JP7655235B2 - Battery Management Device - Google Patents

Description

This disclosure relates to a battery management device.

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 installed in vehicles such as electric vehicles. The batteries in this battery pack are known to expand as they are charged and discharged.

JP 2018-85781 A

As described above, a battery pack such as that 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 degree of deterioration of the battery. In the conventional technology described in Patent Document 1, if the load on the battery or the degree of deterioration 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.

This disclosure has been made to solve these problems, and the purpose of this disclosure is to provide a battery management device that can accurately estimate the amount of battery expansion.

A battery management device according to a first aspect of the present disclosure includes a memory 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 top of each other in a stacking direction, an end 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, and the control unit calculates the start SOC and end 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 start SOC and end SOC and the acquired load information.

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 starting SOC and ending SOC and the acquired load information. This makes it possible to acquire an expansion index according to the load on the battery stack when the battery stack is discharged. As a result, even if the load on 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 discharging.

In the battery management device according to the first aspect, the control unit is preferably configured to correct the expansion index 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.

In this case, the control unit corrects the corresponding expansion index so that the correction amount of the corresponding expansion index decreases as the load indicated by the load information increases. By configuring in this manner, it is possible to prevent the expansion index from being estimated to be excessively large even when the expansion amount decreases due to a large load.

In a battery management device that corrects the expansion index, preferably, the correspondence includes a plurality of expansion index maps that are 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 an 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 amount of expansion of the battery stack can be estimated more accurately.

In this case, the control unit is preferably configured to select one of the multiple expansion index maps based on at least one of the total amount of discharge from the beginning of battery use, the period of use of the battery, and the number of times the battery has been charged and discharged since the beginning of battery use. With this configuration, the expansion index of the battery stack can be obtained based on at least one of the total amount of discharge from the beginning of battery use, the period of use of the battery, and the number of times the battery has been charged and discharged since the beginning of battery 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.

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 a battery stack that is less likely to expand due to a high degree of use from being estimated to be excessively large.

In the battery management device according to the first aspect, preferably, the correspondence includes a plurality of expansion index maps that are different from each other, and the control unit is configured to select one expansion index map to be used to obtain the expansion index from the plurality of expansion index maps based on the load information, and to obtain the expansion index in the selected one expansion index map. With this configuration, the expansion index can be obtained 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 amount of expansion of each battery stack can be accurately estimated based on the selected expansion index map.

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

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 threshold values. 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, user convenience can be improved.

In a battery management device that performs degradation suppression control according to the above-mentioned accumulated value, the degradation suppression control preferably includes at least one of control to notify an external abnormality, control to suppress the current flowing through the battery, and control to charge 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 to notify an external abnormality, control to suppress the current flowing through the battery, and control to charge the battery stack so that the SOC of the battery stack falls within a predetermined SOC range.

A battery management device according to a second aspect of the present disclosure includes a memory unit that stores a correspondence relationship between a start SOC at the start of charging a battery stack including multiple batteries stacked on top of each other in a stacking direction, an end SOC at the end of charging 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, and the control unit calculates the start SOC and end SOC and acquires load information indicating the load applied between the multiple batteries in the stacking direction, and acquires the expansion index using the above correspondence relationship based on the calculated start SOC and end SOC and the acquired load information.

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 starting SOC and ending SOC and the acquired load information. This makes it possible to acquire an expansion index according to the load on the battery stack when the battery stack is being charged. As a result, even if the load on 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 being charged.

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 the degree of use of the battery, and obtains the expansion index corresponding to the starting SOC and ending SOC in the selected correspondence relationship.

In the battery management device according to the third aspect of the present disclosure, as described above, the control unit acquires a battery expansion index corresponding to the starting SOC at the start of discharging the battery and the ending 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 corresponding to the degree of use of the battery when discharging the battery. As a result, even if the degree of use (degree of deterioration) of the battery varies from battery to battery, it is possible to accurately estimate the amount of expansion of each battery when discharging.

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 at the start of charging the battery, an ending SOC at the end of charging 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 the degree of use of the battery, and obtains the expansion index for the selected correspondence relationship.

