Battery system

Abstract

To provide a battery system in which connection of different battery packs in parallel surely minimizes before the connection, voltage imbalance between the different battery packs.SOLUTION: A battery system includes a power bus and a set of battery packs. Each battery pack has a battery pack module, a sensor board, and a power board. The sensor board receives the voltage difference between the battery packs not connected to the power bus and the power bus, determines whether the voltage difference indicates that the battery pack voltage is too high as compared with the power bus voltage, provides a discharge instruction for discharging the battery pack until the battery pack voltage is within a threshold voltage difference of the power bus using a power draw mechanism in accordance with the determination that the voltage difference indicates that the battery pack voltage is too high as compared with the power bus voltage, and provides a connection instruction to connect the disconnected battery pack to the power bus.SELECTED DRAWING: Figure 1B

Description

Background Art

[0001] When batteries are connected in parallel, the total resistance decreases, resulting in an increase in the total current capacity and an increase in the overall ampere-hour capacity. However, if not all of the battery packs in a parallel bank have the same voltage before connection, an overcurrent condition can occur, resulting in equipment damage and / or personal injury. For battery systems deployed in the field, assuming changes in the state of charge of each battery pack during transportation or storage, accurately matching the voltage of the packs before connection is impossible without significant effort and expense. Existing equalization and charging solutions are often complex, costly, time- and / or labor-intensive, and thus not practical for powering critical systems in remote locations.

Summary of the Invention

[0002] Various embodiments of the present invention are disclosed in the following detailed description and the accompanying drawings.

Brief Description of the Drawings

[0003]

Figure 1A

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Figure 1B

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Figure 2

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Figure 3A

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Figure 3B

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Figure 3C

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Figure 4A

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Figure 4B

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Figure 4C

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Figure 5

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Figure 6

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Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention can be realized in a number of ways, including as a method, a process, an apparatus, a system, a composition of an object, a computer program product embodied on a computer-readable storage medium, and / or a processor, for example, a processor configured to execute instructions stored in and / or provided by a memory coupled to the processor. In this specification, these embodiments, or any other form the present invention may take, may sometimes be referred to as techniques. Generally, the order of steps of the disclosed processes can be varied within the scope of the present invention. Unless otherwise stated, a processor or memory described as being configured to perform a task is realized as a general component configured to perform the task at a given time temporarily, or as a specific component manufactured to perform the task. As used herein, the term "processor" refers to one or more devices, circuits, and / or processing cores configured to process data such as computer program instructions.

[0016] A detailed description of one or more embodiments of the present invention is provided below along with the accompanying drawings that illustrate the principles of the present invention. The present invention is described in relation to such embodiments, but the present invention is not limited to any embodiments. The scope of the present invention is limited only by the claims, and the present invention includes numerous alternative forms, modifications, and equivalents. To provide a complete understanding of the present invention, numerous specific details are set forth in the following description. These details are provided for illustrative purposes, and the present invention may be practiced according to the claims without some or all of these specific details. Well-known technical items in the technical field related to the present invention are not described in detail so as not to unnecessarily obscure the present invention.

[0017] A self - equalizing battery system is disclosed. The system includes a power bus and a set of battery packs. One of the battery packs in the set of battery packs includes one or more batteries, a sensor board, and a power board. The power bus of the battery system is used to electrically connect the set of battery packs. The sensor board of one of the battery packs in the set of battery packs receives the voltage difference between a battery pack not connected to the power bus and the power bus, determines whether the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, and in response to determining that the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, provides a discharge instruction to discharge the battery pack using a power draw mechanism until the battery pack voltage is within the threshold voltage difference of the power bus, and provides a connection instruction to connect the disconnected battery pack to the power bus.

[0018] In some embodiments, in response to the battery pack voltage being too low, a signal to disconnect itself is transmitted via a communication bus to other packs connected to the bus, and then the first pack itself connects.

[0019] In some embodiments, the battery system includes a power bus and a set of battery packs. One of the battery packs in the set of battery packs includes one or more batteries, a sensor board, and a power board. The power bus is used to electrically connect the set of battery packs, and the sensor board receives the voltage difference between a battery pack not connected to the power bus and the power bus, determines whether the voltage difference indicates that the battery pack voltage is too low compared to the power bus voltage, and in response to determining that the voltage difference indicates that the battery pack voltage is too low compared to the power bus voltage, no immediate action is taken. The battery packs on the bus will continue to supply power to the load and discharge until both packs are within the voltage threshold for connection.

[0020] In some embodiments, the battery system comprises a power bus and a set of battery packs. One of the battery packs in the set of battery packs comprises one or more batteries, a sensor board, and a power board. The power bus is used to electrically connect the set of battery packs, and the sensor board receives a voltage difference between a battery pack not connected to the power bus and the power bus, determines whether the voltage difference indicates that the battery pack voltage is too low compared to the power bus voltage, and provides an overcharge instruction for transferring excess energy indicated by the voltage difference from the battery pack to one or more battery packs in response to determining that the voltage difference indicates that the battery pack voltage is too low compared to the power bus voltage, resulting in an increase in the voltage of the one or more battery packs.

[0021] Connecting battery packs in parallel presents the challenge of reliably minimizing voltage imbalance between different packs prior to connection. If the packs are connected to each other before such imbalance is corrected, excessive voltage imbalance can lead to high current conditions, which in some cases can lead to energy loss, equipment damage, meltdown, and / or fire. In addition to the attendant human safety issues associated with equipment meltdown and fire (e.g., high heat, toxic smoke, explosion hazard, etc.), loss of the battery system can lead to loss of power to critical loads.

[0022] The reason why the open-circuit voltage of each battery pack must be the same as the float voltage (e.g., the voltage of the distribution bus or the power bus) before connecting the packs in parallel is to avoid the so-called "circulating current" flowing between packs with different states of charge (SOC) or voltages. Connecting a new battery pack with a very low SOC or voltage to other packs with a very high SOC or voltage is particularly dangerous, especially when the existing battery packs are in float charge. This is because the new pack receives charging current not only from the existing packs but also from the battery charger (e.g., a solar charger or other types of chargers). Therefore, the new pack must be charged by a separate charging process until its voltage reaches the existing float voltage.

[0023] In the case of a battery system deployed in the field (e.g., at a remote location), assuming the changes that occur in the SOC of each pack during transportation or storage (e.g., due to variable and often unpredictable transportation times and temperatures, slight differences in the chemical properties of each pack, etc.), it is impossible to accurately match the voltages of the packs before connection without considerable effort and cost. In the case of replacement packs that will be exchanged for or added to an existing operational battery system, the float voltage of the operational system is also an unpredictable variable.

[0024] Existing solutions to this problem include a battery management system (i.e., a "regulation system") having a battery charge / discharge regulator between the battery and the distribution bus, or a connection via a switch / diode between the battery and the distribution bus (i.e., a "non-regulation system").

[0025] The most common approach to the regulation system is to insert a bidirectional DC / DC converter at the output stage of each battery to supply a stable output voltage to the distribution bus even when the battery packs are at different SOCs. The charge / discharge current of each battery pack can also be controlled by each DC / DC converter, and there will be no circulating current between different battery packs. However, this approach increases the number and cost of power electronic components, as well as the complexity of the system.

