Energy transfer system

Abstract

An energy transfer system may combine multiple energy storage sources / systems of different chemical compositions or physical configurations with a common control system configured to output energy from the systems as a function of the different performance characteristics of each system, thereby optimizing the various operating characteristics of the combined system. The control system is configured to use a separate variable impedance network for each energy storage system to regulate the relative output current or discharge rate of each energy storage system, such as optimizing the cycle life, discharge depth, temperature, delivered power, and / or perceived safety of each energy storage system.

Description

Technology Field

[0001] This application is a continuation-in-part application of U.S. Patent Application Serial No. 16 / 760,762 filed on April 30, 2020, which is the national phase application of International Application No. PCT / US2017 / 068301 filed on December 22, 2017, and both of these applications are incorporated herein by reference. This application also claims priority to U.S. Provisional Patent Application Serial No. 62 / 882,817 filed on August 5, 2019, and this Provisional Application is incorporated herein by reference.

[0002] The present invention generally relates to energy sources for electronic devices, and in particular, to an energy storage system or a system for transferring energy from a source. Background Technology

[0003] This section is intended to introduce various aspects of the art that may be associated with the exemplary embodiments of the present disclosure. This discussion is considered to assist in providing a framework to facilitate a better understanding of specific aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, rather than necessarily as an acknowledgment of the prior art.

[0004] More than ever, there is a reliance on energy devices capable of providing electrical power to enable technical conveniences. Primarily, electrical power is derived from a continuously operating network grid. However, due to remote locations or interruptions where the power grid is unavailable, there is a need for electrical power to be supplied from non-grid sources. Energy can be extracted from non-grid devices and systems using these sources, including chemical energy storage, potential energy storage, or kinetic energy storage, and can be delivered or converted to complete electrical tasks while remaining compatible with the existing electrical grid framework. Examples of chemical energy storage systems include, but are not limited to, lithium batteries, nickel batteries, flow cell batteries, and lead acid batteries. Examples of potential energy storage systems include, but are not limited to, parametric devices such as lithium capacitors, supercapacitors, and Electric Double-Layer Capacitors ("ELDC"). Examples of kinetic energy storage systems include, but are not limited to, rotating mass systems such as flywheels and other mechanical devices coupled through a mechanical-electrical conversion process.Throughout this disclosure, these terms may be used interchangeably in relation to energy transfer devices capable of delivering electrical energy to apply voltage, supply current, and / or perform work.

[0005] The performance characteristics of batteries, capacitors, or other energy storage systems are generally determined by the configuration of the device and, in the case of electrochemical storage devices, by its chemical composition. These characteristics include, but are not limited to, capacitance-measurement energy density (watt-hour per unit capacity), gravimetric energy density (watt-hour per unit mass), power density (i.e., the rate at which energy can be extracted from the device), charge / discharge cycle life, operating temperature range, electrode voltage(s), and overall stability against aging. Furthermore, in the case of batteries, some chemical compositions yield batteries that are more stable during fault conditions and, therefore, more resistant to thermal runaway, and thus are considered "safer" than other chemical formulations. For example, lithium-ion batteries are one of the most commonly used electrochemical energy storage devices. Additionally, due to fluctuating market prices for certain raw materials, there may be significant price differences between battery cells of different compositions when considering the unit price per watt-hour of stored energy.

[0006] Battery cells (also referred to herein as “energy cells”) are typically combined in series and / or parallel combinations to form a battery cell stack (also referred to herein as a “cell stack” or “battery stack”) and, when combined with a suitable control system, form the basis of modern battery-based energy storage / transfer systems. However, there is a need for an energy transfer system capable of safely combining multiple energy storage sources or systems that are not yet provided and, therefore, differ from one another (e.g., including battery cells based on more than one chemical composition). Such an energy storage / transfer system may possess electrical performance advantages as well as cost-safety and / or lifespan advantages. For example, by carefully combining cells of different chemical compositions, an energy storage system may be composed of cells chemically optimized for cost, safety, and / or extended calendar and cycle life, while another energy storage system may be composed of cells optimized for some different but otherwise important parameters. Brief explanation of the drawing

[0007] Figure 1 illustrates a schematic diagram of a model for a battery cell. FIG. 2 illustrates plots of direct current internal resistance ("DCIR") and open circuit voltage as a function of the state of charge for an exemplary battery cell. Figure 3 illustrates a schematic diagram of a model for a battery cell under DC current load setting conditions. Figure 4 illustrates a graph of a set of characteristic voltage versus charge state curves, each curve representing a different level of battery current for an exemplary single battery cell. FIG. 5 illustrates a schematic diagram of a model for multiple battery cells combined in series. FIG. 6 illustrates a schematic diagram of a simplified model for multiple battery cells combined in series. Figure 7 illustrates a graph of a set of characteristic voltage versus charge state curves, each taken at a different cell stack current level for an exemplary battery cell stack. Figure 8 illustrates a schematic diagram of a model for a battery cell stack combined with a variable impedance network. FIG. 9 illustrates a circuit block diagram comprising a plurality of switchable diodes combined in series, wherein a variable impedance network. FIG. 10 illustrates a graph demonstrating an example of the effect on a set of characteristic voltage versus state of charge curves for an exemplary battery cell stack as a result of introducing a plurality of switchable diodes connected in series. FIG. 11 illustrates a circuit block diagram comprising a plurality of switchable resistive elements combined in parallel with a variable impedance network. Figure 12 illustrates a graph demonstrating an example of the effect on a set of characteristic voltage versus state of charge curves for an exemplary battery cell stack as a result of introducing a resistive element. Figure 13 illustrates a block diagram of an energy transfer system. FIG. 14 illustrates a block diagram of an energy transfer system configured according to embodiments of the present disclosure. Figure 15 illustrates a schematic diagram of a model for the energy transfer system of Figure 14. FIG. 16 illustrates a schematic diagram of a model of the energy transfer system of FIG. 14 in which a plurality of switchable diodes are combined in series within variable impedance networks. FIG. 17 illustrates a flowchart diagram constructed according to embodiments of the present disclosure. FIG. 18 illustrates a block diagram of an energy transfer system configured according to embodiments of the present disclosure. FIG. 19 illustrates a block diagram of an energy transfer system configured according to embodiments of the present disclosure. FIG. 20 illustrates a graph of a set of characteristic voltage versus state of charge curves during exemplary discharges of two battery cell stacks having different chemical compositions. Figure 21 illustrates diagrams of discharges of two different battery cell stacks. FIG. 22 illustrates a block diagram of an energy transfer system configured according to embodiments of the present disclosure. FIG. 23 illustrates a graph of characteristic voltage versus state of charge for two different battery cell stacks having different chemical compositions. Figure 24 illustrates diagrams of discharges of two different battery cell stacks. Specific details for implementing the invention

[0008] It will be understood that the specific embodiments described herein are illustrated as examples, not as limitations to the embodiments of the invention. The principal features of the invention may be adopted in various embodiments without departing from the scope of the invention.

[0009] The embodiments of the present disclosure describe electrochemical storage systems (e.g., battery technologies) due to their improved energy density and higher expanded applications and uses compared to other types of energy storage and mechanical devices. However, the embodiments of the present disclosure are not limited to the use of battery cells for energy storage systems; the various embodiments of the present disclosure described herein are applicable to the use of any type of energy storage system, including but not limited to potential and kinetic energy storage systems such as those disclosed herein.

[0010] Embodiments of the present disclosure provide an energy transfer system that combines a plurality of energy storage sources / systems of different chemical compositions or physical configurations with a common control system configured to transfer energy from the systems as a function of the different performance characteristics of each system, and thus can optimize various operating characteristics of the combined system. According to some embodiments of the present disclosure, an energy transfer system is provided that combines two or more batteries or other energy storage systems that are combined in parallel and coupled to a common load. Each of the combined energy storage systems comprises battery cells of distinctly different chemical compositions, configurations, or methods of operation. According to embodiments of the present disclosure, the control system is configured to use a separate variable impedance network for each energy storage system to control the relative output current or discharge rate of each energy storage system, such as optimizing the cycle life, depth of discharge, temperature, delivered power, and / or perceived safety of each energy storage system. For example, according to embodiments of the present disclosure, the energy transfer system may comprise two or more battery cell stacks, each having different battery chemical compositions. Such a multi-chemistry system may include two or more separate groups of cells connected in series or in parallel to form two or more battery stacks under the control of a common control system to provide an energy transfer system. In these non-limiting examples, each battery stack may have unique and different performance characteristics determined by the chemical composition of the cells within the battery stack. Two or more separate battery stacks may be combined in parallel to create a battery system that delivers output power to a combined load.According to some embodiments of the present disclosure, the serial cell count of each battery stack may be predetermined so that the total stack voltages of each stack are optimally matched. According to some embodiments of the present disclosure, the parallel cell count of each battery stack may be predetermined to optimize the capacity in watt-hours of each battery stack as required by the end-use application.

