sensor measurements, such as pack-level voltages).

[0204] At step 902, process 900 may collect battery pack level information regarding level(s) (e.g., at least one charge level, at least one current level, at least one power level, combination thereof, etc.) of the at least one battery pack (e.g., receive level measurements and store in memory). In some embodiments, process 900 may collect the voltage of one or more cells (e.g., each cell) within at least one battery pack. For example, in some embodiments, process 900 may receive measurements from voltage sensor(s) of one or more battery pack cells. In some embodiments, process 900 may receive measurements from another device (e.g., via cell management unit (CMU) 105) indicating the voltage of one or more cells (e.g. each cell) within at least one battery pack. In some embodiments, battery pack level information may be exchanged between devices (e.g., across a CAN bus), such as one or more BMUs, one or more CMUs, and one or more FCCs.

[0205] In some embodiments, process 900 may determine a battery pack voltage of one or more battery packs based on the voltages of the battery pack cells. For example, process 900 may add the voltages of the cells within a battery pack (e.g., each battery pack) to determine the overall battery pack voltage. Additionally or alternatively, the process 900 may measure a voltage of the at least one battery pack separate from the cell voltages. For example, process 900 may measure a voltage across high voltage wiring powered by each battery pack. In some embodiments, the battery pack voltage of each connected battery pack (e.g., each battery pack sharing a common bus, such as through cross-link 130) may be collected.

[0206] In some embodiments, process 900 may additionally or alternatively collect information on a cell capacity of one or more battery pack cells. For example, process 900may determine the cell capacity based on coulomb counting, electrochemical models, and / or discharge curves (e.g., stored in a memory, such as a RAM or ROM of BMU 102).

[0207] In some embodiments, process 900 may use a combination of battery cell measurements and battery pack measurements, discussed above, to determine the level(s) (e.g., at least one charge level, at least one current level, at least one power level, combination thereof, etc.) of the at least one battery pack. For example, process 900 may determine a summation, weighted average, temporal trend, or other statistical metric of at least one battery cell measurement and at least one battery pack measurement to determine a level.

[0208] In some embodiments, the battery pack and / or battery pack cell measurements may be collected before the battery pack is disconnected from one or more buses (e.g., main bus feeding a DC / DC for low voltage systems, ECS equipment, and / or paired battery pack(s)). In some embodiments, the battery pack and / or battery pack cell measurements may be collected after battery pack is disconnected from a bus (e.g., a main bus, as described above). In some embodiments, process 900 may determine whether to proceed to step 903 or 904 (e.g., from 902) based on information determined at step 901 and / or 902 (e.g., whether a battery pack level is within a predetermined range, whether a particular user selection was received, etc.).

[0209] At step 903 process 900 may disconnect at least one battery pack from one or more buses (e.g., a main bus, as described above) based on collecting information regarding level(s) of the at least one battery pack in step 902. In some embodiments, process 900 may proceed to step 904 after completing step 903.

[0210] At step 904, process 900 may determine at least one cell balancing criterion to use to balance cells (e.g., voltage levels of the cells, charge levels of the cells, etc.) within at least one (e.g., each) battery pack and / or at least one battery pack balancing criterion to balance battery packs that may be connected (e.g., re-connected) to a common bus (e.g., cross-link 130). In some embodiments, process 900 may determine an adjustment for one or more cells of a battery pack, which may be based on the at least one cell balancing criterion.

[0211] In some embodiments, voltage-based cell balancing may be performed. For at least one (e.g. each) battery pack, i = 1 . . . M, the voltage of one or more cells (e.g., each cell), Vi (e.g., an open circuit voltage), may be collected in step 902 and a minimum cell voltage, Vmin, may be determined. In some embodiments, cell balancing will not be enabled for any cells within a battery pack if the minimum cell voltage Vmin does not exceed a lower voltage limit, viow, such that Vmin Vlow- In some embodiments, process 900 may balance multiple cells (e.g., each cell in a battery pack, some cells in a battery pack, or at least a threshold number of cells in a battery pack) to have an electrical state that is within a first threshold level (e.g.,voltage level, charge level, etc.) of other cells (e.g., some other cells or all other cells) within the battery pack. An electrical state may include, for example, one or more of an amount of charge, voltage, discharge rate, etc. For example, process 900 may determine the difference in voltage between one or more cells (e.g., each cell) and the minimum cell voltage and compare it to a threshold, 5Vset to enable cell balancing. In some embodiments, threshold voltage 5v may be established (e.g., through experimentation or simulation) such that the battery cells arrive at the same voltage when under load (e.g., when re-connected to a bus). For example, a resistivity of one battery cell may be determined to be higher than another battery cell. In some embodiments, a resistance of one or more cells (e.g., each cell) may be determined through a cell model that calculates a resistance in consideration of an effect of impedance growth over time. Therefore, when current is discharged through the higher resistance cell, a larger change in voltage may result. Process 900 may determine a threshold voltage 5v (and / or otherwise determine an adjustment to balance the cells) in consideration of their different resistivities (e.g., voltage drop cell 1 resistivity = Vi - (idisch*nceii) and voltage drop cell 2 resistivity = Vi2 - (idisch*ri2ceii)). In some embodiments, threshold voltage 5v may be set to a value high enough to avoid chattering in the cell balancing enable / disable logic. For one or more cells (e.g., each cell) in a battery pack, i = 1 . . . N, if v- > 5V, balancingmay be enabled until the difference in voltage, Vi- Vmin, drops below a second threshold, cv. The second threshold, cv, may be established such that cvis sufficiently less than 5Vto avoid chattering in the cell balancing enable / disable logic.

[0212] In some embodiments, charge-based cell balancing may be performed. For at least one (e.g., each) battery pack, i =1 . . . M, the cell capacity Qi of one or more cells (e.g., each cell) and charge remaining in one or more cells (e.g., each cell)qi may be collected at step 902. Based on these values, a depth of discharge (e.g., amount of charge and / or voltage until full charge is reached and / or an amount of remaining charge capacity) Ai may be determined for one or more cells (e.g., each cell), i = 1 . . . N. For example, a depth of discharge for one or more cells (e.g., each cell) may be determined using the difference in cell capacity Qi and charge remaining in the cell qi, such that Ai = Qi -qi. Process 900 may determine the difference in depth of discharge between one or more cells (e.g., each cell) and the maximum depth of discharge Amax and compare it to a threshold depth of discharge 5C(e.g., a second threshold with respect to the threshold for cell balancing described above). In some embodiments, threshold depth of discharge 5Cmay be established (e.g., through experimentation or simulation) such that the battery cells arrive at the same depth of discharge when under load (e.g., when re-connected to a bus), as described above. For one ormore cells (e.g., each cell) in a battery pack, i = 1 . . . N, if Amax - Ai > 5C, balancing will be enabled until the difference drops below a second threshold, cc. The second threshold, £c, may be established such that ccis sufficiently less than 5Cto avoid chattering in the cell balancing enable / disable logic. In some embodiments, charge-based cell balancing criteria and / or targets may be determined and balancing may begin without the power-off detection of step 901. In some embodiments, depth of discharge may be measured in amp-hours, but may be converted to volts for comparisons with other metrics, thresholds, measurements, etc.

[0213] In some embodiments, balancing between battery packs may be performed. For at least one (e.g., each) battery pack, i = 1 . . . M, the battery pack voltage, Vk, may be collected at step 902. Once the battery pack disconnects from a load (e.g., disconnects from a main bus, as described above), the battery pack voltage will decrease and converge to its open circuit voltage Vocvkas t — > co. Therefore, in some embodiments, based on at least one (e.g., each) battery pack voltage, Vk, an open circuit voltage Vocvkof the battery pack may be determined based on experimental data and / or modeling that correlates a pack voltage Vkto an expected open circuit voltage VocvkIn some embodiments, the open circuit voltage Vocvkmay be directly measured. For example, process 900 may wait a set amount of time after the battery pack is disconnected (e.g., a time established by determined by experimental data or modeling as required or preferred for a battery pack to reach its open circuit voltage) and then directly measure the open circuit voltage (e.g., via a voltage sensor).