[0026] In contrast, an unregulated system does not have a bidirectional DC / DC converter at the output stage of each battery pack to supply a stable output voltage to the distribution bus. Instead, only a resistor or a diode is inserted between each pack and the distribution bus. For example, an external resistor is inserted to compensate for the deviation of the internal resistance of each battery pack so that the output voltages of each output stage are equal. The advantage of this approach is that the circulating current between different battery packs can be reduced using a resistor. This approach is easy to apply but has the drawback of extra power consumption due to the resistor during charge / discharge. Another solution is to replace the external resistor with a diode. The advantage of this approach is that there will be no circulating current between different battery packs due to the reverse blocking of the diode. However, even a Schottky diode with a small voltage drop, the diode will still cause extra power consumption during discharge. Furthermore, the main drawback of this approach is that the battery pack is only allowed to discharge.

[0027] The disclosed system includes an automated self-balancing system that can connect modular, replaceable battery packs to each other in a safely chainable and expandable manner and to a distribution bus (e.g., a power bus), while at the same time minimizing power consumption, the number of electronic components, system cost, and complexity, which is an improvement over other battery management systems. Additionally, unlike unregulated systems, the present system allows both charging and discharging of the battery packs connected in parallel while connected to the distribution bus, even when the bus is loaded.

[0028] In some embodiments, the system is used to power a remote load (e.g., an active sensor-based monitoring system). The ability to quickly add new battery packs to the power bus and / or replace existing packs that require maintenance minimizes the downtime of the remote load. In some embodiments, the remote load plays an important role in an active safety or security monitoring system (e.g., an anti-drone monitoring system) that needs to be constantly powered on.

[0029] In some embodiments, a monitoring system initially launched in the field benefits from the ability to deploy, install, and connect all necessary components (e.g., battery systems, sets of solar panels, sensor towers, etc.) without waiting for manual equalization of battery pack voltages. Once installed and connected, the disclosed battery system takes over the automated and rapid equalization and connection of battery packs to the power bus and thus energizes critical loads in a minimum amount of time. In some embodiments, the battery packs are manually charged to maximum SOC before transport, such that upon arrival at a remote location, the battery packs are typically at a voltage above the nominal power bus voltage despite losses incurred during transport. In this example, the disclosed battery system need only discharge excess charge from each pack in order to enable equalization of the packs prior to connection. This results in a more rapid connection and energization of the load than if the battery packs needed to be charged in the field.

[0030] In some embodiments, a monitoring system is already launched and operating in the field but additional power is needed (e.g., due to upgrading the monitoring system with additional operating components or replacing components with ones having greater power requirements). In this example, one or more new battery packs can be quickly installed and connected to the power bus without disconnecting any of the other installed battery system components due to their modular and expandable nature.

[0031] In some embodiments, a monitoring system is already launched and operating in the field but replacement of one or more installed battery packs is needed (e.g., due to a defective pack, a pack reaching the end of its useful life, preventive maintenance, etc.). In this example, the monitoring system is powered down, the modular packs are quickly replaced, and the disclosed battery system takes over rapid equalization, connection, and re-energization of the load.

[0032] In some embodiments, battery packs at any charge level can be connected. When the battery system is turned on, the processor determines a way to equalize and / or charge the various packs before connection to bring them all to the same SOC.

[0033] In some embodiments, the battery system includes a communication bus. In some embodiments, the battery packs communicate with each other through the communication bus (e.g., a dedicated serial line).

[0034] In some embodiments, when charging is possible (e.g., a dedicated charger or solar power), the pack with the lowest voltage closes and charging begins. The other packs discharge excess charge to match it and connect to the bus when their voltages match. When there is sufficient voltage on the bus (i.e., the nominal power bus voltage), the load is energized.

[0035] In some embodiments, when charging is not possible, the pack with the highest voltage is connected to the power bus and the load is turned on. As the battery discharges, its voltage will come to match that of the other packs. Charging is disabled until all packs are connected.

[0036] In some embodiments, a set of battery packs includes a master battery pack and one or more slave battery packs. In some embodiments, the master battery pack includes a charging unit. In some embodiments, the charging unit receives power from one or more solar panels.

[0037] In some embodiments, the first housing of the master battery pack and the second housing of the slave battery pack among the one or more slave battery packs are substantially the same in size and shape. In some embodiments, there is one master pack / housing and one or more slave battery packs / housings (e.g., 3, 5, 7, or any suitable number). In some embodiments, the one or more battery pack housings are ruggedized and sealed for use under harsh operating conditions in remote field conditions (e.g., high and low temperature / humidity, rain, snow, wind, dust, sand, etc.).

[0038] In some embodiments, all packs include a contactor for connecting itself to the power bus and a power draw mechanism (e.g., a bleed resistor) for self-discharging for equalization. In some embodiments, the master pack controls the equalization of all packs and the closing of the contactors. In some embodiments, the sensor board of the master battery pack includes a voltage sensor, a processor, and a voltage differential computer used to determine the voltage difference between the disconnected battery pack and the power bus.

[0039] In various embodiments, the power draw mechanism includes a bleed resistor, a small vibration motor, a series of LEDs, or any other device that consumes power.

[0040] In some embodiments, a state machine encoded in the firmware of the master pack sensor board processor monitors the battery voltage, determines which pack should bleed / close its contactor, and also processes the charging of the pack.

[0041] In some embodiments, the master state machine includes the following states: (i) When the battery system is off, all packs have their contactors open and are in a low-power state. (ii) When the battery system is on, the master selects the pack that closes its contactor first. If there is external power available for charging the battery (e.g., solar energy or other external power sources), the pack with the lowest voltage is closed first. (iii) The master enables charging and the pack with the lowest voltage begins to rise. All other packs are discharged to equalize the packs. When the voltages become equal, upon instruction by the master, each pack connects. (iv) If there is no available external power, the master closes the pack with the highest voltage first. The pack discharges power to lower its voltage, or if a load is connected and operating, the load discharges the pack. (v) As the voltage drops, once the voltages are equalized, other packs will be connected. Then, once charging power becomes available, all packs can be charged together. (vi) If a battery pack reports an error where it will not be able to close its contactor, the master ignores that pack and does not attempt to equalize that pack or connect it to the remaining packs. This error is reported to a computer so that the pack can be replaced or repaired.

[0042] In some embodiments, a dedicated serial line transmits commands from the master pack to the slave packs. In some embodiments, a dedicated serial line is used to transmit battery pack voltages and any pack errors (e.g., to the master pack). In some embodiments, when a slave pack needs to discharge excess charge, a command is sent to the slave pack sensor board processor to instruct the power draw mechanism (e.g., bleed resistor) contactor on the slave pack power board to close.

[0043] In some embodiments, in response to determining that the voltage difference indicates that the voltage of the disconnected battery pack is within the threshold of the power bus voltage, the sensor board processor of the master battery pack provides an instruction to connect the disconnected battery pack to the power bus by instructing to close the electrical contactor. In some embodiments, the electrical contactor used to connect the disconnected battery pack to the power bus is located on the power board of the disconnected battery.

[0044] In some embodiments, in response to determining that the voltage difference indicates that the voltage of the disconnected battery pack is too high, the sensor board processor of the master battery pack provides a discharge instruction to discharge the disconnected battery pack using a power draw mechanism (e.g., a bleed resistor) until the battery pack voltage is within the threshold voltage difference of the power bus. In some embodiments, the power draw mechanism (e.g., a bleed resistor) is located within the housing of the disconnected battery pack.