[0011] Lithium-ion battery cells can generally be divided into two classes related to energy capacity or power capacity. Lithium-ion "energy cells" are described as having maximized capacitance or gravimetric energy density and have an internal chemical composition that maximizes lithium-ion storage, but have high internal impedance that limits their ability to deliver high currents exceeding 3C (where "C" refers to battery capacity). These energy cells are used in applications such as laptop computers and cell phones where energy is extracted slowly over periods of time or days. Lithium-ion "power cells" are described as having maximized current delivery capacity and have an internal chemical composition that minimizes internal impedance to allow non-delayed mass transport of lithium ions and, thus, to allow very high pulsed or continuous currents to be delivered without a reduction in cell terminal voltage to cutoff limits. Power cells can have discharge rates exceeding 8C and reaching 50C. Power cells typically have thicker current collectors compared to energy cells. These internal configuration and chemical differences result in lower energy storage capacity and cycle life capabilities compared to energy cells. Power cells are typically used in applications such as cordless drills and other tools where high amounts of energy must be delivered over short time cycles and all of the stored energy is extracted over discharge times, such as less than one hour. Within each cell class (power or energy), there may be a wide range of cell part numbers with varying energy densities and varying internal resistance values.

[0012] Lithium-ion batteries are available in a wide range of chemical compositions and construction methods, each having specific relative advantages and disadvantages in performance related to cycle life, cost, safety, and energy density as listed in the following table:

[0013]

[0014] It can be said that each of the listed battery types has a substantially different chemical composition from the others. It is evident from the table that if a designer is tasked with designing an energy storage system with a required cycle life of 5,000 charge and discharge cycles, lithium iron phosphate ("LFP") or lithium titanium oxide ("LTO") would be more appropriate choices, whereas lithium nickel manganese cobalt ("NMC") would not be due to its relatively shorter cycle life. Furthermore, since LFP and LTO are the two most expensive options available, it is evident that the relative cost of such a system will be higher. Also, because the energy densities of these two cell types are relatively low, more cells will be required to achieve any given system capacity in watt-hours.

[0015] Taking the above exemplary information regarding the different relative characteristics of various energy storage sources / systems, for a large subset of possible energy storage performance requirements, there exist combinations of two or more cell chemicals that can be configured as a single energy transfer system such that at least some characteristics of the system are enhanced compared to what can be achieved using only cells of a single chemical.

[0016] To demonstrate the advantages of the embodiments of the present disclosure, an exemplary energy transfer system will now be described as comprising an energy storage system comprising a first battery stack including LFP cells, and a second battery stack including NMC cells combined in a watt-hour capacity ratio of approximately 60% LFP and 40% NMC, configured to utilize the relatively longer lifespan and enhanced safety characteristics of LFP, but having a lower cost point and smaller size due to the reduced relative cost and higher energy density characteristics of NMC. According to the exemplary embodiments of the present disclosure, system performance and characteristics may be further configured by adjusting the cell chemistry and cell types used and the ratios in which they are combined. While the exemplary embodiments described below each provide a system based on two stacks of energy storage elements based on different chemical compositions of lithium-ion batteries, according to various embodiments of the present disclosure, other energy storage systems may be used, such as a system based on a first stack of battery cells and a second stack of ELDCs, which can be optimized for peak pulse power and allow for faster recharging than is possible using the batteries alone. According to embodiments of the present disclosure, more than two energy storage systems (having at least two or more of these systems composed of different chemical or energy storage technologies (e.g., selected from any potential energy storage systems, chemical energy storage systems, and / or kinetic energy storage systems)) may be included to further customize the overall system performance and / or characteristics of the energy transfer system.

[0017] A battery cell can be modeled as an electronic circuit network as exemplified in FIG. 1 (e.g., see R. Rao et al., “Battery Modeling for Energy-Aware System Design,” Computer, vol. 36, no. 12, pp. 77-87, December 2003, which is incorporated herein by reference). A universally accepted model is the open circuit voltage (hereinafter referred to as “OCV” or “V oc The equivalent of an ideal voltage source expressing "referred to as any one of"), current (I s The internal series resistance (R) through which ) flows s ), and resistors and capacitors (R) connected in series and / or parallel n C n Includes reactive components of combinations of ), where, I n ε is the current flowing through the reactive component. The model comprises a number of components (i.e., n, where ε is the total reactive component of the cell impedance) contributing to the total reactive component. Note that ) RC elements can be included.

[0018] Direct current ("DC") Voltage of battery terminals ("V") under load setting conditions batt ") is expressed according to the following mathematical formula:

[0019]

[0020] Battery's internal series resistance ( ) can also be referred to as the internal resistance of the direct current ("DCIR"). DCIR changes as a function of the state of charge ("SOC") of the battery.

[0021] Figure 2 illustrates a graph plotting both battery cell DCIR and OCV as a function of SOC for a typical NMC battery cell. As the state of charge increases, V ocThe voltage is higher, and the DCIR is lower. The DCIR increases at lower charge states, and especially at less than 30 percent (30%) SOC.

[0022] It is noted that time-based components can account for sudden load changes, transient responses during charge and / or discharge cycles, and Faradaic contributions. Considering the overall behavior of the battery cell under DC load setting conditions where currents do not vary with time, resistive elements can be summed and capacitive elements can be ignored; thus, the model can be simplified as follows:

[0023] V batt = V oc - R batt I batt

[0024] This simplified cell model is exemplified in Fig. 3. As a result, V batt is different I batt It can be characterized by a set of voltage versus SOC curves at various currents taken from current values ​​(also referred to herein as characteristic VI curves). This set of characteristic VI curves for a typical single NMC cell is illustrated in FIG. 4. (In FIG. 4 and other figures illustrating graphs of voltage versus SOC curves, lines represent voltages at different current values ​​such as C, which is related to the rated capacity of the battery).

[0025] Referring to FIG. 5, when a plurality (n) of identical battery cells are combined in series, the model can be expressed as follows:

[0026] V batt = n(V oc - R batt I batt )

[0027] Here, n is the number of battery cells in series. A simplified model is shown in Fig. 6.

[0028] Referring to FIG. 7, as in the previously described example of a single battery cell, a set of exemplary characteristic VI curves can be generated for such a serially connected cell system (in this non-limiting example, a battery stack of typical NMC cells previously described, where 11 cells are connected in series).

[0029] Referring to FIG. 8, the battery stack is a variable impedance circuit (in this specification, "Z var " or "Z variable Can be combined with (referred to as any one of). Z var The term represents the variable impedance of a circuit that can be configured as a network of switchable elements (as such, the variable impedance circuit will also be referred to herein as a "variable impedance network"). For any given output current value, Z var The term is Z var By adjusting the value of, each energy source thus equipped (e.g., a battery cell stack) has its V batt Output characteristic curve position (Z var Allows downward shift relative to the normal characteristic voltage curve position (the discharge curve observed when = 0).

[0030] Embodiments of the present disclosure may be configured to use any suitable circuit portion within a variable impedance circuit and / or network. International patent application PCT / US2017 / 068301 (hereinafter referred to as "PCT / US2017 / 068301") discloses exemplary embodiments of a circuit portion comprising switchable elements that can be used within a variable impedance network according to various embodiments of the present disclosure as described herein. As illustrated in FIG. 9, a first embodiment as disclosed in PCT / US2017 / 068301 (Fig. 6 from PCT / US2017 / 068301 is provided as FIG. 9) uses a plurality of series-connected switchable diode circuits (610a...610c) that can be selectively inserted or removed from the circuit (using switching elements, e.g., FETs) according to a control algorithm performed by a control system (602) that may be monitoring the system (600) in real time. The embodiment illustrated in FIG. 9 shows three series-connected switchable diode circuits (610a to 610c), but more or fewer of these switchable diode circuits may be used depending on the exact system configuration and end-use requirements. It should be noted that the remaining elements exemplified in Fig. 9 are not further explained for the sake of simplicity, but can be referenced by reviewing PCT / US2017 / 068301.