[0214] Process 900 may compare predicted voltages when a cell is subjected to a specified current (e.g., idisch). The predicted voltage under load may be determined and / or expressed as VLoad = Vi - (idisch*n), where Vi is an open circuit voltage. This may involve measuring when the cells are at rest or is determined by converting the cell SOC estimation to an OCV value. The resistance of the cell, n, may be continually estimated as the cell ages by using an algorithm configured to compute an SOH (discussed above) for the cell. Then, the at least one processor may determine the at least one cell balancing criterion based at least in part on an impact of different cell resistances (n) in the pack by balancing the predicted under load voltages.

[0215] If cell balancing is performed, as described above, this will also cause a decrease in the battery pack level (e.g., battery pack voltage). Therefore, to determine balancing criteria or targets across battery packs, battery pack level drops (e.g., decreases) based on returning to open circuit voltage and battery cell balancing may be considered. For example, determining an adjustment for one or more cells of a battery pack may include determining at least one adjustment based on an estimation (e.g., calculation) of a voltage drop as each battery packreturns to open circuit voltage and an expected voltage drop from each battery pack performing cell balancing. In some embodiments, process 900 may determine an expected battery pack level Vdropk(e.g., battery pack voltage) of at least one (e.g., each) battery pack, based on the battery pack converging to its open circuit voltage and performing cell balancing (if required), Vdropk= V ocv 6bal cell sum, where 5bai ceil sum is the expected drop in battery pack voltage based on performing cell balancing, such as voltage-based cell balancing or chargebased cell balancing, as described above. In some embodiments, process 900 may determine (e.g., select as a desired effect, measure as an actual effect) an effect of voltage-based cell balancing as the sum of change in voltage of the cells in the battery pack whose balancing resistor will be enabled, Sbai ceil = Vi- (vmin +£v)). Additionally or alternatively, process 900 may determine (e.g., select as a desired effect, measure as an actual effect) an effect of charge-based cell balancing by using one or more algorithms, tables, and / or graphs that map an overall voltage drop to a change in depth of discharge required or targeted for one or more cells (e.g., each cell) (e.g., via experimental data and / or modeling). For example, an effect of charge-based cell balancing may be determined using one or more OCV-SOC curve(s) (e.g., one curve for each cell) that correlate a change in state of charge (e.g., determined through required or targeted change in depth of discharge) to a change in voltage. Additionally or alternatively, process 900 may determine (e.g., select as a desired effect, measure as an actual effect), an effect of charge-based cell balancing may be the sum of change in voltage of the cells in the battery pack.

[0216] In some embodiments, process 900 may determine a minimum expected battery pack voltage, Vmin droPk. Process 900 may determine the difference in voltage between each expected battery pack voltage Vdropkand the minimum battery pack voltage Vmin droPkand compare it to a threshold A set to enable battery pack balancing. In some embodiments, the threshold A may be established (e.g., through experimentation, simulation, and / or design criteria of pack and high voltage components) to avoid a difference in battery pack levels that may cause an inrush current high enough to damage one or more battery pack and / or high voltage wiring components.

[0217] In some embodiments, battery pack balancing may be enabled (e.g., all cell balancing resistors enabled in a battery pack) when Vdropk- Vmin droPk >A. In some embodiments, a required or targeted decrease in battery pack voltage 6iiaipack for battery pack balancing is determined. For example, 5bai_Pack= max(VdroPk- Vmin droPk- A, 0), where the max operator is applied to enforce a non-negative quantity.

[0218] At step 905, process 900 may control balancing resistor circuits connected to one or more cells of at least one (e.g., each) battery pack based on the one or more balancing criteria (e.g., as established in step 904). For example, process 900 may close one or more switching devices (e.g., transmit a signal to transistors, relays etc.) for each battery cell whose balancing is enabled. In some embodiments, process 900 may direct one or more chips (e.g., by transmitting a signal to CMU 105) associated with one or more cells to engage their balancer (e.g., bleed off current). In some embodiments, process 900 may control balancing resistor circuits according to the one or more battery pack cell balancing criteria first and then according to the one or more battery pack balancing criteria based on determining the cell balancing is complete (e.g., cells requiring balancing are all within a second threshold of the minimum cell level, as described above). In some embodiments, a battery pack balancing criterion may include a difference in voltage between two battery packs being below a threshold. In some embodiments, the threshold may be set or determined according to a precharging process, discussed more at, for example, step 740. For example, the threshold may be set and / or determined according to a pre-charging process, such as those discussed with respect to Figures 7A-7C, that at least one battery pack connected to a common bus is configured to perform.

[0219] In some embodiments, process 900 may control the balancing resistor circuits based on both the battery pack cell balancing and battery pack balancing criteria simultaneously. For example, a total battery pack change in cell level for balancing one or more cells (e.g., each cell) may be determined by summing the cell balancing and pack balancing criteria for one or more cells (e.g., each cell), btot bai ceil = Sbai ceil + (8bai_pack) / N, and the balancing resistor circuit for one or more cells (e.g., each cell) will be controlled to meet the total battery pack change (e.g., through transmitting a single signal indicative of the total battery pack change). In some embodiments, step 905 may include regularly performing steps 906 and 907 (e.g., simultaneously or near simultaneously).

[0220] At step 906, process 900 may monitor the level(s) of the at least one battery pack and the battery pack cells to determine whether all balancing criteria (e.g., established in step 904) are met. For example, as described above with respect to step 902, process 900 may collect voltage and / or capacity information for the at least one battery pack and / or battery pack cells from sensors and / or by receiving measurements from another device (e.g., via cell management unit (CMU) 105). If the criteria are not met, process 900 may revert back to, or continue to operate, step 905 (e.g., steps 905 and 906 may be operated simultaneously).

[0221] At step 908, process 900 may stop all balancing based on determining that the criteria of step 906 are met. In some embodiments, process 900 may send a notification to one or more aircraft components (e.g., a flight control system), indicating that the balancing is completed and / or indicating the at least one battery pack is prepared to be re-connected to one or more buses (e.g., upon a selection on mode switch 116). In some embodiments, process 900 will control a display, light, and / or speaker of a flight control panel and / or maintenance panel to indicate that the balancing is completed and / or indicating the at least one battery pack is prepared to be re-connected to one or more buses.

[0222] At step 907, the process 900 may monitor whether at least one disable balancing condition has been detected. In some embodiments, process 900 may receive measurements from temperature sensors indicating a temperature of the at least one battery pack, one or more battery pack cells, circuit board(s) and / or chips (e.g., CMU 105) configured to control the battery pack(s) and / or cell(s), and / or from other device(s). If a disable condition is detected, process 900 may take one or more actions to disable balancing. In some embodiments, process 900 may disable balancing (e.g., transmit a signal to open a switching device of a balancing resistor circuit) of at least one battery pack cell based on determining its temperature exceeds a threshold. In some embodiments process 900 may disable balancing of all battery pack cells in a battery back based on determining a temperature of a cell within the battery pack has exceeded a threshold and / or a battery pack level temperature has exceeded a threshold. In some embodiments, process 900 may disable balancing of all battery pack cells in a battery back based on determining a temperature of a circuit board that controls one or more electrical components of the battery pack has exceeded a threshold. In some embodiments, process 900 may disable balancing of the at least one battery pack based on receiving a command to energize a bus (e.g., from a flight control system and / or mode switch 116) and / or detecting closing of one or more switching devices associated with energizing a bus (e.g., KI, K2, K3, K5), such as a switching device connecting the at least one battery pack to the common bus. If a disable condition is not detected, process 900 may continue to perform balancing (e.g., step 905).