[0045] In some embodiments, the power draw mechanism comprises a bleed resistor, and the bleed resistor extracts excess energy in the form of heat. In some embodiments, heat is used to reach a target operating temperature specific to the battery system, battery pack, battery pack module, or any other suitable component.

[0046] In some embodiments, a computer is connected to the battery system. In some embodiments, the computer is a stand-alone computer connected to the battery through a Controller Area Network (CAN) bus. In some embodiments, the computer further comprises a memory and / or a user interface coupled to a computer processor and configured to provide instructions to the processor. In some embodiments, the computer is also used as part of controlling and monitoring a larger system (e.g., an active monitoring system) powered by the battery system.

[0047] In some embodiments, the computer is connected to the sensor boards within each battery pack via a CAN bus. In some embodiments, the sensor boards of one or more battery packs include a voltage sensor and a processor. In some embodiments, firmware is used to command the battery pack sensor board processor. In some embodiments, the firmware includes several asynchronous threads. In some embodiments, the asynchronous threads include reading sensor data (e.g., voltage, temperature, etc.), responding to requests for data from the master pack via a dedicated serial line (only for slave packs), receiving and responding to commands via CAN (e.g., returning sensor data, reading contactor status, etc.), and / or communicating with a dedicated BMU to confirm that no battery problems have been detected.

[0048] In some embodiments, the computer is used to monitor and record the status of the battery pack. In some embodiments, each pack includes an independent battery management unit (BMU) that checks whether there are any problems with the battery pack. In some embodiments, the computer locally stores the battery pack status and other diagnostic information, and / or uploads such information to a cloud network for remote communication with the end user. In some embodiments, each battery pack sensor board optionally has its own internal sensor data storage that saves all snapshots of its data. In some embodiments, the internal sensor data storage holds data for several days in a log file.

[0049] Figure 1A is a block diagram showing an embodiment of a battery system that supplies power to a load. In the illustrated example, battery system 2 is used to supply power to load 12. By including an automated self-balancing system, battery system 2 can easily and quickly add or replace battery packs to the power bus, minimizing downtime. For example, load 12 can include a perimeter monitoring system, a perimeter defense system, or any other suitable system that is remotely located from immediately available power. Battery system 2 is charged by external charger 4 or by one or more of solar panel 6, solar panel 8, and solar panel 10. Computer 14 is used to monitor and record battery system conditions (e.g., the SOC or voltage of individual packs, the state of health of the battery, the number and / or timing of charge / discharge cycles, or any other suitable system diagnostics). Computer 14 receives battery system data and other diagnostic information from battery system 2 via communication interface 20 for processing by processor 16. For example, battery system 2 may periodically send to computer 14 battery pack voltage, temperature, depth of discharge, and any other suitable information regarding the state or health of battery system 2 so as to track system performance over time. In other embodiments, computer 14 may request such information from battery system 2. Processor 16 uses memory 18 to temporarily store (e.g., instructions and / or data) and assist in the processing of the received battery system data until this data is moved to long-term storage in data storage unit 22. The processed data becomes available to user display 28 via I / O interface 24. User input 26 is used to input or request additional battery system information from computer 14. Computer 14 stores such information locally (e.g., in data storage unit 22) and / or uploads it to a cloud network (not shown) for transmission to remote end users.

[0050] Figure 1B is a block diagram showing an embodiment of a battery system. In some embodiments, battery system 101 corresponds to battery system 2 in Figure 1A. In some embodiments, one or more battery packs are electrically connected in parallel. In some embodiments, the battery cells among one or more battery packs are electrically connected in series and parallel configurations. For example, a battery pack includes N battery modules connected in parallel, each module includes M sets of cells connected in series, and each set of cells connected in series includes L cells connected in parallel (For example, each of the N parallel modules has M sets of cells connected in series, each of which is L parallel cells. For example, in some cases, for a 4-module 6p3s configuration, N = 4, M = 3, and L = 6).

[0051] In the illustrated example, battery system 101 includes master battery pack 100, slave battery pack 120, slave battery pack 130, and slave battery pack 140. Additional slave battery packs can be added (e.g., expanded) to battery system 101 via power bus expansion node 182 and communication bus expansion node 180. An external battery charger (e.g., an external charger having its own charge regulation circuit) can be connected to power bus expansion node 182.

[0052] The power bus of battery system 101 includes power bus 152, power bus 162, power bus 172, and other power bus wiring (not shown) inside each battery pack. The power bus includes electrical cables selected to support the current requirements and environmental operating conditions of battery system 101. Power bus 152, power bus 162, and power bus 172 connect to power board 108, power board 128, power board 138, and power board 148.

[0053] The communication bus of the battery system 101 includes communication bus 150, communication bus 160, communication bus 170, and other communication bus wirings (not shown) within each battery pack. The communication bus of the battery system 101 includes an electrical cable selected to support the communication requirements of the battery system 101 (e.g., dedicated serial line, parallel line, optical line, etc.) and the environmental operating conditions. Communication bus 150, communication bus 160, and communication bus 170 are used to connect sensor board 104, sensor board 124, sensor board 134, and sensor board 144.

[0054] The master battery pack 100 includes battery module 102, sensor board 104, battery management unit (BMU) 106, power board 108, solar charger 110, solar power input connection 116, and load output connection 112. The battery module 102 includes one or more individual battery modules (e.g., two or any other appropriate number of battery modules). The solar power input connection 116 provides a connection to one or more solar panels (e.g., one, two, three, or any other appropriate number of solar panels that enable charging of the battery module).

[0055] The master battery pack 100 communicates with the slave battery pack 120, the slave battery pack 130, and the slave battery pack 140 via the communication bus of the battery system 101. The master battery pack 100 supplies power to an external load via the power bus and the load output connector 112 of the battery system 101.

[0056] The slave battery pack 120 includes a battery module 122, a sensor board 124, a BMU 126, and a power board 128. Similarly, the slave battery pack 130 includes a battery module 132, a sensor board 134, a BMU 136, and a power board 138, and the slave battery pack 140 includes a battery module 142, a sensor board 144, a BMU 146, and a power board 148. The slave battery pack 120, the slave battery pack 130, and the slave battery pack 140 are substantially similar to each other. In various embodiments, each of the battery module 122, the battery module 132, and the battery module 142 includes one, two, three, four, five, or any other suitable number of individual battery modules.

[0057] In some embodiments, the individual battery modules of the battery module 102, the battery module 122, the battery module 132, and the battery module 142 are substantially the same in size and shape to each other. In some embodiments, the number of the battery modules 102 is selected to allow for the physical space for the solar charger 110 when using a battery pack housing that is substantially the same in size and shape as the housings used for the slave battery pack 120, the slave battery pack 130, and the slave battery pack 140. For example, if four individual battery modules that are substantially the same in size and shape to each other fit within the slave battery pack housing and the solar charger 110 occupies the space of two individual battery modules, up to two individual battery modules will fit within a housing of the same size and shape that includes the master battery pack 100.

[0058] FIG. 2 is a block diagram showing one embodiment of a sensor board. In various embodiments, sensor board 201 includes sensor board 104, sensor board 124, sensor board 134, or sensor board 144 of FIG. 1B. In the illustrated example, sensor board 201 includes a sensor board processor 200, a voltage difference calculator 202, an on-board humidity and temperature sensor 204, an external thermistor 206, a load and ground fault current sensor 208, a high voltage interlock loop (HVIL) connector 210, a battery management unit (BMU) signal connector 212, a communication management unit (CMU) signal connector 214, a memory 216, a user interface 218, a voltage sensor 220, a contactor control board 222, a power draw mechanism switch 224, an LED indicator 226, a voltage reference 228, a power supply unit 230, a solar charger hardware 232, a CAN transceiver / controller 234, and a communication interface 236.