[0031] FIG. 10 illustrates the effect on the position of characteristic curves when a plurality of series-connected diodes (in this case, five ideal diodes) are introduced into a circuit. Each of the characteristic curves has an uninserted impedance (i.e., Z variable Note that for (= 0), it is shifted downward by the same amount (decreased in voltage). In this non-limiting example, Z variable= 5 * Vf, where Vf is the forward voltage of an ideal diode. Note that the battery current is not affected at this level of shift; the curves for each current level are shifted by the same amount. The variable nature of this embodiment using series-connected switchable diodes stems from the fact that any number of diodes (i.e., from zero diodes to the maximum number of implemented diodes) can be added to or removed from the circuit at any time. Thus, the characteristic VI curves associated with the implemented battery cell stack can be shifted up or down at any time during the operation of an energy transfer system composed of such a variable impedance network.

[0032] FIG. 11 provides a second exemplary embodiment of a circuit comprising switchable elements disclosed in PCT / US2017 / 068301 (Fig. 7 from PCT / US2017 / 068301 is provided as FIG. 11). In this exemplary embodiment, the circuit comprising switchable elements is configured as a parallel connection of switchable resistive elements (750a to 750d). Each switchable resistive element can be selectively inserted or removed from the circuit (using switchable elements, e.g., FETs) according to a control algorithm performed by a control system (702), and the total impedance of the switchable resistor network is determined by the number of switchable resistive elements that are switched on or off at a given time. In a manner very similar to that described for FIG. 9, adding or subtracting resistance in this circuit will result in a shift in the position of the characteristic VI curves of the battery cell stack. It should be noted that the remaining elements exemplified in Fig. 11 are not further explained for the sake of simplicity, but can be referenced by reviewing PCT / US2017 / 068301.

[0033] FIG. 12 shows switchable resistive elements (i.e., Z) set to a value of 0 ohms. variable Characteristic curves having a circuit section including = 0), and switchable resistive elements set to a value of 1 ohm (i.e., Z variableAn example of comparing curves having a circuit section including (= 1 ohm) is provided. As can be seen, the resulting characteristic shift is fundamentally different from that demonstrated for exemplary embodiments when switchable diodes are implemented. Rather than shifting all curves downward by the same amount as illustrated in Fig. 10, the magnitude of the downward shift of each curve is proportional to the current represented by each curve. This results in a "spreading apart" of the various characteristic curves, rather than a downward shift of all curves by a fixed voltage value. While the voltage drop across a resistor is current x resistance, the voltage drop across an ideal diode is a fixed voltage independent of the current. Therefore, in the case of a network of switchable resistive elements, the effect on the characteristic VI curves is dependent on the current (e.g., zero current results in zero voltage drop, 1X current results in 1X voltage drop, 2X current results in 2X voltage drop, etc.). This means that the characteristic VI curve at each specific current level will "spread" as a function of resistance; higher inserted resistance results in more spreading. In the case of switchable diodes, the forward voltage drop is fixed regardless of the current magnitude. Therefore, the entire characteristic VI curve is shifted down by the number of diodes switched into the circuit (i.e., the number of diodes not short-circuited by the switches). Regardless of the magnitude of the current present in the diodes, one diode will shift the entire curve down by the same amount (e.g., Vf = 0.75 V); two diodes will shift the curve down by 1.5 V; five diodes will shift the curve down by 3.75 V, and so on.

[0034] Referring to FIG. 13, the battery stack (1301) includes a plurality of series-connected battery cells, and the variable impedance network (1302) is V o A system (1300) that presents a voltage at a positive terminal is illustrated. Each cell in the battery stack (1301) has its voltage monitored by an analog front-end measurement device ("AFE") (1303). The AFE (1303) can also collect temperature data and transmit the collected data to a control system (e.g., a microcontroller "MCU") (1304). The battery stack (1301) V through a sensing resistor (Rsense) (1305). o It can be coupled to the negative. Each side of the sensing resistor (1305) is the battery current to the fuel gauge IC (1306) whenever current is present in the sensing resistor (1305). i 0 It can be coupled to a fuel gauge integrated circuit ("IC") (1306) that provides a voltage representing the value of ). The fuel gauge IC (1306) can communicate information about the state of charge ("SOC") of the battery stack (1301) with the MCU (1304). The MCU (1304) is coupled to a variable impedance network (1302) and controls the variable impedance network (1302). The MCU (1304) can perform one or more control algorithms configured to control (e.g., optimize) the operating state of the system (1300) in a predetermined manner. For example, a control algorithm operated by the control system (1304) determines the state of the battery stack (1301) and the V of the system (1300) by adjusting the position(s) of characteristic VI curves that determine this parameter. oThe variable impedance network (1302) may be configured to operate to control (e.g., adjust or modify) the voltage presented at the positive terminal. The MCU (1304) may be configured to communicate data and / or information to an external host system (e.g., via a communication link or bus (1307)).

[0035] Referring to FIG. 14, an energy transfer system (1400) configured according to embodiments of the present disclosure is illustrated. In the energy transfer system (1400), a first battery cell stack (1401a) is coupled in parallel to a second battery cell stack (1401b), each of which may be coupled to similar control and monitoring circuits. The battery cell stacks (1401a, 1401b) may be coupled to a common control system (e.g., a microcontroller "MCU") (1404) so ​​that parametric information from each battery stack may be collected (e.g., simultaneously) and control algorithms may be performed to control the operations of either or both of the variable impedance networks (1402a, 1402b). The voltage of each cell in the battery stack (1401a) may be monitored by an analog front-end measurement device ("AFE") (1403a). The AFE (1403a) can also collect temperature data and transmit the collected data to the control system (1304). The battery stack (1401a) V through the sensing resistor (Rsense) (1405a). o It can be coupled to the negative. Each side of the sensing resistor (1405a) is the battery current to the fuel gauge IC (1406a) whenever current is present in the sensing resistor (1405a). i 1It can be coupled to a fuel gauge integrated circuit ("IC") (1406a) that provides a voltage representing the value of ). The fuel gauge IC (1406a) can communicate information about the state of charge ("SOC") of the battery stack (1401a) with the control system (1404). The voltage of each cell in the battery stack (1401b) can be monitored by the AFE (1403b). The AFE (1403b) can also collect temperature data and transmit the collected data to the control system (1304). The battery stack (1401b) V through a sensing resistor (Rsense) (1405b). o It can be coupled to the negative. Each side of the sensing resistor (1405b) is the battery current to the fuel gauge IC (1406b) whenever current is present in the sensing resistor (1405b). i 2 It can be coupled to a fuel gauge integrated circuit IC (1406b) that provides a voltage representing the value of the battery stack (1401b). The fuel gauge IC (1406b) can communicate information about the SOC of the battery stack (1401b) with the control system (1304). Essentially, the fuel gauge ICs (1406a, 1406b) can be configured to measure instantaneous current and even battery temperature, and then, from the measured data or data transmitted thereto, calculate the average current, instantaneous state of charge, the number of charge / discharge cycles experienced by the battery stack, the resistance of the battery stack, and other parameters.

[0036] According to some embodiments of the present disclosure, V o Note that the positive output terminal is common between the variable impedance networks (1402a, 1402b). As a result, according to the embodiments of the present disclosure, terminal V as performed in the system (1300). oThe variable impedance networks (1402a, 1402b) under selective control by signals from the control system (1404), rather than controlling the output voltage presented in the positive, can be configured to control the level of current flowing through each variable impedance network (1402a, 1402b) and delivered to the output terminal. The selective control of the variable impedance networks (1402a, 1402b) by the control system (1404) can be performed so that each of the battery stacks (1401a, 1401b) is maintained within a predetermined output current range according to the predetermined performance criteria of the energy transfer system (1400).

[0037] The control system (1404) may be configured to communicate data and / or information to an external host system (e.g., via a communication link or bus (1407)). Internal communications between and / or externally from the control system (1404) may be wired or wireless. Communication protocols that may be used include, but are not limited to, SMB, I2C, RS232, TTL, Serial, USB, CAN, Network, etc.

[0038] In a non-limiting example, variable impedance networks (1402a, 1402b) may include a plurality of switchable resistive elements, such as the configuration of switchable resistive elements (750a...750d) used in the system (700) of FIG. 11. Each switch (710a...710d) may be individually opened or closed by the control system (1404) according to predetermined control algorithms. The resistors (750a...750d) may be composed of the same or different resistance values. By changing the number of resistors (750a...750d) combined in parallel by the corresponding switches (710a...710d), the effective resistance of either or both of the variable impedance networks (1402a, 1402b) can be adjusted over a predetermined range (e.g., from a predetermined minimum resistance value to a predetermined maximum resistance value).

