Battery Management Device

Abstract

To provide a battery management device capable of accurately estimating an expansion amount of a battery.SOLUTION: A battery ECU 10 (battery management device) comprises a memory 12 (storage section) and a processor 11 (control section). The memory 12 stores therein an expansion index map (correspondence) which makes correspondent a start SOC in discharge start of a battery stack 20, an end SOC in discharge end of the battery stack 20 and an expansion index indicating an expansion amount of the battery stack 20. The processor 11 calculates the start SOC and the end SOC and acquires load information indicating a load applied among a plurality of cells 21 (batteries) in a stacking direction. The processor 11 then acquires the expansion index of the battery stack 20 using the expansion index map based on the calculated start SOC and end SOC and the acquired load information.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a battery management device. [Background technology]

[0002] In recent years, vehicles equipped with batteries for driving have become increasingly popular. For example, JP 2018-85781 A (Patent Document 1) discloses a battery pack mounted on an electric vehicle or the like. It is known that the batteries in this battery pack expand when charged and discharged. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-85781 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the battery pack described in Patent Document 1 expands with charging and discharging. Here, the amount of expansion of the battery changes depending on the load on the battery or the deterioration state of the battery. In the conventional technology described in Patent Document 1, if the load on the battery or the deterioration state of the battery varies between battery packs, it may be difficult to accurately estimate the amount of expansion of the battery. Therefore, there is a demand for a battery management device that can accurately estimate the amount of expansion of the battery.

[0005] The present disclosure has been made to solve such problems, and an object of the present disclosure is to provide a battery management device that can accurately estimate the amount of expansion of a battery. [Means for solving the problem]

[0006] A battery management device according to a first aspect of the present disclosure includes a memory unit that stores a correspondence relationship between a starting SOC at the start of discharge of a battery stack including a plurality of batteries stacked on each other in a stacking direction, an ending SOC at the end of discharge of the battery stack, and an expansion index indicating the amount of expansion of the battery stack, and a control unit that performs control to acquire the expansion index during discharge of the battery stack, wherein the control unit calculates the starting SOC and ending SOC and acquires load information indicating the load applied between the plurality of batteries in the stacking direction, and acquires the expansion index using the correspondence relationship based on the calculated starting SOC and ending SOC and the acquired load information.

[0007] In the battery management device according to the first aspect, as described above, the control unit acquires the expansion index of the battery stack based on the calculated start SOC and end SOC and the acquired load information. This makes it possible to acquire an expansion index according to the load applied to the battery stack during discharge of the battery stack. As a result, even if the load applied to the battery stack varies from one battery stack to another, it is possible to accurately estimate the amount of expansion of each battery stack during discharge.

[0008] In the battery management device according to the first aspect, the control unit is preferably configured to correct the expansion indexes corresponding to the calculated start SOC and end SOC in the correspondence relationship based on the load information. With this configuration, it is possible to obtain an expansion index corrected based on the load applied to the battery stack. As a result, the accuracy of estimating the expansion amount of the battery stack can be easily improved by the correction.

[0009] In this case, the control unit corrects the corresponding expansion index such that the correction amount of the corresponding expansion index decreases as the load indicated by the load information increases. With this configuration, even if the expansion amount decreases due to a large load, it is possible to prevent the expansion index from being estimated to be excessively large.

[0010] In the battery management device that corrects the expansion index, preferably, the correspondence relationship includes a plurality of expansion index maps different from each other, and the control unit is configured to select one of the plurality of expansion index maps based on at least the degree of use of the battery stack, and to correct the corresponding expansion index in the selected expansion index map based on the load information. With this configuration, the control unit can obtain the expansion index based on at least the degree of use of the battery stack in addition to the load applied to the battery stack. As a result, the expansion amount of the battery stack can be estimated more accurately.

[0011] In this case, the control unit is preferably configured to select one of the plurality of expansion index maps based on at least one of the total discharge amount since the beginning of use of the battery, the period of use of the battery, and the number of times the battery has been charged and discharged since the beginning of use. With this configuration, the expansion index of the battery stack can be obtained based on at least one of the total discharge amount since the beginning of use of the battery, the period of use of the battery, and the number of times the battery has been charged and discharged since the beginning of use, so that the degree of use (degree of deterioration) of the battery stack can be easily taken into account when obtaining the expansion index of the battery stack.

[0012] In the battery management device that corrects the expansion index based on the degree of use, preferably, among the multiple expansion index maps, the expansion index map corresponding to the battery stack with a higher degree of use has a smaller expansion index. With this configuration, it is possible to prevent the expansion index of the battery stack that is difficult to expand due to its high degree of use from being estimated to be excessively large.