[0223] At step 909, process 900 may monitor whether the one or more disable balancing conditions have been remedied. For example, process 900 may determine whether at least one battery pack and / or cell temperature has dropped below a threshold, whether the at least one battery pack is still being commanded to connect to the bus, and / or whether the one or more closed switching device(s) are still closed. In some embodiments, based determining the one or more disable conditions are no longer being detected, process 900 may resumebalancing at step 905. In some embodiments, process 900 may proceed to step 901 and determine whether a power-off condition of the at least one battery pack is detected. In some embodiments, process 900 may send a notification to one or more aircraft components (e.g., a flight control system), indicating that the balancing is not complete and / or indicating the detected at least one disable condition. In some embodiments, process 900 will control a display, light, and / or speaker of a flight control panel and / or maintenance panel to indicate that the balancing is not complete and / or to indicate the detected at least one disable condition. In some embodiments, based determining the one or more disable conditions have not been remedied (e.g., are still being detected), the process 900 may remain in step 909 (e.g., continue checking whether one or more disable conditions have been remedied).

[0224] Figure 10 is a flowchart of an example process 1000. In some implementations, one or more process blocks of Figure 10 may be performed by a device. In some embodiments, the process 1000 is performed by at least one BMU 102, which may include at least one processor configured to execute instructions stored in a memory. In some embodiments, each BMU 102 of the aircraft may perform the process with respect to the battery pack it is associated with (an “instant battery pack”). Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs. Additionally or alternatively, the process and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component (e.g., a non -BMU processing device, such as an FCC or controller).

[0225] In some embodiments, such as prior to initiating block 1002, process 1000 may determine whether the first battery pack is connected to the second battery pack, such as is discussed with respect to steps 704, 708, 730b, and 732. In some embodiments, process 1000 may receive the first and second selections, as discussed further below, based on determining the first battery pack is connected to the second battery pack. In some embodiments, determining that the first battery pack is connected to the second battery pack may be based on a status of a fuse on a bus connecting the first and second battery packs. For example, process 1000 may detect whether a fuse enabling an electrical connection (e.g., a cross-link) between the first battery pack and the second battery pack is intact or blown.

[0226] As shown in Figure 10, process 1000 may include receiving a first selection of a first or second battery pack to pre-charge circuitry of a first and second battery pack by a first battery management unit associated with the first battery pack (block 1002). For example, process 1000 may receive a first selection of the first battery pack or the second battery pack to pre-charge circuitry of the first and second battery pack by a first BMU associated with thefirst battery pack, as described above with respect to processes 700a, 700b and 700c. By way of further example, receiving the first selection may include one or more of steps 702, 705, 709, 711, 715, 717, 718, 731, 733, 746, and 747.

[0227] As also shown in Figure 10, process 1000 may include receiving a second selection of the first battery pack or the second battery pack to pre-charge the circuitry of the first and second battery packs by a second BMU associated with the second battery pack (block 1004). For example, process 1000 may receive a second selection of the first battery pack or the second battery pack to pre-charge the circuitry of the first and second battery packs by a second BMU associated with the second battery pack, as described above with respect to processes 700a, 700b and 700c. By way of further example, receiving the second selection may include one or more of steps 702, 705, 709, 711, 715, 717, 718, 731, 733, 746, and 747.

[0228] As further shown in Figure 10, process 1000 may include selecting, based on the received first selection and second selection, one of the first and second battery packs to precharge the circuitry of the first and second battery packs (block 1006). For example, process 1000 may select one of the first and second battery packs to pre-charge the circuitry of the first and second battery packs based on the received first selection and second selection, as described above with respect to processes 700a, 700b and 700c. Selecting one of the first and second battery packs to pre-charge the circuitry of the first and second battery packs may include designating or setting one of the first and second battery packs to have a primary role and the other of the first and second battery packs to have a secondary role. By way of further example, selecting the first selection may include one or more of steps 706, 709, 711, 715, 717, 720, 731, 733, 738, 739, 743, 744, 746, 747, and 748.

[0229] Process 1000 may also include refraining from, based on the received first selection and second selection, using the first or second battery pack to pre-charge the circuitry of the first and second battery packs. Refraining from using a battery pack to pre-charge may include preventing that battery pack from performing at least one pre-charge operation, designating that battery pack with a secondary role, instructing that battery pack to open at least one switching device, instructing that battery pack to not close at least one switching device, setting a role of that battery pack to a secondary role, or taking any action so that only a single battery pack can pre-charge circuitry of multiple battery packs.

[0230] For example, when the first battery pack selects itself to pre-charge the circuitry of the first and second battery packs, a BMU (e.g., a BMU associated with the first battery pack) or other processing device may transmit an instruction to the second battery pack (e.g., a BMU of the second battery) to cause it to refrain from pre-charging the circuitry of the first andsecond battery packs. Refraining from pre-charging circuitry may include refraining from closing at least one switching device and / or opening at least one switching device.

[0231] In some embodiments, the first selection of a first or second battery pack to precharge the circuitry of the first and second battery packs may be based on respective battery states of the first and second battery packs. For example, the first selection of the first or second battery pack may be based on comparing the respective battery states. For example, the first selection of the first or second battery pack may be based on comparing the respective battery states to each other and / or to at least one common metric to determine whether the first battery pack has a superior operational status relative to the second battery pack (or vice versa). A superior operational status may be considered a status having more capability to adequately pre-charge circuitry, such as according to one or more of the determinations, checks, and measurements discussed herein. In the same manner, the second selection of the first or second battery pack to pre-charge the circuitry of the first and second battery packs may also be based on respective battery states of the first and second battery packs, such as by being based comparing the respective battery states to each other and / or to at least one common metric to determine whether the second battery pack has a superior operational status relative to the first battery pack.

[0232] A battery state may include any information describing current electrical information of at least one battery cell and / or at least one battery pack, consistent with disclosed embodiments. Additionally or alternatively, a battery state may include a battery status (e.g., functioning without an error, malfunctioning, misperforming, etc.) and / or electrical configuration. An electrical configuration may include a combination of loads connected to a battery, a demand of the connected loads, one or more switching states of components connected in a circuit to the battery, and / or one or more fuse statuses (e.g., blown or intact). Additionally or alternatively, a battery state may include a measurable trait of a battery or components connected to it, such as a voltage of the battery. A battery state may be measured, calculated, estimated, predicted, and / or determined by one or more steps, processes, algorithms, functions, and the like, which may be executable by at least one processor.

[0233] Determining a battery state may include determining whether a pack is paired, whether a pack is capable of pre-charging, whether a pack is actively pre-charging a bus, whether a pack is actively energizing or has energized a bus, a voltage of one or more battery packs, a difference between battery pack voltages, whether a difference between battery pack voltages is less than a threshold, whether a battery pack has a particular selection, whether abattery pack is designated to pre-charge circuitry, and / or whether a battery pack is not designated to pre-charge circuitry, as discussed further with respect to Figures 7A-7C, 8A, and 9. For example, process 1000 may determine respective battery states that each comprise a voltage of a respective battery pack and at least one of the first selection or the second selection is a selection of the battery pack with the highest voltage. By way of further example, at least one of the first selection or the second selection may be based on voltage determinations and a voltage comparison, such as is described with respect to steps 713, 716, 737, 740, and 741.