[0039] The energy transfer system (1400) can be represented by a simplified model illustrated in FIG. 15, which can be explained by the following mathematical equations:

[0040] V o Positive = V1 - R1* i 1 - i 1 *Variable R1

[0041] V o Positive = V2 - R2* i 2 - i 2 *Variable R2

[0042] i 1 + i 2 = i output of power

[0043] Consider an exemplary embodiment of the present disclosure in which an energy transfer system (1400) comprises battery cell stacks having different sets of operating parameters (e.g., due to different materials and / or chemical compositions), wherein cell stack (1401a) comprises cells having a higher cycle life than the cells in cell stack (1401b), and cell stack (1401b) comprises cells having a lower cycle life than cell stack (1401a), but may also include cells having a higher relative energy density. It is assumed that the energy capacities of the two cell stacks are nearly identical. According to embodiments of the present disclosure, during discharge, it may be advantageous for the operation of the energy transfer system (1400) for the cell stack having the higher relative cycle life (i.e., cell stack (1401a)) to transfer most of the energy. For example, according to embodiments of the present disclosure, the control system (1404) may be configured such that, during discharge, in order to utilize a longer cycle life of the cell stack (1401a), the current drawn from the cell stack (1401a) is twice that drawn from the cell stack (1401b), or in other words, the cyclic energy drawn from the cell stack (1401a) is twice that drawn from the cell stack (1401b). Under this exemplary operation scenario, the equations may be rewritten as follows:

[0044] i 1 = 2* i 2 ( i 1 is always i 2 2 times)

[0045] V o Positive = V1 - R1 * 2 i 2 - 2 i 2 *Variable R1; and

[0046] V oPositive = V2 - R2* i 2 - i 2 *Variable R2

[0047] The values ​​V1, V2, R1, and R2 can be known from cell characterization curves associated with the types of battery cells used in cell stacks (1401a, 1401b) (such as those exemplified in FIG. 2), and thus, i 1 = 2* i 2 It is simple to construct variable impedance networks (1402a, 1402b) with appropriate values ​​by deriving mathematical formulas for the values ​​of variable R1 and variable R2 to maintain the conditions.

[0048] The energy transfer system (1400) can also be represented by the simplified model illustrated in FIG. 16, wherein the variable impedance networks (1402a, 1402b) each comprise a plurality of switchable diodes, such as the configuration of the switchable diodes (610a...610c) used in the system (600) of FIG. 9. Each of the switchable diodes (610a...610c) is coupled with a switch (e.g., FET) capable of diverting any current around the diode. The switches can be opened or closed according to control signals received from the control system (1404) (e.g., similar to the control signals (621a...621c) of FIG. 9). Each of the diodes can be configured with the same or different forward voltage drop (Vf) values. The number of diodes that open the associated switches and thus contribute to the forward voltage drop, and the number of diodes that close the associated switches and thus do not contribute to the forward voltage drop for the associated variable impedance networks (1402a, 1402b) are adjustable by the control system (1404), and the sum of the voltage drops is therefore variable.

[0049] As in the example described for FIG. 15, the system can be described by mathematical equations:

[0050] V o Positive = V1 - V var1 - i 1 *R1

[0051] V o Positive = V2 - V var2 - i 2 *R2

[0052] i 1 + i 2 = i output of power

[0053] Again, as in the previous example, the energy transfer system (1400) comprises two different battery cells, for example, here, cell stack (1401a) comprises cells configured with a much higher cycle life compared to cell stack (1401b), and cell stack (1401b) comprises cells configured with a lower cycle life compared to cell stack (1401a), but also may include a higher relative energy density. It is assumed that the energy capacities of the two cell stacks are nearly identical. And, as in the previous example, i 1 = 2* i 2 And, therefore, the mathematical equations consider an energy transfer system (1400) that is preferably rewritten as follows:

[0054] i 1 + i 2 = i output of power

[0055] i 1 = 2* i 2 ( i 1 is always i 2 2 times)

[0056] V o Positive = V1 - V var1 - 2* i 2 *R1

[0057] V o Positive = V2 - V var2 - i 2 *R2

[0058] The values ​​V1, V2, R1, and R2 are again known from cell characterization curves such as those exemplified in Fig. 3, and thus, it is simple to derive mathematical formulas for the exact values ​​of Vvar1 and Vvar2 to maintain the condition i1= 2*i2 and to configure multiple active diodes in each impedance network with appropriate values.

[0059] The values ​​V1, V2, R1, and R2 can be known from cell characterization curves associated with the types of battery cells used in cell stacks (1401a, 1401b) (such as those exemplified in FIG. 2), and thus, i 1 = 2* i 2 V to maintain the condition var1 and V var2 It is simple to derive mathematical formulas for the values ​​and configure multiple active diodes in each variable impedance network (1402a, 1402b) with appropriate values. Since the value of Vf for each diode is a fixed and characteristic value depending on the semiconductor technology and device type, it is important to note that the exact value of each variable impedance network of the variable impedance networks (1402a, 1402b) is not precisely adjustable but is a fixed multiple of some Vf values.

[0060] According to embodiments of the present disclosure, embodiments of the energy transfer system (1400) may use control algorithms programmed within a control system (1404) that embodies the mathematical expressions described with respect to either FIG. 15 or FIG. 16, in order to control the switching of resistive elements or diodes within variable impedance networks (1402a, 1402b), whether the energy transfer system (1400) is implemented with switchable resistive elements, switchable diodes, or a combination thereof. Additionally, according to embodiments of the present disclosure, battery cell specific values ​​V1, V2, R1, and R2 may be determined from their individual cell characterization curves. Since these values ​​are significantly variable depending on the charge state, temperature, and age of the cells, these values ​​can be integrated into some kind of appropriate database, such as lookup tables, to capture characterized data and create models to estimate aging characteristics.

[0061] According to embodiments of the present disclosure, the control system (1404) may use control algorithms based on successive approximations. For example, when the energy transfer system (1400) is initialized and before any discharge of any energy begins, the initial states of the variable impedance networks (1402a, 1402b) may be configured (e.g., by deriving descriptive mathematical expressions). Next, once discharge has started, the control system (1404) does not perform continuous mathematical processing, but rather the control system (1404) can be looped repeatedly through a parametric measurement step in which dynamically changing operating conditions of the energy transfer system (1400), such as the voltage, current, and SOC of each cell stack (1401a, 1401b), are measured, and then a comparison step in which the output currents of each cell stack (1401a, 1401b) or other selected parameters are compared with each other and with respect to the targeted performance, and then a correction step is performed in which the variable impedance networks (1402a, 1402b) are adjusted (e.g., in small, separate steps) to move the controlled parameters toward the behavior desired by each adjustment. A delay may be added in the loop to allow the battery parameters to stabilize after each adjustment of either of the variable impedance networks (1402a, 1402b). For example, using the previous example of the energy transfer system (1400) described with respect to FIG. 14, the control system (1404) i 1 and i 2 as the same thing, or i 1 second i 2 Only when it becomes a fixed percentage, or when the SOC of the cell stack (1401a) exceeds 25% i 1 second i 2It may be configured to be maintained constant by becoming a fixed percentage and a different fixed percentage when the SOC of the cell stack (1401a) is less than 25%, or to reduce the current of the cell stack with the highest temperature to 10% of the current of the cell stack with the lowest temperature whenever the difference between the cell stack temperatures reaches some threshold. The above examples are not limited to possible variations in possible control algorithms.

[0062] FIG. 17 illustrates a flowchart of a process (1700) including exemplary control algorithms performed within a control system (1404) of an energy transfer system (1400) according to embodiments of the present disclosure. As further described, the process (1700) may also be performed within a control system (1804) of a system (1800) described with respect to FIG. 18, FIG. 19, and FIG. 22.

[0063] The energy transfer system (1400) can be initialized (started). In process block (1701) (machine state evaluation), the state of the energy transfer system (1400) can be determined. For example, voltages (e.g., cells in battery stacks (1401a, 1401b) through AFEs (1403a, 1403b), currents (e.g., as detected by sensing resistors (1405a, 1405b)), and temperatures (e.g., cells in battery stacks (1401a, 1401b) through AFEs (1403a, 1403b)) can be measured, and this data can be collected by the control system (1404). Using this data, a determination can be made in process block (1702) regarding whether the energy transfer system (1400) is ready to discharge. Otherwise, some correction action may be taken in the process block (1710).

