Battery system

Abstract

Even when the external charging power is low, it enables relatively accurate detection of battery cell disconnections. [Solution] A battery pack includes multiple single cells connected in parallel. A battery pack consists of multiple battery packs connected in series. The battery ECU selects two battery packs from those included in the battery pack and calculates a threshold S from the current IB, the internal resistance R of one of the selected battery packs, and the function f(n) (S16). The voltage difference ΔV, which is the difference in voltage VB between the two selected battery packs, is compared with the threshold S. If the voltage difference ΔV is greater than or equal to the threshold S, it is determined that a break has occurred in one of the single cells of the two selected battery packs (S17).

Description

Technical Field

[0001] The present disclosure relates to a battery system.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2019-113455 (Patent Document 1) discloses a secondary battery system mounted on a vehicle. This secondary battery system includes a battery pack (battery module) in which a plurality of modules each having battery cells connected in parallel are connected in series. In this secondary battery system, before external charging (plug-in charging) of the battery pack, if the difference between the highest voltage and the lowest voltage of the module is less than a reference value, and after external charging, if the difference between the highest voltage of the module and "a voltage other than the highest voltage and the lowest voltage" is greater than or equal to the reference value, it is diagnosed that an abnormality has occurred in which the current path of the battery cells included in any of the modules is interrupted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, disconnection of battery cells is detected based on the voltages before and after external charging. When the difference in SOC (State Of Charge) before and after external charging is small, in other words, when the amount of external charging power is small, the difference in voltage before and after external charging is small. Therefore, in Patent Document 1, there is a concern that the accuracy of detecting disconnection of battery cells may be low when the amount of external charging power is small.

[0005] An object of the present disclosure is to enable relatively accurate detection of disconnection of battery cells even when the amount of external charging power is small.

Means for Solving the Problems

[0006] The battery system of this disclosure comprises a battery pack including a plurality of battery packs electrically connected in series, and a control device. Each of the plurality of battery packs includes a plurality of battery cells electrically connected in parallel. The control device performs a disconnection detection process to detect a disconnection in a battery cell included in a battery pack. The disconnection detection process compares the voltages of two battery packs and determines that a battery cell in one of the battery packs is disconnected if the voltage difference between the two battery packs is greater than or equal to a threshold.

[0007] In this configuration, since the battery pack consists of multiple battery cells connected in parallel, if a battery cell breaks, the internal resistance of the battery pack increases, and the current flowing through the normal (unbroken) battery cells also increases. Therefore, when a battery cell breaks, the overvoltage during charging and discharging of the battery pack becomes larger compared to when there is no break. Thus, by comparing the voltages of two battery packs, if the voltage difference exceeds a threshold, it can be determined that a battery cell in one of the battery packs is broken. Even when the amount of externally charged power is small, battery cell breakage can be detected with relatively high accuracy.

[0008] Preferably, the control device may perform a wire break detection process when the difference between the maximum and minimum values ​​of the battery pack's SOC is less than or equal to a first predetermined value, the difference between the maximum and minimum values ​​of the battery pack's temperature is less than or equal to a second predetermined value, and the charge / discharge current of the battery pack is greater than or equal to a third predetermined value.

[0009] The voltage of a battery pack changes with its State of Charge (SOC) and temperature. Therefore, when the difference in SOC between two battery packs is large, or when the temperature difference is large, the voltage difference between the battery packs becomes large regardless of whether a battery cell is broken. Furthermore, the larger the charge / discharge current, the greater the overvoltage when a battery cell is broken. With this configuration, a wire break detection procedure is performed when the difference between the maximum and minimum SOC values ​​of the battery packs is less than or equal to a first predetermined value, the difference between the maximum and minimum temperature values ​​of the battery packs is less than or equal to a second predetermined value, and the charge / discharge current of the battery pack is greater than or equal to a third predetermined value. Thus, a wire break in a battery cell can be detected with high accuracy.

[0010] Preferably, the battery pack is mounted on the vehicle as a power source, and the control device may perform wire break detection processing when the battery pack is being externally charged or when the vehicle is running at a steady pace.

[0011] This configuration allows for wire break detection during external charging of the battery pack or during steady-state vehicle operation. During external charging and steady-state operation, the battery pack's charge and discharge current is relatively stable. Therefore, wire breaks in the battery cells can be detected with high accuracy.

[0012] Preferably, the control device may set a limit value for the input and output power of the battery pack based on the voltage difference between the two battery packs.