[0234] As also shown in Figure 10, process 1000 may include controlling circuitry of the selected battery pack to perform the pre-charge (block 1008). For example, process 1000 may control circuitry of the selected battery pack to perform the pre-charge, as described above with respect to process 800. For example, process 1000 change a switch status (e.g., open or closed) of at least one switching device, consistent with disclosed embodiments, such as discussed further with respect to Figures 7A-7C, 8A, and 9. Additionally or alternatively, controlling the selected battery pack to perform the pre-charge may include controlling a flow of current from a low voltage battery pack. For example, process 1000 may instruct one or more switching devices to close, to cause power to flow from an LV battery to a DC / DC (e.g., across the LV power connection shown in Figure 3B, for example).

[0235] Consistent with disclosed embodiments, process 1000 may include receiving a mode selection and pre-charging a portion of the circuitry of the first and second battery packs based on the received mode selection. For example, the mode selection may be received based on an input from a mode switch (e.g., mode switch 116). Process 1000 may precharging a portion of the circuitry of the first and second battery packs according to the selected mode, which may identify a configuration of switch states for one or more switching devices. In some embodiments, the mode selection, such as a selection of a pre-charge mode, may prompt an initiation of process 1000.

[0236] Consistent with disclosed embodiments, pre-charging a portion of the circuitry of the first and second battery packs based on the received mode selection may include pre-charging circuitry configured to power EPUs based on receiving a first mode and / or pre-charging circuitry configured to power low voltage loads based on receiving a second mode. For example, pre-charging a portion of the circuitry of the first and second battery packs based on the received mode selection may include pre-charging circuitry configured to power EPUs according to the mode described above with respect to Figures 2D, 2E, 3D, 3E, 4D, 4E, 5D, and 5E. For example, pre-charging a portion of the circuitry of the first and second batterypacks based on the received mode selection may include pre-charging circuitry configured to power low voltage loads according to the mode described above with respect to Figures 2B, 2C, 3B, 3C, 4B, 4C, 5B, and 5C.

[0237] Figure 11 is a flowchart of an example process 1100. In some implementations, one or more process blocks of Figure 11 may be performed by a device. In some embodiments, the process 1100 is performed by at least one BMU 102, which may include at least one processor configured to execute instructions stored in a memory. In some embodiments, each BMU 102 of the aircraft may perform the process with respect to the battery pack it is associated with (an “instant battery pack”). Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs. Additionally or alternatively, the process and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component (e.g., a non -BMU processing device, such as an FCC or controller).

[0238] As shown in Figure 11, process 1100 may include toggling a first switching device on a pre-charge circuit to raise a voltage on a bus powering at least one electric propulsion unit (block 1102). For example, process 1100 may toggle a first switching device on a pre-charge circuit to raise a voltage on a bus powering at least one electric propulsion unit, as described above with respect to process 800. For example, process 1100 may enable a pre-charge pulse, as discussed above with respect to step 807. In some embodiments, toggling a first switching device may include performing one or more of steps 803, 804, 807, and 808.

[0239] As also shown in Figure 11, process 1100 may include determining whether the bus voltage exceeds a voltage threshold within a time threshold (block 1104). For example, process 1100 may determine whether the bus voltage exceeds a voltage threshold within a time threshold, as described above with respect to process 800. For example, process 1100 may repeatedly determine whether the bus voltage exceeds a voltage threshold while an incrementing timer has not reached a threshold. In some embodiments, determining whether the bus voltage exceeds a voltage threshold within a time threshold may include performing one or more of steps 803, 804, 807, and 808.

[0240] As further shown in Figure 11, process 1100 may include pre-charging the bus based on or in response to determining the bus voltage exceeds the voltage threshold within the time threshold (block 1106). For example, process 1100 may pre-charge the bus based on determining the voltage exceeds the voltage threshold within the time threshold, as described above with respect to process 800. For example, process 1100 may perform one or more of steps 822-832, such as steps 822, 823, 824, 828, 829, 830, and 831.

[0241] Figure 12 is a flowchart of an example process 1200. In some embodiments, the process 1200 is performed by at least one BMU 102, which may include at least one processor configured to execute instructions stored in a memory. In some embodiments, each BMU 102 of an aircraft may perform the process with respect to the battery pack it is associated with (an “instant battery pack”). Additionally or alternatively, one BMU 102 may perform the process for multiple battery packs. Additionally or alternatively, the process and / or one or more steps are performed by at least one processor and memory associated with a different aircraft component (e.g., a non -BMU processing device, such as an FCC or controller).

[0242] As shown in Figure 12, process 1200 may include receiving a signal that a battery pack is to be disconnected (block 1202). For example, device may receive a signal that a battery pack is to be disconnected, as described above with respect to process 900. For example, process 1200 may perform step 901 and / or 903.

[0243] As also shown in Figure 12, process 1200 may include detecting a level of each of multiple cells within the battery pack (block 1204). Detecting a level of each of multiple cells within the battery pack may include determining voltage information, charge information, temperature information, and / or health information of the multiple cells, which may be based on measurements made by one or more sensors, consistent with disclosed embodiments. For example, device may detect a level of each of multiple cells within the battery pack, as described above with respect to process 900. For example, process 1200 may perform one or more of steps 902 and 904.

[0244] As further shown in Figure 12, process 1200 may include detecting a level of each battery pack configured to be connected to a common bus (block 1206). Detecting a level of each battery pack configured to be connected to a common bus may include determining pack-level information for multiple battery packs, which may include aggregating measured and / or estimated information related to multiple battery cells and / or multiple battery packs.

[0245] For example, device may detect a level of each battery pack configured to be connected to a common bus, as described above with respect to process 900. For example, process 1200 may perform one or more of steps 902 and 904.

[0246] As also shown in Figure 12, process 1200 may include determining an adjustment for each of the multiple cells. An adjustment for a cell may include any change to charge stored by the cell, a voltage of the cell, a current provided by the cell, a connection status of the cell, any electrical property of the cell, or any combination thereof, consistent with disclosed embodiments. In some embodiments, the adjustment may (i) balance each of the multiplecells to have an electrical state that is within a first threshold level of other cells (e.g., some other cells or all other cells) within the battery pack and / or (ii) balance the battery pack to have an electrical state that is within a second threshold level of each battery pack connected to the common bus (block 1208). For example, device may determine an adjustment for each of the multiple cells, where the adjustment: balances each of the multiple cells to have an electrical state that is within a first threshold level of the other cells within the battery pack and / or balances the battery pack to have an electrical state that is within a second threshold level of each battery pack connected to the common bus, as described above with respect to process 900.

[0247] As further shown in Figure 12, process 1200 may include controlling, for each of the multiple cells within the battery pack, a balancing resistor circuit according to or otherwise based on the respective adjustment (block 1210). For example, device may control, for each of the multiple cells within the battery pack, a balancing resistor circuit according to the respective adjustment, as described above. In addition to or instead of controlling a balancing resistor circuit, process 1200 may include performing one or more cell and / or pack balancing operations, such as those discussed with respect to step 905. Process 1200 may also include performing any or all steps of process 900.

[0248] The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein.