[0064] For example, if collected data determines that one or both of the cell stacks (1401a, 1401b) are not fully charged, a charging current may be applied from an external energy source (e.g., refer to the chargers (603, 703) in FIG. 9 and FIG. 11, respectively). If collected data determines that one or both of the cell stacks (1401a, 1401b) are too hot, a cooling system (not shown) may be activated. When a passive interlock is engaged, the energy transfer system (1400) may be configured to wait for it to be extinguished. After the correction action is initiated, the process (1700) can return to the process block (1701), and this loop can be continued until the process (1700) within the control system (1404) determines that the energy transfer system (1400) is ready to discharge energy to the load (not shown).

[0065] Once the process (1700) within the control system (1404) determines that the energy transfer system (1400) is ready to discharge, the variable impedance networks (1402a, 1402b) of both can be set to predetermined initial values. These initial values ​​can be determined from equations performed in real time within the control system (1404) (e.g., see equations described for FIGS. 15 and 16), set from a predetermined lookup table of predetermined initial values ​​based on parameters such as SOC, cell stack voltages, temperatures, etc. measured in the process block (1701), and / or set from a predetermined lookup table based on characteristic VI curves associated with the cell stacks (1401a, 1401b).

[0066] Once the initial values ​​of the variable impedance networks (1402a, 1402b) are set, the process (1700) for the energy transfer system (1400) (e.g., V o Positive and V o As with the coupling of the load circuit (for negative terminals), the discharge of the load current may be waited for to begin. This may include a process (1700) looping back to the process block (1701). Once the discharge current is detected in the process block (1704), the process block (1705) collects parameters (also referred to as "parametric data") from the battery cell stacks (1401a, 1401b), variable impedance networks (1402a, 1402b), and / or other parts of the system (1400) (e.g., voltage, current, temperature, SOC, charge / discharge cycles, resistance, impedance, etc.) using AFEs (1403a, 1403b) and current sensors (1405a, 1405b). In the process block (1706), this data may be analyzed to determine whether the discharge can be allowed to continue. For example, parameters that may terminate the discharge include a cell stack voltage below a safe limit, a cell stack current above a safe limit, a cell stack temperature outside the safe limits, engaged passive safety interlocks, and / or any other fault in the control or measurement system. If it is determined in the process block (1706) that the discharge cannot be safely continued, the process (1700) may proceed to the process block (1710) to take appropriate action.

[0067] If it is determined in process block (1706) that the discharge can be safely continued, in process block (1707), it may be determined whether adjustment of either or both of the variable impedance networks (1402a, 1402b) is required. For example, according to a non-limiting embodiment of the present disclosure, a control algorithm performed in the control system (1404) may be configured to maintain the average current of the operation (e.g., as measured over a predetermined time period of the current sensors (1405a, 1405b)) as the same in both cell stacks (1401a, 1401b). Consequently, if the most recently collected parametric data indicates that the average current in the cell stack (1402a) is higher than the average current in the cell stack (1401b), the control algorithm performed by the control system (1404) may be configured to take one of two potential actions to apply a correction. The MCU (1404) may signal the switches in the variable impedance network (1402a) to increase the value of the total impedance, or the control system (1404) may signal the switches in the variable impedance network (1402b) to decrease the value of the total impedance. While either choice may be acceptable, the control system (1404) may be configured to favor one of these correction actions over the other according to any one or more predetermined factors. For example, the variable impedance network (1402a) may already be set near its minimum impedance value, in which case the control system (1404) may be configured to reduce the impedance value of the variable impedance network (1402b) instead. Since the control system (1404) is configured to know the state of both of the variable impedance networks (1402a, 1402b), the control system (1404) may be configured to select the most appropriate action.Once a correction action has been determined within the process block (1707), in the process block (1708), the control system (1404) transmits one or more control signals to one or both of the variable impedance networks (1402a, 1402b) to implement the action (i.e., apply new impedance settings). Once the new settings are applied, the process (1700) transmits the battery cell stack currents (. i 1 , i 2 One or both of the processes (1700) may be configured to implement a delay routine (process block (1709)) to allow stabilization under these new settings. Once this delay has expired, the process (1700) may return to the process block (1705). Note that the algorithms described above for the process block (1707) are exemplary and are not limiting to the embodiments of the present disclosure.

[0068] Embodiments of the present disclosure are further illustrated by the following examples, which are described to illustrate the gist of the invention as disclosed herein and should not be interpreted as limiting. The examples describe testing performed to verify the ability of embodiments of the systems to deliver and release one or more materials under various conditions illustrating various environments in which embodiments of the systems may be used.

[0069] Referring to FIG. 18, an energy transfer system (1800) configured according to embodiments of the present disclosure is illustrated. In the energy transfer system (1800), a first battery cell stack (1801a) is coupled in parallel to a second battery cell stack (1801b), each of which may be coupled to similar control and monitoring circuits. The battery cell stacks (1801a, 1801b) may be coupled to a common control system (e.g., a microcontroller "MCU") (1804) so ​​that parametric information from each battery stack may be collected (e.g., simultaneously) and control algorithms may be performed to control the operation of either or both of the variable impedance networks (1802a, 1802b). The voltage of each cell in the battery stack (1801a) may be monitored by an analog front-end measurement device ("AFE") (1803a). The AFE (1803a) can also collect temperature data and transmit the collected data to the control system (1304). The battery stack (1801a) V through the sensing resistor (Rsense) (1805a). o It can be coupled to the negative. Each side of the sensing resistor (1805a) is the battery current to the fuel gauge IC (1806a) whenever current is present in the sensing resistor (1805a). i 1 It can be coupled to a fuel gauge integrated circuit ("IC") (1806a) that provides a voltage representing the value of ). The fuel gauge IC (1806a) can communicate information about the state of charge ("SOC") of the battery stack (1801a) with the control system (1804). The voltage of each cell in the battery stack (1801b) can be monitored by the AFE (1803b). The AFE (1803b) can also collect temperature data and transmit the collected data to the control system (1304). The battery stack (1801b) V through a sensing resistor (Rsense) (1805b). oIt can be coupled to the negative. Each side of the sensing resistor (1805b) is the battery current to the fuel gauge IC (1806b) whenever current is present in the sensing resistor (1805b). i 2 It may be coupled to a fuel gauge integrated circuit IC (1806b) that provides a voltage representing the value of the fuel gauge. The fuel gauge IC (1806b) may communicate information about the SOC of the battery stack (1801b) with the control system (1804). The control system (1804) may be configured to communicate data and / or information to an external host system (e.g., via a communication link or bus (1807)). Internal communications between and / or externally from the control system (1804) may be wired or wireless. Communication protocols that may be used include, but are not limited to, SMB, I2C, RS232, TTL, serial, USB, CAN, network, etc.

[0070] Each variable impedance network (1802a, 1802b) comprises a plurality of diodes having bypass switches as described with respect to FIG. 16. The number of diodes and corresponding switches is exemplified as being the same in each variable impedance network (1802a, 1802b), but the actual number may be the same or different between the two. The number of diodes present in each variable impedance network (1802a, 1802b) is the sum of the forward voltage (Vf) drops of all diodes, from the output terminal V on the high side of each battery cell stack (1801a, 1801b). oDefines the maximum voltage drop to the positive. According to some embodiments of the present disclosure, one or more of the diodes may have different parametric characteristics so that different forward voltage drops are achieved through each diode. The number of active diodes and the number of diodes bypassed in each variable impedance network (1802a, 1802b) may be controlled by a control system (1804) to produce a predetermined magnitude of downshift in the characteristic curves of each battery stack (1801a, 1801b), and thus to influence the load current contribution of each battery stack (1801a, 1801b) in the energy transfer system (1800).

[0071] FIG. 18 shows the total forward voltage drops of all diodes in each variable impedance network (1802a, 1802b) to each battery stack (1801a, 1801b) and output terminal V o An energy transfer system (1800) having open switches in both of the variable impedance networks (1802a, 1802b) so as to be realized between positives is illustrated. FIG. 18 discloses a dual battery stack energy transfer system, but embodiments of the present disclosure may consist of more than two battery stacks combined in various series and / or parallel combinations and monitored and controlled by a control system (1804).