[0013] In the battery management device according to the first aspect, the correspondence preferably includes a plurality of expansion index maps different from each other, and the control unit is configured to select one expansion index map to be used for acquiring the expansion index from the plurality of expansion index maps based on the load information, and acquire the expansion index in the selected one expansion index map. With this configuration, the expansion index can be acquired using an expansion index map corresponding to the load applied to the battery stack. As a result, even if the load applied to the battery stack varies from battery stack to battery stack, the expansion amount of each battery stack can be accurately estimated based on the selected expansion index map.

[0014] In the battery management device according to the first aspect, the control unit is preferably configured to calculate an accumulated value by accumulating the acquired expansion amount indexes, and to perform degradation suppression control for suppressing degradation of the battery stack according to the accumulated value. With this configuration, it is possible to perform control for suppressing degradation of the battery stack based on the degradation state (degree of use) of the battery stack corresponding to the accumulated value of the expansion index.

[0015] In this case, the control unit is preferably configured to change the type of degradation suppression control in stages based on the magnitude relationship between the accumulated value and each of a plurality of predetermined thresholds. With this configuration, appropriate degradation suppression control can be executed according to the magnitude of the accumulated value, so that degradation of the battery stack can be suppressed more reliably. Furthermore, by changing the type of degradation suppression control in stages, convenience for the user can be improved.

[0016] In the battery management device that performs degradation suppression control according to the accumulated value, the degradation suppression control preferably includes at least one of control for notifying an abnormality to the outside, control for suppressing a current flowing through the battery, and control for charging the battery stack so that the SOC of the battery stack falls within a predetermined SOC range. With this configuration, degradation of the battery stack can be suppressed more reliably by at least one of control for notifying an abnormality to the outside, control for suppressing a current flowing through the battery, and control for charging the battery stack so that the SOC of the battery stack falls within a predetermined SOC range.

[0017] A battery management device according to a second aspect of the present disclosure includes a memory unit that stores a correspondence relationship between a starting SOC at the start of charging of a battery stack including a plurality of batteries stacked on each other in a stacking direction, an ending SOC at the end of charging of the battery stack, and an expansion index indicating the amount of expansion of the battery stack, and a control unit that performs control to acquire the expansion index during charging of the battery stack, wherein the control unit calculates the starting SOC and ending SOC and acquires load information indicating the load applied between the plurality of batteries in the stacking direction, and acquires the expansion index using the correspondence relationship based on the calculated starting SOC and ending SOC and the acquired load information.

[0018] In the battery management device according to the second aspect of the present disclosure, as described above, the control unit acquires the expansion index of the battery stack based on the calculated start SOC and end SOC and the acquired load information. This makes it possible to acquire an expansion index according to the load applied to the battery stack when the battery stack is charged. As a result, even if the load applied to the battery stack varies from one battery stack to another, it is possible to accurately estimate the amount of expansion of each battery stack when charging.

[0019] A battery management device according to a third aspect of the present disclosure includes a memory unit that stores a plurality of different correspondence relationships in which a starting SOC at the start of discharging a battery, an ending SOC at the end of discharging the battery, and an expansion index indicating the amount of expansion of the battery are associated with each other, and a control unit that selects one of the plurality of correspondence relationships based on at least a degree of usage of the battery, and obtains the expansion index corresponding to the starting SOC and ending SOC in the selected correspondence relationship.

[0020] In the battery management device according to the third aspect of the present disclosure, as described above, the control unit acquires an expansion index of the battery according to the start SOC at the start of discharging the battery and the end SOC at the end of discharging the battery, based on at least the degree of use of the battery. This makes it possible to acquire an expansion index according to the degree of use of the battery when discharging the battery. As a result, even if the degree of use (deterioration) of the battery varies from battery to battery, it is possible to accurately estimate the amount of expansion of each battery when discharging.

[0021] A battery management device according to a fourth aspect of the present disclosure includes a memory unit that stores a plurality of different correspondence relationships in which a starting SOC when charging of a battery begins, an ending SOC when charging of the battery ends, and an expansion index indicating the amount of expansion of the battery are associated with each other, and a control unit that selects one of the plurality of correspondence relationships based on at least the degree of usage of the battery, and obtains the expansion index for the selected correspondence relationship.

[0022] In the battery management device according to the fourth aspect of the present disclosure, as described above, the control unit acquires an expansion index of the battery according to the start SOC at the start of charging the battery and the end SOC at the end of charging the battery, based on at least the degree of use of the battery. This makes it possible to acquire an expansion index according to the degree of use of the battery when charging the battery. As a result, even if the degree of use (deterioration) of the battery varies from battery to battery, it is possible to accurately estimate the amount of expansion of each battery during charging. Effect of the Invention

[0023] According to the present disclosure, the amount of battery expansion can be accurately estimated. [Brief description of the drawings]