[0249] Additional aspects of the present disclosure may be further described via the following clauses:1. A method for pre-charge control, comprising: receiving, using at least one hardware processor, a first selection of a first or second battery pack to pre-charge circuitry of a first and second battery pack by a first battery management unit associated with the first battery pack; receiving, using the at least one hardware processor, a second selection of a first or second battery pack to pre-charge the circuitry of the first and second battery packs by a second battery management unit associated with the second battery pack;based on the received first selection and second selection, selecting, using the at least one hardware processor, the first battery pack to pre-charge the circuitry of the first and second battery packs and refraining from using the second battery pack to pre-charge the circuitry of the first and second battery packs; and controlling, using the at least one hardware processor, circuitry of the selected first battery pack to perform the pre-charge. method of clause 1, wherein the first selection of the first or second battery pack is based on comparing, using the at least one hardware processor, respective battery states of the first and second battery packs to each other or to a common metric. ethod of clause 1 or 2, wherein the second selection of the first or second battery pack to pre-charge the circuitry of the first and second battery packs is based on comparing, using the at least one hardware processor, respective battery states of the first and second battery packs to each other or to a common metric. ethod of clause 3, wherein the respective battery states each comprise a voltage of the respective battery pack and at least one of the first selection or the second selection is a selection of the battery pack with the highest voltage. ethod of any of clauses 1-4, further comprising: receiving, using the at least one hardware processor, a mode selection and pre-charging a portion of the circuitry of the first and second battery packs based on the received mode selection. ethod of clause 5, wherein: the received mode selection is a first mode or a second mode; and pre-charging a portion of the circuitry of the first and second battery packs based on the received mode selection comprises: pre-charging circuitry configured to power EPUs if the received mode is the first mode; and otherwise, if the received mode is the second mode, precharging circuitry configured to power low voltage loads based on receiving a second mode. ethod of any of clauses 1-6, further comprising: closing, using the at least one hardware processor, at least one contactor associated with at least one electric propulsion unit to power the at least one electric propulsion unit based on determining that pre-charge of the circuitry of the first and second battery packs is complete. ethod of any of clauses 1-7, further comprising:closing, using the at least one hardware processor, at least one contactor associated with the selected battery pack based on determining that pre-charge is complete; and closing, using the at least one hardware processor, at least one contactor associated with a non-selected battery pack based on determining that pre-charge is complete. ethod of any of clauses 1-8, wherein controlling the selected battery pack to perform the pre-charge comprises closing, using the at least one hardware processor, at least one switching device connected in series with a pre-charge resistor. method of any of clauses 1-9, wherein controlling the selected battery pack to perform the pre-charge comprises controlling, using the at least one hardware processor, a DC / DC converter associated with the selected battery pack. method of clause 10, wherein the DC / DC converter is a bidirectional DC / DC converter associated with an electric propulsion unit or low voltage system. method of any of clauses 1-11, wherein controlling the selected battery pack to perform the pre-charge comprises controlling, using the at least one hardware processor, a flow of current from a low voltage (LV) battery. method of any of clauses 1-12, wherein controlling the selected battery pack to perform the pre-charge comprises controlling, using the at least one hardware processor, a DC / DC converter associated with the selected battery pack to step down current from a high voltage source. method of any of clauses 1-13, further comprising: determining, using the at least one hardware processor, whether the first battery pack is connected to the second battery pack; and receiving, using the at least one hardware processor, the first and second selections after determining the first battery pack is connected to the second battery pack. method of clause 14, wherein determining the first battery pack is connected to the second battery pack is based on a status of a fuse on a bus connecting the first and second battery packs. method of any of clauses 1-15, further comprising: determining, using the at least one hardware processor, whether the first selection and the second selection match; andselecting, using the at least one hardware processor, a battery pack that matches both selections to pre-charge the circuitry of the first and second battery packs based on determining the selections match. method of any of clauses 1-16, further comprising: selecting, using the at least one hardware processor, a default battery pack to pre-charge the circuitry of the first and second battery packs based on determining the first selection selects the second battery pack and the second selection selects the first battery pack. method of clause 17, wherein the default battery pack is determined based on an identifier, a location, or a status of the first and second battery packs. method of any of clauses 1-18, further comprising: receiving, using the at least one hardware processor, a third selection of the first or second battery pack to pre-charge circuitry of the first and second battery packs by the first battery management unit associated with the first battery pack; receiving, using the at least one hardware processor, a fourth selection of the first or second battery pack to pre-charge the circuitry of the first and second battery packs by the second battery management unit associated with the second battery pack; and determining, using the at least one hardware processor, whether the third selection selects the first battery pack to perform the pre-charge and the fourth selection selects the second battery pack to perform precharge; wherein controlling circuitry of the first battery pack to pre-charge circuitry of the first battery pack comprises controlling circuitry of the first battery pack to pre-charge circuitry of the first battery pack but not circuitry of the second battery pack based on determining the third selection selects the first battery pack back and the fourth selection selects the second battery pack. method of any of clauses 1-19, further comprising: receiving, using the at least one hardware processor, a voltage measurement of the first battery pack and the second battery pack; and determining, using the at least one hardware processor, whether a difference in voltage between the first and the second battery packs is within a threshold;wherein controlling circuitry of the selected battery pack to perform the precharge is based on determining the difference is within the threshold. stem for pre-charge control comprising at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of clauses 1-20. omputer-readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any of clauses 1-20. aircraft, comprising: a first battery pack; a first battery management unit; a second battery pack; a second battery management unit; at least one electric propulsion unit powered by at least one of the first or second battery packs; and at least one processor configured to execute instructions to cause the at least one processor perform the method of any of clauses 1-20. electrical system for an aircraft, the system comprising: a first switching device configured to electrically connect a first pre-charge circuit to pre-charge a bus powering a non-propulsion load; a second switching device configured to electrically connect a second precharge circuit to pre-charge a bus powering at least one electric propulsion unit; and at least one battery management unit configured to control the first and second switching devices based on a mode selection made by an input device communicably connected to the system. system of clause 24, wherein the first switching device is a semiconductor device. system of clause 24 or 25, wherein the second switching device is a semiconductor device. system of any of clauses 24-26, wherein at least one of the first switching device or the second switching device is a MOSFET device. system of any of clauses 24-27, wherein the first pre-charge circuit comprises a first pre-charge resistor in series connection with the first switching device.system of clause 28, wherein the second pre-charge circuit comprises a second precharge resistor in series connection with the second switching device. system of any of clauses 24-27, wherein: the first pre-charge circuit is connected in parallel to the second pre-charge circuit; and the first pre-charge circuit and the second pre-charge circuit are connected in series to a pre-charge resistor. system of clause 30, wherein the pre-charge resistor is configured to increase resistance based on a temperature increase. system of any of clauses 24-31, wherein the first pre-charge circuit comprises a first diode in series connection with the first switching device. system of any of clauses 24-32, wherein the second pre-charge circuit comprises a second diode in series connection with the second switching device. system of any of clauses 24-33, further comprising a fuse configured to disconnect the first pre-charge circuit from the second pre-charge circuit. system of clause 34, wherein the fuse is further configured to disconnect the at least one battery management unit from a power source. system of any of clauses 24-35, wherein the non-propulsion load comprises at least one of: environmental conditioning system (ECS) equipment, avionics, flight control computer, or flight control surface. stem for an aircraft, the system comprising: a switching device configured to electrically connect a pre-charge circuit to pre-charge a bus powering a propulsion load; a bidirectional DC / DC converter configured to pre-charge a bus powering a non-propulsion load; and