[0072] According to an exemplary embodiment of the energy transfer system (1800), the battery stack (1801a) comprises battery cells composed of a relatively high cycle life battery chemical (e.g., LFP or LTO) such that its terminal voltage and characteristic VI curves overlap with those of the battery stack (1801b) comprising NMC battery cells, as illustrated by the exemplary characteristic VI curves in FIG. 20. The LFP stack (1801a) comprises 13 cells having a typical total charge voltage (3.6 V / cell) between 44 V and 46.8 V. The NMC battery stack (1801b) comprises 11 cells having a typical total charge voltage (4.0 V / cell) between 43.3 V and 46.2 V. Both the LFP and NMC battery stacks can be charged to the same voltage in a full charge, or alternatively, the maximum charge voltage can be adjusted so that the voltage of one of the battery stacks is maintained higher than the voltage of the other battery stack. In this embodiment, the LFP battery stack (1801a) and the NMC battery stack (1801b) are configured to have similar chemical capacities in ampere-hours (Amp-hour).

[0073] Referring to FIG. 19, in the default operating mode, the system (1800) can be configured such that all diode switches within both of the variable impedance networks (1802a, 1802b) are closed, so that the characteristic VI curves of each battery stack (1801a, 1801b) V oDiodes can be bypassed to be presented at the positive terminal. Within the load current ranges of interest, the battery stacks (1801a, 1801b) will share the load based on the stack voltage defined by the characteristic VI curves at all points in time during discharge, because the two sets of characteristic VI curves lie above each other under most conditions of the charge state. At any given moment, the currents in each battery stack are the currents in the LFP stack (1801a). i 1 and current in the NMC stack (1801b) i 2 There will be individual characteristic VI curves corresponding to the same voltage on the battery terminals. The greater the difference in the positions of the characteristic VI curves, the greater the current gap will be between the stacks (1801a, 1801b). Referring to the battery stack voltage(s) as a function of charge state illustrated in FIG. 20, it can be seen from the exemplary discharge of the parallel-coupled LFP battery stack (1801a) and NMC battery stack (1801b) that at certain load points, the NMC battery stack (1801b) initially has a higher terminal voltage for a first approximately 10% depth of discharge. During the remainder of the depth of discharge, the LFP battery stack (1801a) will have a higher terminal voltage and will have a proportionally larger share of the current during discharge.

[0074] FIG. 21 illustrates a graph of an exemplary discharge of a system (1800) configured in FIG. 19 at a constant power of 100 W (all diode switches in both of the variable impedance networks (1802a, 1802b) are Z for both). var(Becomes 0, so that the battery stack voltages are closed to be directly coupled to the output load). Each battery stack (1801a, 1801b) is charged with a starting voltage of 44 V. The discharge period is approximately 1.8 hours. The battery stacks (1801a, 1801b) can discharge and balance current based on the characteristic VI curves of each battery stack. In accordance with the voltage curves in FIG. 20, when the load is coupled to the energy transfer system (1800), FIG. 21 shows the current i 1This illustrates the rise in the LFP stack (1801a) and the rapid drop in voltage below that of the NMC stack (1801b). This is attributed to the sharp open-circuit voltage curve for the LFP chemical near the full charge state, and the shift at the operating point from the VI curve of a light load to a higher current VI curve. The NMC stack (1801b) soon achieves a slightly higher terminal voltage compared to the LFP stack (1801a) and carries a significant majority of the load current. After approximately 0.18 hours of discharge, the NMC voltage drops due to its reduced SOC, and the stack voltage begins to dip into the range of the LFP stack (1801a). At this point in the discharge, the LFP stack (1801a) begins to carry a higher percentage of current. From this point, the LFP stack (1801a) maintains a higher voltage and higher current than the NMC stack (1801b) so that the LFP stack (1801a) drops in SOC faster than the NMC stack (1801b) and is ultimately depleted. The SOC for the LFP stack (1801a) moves slowly from 100% to approximately 5% over a cycle of approximately 1.4 hours. At this point in the discharge event, the LFP stack (1801a) is nearly depleted of energy so that its terminal voltage drops below that of the NMC battery stack (1801b). The NMC battery stack (1801b) then takes over increasing its current allocation to nearly 100% during the final few minutes of the discharge.

[0075] FIG. 22 shows the LFP current from the start of the discharge until the energy in the LFP stack (1801a) is completely depleted. i 1 This NMC current i 2This illustrates an exemplary embodiment of the operation of process blocks (1707 to 1708) for a system (1800), the purpose of which is to configure the system (1800) so that the energy discharge is always higher than that of the NMC stack (1801b) and biased toward the LFP stack (1801a). In this exemplary embodiment, the diode switches in the variable impedance network (1802a) for the LFP stack (1801a) are closed, so that Z with respect to the LFP stack (1801a) var = 0 is generated, and the diode switches in the variable impedance network (1802b) for the NMC stack (1801b) are opened, Z var (Z var It generates a maximum value of = 3*Vf). As can be seen from the graph exemplified in Fig. 23, the LFP characteristic VI curves remain as in the previous example (see Fig. 20), but the NMC characteristic VI curves are now shifted downward by an amount equal to 3*Vf.

[0076] As expected, based on the configuration of the energy transfer system (1800) illustrated in FIG. 22, the voltage curves for the NMC stack (1801b) are Z var Due to the contribution, it will be offset lower than the LFP stack (1801a). The shifted voltage curves are shown in Fig. 23. The LFP voltage is nearly greater than the NMC voltage over the entire SOC range, and its associated Z var This downward shift in NMC voltage caused by translates into a significant bias of current for the LFP stack (1801a) during most of the discharge.

[0077] FIG. 24 illustrates a graph of an exemplary discharge of the system (1800) configured in FIG. 22 at a constant power of 100 W. Each battery stack (1801a, 1801b) is charged with a starting voltage of 44 V. The discharge period is approximately 1.8 hours. In this example, the diode switches in the variable impedance network (1802a) are its Z var = 0 and the LFP battery stack voltage is output load V o While closed to be directly coupled to the positive, the diode switches in the variable impedance network (1802b) are kept open so that the NMC stack voltage is offset downward by 3*Vf. The operating points of each battery stack of the battery stacks (1801a, 1801b) are located at points on their respective characteristic VI curves so that the output current of the energy transfer system (1800) is biased much more toward the LFP stack (1801a) than in the examples in FIG. 20 and 21. Contrasting the discharge exemplified in FIG. 24 with the discharge exemplified in FIG. 21, it can be seen that the NMC stack (1801b) initially delivers approximately 20% of the load current due to the lower position of the NMC characteristic VI curves. Until the system operating points suddenly reverse for a short time later as they switch through the characteristic VI curves according to the changing SOC of the various battery stacks, the NMC current ( i 2 ) initially LFP current( i 1There is no current "reversal" that occurs when it rises above ). The LFP stack (1801a) maintains a higher rate of total discharge current until this time when the LFP stack (1801a) is nearly depleted. The SOC for the LFP stack (1801a) slowly transitions from 100% to approximately 5% over a cycle of approximately 1.4 hours. At this point in the discharge event, the LFP battery stack (1801a) is nearly depleted of energy, and in low states of charge such as here, the LFP characteristic VI curves drop below the corresponding NMC characteristic VI curves at a much higher NMC SOC, and thus, the NMC stack (1801b) takes on the task of steadily increasing its rate of total output until the end of discharge.

[0078] By adjusting each variable impedance network (1802a, 1802b) so that the positions of the corresponding characteristic VI curves are also adjusted, current sharing between different battery stacks can be shifted, and discharge current can be biased toward one stack or another to meet specific purposes and optimize specific performance characteristics. For example, in the case of hundreds of intermediate discharge events, discharge current is biased toward the battery stack with a relatively higher cycle life and away from the stack with a relatively lower cycle life so that the higher cycle life battery stack delivers many times the cyclic energy of the other battery stack.

[0079] The total discharge depth for an energy storage system will be dependent on the load duration. Often, battery stacks only complete partial discharges in which 40% to 70% of the total stored energy is delivered. As demonstrated in the example in FIG. 24, in the case of a partial discharge lasting 1.3 hours, the high cycle life LFP battery stack (1801a) discharged 95% of its energy (completed 0.95 cycles), while the NMC stack (1801b) discharged only about 40% of its energy (completed 0.40 cycles). If this same discharge occurred 1,000 times, the LFP battery stack (1801a) would be considered to have completed 950 cycles compared to the NMC battery stack (1801b), which would have completed only 400 cycles.

[0080] According to various embodiments of the present disclosure, energy transfer systems (1400 and 1800) can be configured similarly, and thus, control systems, AFEs, fuel gauge ICs, and sensing resistors operate in substantially similar ways, except for modifications that can be made to any one of the systems depending on the type of energy storage systems to which they are combined and the type of configurations used in variable impedance networks.