[0013] The more broken battery cells there are, the greater the internal resistance of the battery pack. The larger the voltage difference between two battery packs, the more broken battery cells there are, and the fewer normal (unbroken) battery cells there are. Therefore, by setting input / output power limits for the battery pack based on the voltage difference between two battery packs, it is possible to set limits according to the number of normal battery cells, thereby properly protecting the battery cells included in the battery pack. [Effects of the Invention]

[0014] According to this disclosure, even when the external charging power is low, disconnections in battery cells can be detected with relatively high accuracy. [Brief explanation of the drawing]

[0015] [Figure 1] This is an overall configuration diagram of an electric vehicle equipped with the battery system according to this embodiment. [Figure 2] This diagram shows the relationship between the voltage VB and current IB of a battery pack. [Figure 3] This flowchart shows an example of the limit value calculation process performed by the battery ECU. [Modes for carrying out the invention]

[0016] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0017] Figure 1 is an overall configuration diagram of an electric vehicle 1 equipped with a battery system B according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, an electric vehicle (BEV: Battery Electric Vehicle). The electric vehicle 1 may also be a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle) equipped with an internal combustion engine and a battery. The electric vehicle 1 comprises a motor generator (MG: Motor Generator) 10 which is a rotating electric machine, a power transmission gear 20, drive wheels 30, a power control unit (PCU: Power Control Unit) 40, a system main relay (SMR: System Main Relay) 50, a battery pack BP, a monitoring unit 200, a battery ECU (Electronic Control Unit) 300, and a control ECU 500. The battery ECU 300 and the control ECU 500 correspond to examples of "control devices" in this disclosure.

[0018] MG10 is, for example, an embedded permanent magnet synchronous motor (IPM motor) that has both the function of a motor and the function of a generator. The output torque of MG10 is transmitted to the drive wheels 30 via a power transmission gear 20 which includes a reduction gear and a differential gear.

[0019] When the electric vehicle 1 is braked, the MG10 is driven by the drive wheels 30, and the MG10 operates as a generator. As a result, the MG10 also functions as a braking device that performs regenerative braking, converting the kinetic energy of the electric vehicle 1 into electrical power. The regenerative power generated by the regenerative braking force in the MG10 is stored in the battery pack BP.

[0020] The PCU 40 is a power conversion device that converts power bidirectionally between the MG 10 and the battery pack BP. The PCU 40 includes, for example, an inverter and a converter that operate based on a control signal from the control ECU 500.

[0021] The SMR 50 is electrically connected to the power line connecting the battery pack BP and the PCU 40. When the SMR 50 is ON (closed) in response to a control signal from the control ECU 500, power can be exchanged between the battery pack BP and the PCU 40. On the other hand, when the SMR 50 is OFF (open) in response to a control signal from the control ECU 500, the electrical connection between the battery pack BP and the PCU 40 is interrupted.

[0022] The battery pack BP stores power for driving the MG 10. The battery pack BP is a rechargeable DC power source (secondary battery), and a plurality of battery modules 100 are electrically connected in series. The battery module 100 is composed of a plurality of single cells (battery cells) 101 that are electrically connected in parallel. The symbol r represents the internal resistance of the single cell 101. The single cell 101 may be composed of, for example, a lithium-ion battery. The number of the battery modules 100 and the single cells 101 may be plural and arbitrary.

[0023] The monitoring unit 200 includes a voltage sensor 210, a current sensor 220, and a temperature sensor 230. The voltage sensor 210 is provided for each battery module 100 and detects the voltage VB of the battery module 100. The voltage VB is the voltage between the terminals of the battery module 100. The current sensor 220 detects the current IB input to and output from the battery pack BP (battery module 100). When the battery pack BP discharges, the current IB has a negative (-) value, and when the battery pack BP charges, the current IB has a positive (+) value. The temperature sensor 230 is provided for each battery module 100 and detects the temperature TB of the battery module 100.

[0024] The electric vehicle 1 is equipped with an inlet 60, and the battery pack BP can be externally charged using the charging equipment (EVSE: Electric Vehicle Supply Equipment) 400. The inlet 60 is configured to be connectable to a connector 420 provided at the end of the charging cable 410 of the EVSE 400. The inlet 60 is electrically connected to the power line connected to the battery pack BP. In this embodiment, the EVSE 400 outputs DC power to charge the battery pack BP (external charging), but it may also be configured to supply AC power from the EVSE 400 to charge the battery pack BP. In this case, the electric vehicle 1 is equipped with a charger that converts AC power to DC power. In this embodiment, when the SMR 50 is closed, the inlet 60 and the battery pack BP are connected, enabling external charging. Alternatively, the inlet 60 may be connected to the power line between the battery pack BP and the SMR 50 via a charging relay, and the battery pack BP may be configured to be externally charged when the charging relay is closed.