[0024] [Figure 1] 1 is a diagram illustrating an overall configuration of a vehicle equipped with a battery ECU according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of a battery stack. [Diagram 3] FIG. 13 is a diagram showing an example of an expansion index map during discharge. [Figure 4] FIG. 1 illustrates a number of expansion index maps stored in a memory. [Diagram 5] FIG. 13 is a diagram showing a table showing the correspondence relationship between an initial restraint load and a correction coefficient. [Figure 6] FIG. 4 is a flow chart showing estimation control of an expansion index during discharging by a processor of the battery ECU. [Figure 7] Fig. 7(A) is a diagram showing the change over time in the value of the current flowing through the battery, and Fig. 7(B) is a diagram showing the change over time in the SOC of the battery and the temperature of the battery. [Figure 8] FIG. 4 is a flow chart showing estimation control of an expansion index during charging by a processor of the battery ECU. [Figure 9] FIG. 13 is a diagram showing evaluation results by control of the present embodiment and a comparative example. [Figure 10] FIG. 4 is a diagram showing the configuration of a battery ECU according to a first modified example of the present embodiment. [Figure 11] 11 is a flow chart showing the expansion index estimation control by the processor of the battery ECU of FIG. 10. [Figure 12] FIG. 11 is a flow chart showing estimation control of an expansion index during discharge according to a second modified example of the present embodiment. [Figure 13] FIG. 11 is a flow chart showing estimation control of an expansion index during charging according to a second modified example of the present embodiment. [Figure 14] FIG. 11 is a diagram showing evaluation results obtained by controlling a second modified example of the present embodiment and a comparative example. [Figure 15] FIG. 13 is a diagram showing evaluation results obtained by controlling a third modified example of the present embodiment and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters, and the description thereof will not be repeated. [Embodiment Mode] In the following, an example in which a battery ECU (Electronic Control Unit) 10 according to the present disclosure is mounted on a vehicle will be described. Note that the use of the battery ECU 10 according to the present disclosure is not limited to vehicle use, and may be, for example, stationary use. Also, the battery ECU 10 is an example of a "battery management device" in the claims.

[0026] As shown in Fig. 1, a battery management system 100 is mounted on a vehicle 1. The vehicle 1 is, for example, an electric vehicle. Note that vehicles in which the battery management system 100 according to the present disclosure can be mounted are not limited to electric vehicles. The battery management system 100 according to the present disclosure can be mounted on any vehicle that generates driving force using electric power supplied from the battery management system 100. For example, the vehicle 1 may be a hybrid vehicle (including a plug-in hybrid vehicle) or a fuel cell vehicle.

[0027] The battery management system 100 includes a battery ECU 10, a battery stack 20, a monitoring unit 30, and a system main relay (SMR) 40. The vehicle 1 further includes an inlet 81, a power conversion device 82, a charging relay 83, a power control unit (PCU) 84, a motor generator 85, a power transmission gear 86, driving wheels 87, and an ECU 90.

[0028] The battery ECU 10 includes a processor 11 such as a CPU (Central Processing Unit), a memory 12 such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and an input / output port (not shown) through which various signals are input and output. The battery ECU 10 manages the battery stack 20 based on signals received from each sensor and a program and a map (for example, an expansion index map described later) stored in the memory 12. More specifically, the battery ECU 10 calculates the SOC (State Of Charge) of the battery stack 20 and estimates the deterioration state of the battery stack 20. In this embodiment, the process executed by the battery ECU 10 includes a process of estimating (obtaining) the expansion index of the battery stack 20 (cells 21 in the battery stack 20). This process will be described in detail later. The processor 11 and the memory 12 are examples of the "control unit" and the "storage unit" in the claims, respectively. The cells 21 are an example of the "battery" in the claims.

[0029] 2, the battery stack 20 includes a plurality of cells 21 stacked on top of each other in a stacking direction (X direction). The cells 21 are secondary batteries (non-aqueous secondary batteries) such as lithium ion batteries. The battery stack 20 stores power for driving the motor generator 85 and supplies the power to the motor generator 85 via a PCU 84. The battery stack 20 is charged by receiving the generated power via the PCU 84 when the motor generator 85 generates power.

[0030] Here, a non-aqueous secondary battery expands in the stacking direction due to deterioration accompanying charging and discharging of the battery. This expansion is mainly due to the expansion of the battery electrodes. If an external force is applied to restrict the expansion direction of the battery in order to suppress the expansion of the battery, waste electrolyte between the electrodes is discharged outside the electrodes, and the electrolyte decreases. This leads to an increase in the resistance of the battery. Furthermore, if the expansion of the battery progresses, it may lead to damage to the stack members (e.g., end plates 23 described below) that restrain the battery stack. Therefore, it is desirable to accurately estimate the amount of expansion of the battery.

[0031] The battery stack 20 also has a spacer 22 and a pair of end plates 23. The spacer 22 is provided so as to be sandwiched between the cells 21 adjacent to each other in the X direction. The pair of end plates 23 are also disposed on both ends of the multiple cells 21 in the X direction.