[0081] Digital communication links (1407, 1807) may be configured to transmit some data from a control system (1404, 1804) to a host system (not shown). Energy transfer systems such as 1400, 1800 may be embedded within larger systems such as computers, electric bicycles or scooters, electric vehicles, etc. As such, these larger systems are considered as hosts for the embedded energy transfer systems and may have other systems such as motor controls, user or operator interfaces, and similar ones that can rely on the latest status of the supporting energy transfer systems for safe operation. In the case of an electric vehicle, this host system may be a motor control system capable of reducing the speed of the motors when the battery temperature exceeds a certain threshold or when the available energy falls below a certain threshold. Digital communication links (1407, 1807) can be configured to transmit an instantaneous description of the status of the energy transfer system (1400, 1800) upstream to the supplied equipment.

[0082] According to embodiments of the present disclosure, the fuel gauges disclosed for energy transfer systems (1400, 1800) may be implemented as integrated circuits that may be in a separate package from an MCU (1404, 1804), but the functions may also be integrated into the MCU (1404, 1804). The fuel gauges may be configured to receive battery temperature information and battery cell voltage information by direct measurement or as packets of digital data from AFEs relayed to the fuel gauge by the MCU (1404, 1804), and / or may include an analog-to-digital converter configured as a coulomb counter that measures an analog voltage appearing across a current sensing resistor and mathematically integrates these measurements in either a digital or analog domain. This voltage developed across the sensing resistor is a direct representation of the current flowing into or out of the battery cell stack, where negative voltages represent the current flowing out of the battery cell stack (discharge), and positive voltages represent the current flowing into the battery cell stack (charge). By mathematically integrating these currents over time, the net change in charge contained within the battery cell stack can be determined, and by summing the net change in charge at any given time with a known starting SOC, the current SOC can be determined.The fuel gauge may also be configured to include digital hardware and programmed commands to compute other parameters, such as the instantaneous current in the sensing resistor, the average current in the sensing resistor over some averaging time period (such as seconds or tens of seconds), the total number of charge and discharge cycles (determined by the total charge passed in each direction starting from the operating date of the battery cell stack), and the resistance of the battery cells for individual cells and / or all cells as a whole.

[0083] According to embodiments of the present disclosure, the battery stacks disclosed for energy transfer systems (1400 and 1800) may also include an anti-backflow device managed by a common control system. The function of such an anti-backflow device is to prevent the unwanted transfer of energy from one battery stack to another. The operation of such an anti-backflow device is described in PCT / US2017 / 068301.

[0084] According to alternative embodiments of the present disclosure, the variable impedance network(s) may be composed of a plurality of resistors connected in series and associated switches subsequently connected in parallel. An energy transfer system composed of such a variable impedance network provides the ability to manipulate the characteristic VI curves of separate battery stacks in a similar manner and can achieve similar results when biasing discharge currents between battery stacks or energy storage systems.

[0085] In another embodiment of the present disclosure, the variable impedance network(s) may be composed of resistors connected in parallel to provide finer resolution in current-dependent voltage drops than resistors in series. The increased resolution for voltage steps may be used to further adjust the output voltage of the energy transfer system (1400, 1800).

[0086] According to alternative embodiments of the present disclosure, one or more of the switchable diodes in any or all of the variable impedance networks may be replaced with a network of parallel switchable resistors. Under these configurations, the control system may use series diodes for "rough" control and parallel resistors for "fine" control. Nevertheless, embodiments of the present disclosure may be implemented with one or more of the variable impedance networks comprising switchable diodes, switchable resistors, or a combination of both.

[0087] The embodiments of the disclosure described herein may be used in uninterruptible power supply ("UPS") systems and energy storage systems that require high energy density to maximize capacity-measured energy storage. These also require high cycle life, particularly under repetitive deep discharge conditions. Energy storage systems may be configured to undergo a full charge / discharge cycle once a day. However, the depth of discharge for the system will vary based on load demand. Low load demand will reduce the required energy delivered by the energy storage system, so that the battery stack designed for high cycle count will be drained first, rather than the battery stack designed for power density.

[0088] The embodiments of the disclosure described herein may be used for vehicle applications where long cycle life and long run times are prioritized, but there are periodic demands for instantaneous high current loads.

[0089] As recognized by a person skilled in the art, embodiments of the present invention (e.g., control systems (1404, 1804) and process (1700)) may be embodied as systems, methods, and / or program products. Accordingly, embodiments of the present invention (e.g., control systems (1404, 1804), AFEs, fuel gauges, variable impedance networks) may take the form of entirely hardware embodiments, entirely software embodiments (including firmware, resident software, micro-code, etc.), or embodiments combining software and hardware embodiments which may all generally be referred to herein as “circuit,” “circuit part,” “module,” or “system.” Additionally, embodiments of the present invention (e.g., process (1700)) may take the form of program products embodied in one or more computer-readable storage media(s) having computer-readable program code embodied on the medium. (However, any combination of one or more computer-readable media(s) may be used. A computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium.)

[0090] Additionally, it will also be noted that each block of circuit blocks and / or functions represented in process (1700), and combinations of blocks in circuit blocks and / or functions represented in process (1700), may be implemented by special-purpose hardware-based systems that perform specific functions or acts, or by combinations of special-purpose hardware and computer instructions. For example, a module (e.g., control systems (1404, 1804), AFEs, fuel gauges, variable impedance networks) may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, controllers, or other individual components. A module (e.g., control systems (1404, 1804), AFEs, fuel gauges, variable impedance networks) may also be implemented in programmable hardware devices such as field-programmable gate arrays, programmable array logic, programmable logic devices, etc.

[0091] Titles used in this specification are for organizational purposes only and are not intended to be used to limit the scope of the description. As used throughout this application, the word "may" is used in a permissive sense (i.e., to have the possibility) rather than in a mandatory sense (i.e., to mean must). Similarly, the words "include," "including," and "includes," "contain," "containing," and "contains" mean to include, but are not limited thereto.

[0092] Various units, circuits, circuitry, or other components (e.g., control systems (1404, 1804), AFEs, fuel gauges, variable impedance networks) may be described as having a task or being "configured to" perform tasks. In these contexts, "configured to" is a broad approximation of a structure that generally means having circuitry that is capable of performing a task or tasks during operation. As such, a unit / circuit / component may be configured to perform a task even if the unit / circuit / component is not currently on. Generally, the circuitry forming the structure corresponding to "configured to" may include hardware circuits and / or software (including firmware, resident software, microcode, etc.). Similarly, various units / circuits / components may be described as having a task or performing tasks for convenience of description. Such descriptions should be interpreted as including the phrase "configured to." Citing a unit / circuit / component configured to perform one or more tasks is expressly intended not to invoke the interpretation of 35 USC §112 Paragraph 6 for that unit / circuit / component.

[0093] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as universally understood by a person skilled in the art to which the essence of the invention disclosed herein belongs.

[0094] As used herein, the terms “about” and “approximately” are used to provide flexibility regarding numerical range endpoints by defining that a given value may be “a little above” or “a little below” the endpoint.

[0095] In the description herein, flowchart techniques may be described as a series of sequential actions. The sequence of actions and the parties performing the actions may be freely modified without departing from the scope of the teachings. Actions may be added, deleted, or modified in some manner. Similarly, actions may be reordered or looped. Furthermore, while processes, methods, algorithms, etc. may be described in a sequential order, such processes, methods, algorithms, or any combination thereof may be operable to be performed in an alternative order. Additionally, some actions within a process, method, or algorithm that may be performed simultaneously at least for a certain period of time (e.g., actions performed in parallel) may also be performed wholly, partially, or in any combination thereof.

[0096] Conversely, unless explicitly stated, "or" refers to inclusive-or rather than exclusive-or. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0097] As used herein, the use of the character " / " between two words when used in the context of the term "and / or" and a list of entities refers to entities existing alone or in combination. Thus, for example, the phrase "A, B, C, and / or D" includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D.

[0098] Additionally, the use of singular expressions is employed to describe the elements and resources described herein. This is done merely for convenience and to give a general meaning to the scope of the invention. This description should be read to include one or at least one, and the singular also includes the plural, or vice versa, unless it is clear that the singular is otherwise intended. For example, when a single device is described herein, more than one device may be used in place of the single device. Similarly, when more than one device is described herein, the single device may be substituted for that single device.

[0099] To the extent not described herein, many details regarding specific materials, processing acts, and circuits are existing and can be found in textbooks and other sources within the fields of computing, electronics, and software technology.