at least one battery management unit configured to control the switching device and the bidirectional DC / DC converter based on a mode selection made by an input device communicably connected to the system. stem for an aircraft, the system comprising: a first bidirectional DC / DC converter configured to pre-charge a bus powering a non-propulsion load and provide current to at least one second bidirectional DC / DC converter,wherein the at least one second bidirectional DC / DC converter is configured to receive the current from the first bidirectional DC / DC converter and pre-charge a bus powering a propulsion load; and at least one battery management unit configured to control, based on a mode selection made by an input device communicably connected to the system, the first bidirectional DC / DC converter and the at least one second bidirectional DC / DC converter. aircraft comprising at least one electric propulsion unit and the system of any of clauses 21 or 24-38. ethod for high voltage power control, comprising: toggling, using at least one hardware processor, a first switching device on a pre-charge circuit to raise a voltage on a bus powering at least one electric propulsion unit; determining, using the at least one hardware processor, whether the bus voltage exceeds a voltage threshold within a time threshold; and pre-charging, using the at least one hardware processor, the bus in response to determining the bus voltage exceeds the voltage threshold within the time threshold. method of clause 40, further comprising; controlling, using the at least one hardware processor, the first switching device to maintain the bus voltage above the voltage threshold in response to determining the bus voltage exceeds the voltage threshold within the time threshold; determining, using the at least one hardware processor, whether a voltage at the at least one electric propulsion unit exceeds the voltage threshold; and wherein the pre-charging of the bus is in response to determining the bus voltage exceeds the voltage threshold within the time threshold and the voltage at the at least one electric propulsion unit exceeds the voltage threshold. method of clause 41, further comprising: determining, using the at least one hardware processor, whether a voltage associated with at the at least one electric propulsion unit exceeds the voltage threshold within another time threshold; andpre-charging, using at least one battery pack, the bus in response to determining the bus voltage exceeds the voltage threshold within the time threshold and the voltage at the at least one electric propulsion unit exceeds the voltage threshold in the another time threshold. method of clause 42, wherein the another time threshold is a longer time than the time threshold. method of clause 41, wherein controlling the first switching device to maintain the bus voltage above the voltage threshold comprises closing, using the at least one hardware processor, the first switching device in response to detecting a drop in the bus voltage. method of clause 41, further comprising: stopping controlling, using the at least one hardware processor, the first switching device to maintain the bus voltage above the voltage threshold based on determining the voltage at the at least one electric propulsion unit does not exceed the voltage threshold. method of clause 41, further comprising: providing, using the at least one hardware processor, a notification to a user device in response to determining the voltage at the at least one electric propulsion unit does not exceed the voltage threshold. method of any of clauses 41-46, wherein the first switching device is a semiconductor device. method of any of clauses 41-47, wherein toggling the first switching device comprises closing, using the at least one hardware processor, the first switching device to allow current flow through the first switching device during an amount of time that is between 0.5-10% of a duty cycle, before opening the first switching device. method of any of clauses 41-48, wherein toggling the first switching device open and closed comprises toggling, using the at least one hardware processor, the switching device to apply a voltage periodically at a set interval. method of any of clauses 41-49, wherein the voltage threshold comprises a value in a range of 5 -60V, inclusive. method of any of clauses 41-50, further comprising:stopping toggling, using the at least one hardware processor, the first switching device based on determining the voltage does not exceed the voltage threshold within the time threshold. method of any of clauses 41-51, further comprising: providing, using the at least one hardware processor, a notification to a user device based on determining the voltage does not exceed the voltage threshold within the time threshold. method of clause 52, wherein the notification indicates an electrical issue. method of any of clauses 41-53, further comprising: providing, using the at least one hardware processor, a single voltage pulse by closing and then opening the first switching device; and determining, using the at least one hardware processor, whether the bus voltage exceeds another voltage threshold, wherein pre-charging the bus is performed in response to determining the bus voltage does not exceed a second voltage threshold based on receiving the single voltage pulse. method of clause 54, wherein the second voltage threshold is zero. method of clause 55, further comprising: providing, using the at least one hardware processor, a notification to a user device in response to determining the bus voltage exceeds the second voltage threshold based on receiving the single voltage pulse. stem for high voltage power control comprising at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of clauses 40-56. omputer-readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any of clauses 40-56. aircraft, comprising: a battery pack; at least one electric propulsion unit powered by the battery pack; and at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of clauses 40-56. ethod for battery balancing a battery pack of an aircraft, comprising: receiving, using at least one hardware processor, a signal that a battery pack is to be disconnected from a common bus;detecting, using the at least one hardware processor, a level of each of multiple cells within the battery pack; detecting, using the at least one hardware processor, a level of each battery pack configured to be connected to the common bus; determining, using the at least one hardware processor, an adjustment for each of the multiple cells, wherein the adjustment: balances each of the multiple cells to have a first electrical state within a first threshold level of other cells within the battery pack; or balances the battery pack to have a second electrical state within a second threshold level of each battery pack connected to the common bus; and controlling, using the at least one hardware processor, for each of the multiple cells, a balancing resistor circuit according to the respective adjustment.he method of clause 60, wherein the signal indicates a user selection made on an input device communicably connected to the aircraft. he method of clause 61, wherein the input device is at least one of: a manual switch, knob, button, lever, or user interface element. he method of any of clauses 60-62, wherein detecting the level of each of the multiple cells within the battery pack comprises at least one of: detecting, using the at least one hardware processor, a voltage level or detecting, using the at least one hardware processor, a charge level of each of the multiple cells. he method of any of clauses 60-63, wherein detecting the level of each battery pack comprises detecting a voltage level of each battery pack. he method of any of clauses 60-64, wherein determining an adjustment required for each of the multiple cells within the battery pack comprises determining, using the at least one hardware processor, an adjustment based on an estimation of a voltage drop as each battery pack returns to open circuit voltage and an expected voltage drop from the each battery pack performing cell balancing. he method of any of clauses 60-65, wherein determining the adjustment required for each of the multiple cells is based on a respective resistivity of each of the multiple cells.he method of any of clauses 60-66, wherein, for each of the multiple cells, controlling the balancing resistor circuit comprises at least one of: transmitting, using the at least one hardware processor, a signal to a switching device of the balancing resistor circuit or transmitting, using the at least one hardware processor, a signal to a chip comprising the balancing resistor circuit. he method of any of clauses 60-67, wherein, for each of the multiple cells, controlling the balancing resistor circuit comprises transmitting, using the at least one hardware processor, a single signal indicative of a battery pack adjustment to balance the first electrical state of the respective cell within the first threshold of other cells. he method of any of clauses 60-68, wherein, for each of the multiple cells, controlling the balancing resistor circuit further comprises: monitoring, using the at least one hardware processor, a temperature of at least one of the battery pack, one or more cells of the battery pack, or a circuit board of the battery pack; and controlling, using the at least one hardware processor, the balancing resistor circuit to disable balancing in response to detecting the temperature exceeds a threshold. he method of any of clauses 60-69, wherein, for each of the multiple cells, controlling the balancing resistor circuit further comprises: controlling, using the at least one hardware processor, the balancing resistor circuit to disable balancing in response to detecting a switching device connecting the battery pack to the common bus is closed. he method of any of clauses 60-70, wherein the second threshold level is set or determined according to a pre-charging process that at least one battery pack connected to the common bus is configured to perform. system for high voltage power control comprising at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of clauses 60-71. computer-readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any of clauses 60-71. n aircraft, comprising: a battery pack; at least one electric propulsion unit powered by the battery pack; andat least one processor configured to execute instructions to cause the at least one processor to perform the method of any of clauses 60-71.