[0032] Each of the cells 21 includes a housing 21a, electrodes (not shown), an electrolyte (not shown), a positive electrode terminal 21b, and a negative electrode terminal 21c. The electrodes and the electrolyte are each contained in the housing 21a.

[0033] The memory 12 of the battery ECU 10 stores information about the load acting between the multiple cells 21 in the X direction. The load information is an initial restraint load measured by a load measuring device 101 (see FIG. 2) provided in a manufacturing facility (not shown) when the battery stack 20 is assembled (manufactured).

[0034] 1, the monitoring unit 30 includes various sensors for monitoring the state of the battery stack 20. Specifically, the monitoring unit 30 includes a voltage sensor 31, a current sensor 32, a battery temperature sensor 33, an ambient temperature sensor 34, and a bus bar temperature sensor 35. Each sensor outputs a signal indicating its detection result to the battery ECU 10.

[0035] The SMR 40 is electrically connected to a power line connecting the battery stack 20 and the PCU 84. The SMR 40 is opened and closed in accordance with a command from the battery ECU 10, for example.

[0036] The inlet 81 is configured so that a charging connector (not shown) provided at the tip of a charging cable can be connected by a mechanical coupling. By connecting the inlet 81 and the charging connector, an electrical connection is established between the charging equipment (not shown) and the vehicle 1. Furthermore, the ECU 90 of the vehicle 1 and a control device (not shown) of the charging equipment can transmit and receive various commands and data to and from each other in accordance with a communication standard such as CAN (Controller Area Network).

[0037] The power conversion device 82 is, for example, an AC / DC converter. The power conversion device 82 converts AC power supplied from the charging facility via a charging cable into DC power for charging the battery stack 20.

[0038] The charging relay 83 is electrically connected to a power line connecting the SMR 40 and the PCU 84. The charging relay 83 is opened and closed, for example, in accordance with a command from the ECU 90. When the charging relay 83 is closed and the SMR 40 is closed, power transmission between the inlet 81 and the battery stack 20 becomes possible.

[0039] The PCU 84 is electrically connected between the SMR 40 and the motor generator 85. The PCU 84 includes a converter and an inverter (neither of which are shown), and drives the motor generator 85 in accordance with a command from the ECU 90.

[0040] The motor generator 85 is an AC rotating electric machine, for example a permanent magnet type synchronous motor with a rotor in which a permanent magnet is embedded. The output torque of the motor generator 85 is transmitted to drive wheels 87 through a power transmission gear 86, thereby causing the vehicle 1 to run. Furthermore, when the vehicle 1 is braking, the motor generator 85 generates electricity using the rotational force of the drive wheels 87. The generated electricity by the motor generator 85 is converted by the PCU 84 into charging electricity for the battery stack 20.

[0041] The ECU 90 includes a processor 91, a memory 92, and an input / output port (not shown), similar to the battery ECU 10. The ECU 90 executes various controls for controlling the vehicle 1 to a desired state, based on signals received from each sensor and programs and maps stored in the memory 92. For example, the ECU 90 controls the charging and discharging of the battery stack 20 by controlling the PCU 84 in cooperation with the battery ECU 10.

[0042] In addition, the memory 12 of the battery ECU 10 stores an expansion index map shown in Fig. 3. The expansion index map is a map used to estimate the expansion amount of the battery stack 20. In the expansion index map, a start SOC (State of Charge) at the start of discharging the battery stack 20, an end SOC at the end of discharging the battery stack 20, and an expansion index of the battery stack 20 are associated with each other. Note that the above expansion index is an example of an "expansion index" in the claims. In addition, although the expansion index map shown in Fig. 3 does not indicate a specific expansion index, an expansion index is actually set for each open cell.

[0043] As shown in FIG. 4, the memory 12 stores a plurality of expansion index maps that are different from each other. As will be described later in detail, the expansion index maps are provided separately from each other based on the degree of use of the cells 21 and the temperature of the cells 21. That is, when estimating (obtaining) the expansion amount of the battery stack 20, one expansion index map to be used is selected based on the temperature of the cells 21 (low temperature, medium temperature, and high temperature) and the degree of use of the cells 21 (initial use and final use). In this embodiment, one expansion index map is selected from six expansion index maps (maps A to F) based on the temperature of the cells 21 and the degree of use of the cells 21. As an example, when the temperature of the cells 21 is high and the cells 21 are in the initial use, map A is used.

[0044] The expansion index of the expansion index map corresponding to the battery stack 20 with a greater degree of use is smaller. Specifically, the expansion index of the expansion index map corresponding to the battery stack 20 in the final stage of use is larger than the expansion index of the expansion index map corresponding to the battery stack 20 in the initial stage of use. The expansion index maps may be divided into three or more stages of use (for example, initial stage, intermediate stage, and final stage).