[0059] The sensor board processor 200 controls one or more switches (e.g., contactors on the power board) via the contactor control board 222 and uses this switch to (i) connect one or more battery modules to the power bus or the power draw mechanism; (ii) connect a solar charger or an external charger to the power bus; or (iii) connect the power bus to an external load.

[0060] The voltage difference calculator 202 is used to determine the voltage difference between the battery pack and the power bus. In some embodiments, the voltage difference calculator 202 is implemented on the master battery pack sensor board to calculate the voltage difference between the battery and bus voltage values received from one or more slave battery packs and the power bus.

[0061] The sensor board processor 200 is powered via the power supply unit 230 in cooperation with the voltage reference 228, and the sensor board processor is used to receive the voltage difference between the battery pack not connected to the power bus (i.e., the disconnected battery pack) and the power bus and store it in the memory 216; Using the voltage difference calculator 202, it is determined whether the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage; In response to determining that the voltage difference indicates that the disconnected battery pack voltage is too high compared to the power bus voltage, a command to close the bleed resistor switch in the disconnected battery pack is transmitted via the communication interface 236, or if the disconnected battery pack includes a sensor board 201, a discharge instruction for discharging the battery pack is provided by transmitting a connection instruction to the power draw mechanism switch 224 until the voltage of the disconnected battery pack is within the threshold voltage difference of the power bus; And a connection instruction for connecting the disconnected battery pack to the power bus is provided via the communication interface 236, or if the disconnected battery pack includes a sensor board 201, a connection instruction is provided by transmitting a connection instruction via the contactor control board 222.

[0062] Firmware is used to command the sensor board processor 200. In various embodiments, a state machine encoded in the firmware of the sensor board processor 200 monitors the voltages of one or more battery packs, determines which packs to draw power from (e.g., bleeding / closing their bleed resistor contactors), and also processes the charging of the packs.

[0063] In some embodiments, the firmware includes several asynchronous threads. In the illustrated example, the asynchronous threads include reading sensor data from the on-board humidity and temperature sensor 204 for measuring the humidity and temperature inside the battery system, the external thermistor 206 for measuring the temperature outside the battery system, the load and ground fault current sensor 208 for measuring the current supplied to the external load and identifying ground faults (e.g., due to insulation breakdown), and the voltage sensor 220 for measuring the voltage of the power bus.

[0064] In some embodiments, the asynchronous thread includes responding to data requests from a master pack via a dedicated serial line, e.g., via a communication management unit (CMU) signal connector 214.

[0065] In various embodiments, the asynchronous thread includes receiving and responding to commands via a controller area network (CAN) (e.g., returning sensor data, reading contactor states, etc.), and / or communicating with a dedicated battery management unit (BMU) via a BMU signal connector 212 to confirm that no battery problems have been detected.

[0066] The sensor board processor 200 is used to communicate with other battery packs through a communication bus (e.g., a dedicated serial line) via a CAN transceiver / controller 234 and a communication interface 236. In some embodiments, a computer is connected to the sensor board processor 200 via a CAN bus. In some embodiments, user commands can be communicated to the sensor board processor 200 via a user interface 218.

[0067] In some embodiments, a solar charger 232 is used in a master battery pack (e.g., master battery pack 100 of FIG. 1B). In various embodiments, the solar charger 232 is used to read the solar voltage or to operate a solar / load contactor. In some embodiments, a load and ground fault current sensor 208 is used as a battery current sensor (e.g., in a slave battery pack). In some embodiments, the load and ground fault current sensor 208 is used to monitor the current supplied to an external load. In some embodiments, a high voltage interlock loop (HVIL) connector 210 is used as a safety mechanism to provide an alarm to a system operator if any of the high voltage access points are open. In some embodiments, the alarm includes illuminating one or more LED indicators 226. In some embodiments, the LED indicators 226 are installed on the battery pack housing including the sensor board 201 (e.g., on an external panel). In various embodiments, the LED indicators 226 are used to indicate the state of one or more of the following battery pack conditions: A battery module is connected to the power bus; A battery module is connected to the power draw mechanism; Or, the power bus is connected to an external load.

[0068] Figure 3A is a block diagram showing an embodiment of a power board in relation to main components including a slave battery pack. In various embodiments, the slave battery pack 301 includes the power board and related components of the slave battery pack 120, slave battery pack 130, or slave battery pack 140 of FIG. 1B. In the illustrated example, the power board 300 includes one or more electrical contactors, and the electrical contactor among the one or more electrical contactors receives an instruction to open or close from the sensor board 310. Using the electrical contactor among the one or more electrical contactors on the power board 300, the battery modules 302, 304, 306, and / or 308 are connected to or disconnected from the power bus via the power bus connectors 326 and 328. The battery modules 302, 304, 306, and 308 are connected to the power board 300 via electrical cables.

[0069] The sensor board 310 receives, via the communication bus connector 324, a discharge instruction from a master battery pack (not shown) to discharge the battery modules 302, 304, 306, and / or 308 using the power draw mechanism 322 until the voltages of the battery modules 302, 304, 306, and / or 308 fall within the threshold voltage difference of the power bus. The power draw mechanism 322 is used to extract excess energy in the form of heat (i.e., resistive heating). In some embodiments, other power draw mechanisms (not shown) send excess energy from the battery modules 302, 304, 306, and / or 308 to one or more other battery packs (not shown) to increase the state of charge (SOC) of the one or more other battery packs.

[0070] Battery modules 302, 304, 306, and 308 are modular (i.e., each module can be replaced without affecting the rest of the system). Battery modules 302, 304, 306, and 308 each comprise one or more battery cells. A battery management unit (BMU) 316 is used to determine the voltage of the one or more battery cells. BMU 316 equalizes the voltage across the battery cells of battery modules 302, 304, 306, and 308. In some embodiments, BMU 316 depends on current sensor 314 to limit the current between cells to a safe level while equalizing the cell voltages (e.g., to prevent overheating or equipment damage). In some embodiments, current sensor 314 comprises a current sense amplifier and a microcontroller unit (e.g., having an integrated analog-to-digital converter). In some embodiments, current sensor 314 comprises a “battery fuel gauge,” also known as a “battery gas gauge,” for determining the battery state of charge (SOC) and health. The battery fuel gauge integrated circuit can predict how long the battery can supply power under specific operating conditions.

[0071] BMU 316 communicates with the battery cells in battery modules 302, 304, 306, and 308 via BMU communication bus 318. In some embodiments, additional battery modules can be added to BMU 316 via expansion node 320. In some embodiments, panel LED 312 is used to notify the system operator whether battery modules 302, 304, 306, and / or 308 are connected to or disconnected from the power bus.

[0072] Figure 3B is a block diagram showing an embodiment of a sensor board control switch used to connect one or more battery modules to a power bus. In some embodiments, the sensor board control switch includes the slave battery pack 301 of FIG. 3A. In some embodiments, the sensor board control switch includes a master battery pack. In the illustrated example, battery module 342, battery module 344, battery module 346, and battery module 348 are connected in parallel by electrical cables to power board 340 (i.e., battery modules connected in parallel). The battery modules connected in parallel send power through switch 352 and supply power to the power bus via power bus connector 356 and power bus connector 358. Power bus connector 356 and power bus connector 358 are used to connect the battery modules connected in parallel to one or more other battery packs (e.g., other slave battery packs or master battery packs). Sensor board 350 controls and monitors the position of switch 352 (e.g., an electrical contactor) to connect or disconnect the battery modules connected in parallel to the power bus. [[ID=!]]