[0025] The battery ECU 300 includes a CPU (Central Processing Unit) 301 and a memory 302. The battery ECU 300 uses signals received from the monitoring unit 200 to estimate the State of Charge (SOC) of the battery pack 100 and outputs it to the control ECU 500. The SOC of the battery pack 100 may be estimated, for example, from the SOC-OCV (Open Circuit Voltage) characteristics of the battery pack 100, or the SOC may be estimated using the Coulomb counting method in combination.

[0026] Furthermore, the battery ECU 300 calculates the internal resistance R of each battery pack 100 and outputs it to the control ECU 500. The internal resistance R may be calculated using an IV plot. For example, during the charging and discharging of the battery pack BP, the current IB and voltage VB are plotted on a graph with current on the vertical axis and voltage on the horizontal axis for a certain period of time, and the slope of the resulting straight line is used to calculate the internal resistance R.

[0027] The control ECU 500 includes a CPU 501 and a memory 502. Based on signals received from the battery ECU 300, signals from various sensors (not shown) (for example, accelerator opening signal, vehicle speed signal, etc.), and information such as maps and programs stored in the memory 502, the control ECU 500 controls each device so that the electric vehicle 1 reaches a desired state.

[0028] Figure 2 shows the relationship between the voltage VB and current IB of the battery pack 100. In Figure 2, the vertical axis represents the voltage VB of the battery pack 100, and the horizontal axis represents the current IB during charging of the battery pack 100. The solid line shows the relationship between voltage VB and current IB for a battery pack 100 in which there are no broken individual cells 101 and the SOC is 50%. The dashed line shows the relationship between voltage VB and current IB for a battery pack 100 in which one individual cell 101 is broken and the SOC is 50%. The broken line shows the relationship between voltage VB and current IB for a battery pack 100 in which there are no broken individual cells 101 and the SOC is 55%.

[0029] Due to the internal resistance R of the battery pack 100, the overvoltage increases as the current IB increases; therefore, during charging, the voltage VB increases in proportion to the increase in current IB. The electromotive force of the battery pack 100 is greater when the state of charge (SOC) is higher. For this reason, if there is no break in the individual cell 101, as shown by the solid line (SOC 50%) and dashed line (SOC 55%) in Figure 2, the voltage VB increases almost parallel to the increase in current IB while maintaining a voltage difference corresponding to the SOC.

[0030] Since the battery pack 100 is composed of multiple individual cells 101 connected in parallel, if an individual cell 101 breaks open, the internal resistance R of the battery pack 100 increases, and the current flowing through the normal (unbroken) individual cell 101 increases. Therefore, when an individual cell 101 breaks open, as shown by the dashed line (SOC 50%) in Figure 2, the voltage VB increases with increasing current IB, with a steeper slope than the solid line (SOC 50%) which indicates that an individual cell 101 is not broken. Thus, for battery packs 100 with the same SOC, it is possible to determine whether an individual cell 101 in the battery pack 100 has broken open by the voltage difference ΔV at the same current IB. Note that during discharge of the battery pack 100 (battery pack BP), the voltage VB decreases according to the magnitude of the overvoltage, but the relationship is similar to that in Figure 2, and for battery packs 100 with the same SOC, it is possible to determine whether an individual cell 101 in the battery pack 100 has broken open by the voltage difference ΔV at the same current IB.

[0031] Figure 3 is a flowchart showing an example of a limit value calculation process performed by the battery ECU 300. This process may be performed by the control ECU 500, or the battery ECU 300 and the control ECU 500 may perform the process in cooperation. This flowchart shows that the process starts when the battery pack BP is externally charged and when the electric vehicle 1 is running at a steady speed. When the connector 420 is connected to the inlet 60 and power is supplied from the EVSE 400, and external charging of the battery pack BP begins, the process of step 10 (hereinafter, steps are abbreviated as "S") 10 starts. Also, when the running state of the electric vehicle 1 becomes steady-state, the process of S10 starts. For example, when the vehicle speed of the electric vehicle 1 is above a predetermined vehicle speed and the change in accelerator opening is below a predetermined value, the control ECU 500 determines that the running state of the electric vehicle 1 is steady-state, and the battery ECU 300 or the control ECU 500 may start the process of S10.