[0045] The expansion index is largest in the expansion index map corresponding to a low temperature (e.g., 25° C.), followed by the expansion index map corresponding to a medium temperature (e.g., 40° C.), and finally the expansion index map corresponding to a high temperature (e.g., 60° C.). The number of expansion index maps stored in the memory 12 is not limited to the above example. For example, the expansion index maps may be divided for each predetermined temperature (e.g., 5° C. or 10° C.).

[0046] As shown in FIG. 5, the memory 12 of the battery ECU 10 stores a table indicating correction coefficients corresponding to the initial restraint loads applied to the cells 21. In the table, a correction coefficient Bi is associated with each 2 kN in the range of initial restraint loads from 2 kN to 24 kN (i.e., 2 kN, 4 kN, 22 kN, and 24 kN). The correction coefficient in the table is smaller as the initial restraint load is larger. The expansion index is corrected using the correction coefficient. This correction will be described in detail later. Although the table shown in FIG. 5 does not include specific correction coefficients, a correction coefficient is actually set for each open cell. The initial restraint load is an example of the "load" in the claims.

[0047] Also, instead of the above-mentioned expansion index map, the start SOC and end SOC may be associated with the expansion index by a data table, a function, or a relational expression. Also, the expansion index map of Fig. 4 and the table of Fig. 5 may be expressed by one map. Specifically, a map in which the start SOC, end SOC, and initial restraint load are associated with the expansion index may be used. <Discharging flow> Next, control by the processor 11 for acquiring (estimating) the expansion index of the battery stack 20 (cells 21) will be described with reference to a flow diagram of discharging the battery stack 20 shown in Fig. 6. In this embodiment, the current i is positive during discharging, and the current i is negative during charging.

[0048] First, in step S1, it is determined whether or not the current i (see FIG. 7(A)) flowing through the battery stack 20 detected by the current sensor 32 (see FIG. 1) is greater than 0. If the current i is greater than 0 (i.e., the battery stack 20 is discharging) (Yes in S1), the process proceeds to step S2. If the current i is equal to or less than 0 (i.e., the battery stack 20 is not discharging) (No in S1), step S1 is repeated.

[0049] Next, in step S2, a start SOC (see S1 in FIG. 7B) which is the SOC at time t1 when discharge starts is detected. Also, a temperature Tmax (see FIG. 7B) which is the maximum value of the temperature T of the battery stack 20 detected by the battery temperature sensor 33 (see FIG. 1) from time t1 to time t2 (described later) is detected.

[0050] Next, in step S3, it is determined whether the current i is 0. If the current i is 0 (i.e., the discharge has ended) (Yes in S3), the process proceeds to step S4. If the current i is not 0 (i.e., the discharge has not ended) (No in S3), step S3 continues until the current i becomes 0.

[0051] Next, in step S4, the end SOC (see S2 in FIG. 7B), which is the SOC at the time t2 when the discharge ends, is detected.

[0052] Here, the expansion amount of the battery stack 20 changes depending on the deterioration state of the battery stack 20. That is, if the deterioration state of the battery stack 20 varies for each battery stack 20, it may be difficult to accurately estimate the expansion amount of the battery stack 20. Therefore, in the present embodiment, the processor 11 is configured to select one of a plurality of expansion index maps stored in the memory 12 based on at least the degree of use of the battery stack 20. In other words, the weighting when quantifying the expansion of the battery stack 20 is changed depending on the degree of use of the battery stack 20.

[0053] Specifically, the processor 11 selects one of a plurality of expansion index maps (see maps A to F in FIG. 4) stored in the memory 12 based on the degree of use of the battery stack 20 and the temperature Tmax that is the maximum temperature of the battery stack 20. Then, the processor 11 acquires the expansion index corresponding to the start SOC and the end SOC in the selected expansion index map.

[0054] In detail, in step S5, the total discharge amount of the cells 21 (battery stack 20) ​​from the beginning of use is determined to be equal to or smaller than a predetermined threshold Th A It is determined whether the total discharge amount is smaller than the threshold value Th A If the total discharge amount is smaller than the threshold value Th (Yes in S5), it is determined that the degree of use of the battery stack 20 is small (i.e., it is in the early stage of use), and the process proceeds to step S6. A In the above cases (No in S5), it is determined that the battery stack 20 has been used to a large extent (i.e., is in the final stages of use), and the process proceeds to step S7.

[0055] In step S6, the expansion index SW is acquired (calculated) based on the expansion index maps (maps A to C) for the initial period of use of the battery stack 20. For example, when the temperature Tmax is 25° C. (i.e., a low temperature), the expansion index SW is acquired (calculated) using map C in Fig. 4. In this case, the expansion index SW corresponding to the start SOC acquired in step S2 and the end SOC acquired in step S4 is acquired (calculated) based on map C.