[0073] In some embodiments, a master battery pack (not shown) sends an instruction to sensor board 350 to open or close switch 352. In various embodiments, sensor board 350 reports the position of switch 352 (e.g., open position or closed position) to the master battery pack at periodic time intervals, when the switch position changes and is confirmed, or at any other appropriate time when queried by the master battery pack. In various embodiments, sensor board 350 reports the position of switch 352 to a computer (e.g., computer 14 of FIG. 1A) or to panel LEDs outside the battery pack housing. In some embodiments, the position of switch 350 is inferred from the presence or absence of a control signal applied to switch 352 by sensor board 350.

[0074] In some embodiments, the power board 340 includes more switches to switch battery modules (e.g., battery module 342, battery module 344, battery module 346, battery module 348, etc.) to the power bus connector 356 and / or the power bus connector 358 either in groups or individually.

[0075] Figure 3C is a block diagram showing an embodiment of a sensor board control switch used to connect one or more battery modules to a bleed resistor. In some embodiments, the sensor board control switch comprises the slave battery pack 301 of FIG. 3A. In some embodiments, the sensor board control switch comprises a master battery pack. In the illustrated example, battery modules 372, 374, 376, and 378 are connected in parallel (i.e., parallel-connected battery modules) by electrical cables to the power board 370. The parallel-connected battery modules allow current to flow through switch 384 and sensor board 380 to the power draw mechanism 382 so as to discharge excess charge (e.g., in the form of resistive heating). The sensor board 380 controls and monitors the position of a switch 384 (e.g., an electrical contactor) to connect or disconnect the parallel-connected battery modules to / from the power draw mechanism 382.

[0076] In some embodiments, a master battery pack (not shown) sends an instruction to the sensor board 380 to open or close the switch 384. In various embodiments, when the switch position changes and the switch position is confirmed, at periodic time intervals, or at any other appropriate time when queried by the master battery pack, the sensor board 380 reports the position of the switch 384 (e.g., open position or closed position) to the master battery pack. In various embodiments, the sensor board 380 reports the position of the switch 384 to a computer (e.g., the computer 14 of FIG. 1A) or to a panel LED outside the battery pack housing. In some embodiments, the position of the switch 384 is estimated from the presence or absence of a control signal applied to the switch 384 by the sensor board 380.

[0077] In some embodiments, the power board 370 includes more switches to switch battery modules (e.g., battery module 372, battery module 374, battery module 376, battery module 378, etc.) to the power draw mechanism 382 in groups or individually.

[0078] FIG. 4A is a block diagram showing an embodiment of a power board in relation to the main components including a master battery pack. In some embodiments, the master battery pack 401 includes the power board and related components of the master battery pack 100 of FIG. 1B. In the illustrated example, the battery module 404 and the battery module 406 are connected in parallel to the power board 400 via electrical cables. The power board 400 includes one or more electrical contactors, and the electrical contactor among the one or more electrical contactors receives an instruction to open or close from the sensor board 410. The electrical contactor among the one or more electrical contactors on the power board 400 is used to connect or disconnect the battery module 404 and the battery module 406 to / from the power bus (e.g., determined and controlled by a firmware program operating on the sensor board 410) via the power bus connector 426.

[0079] Using other electrical contactors among one or more electrical contactors on the power board 400, the solar charger 402 is connected to the solar connector 428. Using the solar charger 402, the battery module 404 and the battery module 406, and / or other battery packs connected to the power bus as determined by a firmware program operating on the sensor board 410 are charged. The solar power input connection 428 provides a connection to one or more solar panels (e.g., one, two, three, or any other suitable number of solar panels that enable charging of the battery module).

[0080] The sensor board 410 receives voltage data from one or more voltage sensors, for example, from a voltage sensor on the sensor board 410 or from another sensor board on another battery pack (e.g., from a slave battery pack via the communication bus connector 424), and receives voltage data from the power bus (e.g., via a voltage sensor on the sensor board 410). The sensor board 410 determines whether the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, and in response to determining that the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, provides a discharge instruction to discharge the battery pack using a power draw mechanism (e.g., a bleed resistor, a motor, an LED, etc.) until the battery pack voltage is within the threshold voltage difference of the power bus.

[0081] In the illustrated example, if the voltages of the parallel-connected battery modules 404 and 406 are too high compared to the power bus voltage, the sensor board 410 provides a discharge instruction for discharging the battery modules 404 and 406 using the power draw mechanism 422 to the switches on the power board 400. If the voltages of other battery packs are too high compared to the power bus voltage, the sensor board 410 provides a discharge instruction for discharging their battery modules using their on-board power draw mechanisms to one or more other battery packs via the communication bus connector 424.

[0082] The power draw mechanism 422 is used to extract excess energy in the form of heat. In some embodiments, other power draw mechanisms (not shown) send the excess energy from the battery modules 404 and 406 to one or more other battery packs to increase the SOC of the one or more other battery packs.

[0083] When the battery modules 404 and 406 are within the threshold voltage difference of the power bus, the sensor board 410 provides a connection instruction for connecting the battery modules 404 and 406 to the power bus to one or more electrical contactors on the power board 400.

[0084] If one or more battery packs are fully charged and connected to the power bus such that they are sufficient to power an external load as determined by the sensor board 410, the sensor board 410 provides a connection instruction to one or more electrical contactors on the power board 400 to connect the power bus to the external load via the load connector 430. The Ethernet connector 432 provides a communication path for a computer program (e.g., via an Ethernet cable or via a wireless Ethernet adapter), and / or the system operator determines whether to remotely connect or disconnect the power bus from the external load (e.g., for system malfunction, fire, or any other suitable safety or maintenance purpose). The user interface 408 provides local means for the system operator to control the state of the battery system (e.g., connect or disconnect the external load from the power bus). In some embodiments, the user interface 408 includes a key switch for controlling the state of the battery system.

[0085] The battery modules 404 and 406 are modular. The battery modules 404 and 406 each include one or more battery cells. A battery management unit (BMU) 416 is used to determine the voltage of the one or more battery cells. The BMU 416 equalizes the voltage across all the battery cells of the battery modules 404 and 406. In some embodiments, the BMU 416 relies on the current sensor 414 to limit the current between cells to a safe level while equalizing the cell voltages. In some embodiments, the current sensor 414 includes a current sense amplifier and a microcontroller unit. In some embodiments, the current sensor 414 includes a battery fuel gauge for determining the battery state of charge and health.

[0086] The BMU 416 communicates with the battery cells in the battery modules 404 and 406 via the BMU communication bus 418. In some embodiments, additional battery modules can be added to the BMU 416 via the expansion node 420. In some embodiments, the panel LED 412 is used to notify the system operator whether the battery modules 404 and 406 are connected to the power bus or disconnected from the power bus.