[0032] First, in S10, the voltage VB, temperature TB, current IB, and SOC of the battery pack 100 are obtained. These values ​​are obtained for each battery pack 100. Note that the current IB is the same value for all battery packs 100.

[0033] In the following step S11, it is determined whether the absolute value of the current IB (|IB|) is greater than or equal to a predetermined value α. The predetermined value α may be a current value that allows for the determination of whether or not a break has occurred in a single cell 101 included in the battery pack 100 using the voltage difference ΔV, and may be set in advance by experimentation, for example. If the absolute value of the current IB is greater than or equal to the predetermined value α, the determination is affirmative and the process proceeds to S12. If the absolute value of the current IB is less than the predetermined value α, the determination is negative and the process returns to S10. The predetermined value α corresponds to an example of the "third predetermined value" in this disclosure.

[0034] In S12, it is determined whether the difference ΔSOCm between the maximum and minimum values ​​of the State of Charge (SOC) of the battery pack 100 included in the battery pack BP is less than or equal to a predetermined value β. If the difference in SOC of the battery pack 100 included in the battery pack BP is large, the accuracy of wire break detection of the single cell 101 using the voltage difference ΔV deteriorates. Therefore, wire break detection is performed only when ΔSOCm is less than or equal to the predetermined value β. The predetermined value β may be set in advance by experimentation or the like. If ΔSOCm is less than or equal to the predetermined value β, it is determined to be positive and the process proceeds to S13. If ΔSOCm is greater than the predetermined value β, it is determined to be negative and the process returns to S10. The predetermined value β corresponds to an example of the "first predetermined value" in this disclosure.

[0035] In S13, it is determined whether the difference ΔTBm between the maximum and minimum temperature TB of the battery pack 100 contained in the battery pack BP is less than or equal to a predetermined value γ. If the difference in temperature TB of the battery pack 100 contained in the battery pack BP is large, the accuracy of wire break detection of the single cell 101 using the voltage difference ΔV deteriorates. Therefore, wire break detection is performed only when ΔTBm is less than or equal to the predetermined value γ. The predetermined value γ may be set in advance by experimentation or the like. If ΔTBm is less than or equal to the predetermined value γ, it is determined to be positive and the process proceeds to S14. If ΔTBm is greater than the predetermined value γ, it is determined to be negative and the process returns to S10. The predetermined value γ corresponds to an example of the "second predetermined value" in this disclosure.

[0036] Steps S10 to S13 are repeated until a positive result is obtained in S13. During this repeated process, if external charging is completed or steady-state driving is completed, the process in S14 is not executed, and the routine is terminated. In this case, the wire break detection process in S17 and the limit value calculation process in S21, which will be described later, are not executed during the current external charging or steady-state driving.

[0037] In S14, the voltage VB of each battery pack 100 is corrected using the State of Charge (SOC) of that battery pack 100. For example, the voltage VB is corrected using the maximum SOC of the battery pack 100 included in the battery pack BP as a reference. The voltage VB is corrected by multiplying by a correction coefficient that increases the voltage VB as the difference between the maximum SOC and the SOC of the battery pack 100 increases, or by adding a correction amount that increases the voltage VB. This eliminates the difference in electromotive force due to the difference in SCO (reduces the difference in electromotive force) in each battery pack 100. The correction coefficient or correction amount may be set in advance through experiments, etc., and stored in memory as a map. The reference SOC may be the minimum value, or it may be the average value of the SOCs of the battery pack 100 included in the battery pack BP, as long as the voltage VB can be corrected in a way that eliminates the difference in electromotive force due to the difference in SOC.

[0038] In the subsequent S15, the internal resistance R of each battery pack 100 is obtained. As described above, the internal resistance R is calculated by plotting the current IB and voltage VB for a certain period of time during the charging and discharging of the battery pack BP and obtaining the slope of the straight line, and is stored in memory. In S15, the internal resistance R of each battery pack 100 may be obtained by reading the internal resistance R stored in memory.