[0056] In step S7, the expansion index SW is acquired (calculated) based on the expansion index maps (maps D to F) for the end of use of the battery stack 20. Note that in step S8, only the map used is different from that in step S7, and other controls are the same as those in step S7, so detailed description of step S7 will not be repeated.

[0057] Here, the expansion amount of the battery stack 20 (cells 21) changes depending on the load (weight) applied to the battery stack 20, in addition to the degree of use of the battery stack 20 described above. That is, when the load (weight) applied to the battery stack 20 varies for each battery stack 20, it may be difficult to accurately estimate the expansion amount of the battery stack 20. Therefore, in this embodiment, the processor 11 is configured to acquire the expansion index of the battery stack 20 based on the load applied to the battery stack 20 (between the multiple cells 21).

[0058] Specifically, the processor 11 is configured to obtain the expansion index of the battery stack 20 based on the initial restraint load at the time of assembly (manufacturing) of the battery stack 20 stored in the memory 12.

[0059] Specifically, in step S8, the expansion index SW obtained in step S6 or step S7 is corrected by a correction coefficient Bi corresponding to the initial restraint load of the battery stack 20.

[0060] Next, in step S9, the expansion indexes are accumulated to calculate an accumulated value SWsum. B is added to the accumulated value SWsum accumulated from the beginning of charging and discharging of the battery stack 20 (for example, at the time of shipping the vehicle 1).

[0061] In this embodiment, the processor 11 is configured to perform degradation suppression control for suppressing degradation of the battery stack 20 according to the accumulated value SWsum calculated in step S9. Specifically, the processor 11 is configured to change the type of the degradation suppression control stepwise based on the magnitude relationship between the accumulated value SWsum calculated in step S9 and each of a plurality of predetermined thresholds (thresholds Th1 to Th3 described later). The degradation suppression control includes control for notifying the outside of an abnormality and control for suppressing a current flowing through the cell 21 (battery stack 20), as described later. Details will be described with reference to steps S10 to S15 described later.

[0062] In step S10, it is determined whether the cumulative value SWsum is greater than the threshold value Th1. If the cumulative value SWsum is greater than the threshold value Th1 (Yes in S10), the process proceeds to step S12. If the cumulative value SWsum is equal to or less than the threshold value Th1 (No in S10), the process proceeds to step S11.

[0063] In step S11, a diagnostic command is generated to notify the outside of the abnormality in the battery stack 20 (for example, by turning on a warning light on the instrument panel).

[0064] In step S12, it is determined whether the cumulative value SWsum is greater than a threshold value Th2. Note that the threshold value Th2 is a value smaller than the threshold value Th1. If the cumulative value SWsum is greater than the threshold value Th2 (Yes in S12), the process proceeds to step S14. On the other hand, if the cumulative value SWsum is equal to or smaller than the threshold value Th2 (No in S12), the process proceeds to step S13.

[0065] In step S13, a command to reduce the upper limit of the SOC is generated compared to when the accumulated value SWsum is equal to or less than the threshold value Th2, and control is executed to suppress the current flowing through the cells 21 (battery stack 20). This suppresses the charge amount of the battery stack 20, making it possible to suppress expansion of the battery stack 20. Note that in step S13, instead of (or in addition to) reducing the upper limit of the SOC, control may be performed to lower the upper limit of the maximum charging rate, or control may be performed to reduce the number of charging times (charging time) for each charging rate.

[0066] In step S14, it is determined whether the cumulative value SWsum is greater than a threshold value Th3. Note that the threshold value Th3 is a value smaller than the threshold value Th2. If the cumulative value SWsum is equal to or smaller than the threshold value Th3 (No in S14), the process proceeds to step S15.

[0067] In step S15, if the vehicle 1 is an EV (PHEV), a command is issued to the user to charge and discharge the battery so that the SOC falls within a predetermined range (e.g., 30% to 60%). When the SOC falls within the predetermined range, the cells 21 are less likely to expand than when the SOC is outside the predetermined range. Therefore, by charging the cells 21 so that the SOC falls within the predetermined range, it is possible to suppress expansion of the battery stack 20.

[0068] Note that instead of the control of suppressing the current flowing through the cell 21 (battery stack 20) ​​as in steps S14 and S15, a command to lower the target cooling value of the battery may be generated.

[0069] The degradation suppression control may include only one of the control for notifying an abnormality to the outside and the control for suppressing the current flowing through the cell 21 (battery stack 20). The number of thresholds is not limited to three, the thresholds Th1 to Th3. <Charging flow> Fig. 8 shows a flow diagram during charging of the battery stack 20. Below, only the differences from the flow diagram in Fig. 6 will be explained. Note that in Fig. 8, the same step numbers are assigned to the parts where the same controls as in Fig. 6 are performed.