[0250] The features and advantages of the disclosure are apparent from the detailed specification, and thus, it is intended that the appended clauses cover all systems and methods falling within the true spirit and scope of the disclosure. As used herein, the indefinite articles “a” and “an” mean “one or more.” Similarly, the use of a plural term does not necessarily denote a plurality unless it is unambiguous in the given context. Words such as “and” or “or” mean “and / or” unless specifically directed otherwise. Also, words such as “be” or “is” or “are” may refer to “include” or “includes” unless specifically directed otherwise. As used herein, unless specifically stated otherwise, being “based on” may include being dependent on, being interdependent with, being derived from (e.g., using), being associated with, being defined at least in part by, being influenced by, occurring upon, occurring after, and / or being responsive to. As used herein, “related to” or “relating to” may include being inclusive of, being expressed by, being indicated by, or being based on. Further, since numerous modifications and variations will readily occur from studying the present disclosure, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.

[0251] Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the implementations disclosed herein. It is intended that the architectures and circuit arrangements shown in figures are only for illustrative purposes and are not intended to be limited to the specific arrangements and circuit arrangements as described and shown in the figures. It is also intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following clauses. The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein. It is also intended that the sequence of steps shown in figures is only for illustrative purposes and is not intended to be limited to any particular sequence of steps. As such, those skilled in the art can appreciate that these steps can be performed in a different order, only a subset of the steps may be performed, and / or one or more steps may be repeated while implementing the same method. Moreover, while the steps or blocks may be described as performed by a particular entity, such as at least oneprocessor or a process, it is appreciated that all steps may be performed by at least one processor, such as a computer. For example, at least one processor may be configured to execute the steps or blocks as expressed in instructions stored in a storage medium.

Claims

CLAIMS1. A computer-implemented method for pre-charge control, comprising: receiving, by at least one hardware processor, a first selection of a first or second battery pack to pre-charge circuitry of a first and second battery pack by a first battery management unit associated with the first battery pack; receiving a second selection of a first or second battery pack to pre-charge the circuitry of the first and second battery packs by a second battery management unit associated with the second battery pack; based on the received first selection and second selection, selecting the first battery pack to pre-charge the circuitry of the first and second battery packs and refraining from using the second battery pack to pre-charge the circuitry of the first and second battery packs; and controlling circuitry of the selected first battery pack to perform the precharge.

2. The computer-implemented method of claim 1, wherein the first selection of the first or second battery pack is based on comparing respective battery states of the first and second battery packs to each other or to a common metric.

3. The computer-implemented method of claim 1 or 2, wherein the second selection of the first or second battery pack to pre-charge the circuitry of the first and second battery packs is based on comparing respective battery states of the first and second battery packs to each other or to a common metric.

4. The computer-implemented method of claim 3, wherein the respective battery states each comprise a voltage of the respective battery pack and at least one of the first selection or the second selection is a selection of the battery pack with the highest voltage.

5. The computer-implemented method of any of claims 1-4, further comprising: receiving a mode selection and pre-charging a portion of the circuitry of the first and second battery packs based on the received mode selection.

6. The computer-implemented method of claim 5, wherein: the received mode selection is a first mode or a second mode; and pre-charging a portion of the circuitry of the first and second battery packs based on the received mode selection comprises: pre-charging circuitry configured to power EPUs if the received mode is the first mode; andotherwise, if the received mode is the second mode, precharging circuitry configured to power low voltage loads based on receiving a second mode.

7. The computer-implemented method of any of claims 1-6, further comprising: closing at least one contactor associated with at least one electric propulsion unit to power the at least one electric propulsion unit based on determining that pre-charge of the circuitry of the first and second battery packs is complete.

8. The computer-implemented method of any of claims 1-7, further comprising: closing at least one contactor associated with the selected battery pack based on determining that pre-charge is complete; and closing at least one contactor associated with a non-selected battery pack based on determining that pre-charge is complete.

9. The computer-implemented method of any of claims 1-8, wherein controlling the selected battery pack to perform the pre-charge comprises closing at least one switching device connected in series with a pre-charge resistor.

10. The computer-implemented method of any of claims 1-9, wherein controlling the selected battery pack to perform the pre-charge comprises controlling a DC / DC converter associated with the selected battery pack.

11. The computer-implemented method of claim 10, wherein the DC / DC converter is a bidirectional DC / DC converter associated with an electric propulsion unit or low voltage system.

12. The computer-implemented method of any of claims 1-11, wherein controlling the selected battery pack to perform the pre-charge comprises controlling a flow of current from a low voltage (LV) battery.

13. The computer-implemented method of any of claims 1-12, wherein controlling the selected battery pack to perform the pre-charge comprises controlling a DC / DC converter associated with the selected battery pack to step down current from a high voltage source.

14. The computer-implemented method of any of claims 1-13, further comprising: determining whether the first battery pack is connected to the second battery pack; and receiving the first and second selections after determining the first battery pack is connected to the second battery pack.

15. The computer-implemented method of claim 14, wherein determining the first battery pack is connected to the second battery pack is based on a status of a fuse on a bus connecting the first and second battery packs.

16. The computer-implemented method of any of claims 1-15, further comprising: determining whether the first selection and the second selection match; and selecting a battery pack that matches both selections to pre-charge the circuitry of the first and second battery packs based on determining the selections match.

17. The computer-implemented method of any of claims 1-16, further comprising: selecting a default battery pack to pre-charge the circuitry of the first and second battery packs based on determining the first selection selects the second battery pack and the second selection selects the first battery pack.

18. The computer-implemented method of claim 17, wherein the default battery pack is determined based on an identifier, a location, or a status of the first and second battery packs.

19. The computer-implemented method of any of claims 1-18, further comprising: receiving a third selection of the first or second battery pack to pre-charge circuitry of the first and second battery packs by the first battery management unit associated with the first battery pack; receiving a fourth selection of the first or second battery pack to pre-charge the circuitry of the first and second battery packs by the second battery management unit associated with the second battery pack; and determining whether the third selection selects the first battery pack to perform the pre-charge and the fourth selection selects the second battery pack to perform pre-charge; wherein controlling circuitry of the first battery pack to pre-charge circuitry of the first battery pack comprises controlling circuitry of the first battery pack to pre-charge circuitry of the first battery pack but not circuitry of the second battery pack based on determining the third selection selects the first battery pack back and the fourth selection selects the second battery pack.

20. The computer-implemented method of any of claims 1-19, further comprising: receiving a voltage measurement of the first battery pack and the second battery pack; anddetermining whether a difference in voltage between the first and the second battery packs is within a threshold; wherein controlling circuitry of the selected battery pack to perform the precharge is based on determining the difference is within the threshold.

21. A system for pre-charge control comprising at least one processor configured to execute instructions to cause the at least one processor to perform the computer-implemented method of any of claims 1-20.

22. A computer-readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the computer- implemented method of any of claims 1-20.

23. An aircraft, comprising: a first battery pack; a first battery management unit; a second battery pack; a second battery management unit; at least one electric propulsion unit powered by at least one of the first or second battery packs; and at least one processor configured to execute instructions to cause the at least one processor to perform the computer-implemented method of any of claims 1-20.

24. An electrical system for an aircraft, the system comprising: a first switching device configured to electrically connect a first pre-charge circuit to pre-charge a bus powering a non-propulsion load; a second switching device configured to electrically connect a second precharge circuit to pre-charge a bus powering at least one electric propulsion unit; and at least one battery management unit configured to control the first and second switching devices based on a mode selection made by an input device communicably connected to the system.

25. The system of claim 24, wherein the first switching device is a semiconductor device.

26. The system of any of claims 24-25, wherein the second switching device is a semiconductor device.

27. The system of any of claims 24-26, wherein at least one of the first switching device or the second switching device is a MOSFET device.

28. The system of any of claims 24-27, wherein the first pre-charge circuit comprises a first pre-charge resistor in series connection with the first switching device.

29. The system of claim 28, wherein the second pre-charge circuit comprises a second precharge resistor in series connection with the second switching device.

30. The system of any of claims 24-27, wherein: the first pre-charge circuit is connected in parallel to the second pre-charge circuit; and the first pre-charge circuit and the second pre-charge circuit are connected in series to a pre-charge resistor.

31. The system of claim 30, wherein the pre-charge resistor is configured to increase resistance based on a temperature increase.

32. The system of any of claims 24-31, wherein the first pre-charge circuit comprises a first diode in series connection with the first switching device.

33. The system of any of claims 24-32, wherein the second pre-charge circuit comprises a second diode in series connection with the second switching device.

34. The system of any of claims 24-33, further comprising a fuse configured to disconnect the first pre-charge circuit from the second pre-charge circuit.

35. The system of claim 34, wherein the fuse is further configured to disconnect the at least one battery management unit from a power source.