[0039] In S16, the threshold S is calculated. First, two battery packs 100 are selected from the battery packs 100 included in the battery pack BP. Then, the threshold S is calculated based on the current IB and the internal resistance R of one of the selected battery packs 100. For example, adjacent battery packs 100 are selected, and the threshold S is calculated from the internal resistance R of one of the battery packs 100, the current IB, and the function f(n). f(n) is a function based on the number of broken wires in the individual cells 101 included in the battery pack 100, and is derived through experimentation or simulation, where n represents the number of broken wires. For example, the threshold S calculated using the function f(1) is the threshold for determining whether the number of broken wires in the individual cells 101 is 1 or more. Also, the threshold S calculated using the function f(n) is the threshold for determining whether the number of broken wires in the individual cells 101 is n or more. In this embodiment, the threshold S is calculated from "S = R × IB × f(1)" using the function f(1) where the number of broken wires is 1.

[0040] In the subsequent S17, the voltage difference ΔV, which is the difference in voltage VB between the two selected battery packs 100, is compared with a threshold S to determine whether the voltage difference ΔV is greater than or equal to the threshold S. If the voltage difference ΔV is greater than or equal to the threshold S, it is determined that a break has occurred in one of the single cells 101 of the two selected battery packs 100, and the process proceeds to S18. If the voltage difference ΔV is less than the threshold S, the determination is negative, and the process proceeds to S19. The process in S17 corresponds to an example of the "break detection process" in this disclosure.

[0041] In S18, the flag F is set to 1. The voltage difference ΔV is then stored in memory, associated with the two selected battery packs 100 and the internal resistance R used when calculating the threshold S, before proceeding to S19. The initial value of the flag F is 0, and it is set to 0 when the electric vehicle 1 is manufactured. The flag F is also set to 0 when the battery pack BP and battery pack 100 are replaced.

[0042] In S19, it is determined whether the processes in S16 and S17 have been completed for all battery packs 100 included in the battery pack BP. If the processes in S16 and S17 have been completed for all battery packs 100, the result is positive and the process proceeds to S20; otherwise, the result is negative and the process returns to S16.

[0043] Returning from S19 to S16, two battery packs 100 are selected from battery packs 100 that are different from the battery pack 100 selected in the previous S16, and a threshold S is calculated. For example, if the first and second adjacent battery packs 100 were selected in the previous S16, in this process, the third and fourth adjacent battery packs 100 are selected, and the threshold S is calculated. Then, in the following S17, the voltage difference ΔV, which is the difference between the voltage VB of the third battery pack 100 and the voltage VB of the fourth battery pack 100, is compared with the threshold S, and it is determined whether the voltage difference ΔV is greater than or equal to the threshold S.

[0044] In this manner, once the processing in S16 and S17 is completed for all battery packs 100 and the process proceeds to S20, it is determined whether flag F is 1 or not. If flag F is 1, the result is positive and the process proceeds to S21. If flag F is 0, the result is negative and the current routine is terminated.

[0045] In S21, the input / output power limit of the battery pack BP is calculated, and the routine ends. In this embodiment, the input / output power limit is calculated based on the maximum value of the voltage difference ΔV stored in memory. For example, if the maximum value of the voltage difference ΔV is ΔVm, the internal resistance R associated with the maximum value ΔVm is read from memory. When this internal resistance R is Rm, "D(n) = Rm × IB × f(n)" is calculated. As mentioned above, f(n) is a function based on the number of broken wires in the single cells 101 included in the battery pack 100, and n represents the number of broken wires. D(n) is calculated by sequentially incrementing the number of n from n=1. The value of n when the calculated D(n) exceeds the maximum value ΔVm is taken as C. C corresponds to the number of broken single cells 101 included in the battery pack 100.

[0046] In S21, the input and output power limits for the battery pack BP are calculated based on the value obtained by subtracting the number of broken single cells 101 C from the total number of single cells 101 in the battery pack 100. The value obtained by subtracting the number of broken single cells 101 C from the total number of single cells 101 in the battery pack 100 is the number of normal (unbroken) single cells 101 in the battery pack 100, and this number is denoted as M. In S21, the input power limit value Win for the battery pack BP is calculated based on M, and the output power limit value Wout for the battery pack BP is calculated based on M. The larger the value of M, the larger the input power limit value Win and the output power limit value Wout may be calculated. The battery ECU 300 controls the input and output currents of the battery pack BP so that the input power (charging power) of the battery pack BP does not exceed the input power limit value Win, and the output power (discharging power) of the battery pack BP does not exceed the output power limit value Wout.