[0070] First, in step S21, it is determined whether or not the current i (see FIG. 7(A)) flowing through the battery stack 20 detected by the current sensor 32 (see FIG. 1) is less than 0. If the current i is less than 0 (i.e., the battery stack 20 is being charged), the process proceeds to step S2. If the current i is equal to or greater than 0 (i.e., the battery stack 20 is not being charged), step S21 is repeated.

[0071] Also, in step S6 (S7) during discharge in Fig. 6, the expansion index map for discharge (see Figs. 3 and 4) is used, whereas in step S26 (S27) in Fig. 8, the expansion index map for charge (not shown) is used. In other respects, the control in step S26 (S27) is similar to the control in step S6 (S7). <Evaluation Results> Fig. 9 is a diagram showing the results of evaluating the control of the expansion index estimation process in the present embodiment. Fig. 9 compares the present embodiment, which is a control that takes into account the load on the battery stack 20 and the degree of use of the battery stack 20, with a comparative example, which is a control that does not take into account the load on the battery stack 20 and the degree of use of the battery stack 20. Fig. 9 also shows the total discharge amount of the battery stack 20 in each control at the time when the expansion index of the battery stack 20 reaches a level that protects the battery stack 20 from damage.

[0072] As shown in Fig. 9, the total discharge amount by the control of this embodiment is larger than the total discharge amount by the comparative example. This result shows that the control of this embodiment allows a larger number of charge / discharge cycles to be performed before the expansion index reaches a level that protects against the above-mentioned damage, compared to the control of the comparative example. This is because the control of this embodiment allows the expansion index of the battery stack 20 to be more accurately estimated, thereby preventing the cumulative value of the expansion index from becoming excessively large.

[0073] As described above, in the present embodiment, the processor 11 is configured to acquire an expansion index of the battery stack 20 corresponding to the start SOC and the end SOC in the expansion index map stored in the memory 12, based on the load applied between the multiple cells 21. This makes it possible to acquire an expansion index corresponding to the load applied to the battery stack 20 when the battery stack 20 is discharged (charged). As a result, even if the load applied to the battery stack 20 varies for each battery stack 20 at the time of manufacturing the battery stacks 20 (manufacturing errors occur), it is possible to accurately estimate the amount of expansion of each battery stack 20 when the battery stack 20 is discharged (charged).

[0074] In the present embodiment, the processor 11 is configured to correct the expansion indexes corresponding to the start SOC and the end SOC in the expansion index map stored in the memory 12 based on the load. This makes it possible to appropriately correct the expansion amount of the battery stack 20 based on the load applied to the battery stack 20. As a result, it is possible to prevent the expansion amount of the battery stack 20 from being estimated inappropriately due to the load applied to the battery stack 20.

[0075] In the present embodiment, the processor 11 selects one of a plurality of expansion index maps stored in the memory 12 based on at least the degree of use of the battery stack 20. The processor 11 is configured to correct the expansion indexes corresponding to the start SOC and end SOC in the selected expansion index map based on the load. This allows the control unit to obtain an index indicating the amount of expansion based on at least the degree of use of the battery stack. As a result, it is possible to prevent the amount of expansion of the battery stack 20 from being estimated inappropriately due to the degree of use (deterioration) of the battery stack 20.

[0076] Also, unlike the case where the expansion state of the battery stack 20 is detected by, for example, sandwiching a sensor, a probe, or the like between the cells 21 of the battery stack 20, in this embodiment, the insulation of the battery stack 20 (between the cells 21) is not deteriorated due to the sensor, the probe, etc. As a result, it is possible to suppress the performance of the battery stack 20 from being deteriorated.

[0077] For example, in the above embodiment, an example has been described in which the expansion indexes corresponding to the start SOC and the end SOC in the expansion index map are corrected based on the load applied to the battery stack 20, but the present disclosure is not limited to this. For example, different expansion index maps may be associated with each of a plurality of initial restraint loads, and the expansion index map to be used may be switched based on the measured initial restraint load.

[0078] Specifically, as shown in FIG. 10, a battery ECU 110 according to a first modified example of the above embodiment includes a processor 111 and a memory 112. The memory 111 stores a plurality of expansion index maps that are different from each other. The plurality of expansion index maps correspond to (are associated with) a plurality of initial restraint loads. The battery ECU 110 is an example of a "battery management device" in the claims. The processor 111 and the memory 112 are examples of a "control unit" and a "storage unit" in the claims, respectively.

[0079] 11, in step S36, the processor 111 selects one expansion index map corresponding to the initial restraint load measured when the battery stack 20 is assembled. Then, the processor 111 acquires the expansion index corresponding to the start SOC and the end SOC in the selected one expansion index map. In this case, step S36 is executed instead of steps S5 to S8 in FIG. 6 of the above embodiment (S5, S26, S27, and S8 in FIG. 8).