Claims

Claim 1 As an energy transfer system, a first energy storage system having a set of first characteristic VI curves; a second energy storage system having a set of second characteristic VI curves ― said second energy storage system is substantially different from said first energy storage system in a predetermined manner, and said set of first characteristic VI curves intersects at least one of said set of second characteristic VI curves ―; a first variable impedance network coupled in series between said first energy storage system and an output terminal ― said first variable impedance network has a first adjustable impedance ―; a second variable impedance network coupled in series between said second energy storage system and the output terminal ― said second variable impedance network has a second adjustable impedance ―;and a control system configured to (1) collect parametric data from each of the first energy storage system and the second energy storage system, (2) optionally, signal to the first variable impedance network to adjust the first variable impedance so as to shift the position of the set of first characteristic VI curves associated with the first energy storage system relative to the set of second characteristic VI curves of the second energy storage system and thereby change the level of the first current delivered to the output terminal by the first energy storage system, and (3) signal to the second variable impedance network to adjust the second variable impedance so as to shift the position of the set of second characteristic VI curves associated with the second energy storage system relative to the position of the set of first characteristic VI curves of the first energy storage system and thereby change the level of the second current delivered to the output terminal by the second energy storage system, wherein the control system comprises, in a predetermined manner, the parametric data of the first energy storage system and the second energy storage system as a function of the An energy transfer system configured to signal at least one of the first variable impedance network and the second variable impedance network to control the relative percentage of the total current supplied to the output terminal by each of the first energy storage system and the second energy storage system. Claim 2 An energy transfer system according to claim 1, wherein the first variable impedance network comprises a plurality of switchable resistive elements configured to adjust the effective resistance of the first variable impedance network over a predetermined range under the control of the control system. Claim 3 An energy transfer system according to claim 1, wherein the first variable impedance network comprises a plurality of switchable diodes configured to adjust the number of forward diode voltage drops existing in the first variable impedance network over a predetermined range under the control of the control system. Claim 4 In claim 1, the first energy storage system and the first variable impedance network are coupled in parallel with the second energy storage system and the second variable impedance network with respect to the output terminal, and the first energy storage system is substantially different from the second energy storage system in at least one of chemical composition, terminal voltage characteristics, optimal temperature range, temperature operating point, and operating current. Claim 5 An energy transfer system according to claim 4, wherein at least one of the first characteristic VI curves intersects at least one of the second characteristic VI curves in a predetermined charge state. Claim 6 In claim 5, the energy transfer system is configured to signal at least one of the first variable impedance network and at least one of the second variable impedance network to control where at least one of the first characteristic VI curves intersects at least one of the second characteristic VI curves. Claim 7 In claim 4, the first energy storage system comprises a first battery cell stack of a plurality of battery cells, each having a first chemical composition, and the second energy storage system comprises a second battery cell stack of a plurality of battery cells, each having a second chemical composition, wherein the first chemical composition is different from the second chemical composition, an energy transfer system. Claim 8 In claim 7, the first battery cell stack comprises a first number of series-connected battery cells, the second battery cell stack comprises a second number of series-connected battery cells, and the first number is different from the second number, an energy transfer system. Claim 9 An energy transfer system according to claim 4, wherein the first energy storage system is selected from a first group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system, and the second energy storage system is selected from a second group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system. Claim 10 An energy transfer system according to claim 5, wherein the control system is configured to update the values ​​of parametric data of the first energy storage system and the second energy storage system and to transmit an updated signal to at least one of the first variable impedance network and the second variable impedance network in order to maintain the at least one operating characteristic of the energy transfer system at a predetermined level. Claim 11 In claim 7, the control system is configured to selectively signal the first variable impedance network and the second variable impedance network as a function of parametric data collected from the first energy storage system and the second energy storage system, wherein the parametric data includes voltage, current, temperature, and state of charge (SOC) measurements associated with the transfer of the first current by the first energy storage system and the transfer of the second current by the second energy storage system. Claim 12 In claim 1, a first analog front end configured to measure cell voltages associated with the first energy storage system and to communicate said cell voltages to the control system; a second analog front end configured to measure cell voltages associated with the second energy storage system and to communicate said cell voltages to the control system; a set of first temperature sensors coupled to cells included in the first energy storage system and a circuit for communicating said temperature data to the control system; a set of second temperature sensors coupled to cells included in the second energy storage system and a circuit for communicating said temperature data to the control system; a first sensing resistor coupled to the first energy storage system; a second sensing resistor coupled to the second energy storage system; a first fuel gauge circuit coupled to the first sensing resistor — the first fuel gauge circuit is configured to determine first information as a function of the first current detected by the first sensing resistor and to communicate said first information to the control system —; a second fuel gauge circuit coupled to the second sensing resistor — the second fuel gauge circuit is configured to determine second information as a function of the second current detected by the second sensing resistor and to communicate said second information to the control An energy transfer system further comprising—configured to communicate with a system, wherein the control system is configured to selectively signal the first variable impedance network and the second variable impedance network as a function of cell voltages associated with the first energy storage system, cell voltages associated with the second energy storage system, the first information, and the second information. Claim 13 A method for delivering energy to a load, comprising: collecting first parametric data including voltage, current, charge state, and temperature information related to the supply of a first current to the load by a first energy storage system within an energy transfer system; collecting second parametric data including voltage, current, charge state, and temperature information related to the supply of a second current to the load by a second energy storage system within the energy transfer system; adjusting the first current by a first variable impedance network as a function of the collected first parametric data and the second parametric data by shifting the position of a set of first characteristic VI curves associated with the first energy storage system relative to a set of second characteristic VI curves associated with the second energy storage system — the first variable impedance network is coupled in series between the first energy storage system and the load —; and adjusting the second variable impedance as a function of the collected first parametric data and the second parametric data by shifting the position of the set of second characteristic VI curves associated with the second energy storage system relative to the set of first characteristic VI curves. A step of regulating the second current through a network — the second variable impedance network is coupled in series between the second energy storage system and the load, the first energy storage system and the second energy storage system are coupled in parallel with respect to the load, and the first energy storage system has a chemical composition or physical configuration different from that of the second energy storage system —;A method for delivering energy to a load, comprising the step of signaling at least one of the first variable impedance network and the second variable impedance network to shift the relative positions of sets of characteristic VI curves associated with the first energy storage system and / or the second energy storage system in order to control the relative percentage of the total current provided to an output terminal in the energy transfer system by each of the first energy storage system and the second energy storage system in a predetermined manner as a function of the first parametric data and the second parametric data in order to optimize at least one operating characteristic of the energy transfer system. Claim 14 A method for delivering energy to a load according to claim 13, wherein the shifting of the set of first characteristic VI curves associated with the first energy storage system and the corresponding adjustment of the first current are performed in response to a first control signal received from a control system that has collected the first parametric data, and the shifting of the set of second characteristic VI curves and the corresponding adjustment of the second current are performed in response to a second control signal received from a control system that has also collected the second parametric data. Claim 15 A method for delivering energy to a load, wherein, in claim 14, the first variable impedance network comprises a plurality of switchable resistive elements configured to adjust the effective resistance of the first variable impedance network in response to the first control signal, and the second variable impedance network comprises a plurality of switchable resistive elements configured to adjust the effective resistance of the second variable impedance network in response to the second control signal. Claim 16 A method for delivering energy to a load, wherein the first variable impedance network comprises a plurality of switchable diodes configured to control the number of forward diode voltage drops present in the first variable impedance network in response to the first control signal, and the second variable impedance network comprises a plurality of switchable diodes configured to control the number of forward diode voltage drops present in the second variable impedance network in response to the second control signal. Claim 17 A method for delivering energy to a load, wherein, in claim 14, at least one of the first characteristic VI curves intersects at least one of the second characteristic VI curves in a predetermined charge state, and the control system is configured to signal at least one of the first variable impedance network and at least one of the second variable impedance network to adjust the first impedance of the first variable impedance network and at least one of the second variable impedance network in order to adjust the point where at least one of the first characteristic VI curves intersects at least one of the second characteristic VI curves. Claim 18 A method for delivering energy to a load, wherein the first energy storage system comprises a first battery cell stack of a plurality of battery cells, each having a first chemical composition, and the second energy storage system comprises a second battery cell stack of a plurality of battery cells, each having a second chemical composition, and the first chemical composition is different from the second chemical composition. Claim 19 A method for delivering energy to a load, wherein, in claim 14, the first energy storage system is selected from a first group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system, and the second energy storage system is selected from a second group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system. Claim 20 delete

Images