[0047] According to this embodiment, the battery system B includes a battery pack 100 containing a plurality of single cells 101 connected in parallel, and a battery pack BP containing a plurality of battery packs 100 connected in series. The battery ECU 300 (or control ECU 500) performs a wire break detection process (S17) to detect a wire break in a single cell 101 included in the battery pack 100. The wire break detection process (S17) compares the voltages VB of the two battery packs 100, and if the voltage difference ΔVB is greater than or equal to a threshold S, it is determined that a single cell 101 included in one of the battery packs 100 whose voltages were compared is broken (affirmative determination in S17).

[0048] According to this embodiment, when a disconnection of a single cell 101 is detected, the battery ECU 300 (or control ECU 500) sets a limit value for the input and output power of the battery pack BP based on the voltage difference ΔV of the battery pack 100 (S21). By setting the limit value for the input and output power of the battery pack BP based on the voltage difference ΔV of the battery pack 100, the limit value can be set according to the number of normal single cells 101, making it possible to properly protect the single cells 101 included in the battery pack 100.

[0049] In the above embodiment, in S16, the threshold S was calculated using a function f(1) with a number of broken wires of 1. However, the number of broken wires in the function f(n) used to calculate the threshold S may be 2 or more. For example, in the case of a battery pack 100 having characteristics such that a significant voltage difference ΔV occurs when the number of broken wires is 2 or more, the number of broken wires in the function f(n) used to calculate the threshold S may be 2 or more. Furthermore, the combination of the two selected battery packs 100 can be any combination, and ultimately, it is sufficient that broken wire detection of the single cells 101 can be performed for all battery packs 100 included in the battery pack BP.

[0050] In the above embodiment, in S21, the input and output power limits (input power limit Win, output power limit Wout) were calculated using the function f(n) based on the maximum value ΔVm of the voltage difference ΔV. However, for example, a map showing the relationship between current IB, maximum value ΔVm, and the number of broken wires C may be created, and the number of broken wires C may be determined by searching the map using current IB and maximum value ΔVm as parameters. Also, although the limits (input power limit Win, output power limit Wout) were calculated based on the number M of normal (non-broken) single cells 101, the limits may be calculated based on the number of broken wires C.

[0051] In S21, the Malfunction Indicator Lamp (MIL) 260 may be illuminated to trigger an alarm. Alternatively, in S21, information about the battery pack 100 in which a single cell 101 has been disconnected may be stored as a diagnostic trouble code (DCT) in the non-volatile area of ​​memory 502.

[0052] In the above embodiment, the battery pack BP is composed of multiple battery packs 100 connected in series. Alternatively, multiple stacks (battery modules) of multiple battery packs 100 connected in series may be prepared, and these stacks may be electrically connected in series or in parallel to constitute the battery pack BP. In this case, disconnection detection of the individual cells 101 included in the battery pack 100 may be performed for each stack.

[0053] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0054] 1 Electric vehicle, 10 Motor generator (MG), 20 Drive transmission gear, 30 Drive wheels, 40 PCU, 50 SMR, 60 Inlet, 100 Battery pack, 101 Single cell (battery cell), 200 Monitoring unit, 210 Voltage sensor, 220 Current sensor, 230 Temperature sensor, 300 Battery ECU, 301 CPU, 302 Memory, 400 EVSE, 420 Connector, 500 Control ECU, 501 CPU, 502 Memory, B Battery system, BP Battery pack.

Claims

1. A battery pack including multiple battery packs electrically connected in series, A control device is provided, Each of the aforementioned plurality of battery packs includes a plurality of battery cells electrically connected in parallel, The control device is A wire break detection process is performed to detect a wire break in the battery cell included in the battery pack. The aforementioned wire break detection process compares the voltages of two battery packs, and if the voltage difference between the two battery packs is greater than or equal to a threshold, it determines that a battery cell in one of the battery packs is broken.

2. The control device is The difference between the maximum and minimum values ​​of the SOC of the aforementioned battery pack is less than or equal to a first predetermined value. The difference between the maximum and minimum temperatures of the aforementioned battery pack is less than or equal to a second predetermined value. The battery system according to claim 1, wherein the wire break detection process is executed when the charge / discharge current of the battery pack is greater than or equal to a third predetermined value.

3. The aforementioned battery pack is mounted on the vehicle as a power source. The control device is The battery system according to claim 2, wherein the wire break detection process is performed when the battery pack is being charged externally or when the vehicle is running at a steady pace.

4. The control device is The battery system according to any one of claims 1 to 3, wherein a limit value for the input and output power of the battery pack is set based on the voltage difference between the two battery packs.

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