[0080] In the above embodiment, an example has been shown in which control is performed to obtain the expansion index based on the load on the battery stack 20, but the present disclosure is not limited thereto. In the control to obtain the expansion index, the load on the battery stack 20 does not have to be taken into account. Specifically, as shown in FIG. 12, a flow is executed in which step S8 is omitted from the flow during discharging in the above embodiment (see FIG. 6). Also, as shown in FIG. 13, in the second modified example, a flow is executed in which step S8 is omitted from the flow during charging in the above embodiment (see FIG. 8). Even in this case, as shown in FIG. 14, a result was obtained in which the total discharge amount of the cells 21 was greater than the total discharge amount of the cells 21 in the comparative example (control that does not take into account the load and the degree of use).

[0081] In addition, in the above embodiment, an example has been shown in which the expansion index map to be selected is switched based on the degree of use of the battery stack 20, but the present disclosure is not limited to this. In the estimation control of the expansion index in the above embodiment, only the initial restraining load may be taken into account without taking into account the degree of use of the battery stack 20. Even in this case, as shown in FIG. 15, a result was obtained in which the total discharge amount of the cells 21 was greater than the total discharge amount of the cells 21 in the comparative example (control that does not take into account the load and degree of use).

[0082] In addition, in the above embodiment, an example has been shown in which the expansion index map is selected based on the total discharge amount of the cell 21, but the present disclosure is not limited to this. For example, the expansion index map may be selected based on the period of use of the cell 21 and the number of times the cell 21 has been charged and discharged. Also, the expansion index map may be selected based on the cumulative value SWsum of the expansion index.

[0083] In the above embodiment, an example has been described in which control is performed to correct the expansion index based on the initial restraining load measured by the load measuring instrument 101 when the battery stack 20 is assembled, but the present disclosure is not limited to this. For example, control to correct the expansion index may be performed based on a detection value of a load sensor provided in the battery stack 20. In this case, the correction may be performed based on a load at a time point other than when the battery stack 20 is assembled (for example, at the start or end of charging / discharging).

[0084] In addition, in the above embodiment, an example has been described in which the expansion index map is selected based on the temperature and the degree of use of the battery stack 20, but the present disclosure is not limited to this. For example, the expansion index map may be selected based on the degree of use of the battery stack 20 without taking into account the temperature of the battery stack 20.

[0085] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0086] 10,110 battery ECU (battery management unit), 11,111 processor (control unit), 12,112 memory (storage unit), 20 battery stack, 21 battery.

Claims

1. a storage unit that stores a correspondence relationship between a start SOC at the start of discharge of a battery stack including a plurality of batteries stacked on each other in a stacking direction, an end SOC at the end of discharge of the battery stack, and an expansion index indicating an amount of expansion of the battery stack; a control unit that performs control to acquire the expansion index during discharging of the battery stack, The control unit is calculating the start SOC and the end SOC, and acquiring load information indicating a load applied between the plurality of batteries in the stacking direction; and acquiring the expansion index using the correspondence relationship based on the calculated start SOC and the end SOC and the acquired load information; The battery management device is configured to correct an expansion index corresponding to the calculated starting SOC and ending SOC in the correspondence relationship based on the load information.

2. The battery management device according to claim 1 , wherein the control unit corrects the corresponding expansion index such that a correction amount of the corresponding expansion index becomes smaller as the load indicated by the load information becomes larger.

3. The correspondence relationship includes a plurality of expansion index maps that are different from each other, The battery management device of claim 1 or 2, wherein the control unit is configured to select one of the plurality of expansion index maps based on at least a degree of usage of the battery stack, and to correct the corresponding expansion index in the selected expansion index map based on the load information.

4. The battery management device of claim 3, wherein the control unit is configured to select one of the plurality of expansion index maps based on at least one of a total amount of discharge from an initial use of the battery, a period of use of the battery, and a number of times the battery has been charged and discharged from an initial use of the battery.

5. The battery management device according to claim 3 , wherein the expansion index map corresponding to the battery stack having a greater degree of usage among the plurality of expansion index maps has a smaller expansion index.

6. The correspondence relationship includes a plurality of expansion index maps that are different from each other, The battery management device of claim 1, wherein the control unit is configured to select one of the expansion index maps to be used to obtain the expansion index based on the load information, and to obtain the expansion index in the selected one of the expansion index maps.

7. The control unit is configured to calculate a cumulative value by accumulating the acquired expansion indices, and to perform deterioration suppression control to suppress deterioration of the battery stack according to the cumulative value.A battery management device as described in any one of claims 1 to 6.

8. The battery management device according to claim 7 , wherein the control unit is configured to change the type of the degradation suppression control in a stepwise manner based on a magnitude relationship between the accumulated value and each of a plurality of predetermined threshold values.

9. 9. The battery management device according to claim 7, wherein the degradation suppression control includes at least one of control for notifying an external abnormality, control for suppressing a current flowing through the battery stack, and control for charging the battery stack so that the SOC of the battery stack falls within a predetermined SOC range.

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