36. The system of any of claims 24-35, wherein the non-propulsion load comprises at least one of: environmental conditioning system (ECS) equipment, avionics, flight control computer, or flight control surface.

37. A system for an aircraft, the system comprising: a switching device configured to electrically connect a pre-charge circuit to pre-charge a bus powering a propulsion load; a bidirectional DC / DC converter configured to pre-charge a bus powering a non-propulsion load; and at least one battery management unit configured to control the switching device and the bidirectional DC / DC converter based on a mode selection made by an input device communicably connected to the system.

38. A system for an aircraft, the system comprising:a first bidirectional DC / DC converter configured to pre-charge a bus powering a non-propulsion load and provide current to at least one second bidirectional DC / DC converter, wherein the at least one second bidirectional DC / DC converter is configured to receive the current from the first bidirectional DC / DC converter and pre-charge a bus powering a propulsion load; and at least one battery management unit configured to control, based on a mode selection made by an input device communicably connected to the system, the first bidirectional DC / DC converter and the at least one second bidirectional DC / DC converter.

39. An aircraft comprising at least one electric propulsion unit and the system of any of claims 21 or 24-38.

40. A computer-implemented method for high voltage power control, comprising: toggling a first switching device on a pre-charge circuit to raise a voltage on a bus powering at least one electric propulsion unit; determining whether the bus voltage exceeds a voltage threshold within a time threshold; and pre-charging the bus in response to determining the bus voltage exceeds the voltage threshold within the time threshold.

41. The computer-implemented method of claim 40, further comprising; controlling the first switching device to maintain the bus voltage above the voltage threshold in response to determining the bus voltage exceeds the voltage threshold within the time threshold; determining whether a voltage at the at least one electric propulsion unit exceeds the voltage threshold; and wherein the pre-charging of the bus is in response to determining the bus voltage exceeds the voltage threshold within the time threshold and the voltage at the at least one electric propulsion unit exceeds the voltage threshold.

42. The computer-implemented method of claim 41, further comprising: determining whether a voltage associated with at the at least one electric propulsion unit exceeds the voltage threshold within another time threshold; andpre-charging the bus in response to determining the bus voltage exceeds the voltage threshold within the time threshold and the voltage at the at least one electric propulsion unit exceeds the voltage threshold in the another time threshold.

43. The computer-implemented method of claim 42, wherein the another time threshold is a longer time than the time threshold.

44. The computer-implemented method of claim 41, wherein controlling the first switching device to maintain the bus voltage above the voltage threshold comprises closing the first switching device in response to detecting a drop in the bus voltage.

45. The computer-implemented method of claim 41, further comprising: stopping controlling the first switching device to maintain the bus voltage above the voltage threshold based on determining the voltage at the at least one electric propulsion unit does not exceed the voltage threshold.

46. The computer-implemented method of claim 41, further comprising: providing a notification to a user device in response to determining the voltage at the at least one electric propulsion unit does not exceed the voltage threshold.

47. The computer-implemented method of any of claims 41-46, wherein the first switching device is a semiconductor device.

48. The computer-implemented method of any of claims 41-47, wherein toggling the first switching device comprises closing the first switching device to allow current flow through the first switching device during an amount of time that is between 0.5-10% of a duty cycle, before opening the first switching device.

49. The computer-implemented method of any of claims 41-48, wherein toggling the first switching device open and closed comprises toggling the switching device to apply a voltage periodically at a set interval.

50. The computer-implemented method of any of claims 41-49, wherein the voltage threshold comprises a value in a range of 5-60V, inclusive.

51. The computer-implemented method of any of claims 41-50, further comprising: stopping toggling the first switching device based on determining the voltage does not exceed the voltage threshold within the time threshold.

52. The computer-implemented method of any of claims 41-51, further comprising: providing a notification to a user device based on determining the voltage does not exceed the voltage threshold within the time threshold.

53. The computer-implemented method of claim 52, wherein the notification indicates an electrical issue.

54. The computer-implemented method of any of claims 41-53, further comprising: providing a single voltage pulse by closing and then opening the first switching device; and determining whether the bus voltage exceeds another voltage threshold, wherein pre-charging the bus is performed in response to determining the bus voltage does not exceed a second voltage threshold based on receiving the single voltage pulse.

55. The computer-implemented method of claim 54, wherein the second voltage threshold is zero.

56. The computer-implemented method of claim 55, further comprising: providing a notification to a user device in response to determining the bus voltage exceeds the second voltage threshold based on receiving the single voltage pulse.

57. A system for high voltage power control comprising at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of claims 40-56.

58. A computer-readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any of claims 40-56.

59. An aircraft, comprising: a battery pack; at least one electric propulsion unit powered by the battery pack; and at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of claims 40-56.

60. A computer-implemented method for battery balancing a battery pack of an aircraft, comprising: receiving a signal that a battery pack is to be disconnected from a common bus; detecting a level of each of multiple cells within the battery pack; detecting a level of each battery pack configured to be connected to the common bus; determining an adjustment for each of the multiple cells, wherein the adjustment: balances each of the multiple cells to have a first electrical state within a first threshold level of other cells within the battery pack; andbalances the battery pack to have a second electrical state within a second threshold level of each battery pack connected to the common bus; and controlling, for each of the multiple cells, a balancing resistor circuit according to the respective adjustment.

61. The computer-implemented method of claim 60, wherein the signal indicates a user selection made on an input device communicably connected to the aircraft.

62. The computer-implemented method of claim 61, wherein the input device is at least one of: a manual switch, knob, button, lever, or user interface element.

63. The computer-implemented method of any of claims 60-62, wherein detecting the level of each of the multiple cells within the battery pack comprises at least one of: detecting a voltage level or detecting a charge level of each of the multiple cells.

64. The computer-implemented method of any of claims 60-63, wherein detecting the level of each battery pack comprises detecting a voltage level of each battery pack.

65. The computer-implemented method of any of claims 60-64, wherein determining an adjustment required for each of the multiple cells within the battery pack comprises determining an adjustment based on an estimation of a voltage drop as each battery pack returns to open circuit voltage and an expected voltage drop from the each battery pack performing cell balancing.

66. The computer-implemented method of any of claims 60-65, wherein determining the adjustment required for each of the multiple cells is based on a respective resistivity of each of the multiple cells.

67. The computer-implemented method of any of claims 60-66, wherein, for each of the multiple cells, controlling the balancing resistor circuit comprises at least one of: transmitting a signal to a switching device of the balancing resistor circuit or transmitting a signal to a chip comprising the balancing resistor circuit.

68. The computer-implemented method of any of claims 60-67, wherein, for each of the multiple cells, controlling the balancing resistor circuit comprises transmitting a single signal indicative of a battery pack adjustment to balance the first electrical state of the respective cell within the first threshold of other cells.

69. The computer-implemented method of any of claims 60-68, wherein, for each of the multiple cells, controlling the balancing resistor circuit further comprises: monitoring a temperature of at least one of the battery pack, one or more cells of the battery pack, or a circuit board of the battery pack; andcontrolling the balancing resistor circuit to disable balancing in response to detecting the temperature exceeds a threshold.

70. The computer-implemented method of any of claims 60-69, wherein, for each of the multiple cells, controlling the balancing resistor circuit further comprises: controlling the balancing resistor circuit to disable balancing in response to detecting a switching device connecting the battery pack to the common bus is closed.

71. The computer-implemented method of any of claims 60-70, wherein the second threshold level is set or determined according to a pre-charging process that at least one battery pack connected to the common bus is configured to perform.

72. A system for high voltage power control comprising at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of claims 60-71.

73. A computer-readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any of claims 60-71.

74. An aircraft, comprising: a battery pack; at least one electric propulsion unit powered by the battery pack; and at least one processor configured to execute instructions to cause the at least one processor to perform the method of any of claims 60-71.

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