[0087] FIG. 4B is a block diagram showing an embodiment of a sensor board control switch used to connect a set of photovoltaic panels to the power bus via a solar charger. In some embodiments, the sensor board control switch and the solar charger comprise the master battery pack 401 of FIG. 4A. In some embodiments, the set of photovoltaic panels comprises the solar panels 6, 8, and 10 of FIG. 1A. In the illustrated example, the battery modules 444 and 446 are connected in parallel to the power board 440 via electrical cables. A set of photovoltaic panels (not shown) is connected to the power board 440 via the solar connector 458. When the switch 452 is open, the solar charger 442 is connected to the power board 440 and is electrically floating on the power bus via the power bus connector 456.

[0088] The power board 440 comprises one or more electrical contactors, and the electrical contactor among the one or more electrical contactors receives an instruction to open or close from the sensor board 450. The electrical contactor among the one or more electrical contactors on the power board 440 is used such that the solar charger 442 is connected to or disconnected from the set of photovoltaic panels (determined and controlled by, for example, a firmware program operating on the sensor board 450). The sensor board 450 controls and monitors the position of the switch 452 (for example, by opening or closing the electrical contactor).

[0089] In various embodiments, the sensor board 450 reports the position of the switch 452 to a computer (e.g., computer 14 of FIG. 1A) or to panel LEDs outside the battery pack housing. In some embodiments, the position of the switch 450 is inferred from the presence or absence of a control signal applied to the switch 452 by the sensor board 450.

[0090] FIG. 4C is a block diagram showing one embodiment of a set of sensor board control switches used to connect one or more battery modules to a power bus and / or to an external load. In some embodiments, the sensor board control switch comprises the master battery pack 401 of FIG. 4A. In some embodiments, the external load comprises the load 12 of FIG. 1A. In the illustrated example, battery modules 464 and 466 are connected in parallel to the power board 460 via electrical cables. An external load (not shown) is connected to the power board 460 via a load connector 480. The solar charger 462 is used to charge the battery modules 464 and 466 and / or other battery packs connected to the power bus as determined by a firmware program operating on the sensor board 470.

[0091] The power board 460 comprises one or more electrical contactors, and the electrical contactor among the one or more electrical contactors receives an instruction to open or close from the sensor board 470. The electrical contactor among the one or more electrical contactors on the power board 460 is used to connect or disconnect the battery modules 464 and 466 via the power bus connector 476 as determined and controlled by a firmware program operating on the sensor board 470 (e.g., to connect to or disconnect from the power bus). The sensor board 470 controls and monitors the positions of the switches 472 and 474 (e.g., by opening or closing the electrical contactors).

[0092] In various embodiments, the sensor board 470 reports the positions of switch 472 and / or switch 474 to a computer (e.g., computer 14 of FIG. 1A) or to panel LEDs outside the battery pack housing. In various embodiments, the positions of switch 472 and switch 474 are estimated from the presence or absence of control signals applied to switches 472 and 474 by sensor board 470. In some embodiments, a voltage sensor (e.g., a voltage sensor on sensor board 470) measures the voltage between switch 474 and load connector 480 to determine whether switch 474 is open or closed.

[0093] FIG. 5 is a flow diagram illustrating one embodiment of a method for equalizing a battery system. In some embodiments, the process of FIG. 5 is executed using the processor of sensor board 201 of FIG. 2. In various embodiments, the process of FIG. 5 is executed, in whole or in part, using the sensor board processors of one or more slave battery packs. In various embodiments, the process of FIG. 5 is executed, in whole or in part, using the sensor board processor of the master battery pack. In various embodiments, the process of FIG. 5 is executed using any suitable combination of one or more sensor board processors.

[0094] In the illustrated example, the process of FIG. 5 is to receive, at the sensor board, the voltage difference between the battery pack not connected to the power bus and the power bus, wherein one battery pack of the set of battery packs includes one or more batteries, a sensor board, and a power board, and the power bus is used to electrically connect the set of battery packs, and to use the sensor board to determine whether the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, and in response to determining that the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, to provide a discharge instruction to discharge the battery pack using a bleed resistor until the battery pack voltage is within the threshold voltage difference of the power bus, and to provide a connection instruction to connect the disconnected battery pack to the power bus.

[0095] In the illustrated example, at 500, the voltage difference between the battery pack not connected to the power bus and the set of battery packs connected to the power bus is received. For example, the voltage difference between a slave battery pack not connected to the power bus and the power bus connected to one or more other battery packs is received. In some embodiments, the voltage difference is calculated by the slave battery pack and transmitted to the master battery pack. In some embodiments, voltage data from the slave battery pack is transmitted to the master battery pack and used by the master battery pack sensor board to determine the voltage difference between the slave battery pack and the power bus. In another example, the voltage difference of the master battery pack from the power bus voltage (i.e., the voltage corresponding to one or more other battery packs connected to the power bus) is determined by the master battery pack (e.g., for use in determining whether the master battery pack is ready to be connected to the power bus).

[0096] At 502, it is determined whether the voltage difference indicates that the voltage of the disconnected battery pack is too high compared to the voltage of the power bus. For example, the voltage measurement of the disconnected battery pack and the power bus is performed by the on-board voltage sensor of the disconnected battery pack, and the data is transmitted to the sensor board of the disconnected battery pack to calculate the voltage difference. In some embodiments, the voltage data is transmitted to the master battery pack sensor board to calculate the voltage difference.

[0097] In some embodiments, the disconnected battery pack will be discharged if its voltage is too high. In some embodiments, the disconnected battery pack will wait indefinitely for the power bus voltage to naturally equalize with respect to the disconnected battery pack (e.g., due to the load discharging the battery pack connected to the bus).

[0098] In response to determining that the voltage difference indicates that the voltage of the disconnected battery pack is too high compared to the voltage of the power bus, the control moves to 504. For example, the disconnected battery pack is pre-charged to the maximum SOC before transportation, and as a result, upon arrival at the installation location, before installation into the battery system (e.g., attached to a rack, cabinet, box, or any other suitable type of battery system enclosure or support and connected to other battery packs via cables), despite the losses incurred during transportation, the battery pack is at a voltage above the nominal power bus voltage despite the losses suffered during transportation. In some embodiments, the excessive voltage value is transmitted to the local or remote system operator through the communication bus.

[0099] At 504, a discharge instruction is provided to discharge the battery pack using the power draw mechanism. For example, the discharge instruction is sent from the master battery pack (e.g., the master battery pack that has determined to be in too high a voltage state) to the battery pack sensor board, closing a switch or contactor on the battery pack power board, and connecting the battery module with too high a voltage to the power draw mechanism incorporated in the battery pack housing with too high a voltage. In various embodiments, other power draw mechanisms, or any other suitable intelligent circuit that limits or controls the flow of current during charging, send excess energy from the battery module with too high a voltage to one or more other battery packs to increase the SOC of the one or more other battery packs.

[0100] At 502, in response to determining that the voltage difference indicates that the voltage of the disconnected battery pack is too high compared to the voltage of the power bus, the control moves to 506. At 506, it is determined whether the battery pack voltage is within the threshold voltage difference of the power bus. For example, it is determined whether the battery pack voltage is within 100 mV, or within any other suitable threshold voltage difference of the power bus. The threshold voltage difference is determined based on various battery system design parameters, such as load power requirements, internal battery resistance (e.g., about 6 milliohms), peak current conditions (e.g., switch-on inrush current or switch-off voltage spike), and the maximum allowable current for electrical cables and other electrical components of the battery system (e.g., 120 amperes or any other suitable maximum allowable current). In various embodiments, the threshold voltage difference is stored in the system memory (e.g., the memory of the sensor board processor) or programmed into the firmware used to control the battery system.

[0101] In response to determining that the battery pack voltage is not within the power bus threshold voltage difference, control returns to 502. In response to determining that the battery pack voltage is within the power bus threshold voltage difference, control moves to 508. At 508, a connection instruction for connecting the disconnected battery pack to the power bus is provided and the process ends. For example, the connection instruction is communicated to the local sensor board, master battery pack sensor board, external computer, and / or system user by any suitable means (e.g., Ethernet connection, wireless network, cloud-based network, etc.).

[0102] FIG. 6 is a flowchart illustrating one embodiment of a method for charging a battery system. In some embodiments, the process of FIG. 6 is performed using the master battery pack 401 of FIG. 4A. In some embodiments, the process of FIG. 6 utilizes a solar charger (e.g., solar charger 402 of FIG. 4A) provided by a photovoltaic panel (e.g., one or more of solar panels 6, 8, or 10 of FIG. 1A).

[0103] In various embodiments, the process of FIG. 6 utilizes an external charger (e.g., trickle charger, rapid charger, intelligent charger, pulse charger, portable charger, diesel-driven charger, solar power charger, or any other suitable type of charger). In some embodiments, the external charger (i.e., external to the battery system) is connected to the power bus through an empty power bus connector (e.g., power bus expansion node) in the last slave pack in a set of battery packs. In some embodiments, the external charger includes a switch used to connect or disconnect the external charger from the power bus (e.g., manual switch or remotely controllable switch). In various embodiments, connecting or disconnecting the external charger is performed remotely (e.g., using a signal transmitted to the external charger via a communication bus) or manually (e.g., commanded by a system operator via a user display).

[0104] In the illustrated example, the process of FIG. 6 is used to charge one or more battery packs. In various embodiments, the battery pack includes a master battery pack and one or more slave battery packs. In some embodiments, charging is determined and controlled by firmware encoded (e.g., using a state machine) and placed within the master pack sensor board processor.

[0105] In the illustrated example, at 600, an instruction to start the charging program is received. For example, a system operator instructs the master battery pack to start the charging program via a user interface or communication bus. In some embodiments, the user interface includes a manual switch to start the charging program. In some embodiments, the start instruction is provided to a computer by user input and transmitted to the master battery pack via a communication bus or any other suitable means (e.g., Ethernet connection, wireless network, cloud-based network, etc.). In some embodiments, the decision to start the charging program is implemented by a state machine encoded in the firmware of the master pack sensor board processor.

[0106] At 602, the voltage of the power bus is received. For example, a voltage measurement of the power bus is performed by an on-board voltage sensor within the master battery pack and transmitted to the sensor board of the master battery pack.

[0107] At 604, it is determined whether the voltage of the power bus is within a desired power bus voltage range. For example, the sensor board processor of the master battery pack compares the power bus voltage with the voltage range (e.g., nominal voltage range) required to operate a load (e.g., a sensor-based monitoring system).

[0108] In response to determining that the voltage of the power bus is within the desired power bus voltage range, the control returns to 602. In this example, there is no need to charge the battery system, and the process loops until charging is required. For example, the power bus voltage is periodically measured such that it is determined by the firmware operating on the master pack sensor board until the voltage drops below the desired power bus voltage range.

[0109] At 606, an indication of the charger switch state is received. For example, using the presence or absence of a control signal applied to the charger switch, the charger switch state (i.e., whether the charger switch is open or closed) is determined, and that state is communicated (e.g., via a communication bus) to the sensor board of the master battery pack and received by the sensor board of the master battery pack. For a manual switch on an external charger, the system operator visually determines the switch state, and that state is communicated to the sensor board of the master battery pack via user input.

[0110] At 608, it is determined whether the voltage of the power bus is above or below the desired power bus voltage range. For example, if the voltage of the power bus is below the desired power bus voltage range, charging is required, but if the voltage of the power bus is above the desired power bus voltage range, no further charging is needed.

[0111] In response to the voltage of the power bus being below the desired power bus voltage range, the control moves to 610. At 610, it is determined whether the charger switch is open or closed. For example, using the presence or absence of a control signal applied to the charger switch, it is determined whether the charger switch is open or closed, and for a manual switch on an external charger, the system operator visually determines the switch state.

[0112] In response to the charger switch being open, control moves to 612. At 612, a connection instruction for connecting the charger to the power bus is provided. For example, the sensor board of the master battery pack sends a signal to (i) close a switch that connects any one of one or more solar panels to the solar charger of the master battery pack; (ii) close a switch that connects an external charger to the power bus; or (iii) instruct the system operator (e.g., via a user display) to close a switch (e.g., a manual switch) that connects an external charger to the power bus.

[0113] In response to the charger being connected to the power bus, control moves to 618. At 618, an indication of the charger switch state is provided. In this example, a close indication is provided to the sensor board of the master battery pack, control returns to 602, and monitoring of the power bus voltage during charging is performed. For example, the state of the charger switch is determined using the presence or absence of a control signal applied to the charger switch, and that state is communicated to the sensor board of the master battery pack. For a manual switch on an external charger, the system operator visually determines the switch state, and that state is communicated to the sensor board of the master battery pack via user input.

[0114] At 610, in response to the charger switch being closed, control moves to 618. At 618, an indication of the charger switch state is provided. In this example, a close indication is provided to the sensor board of the master battery pack, control moves to 602, and the process loops. In this example, the battery system requires charging until it is determined that the voltage of the power bus exceeds the desired power bus voltage range.

[0115] At 608, in response to the power bus voltage exceeding the desired power bus voltage range, control moves to 614. At 614, it is determined whether the charger switch is open or closed. For example, the presence or absence of a control signal applied to the charger switch is used to determine whether the charger switch is open or closed, and for a manual switch on an external charger, the system operator visually determines the switch state. In response to the charger switch being closed, control moves to 616.

[0116] At 616, a disconnection instruction is provided to disconnect the charger from the power bus. For example, the sensor board of the master battery pack sends a signal to (i) open the switch connecting any one of the one or more solar panels to the solar charger of the master battery pack, (ii) open the switch connecting the external charger to the power bus, or (iii) instruct the system operator (e.g., via a user display) to open the switch (e.g., a manual switch) connecting the external charger to the power bus. In this example, the battery system does not require charging until it is determined that the power bus voltage is below the desired power bus voltage range.

[0117] In response to the charger being disconnected from the power bus, control moves to 618. At 618, an indication of the charger switch state is provided. For example, the presence or absence of a control signal applied to the charger switch is used to determine whether the charger switch is open or closed, and for a manual switch on an external charger, the system operator visually determines the switch state. In this example, an open indication is provided to the sensor board of the master battery pack, control returns to 602, and the power bus voltage is monitored (e.g., while discharging while supplying power to an external load).

[0118] FIG. 7 is a flowchart showing one embodiment of a method of connecting a load to a power bus. In some embodiments, the process of FIG. 7 is performed using the master battery pack 401 of FIG. 4A. In some embodiments, the process of FIG. 7 is performed using a computer program. In various embodiments, the process of FIG. 7 is performed using any suitable combination of a master battery pack and a computer program. In some embodiments, the process of FIG. 7 is used to connect the load 12 of FIG. 1A to the battery system 2. In some embodiments, the process of FIG. 7 is used to connect a load via the load connector 480 and the sensor board control switch 474 of FIG. 4C.

[0119] At 700, an instruction to connect a load to a power bus is received. For example, a system operator instructs the master battery pack to connect a load to a power bus via a user interface or a communication bus. In some embodiments, the user interface includes a manual switch for connecting a load to a power bus. In some embodiments, an instruction to connect a load to a power bus is provided to a computer by a user input and transmitted to the master battery pack via a communication bus or any other suitable means (e.g., Ethernet connection, wireless network, cloud-based network, etc.). In some embodiments, the decision to connect a load to a power bus is made and shown to be executed by a computer program.

[0120] At 702, the voltage of the power bus is received. For example, a voltage measurement of the power bus is performed by an on-board voltage sensor in the master battery pack and transmitted to the sensor board of the master battery pack and / or to a computer.

[0121] At 704, it is determined whether the voltage measurement value indicates that the power bus is within the voltage range for supplying power to the load. For example, a sensor board processor or a computer program of the master battery pack compares the power bus voltage with the voltage range (e.g., the nominal voltage range) required to operate the load (e.g., the sensor-based monitoring system). In response to determining that the voltage measurement value indicates that the power bus is within the voltage range for supplying power to the load, the control moves to 706.

[0122] At 706, a close command is provided to close the switch on the power board and connect the load to the power bus. For example, a sensor board processor or a computer program of the master battery pack instructs to close the sensor board control switch to connect the load to the power bus.

[0123] At 708, an indication of the switch state is provided and the process ends. For example, using the presence or absence of a control signal applied to the load switch, the charger switch state (i.e., whether the charger switch is open or closed) is determined, and that state is provided to the sensor board of the master battery pack and / or the computer (e.g., via a communication bus).

[0124] In response to determining that the voltage measurement indicates that the power bus is not within the voltage range for supplying power to the load, control moves to 710. At 710, an indication that the voltage of the power bus is not within the voltage range for supplying power to the load is provided, and control moves to 708. For example, an indication that the power bus is not within the voltage range for supplying power to the load is provided to the system operator via a computer display. At 708, an indication of the switch state is provided and the process ends. For example, if the power bus is not within the voltage range for supplying power to the load, an indication that the load switch is open (e.g., to prevent under - or over - supplying power to the load) must be provided. In other examples, if the system operator or computer program is instructed to close the load switch due to a malfunction of the system or component, the load will be disconnected.

[0125] The foregoing embodiments have been described in some detail for purposes of clarity of understanding, but the present invention is not limited to the details provided. There are many alternative ways to implement the present invention. The disclosed embodiments are illustrative and not restrictive.

Claims

1. A battery system, comprising: a power bus; a set of battery packs, wherein one of the battery packs in the set of battery packs comprises one or more batteries, a sensor board, and a power board; the power bus is used to electrically connect the set of battery packs; the sensor board is configured to: receive a voltage difference between a battery pack not connected to the power bus and the power bus; determine whether the voltage difference indicates that the voltage of the battery pack is too high compared to the power bus voltage; in response to determining that the voltage difference indicates that the voltage of the battery pack is too high compared to the power bus voltage, provide a discharge instruction to discharge the battery pack using a power draw mechanism until the voltage of the battery pack is within a threshold voltage difference of the power bus; provide a connection instruction to connect the disconnected battery pack to the power bus.

2. The system according to claim 1, wherein the set of battery packs includes one master battery pack and one or more slave battery packs, and the master battery pack includes a charging unit.

3. The system according to claim 2, wherein one of the one or more slave battery packs can be disconnected from the power bus, removed from the set of battery packs, and replaced with another slave battery pack.

4. The system according to claim 2, wherein the charging unit receives power from one or more solar panels.

5. The system according to claim 2, wherein a first housing of the master battery pack and a second housing of one of the one or more slave battery packs are substantially the same in size and shape.

6. The system according to claim 1, wherein the sensor board comprises a sensor board processor.

7. The system according to claim 1, wherein the sensor board comprises a voltage sensor, a processor, and a voltage calculator used to determine the voltage difference between the battery pack and the power bus.

8. ​ The system according to claim 6, wherein the sensor board processor provides an instruction to connect the battery pack to the power bus by instructing to close an electrical contactor.

9. The system according to claim 1, wherein the power board includes one or more electrical contactors. A system, wherein one of the one or more electrical contactors receives an instruction to open or close from the sensor board.

10. The system according to claim 9, wherein the electrical contactor among the one or more electrical contactors is used to connect or disconnect a master battery pack or one or more slave battery packs to or from the power bus.

11. The system according to claim 9, wherein another electrical contactor among the one or more electrical contactors is used to connect or disconnect a charging unit to or from the power bus.

12. The system according to claim 1, wherein the power draw mechanism includes a bleeder resistor. The bleeder resistor extracts excess energy in the form of heat.

13. The system according to claim 12, wherein the heat is used to reach a target operating temperature specific to the battery pack.

14. The system according to claim 1, wherein excess energy indicated by the voltage difference is transferred from one battery pack to one or more battery packs, as a result, the voltage of the one or more battery packs is increased.

15. The system according to claim 1, further comprising a communication bus.

16. The system according to claim 1, wherein the one or more batteries of each battery pack are modular.

17. The system according to claim 16, wherein each of the one or more modular batteries includes one or more battery cells.

18. The system according to claim 16, wherein the battery packs of the set of battery packs include a battery management unit, and the battery management unit is used to determine the voltage of one or more battery cells.

19. The system according to claim 16, wherein the battery management unit equalizes the voltage across one or more battery cells of the battery pack.

20. A method for equalizing a battery system, the method comprising: receiving, at a sensor board, a voltage difference between a battery pack not connected to a power bus and the power bus, wherein the battery pack of the set of battery packs comprises one or more batteries, a sensor board, and a power board, and the power bus is used to electrically connect the set of battery packs; receiving the voltage difference; determining, using the sensor board, whether the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage; providing, in response to determining that the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, a discharge instruction to discharge the battery pack using a power draw mechanism until the battery pack voltage is within a threshold voltage difference of the power bus; providing a connection instruction to connect the disconnected battery pack to the power bus.

21. A computer program product for equalizing a battery system, the computer program product comprising: embodied on a non-transitory computer-readable storage medium; receiving, at a sensor board, a voltage difference between a battery pack not connected to a power bus and the power bus, wherein the battery pack of the set of battery packs comprises one or more batteries, a sensor board, and a power board, and the power bus is used to electrically connect the set of battery packs; receiving the voltage difference; determining, using the sensor board, whether the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage; providing, in response to determining that the voltage difference indicates that the battery pack voltage is too high compared to the power bus voltage, a discharge instruction to discharge the battery pack using a power draw mechanism until the battery pack voltage is within a threshold voltage difference of the power bus; Providing a connection instruction to connect the disconnected battery pack to the power bus; A computer program product including computer instructions therefor. **Claim 22** A battery system, comprising: A power bus; A set of battery packs, One of the battery packs in the set of battery packs includes one or more batteries, a sensor board, and a power board, and the power bus is used to electrically connect the set of battery packs; The sensor board: Receives a voltage difference between a battery pack not connected to the power bus and the power bus; Determines whether the voltage difference indicates that the battery pack voltage is too low compared to the power bus voltage; In response to determining that the voltage difference indicates that the battery pack voltage is too low compared to the power bus voltage, provides an excess instruction to transfer excess energy indicated by the voltage difference from the battery pack to one or more of the battery packs, resulting in an increase in the voltage of one or more of the battery packs.

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