In the battery management device according to the fourth aspect of the present disclosure, as described above, the control unit obtains a battery expansion index corresponding to the starting SOC when charging of the battery begins and the ending SOC when charging of the battery ends, based on at least the degree of use of the battery. This makes it possible to obtain an expansion index corresponding to the degree of use of the battery when charging the battery. As a result, even if the degree of use (degree of deterioration) of the battery varies from battery to battery, it is possible to accurately estimate the amount of expansion of each battery during charging.

This disclosure makes it possible to accurately estimate the amount of battery expansion.

1 is a diagram showing an outline of the overall configuration of a vehicle equipped with a battery ECU according to an embodiment of the present invention; FIG. 2 is a diagram showing the configuration of a battery stack. FIG. 13 is a diagram showing an example of an expansion index map during discharge. FIG. 1 illustrates a number of expansion index maps stored in a memory. FIG. 13 is a diagram showing a table showing the correspondence relationship between an initial restraint load and a correction coefficient. FIG. 4 is a flow chart showing estimation control of an expansion index during discharge by a processor of the battery ECU. 7A is a diagram showing the change over time in the value of the current flowing through the battery, and FIG 7B is a diagram showing the change over time in the SOC and temperature of the battery. FIG. 4 is a flow chart showing estimation control of an expansion index during charging by a processor of a battery ECU. FIG. 13 is a diagram showing evaluation results by control of the present embodiment and a comparative example. FIG. 2 is a diagram showing a configuration of a battery ECU according to a first modified example of the present embodiment. FIG. 11 is a flow chart showing expansion index estimation control by a processor of the battery ECU of FIG. 10; FIG. 11 is a flow chart showing estimation control of the expansion index during discharge according to a second modified example of the present embodiment. 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. 13A and 13B are diagrams showing evaluation results of control according to the second modified example of the present embodiment and a comparative example. 13A and 13B are diagrams showing evaluation results of control according to the third modified example of the present embodiment and a comparative example.

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]
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.

As shown in FIG. 1, a battery management system 100 is installed in 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 installed are not limited to electric vehicles. The battery management system 100 according to the present disclosure can be installed in any vehicle that generates driving force using 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.

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, drive wheels 87, and an ECU 90.

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 programs and maps (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 "storage unit" in the claims, respectively. The cells 21 are an example of the "battery" in the claims.

As shown in FIG. 2, the battery stack 20 includes a plurality of cells 21 stacked on top of each other in the 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 power to the motor generator 85 through the PCU 84. The battery stack 20 is charged by receiving the generated power through the PCU 84 when the motor generator 85 generates power.

Here, non-aqueous secondary batteries expand in the stacking direction due to deterioration associated with charging and discharging the battery. This expansion is mainly due to the expansion of the battery electrodes. If an external force is used to restrict the expansion direction in order to suppress the battery expansion, the waste electrolyte between the electrodes is discharged outside the electrodes, and the electrolyte decreases. In this case, the resistance of the battery increases. Furthermore, if the battery expansion progresses, there is a risk that 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 battery expansion.

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 adjacent cells 21 in the X direction. The pair of end plates 23 are also disposed at both ends of the multiple cells 21 in the X direction.

Each of the cells 21 includes a housing 21a, an electrode (not shown), an electrolyte (not shown), a positive terminal 21b, and a negative terminal 21c. Each of the electrodes and the electrolyte is contained in the housing 21a.

In addition, 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 the initial restraint load measured by a load measuring device 101 (see FIG. 2) provided in the manufacturing facility (not shown) when the battery stack 20 is assembled (manufactured).

As shown in FIG. 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 busbar temperature sensor 35. Each sensor outputs a signal indicating its detection result to the battery ECU 10.

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 according to commands from, for example, the battery ECU 10.

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

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

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 according to commands from, for example, 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.

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 shown), and drives the motor generator 85 according to commands from the ECU 90.

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 the drive wheels 87 through the power transmission gear 86, causing the vehicle 1 to run. In addition, the motor generator 85 generates electricity using the rotational force of the drive wheels 87 when the vehicle 1 is braking. The power generated by the motor generator 85 is converted by the PCU 84 into charging power for the battery stack 20.

The ECU 90, like the battery ECU 10, includes a processor 91, a memory 92, and an input/output port (not shown). The ECU 90 executes various controls to control 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.

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, the start SOC (State of Charge) at the start of discharge of the battery stack 20, the end SOC at the end of discharge of the battery stack 20, and the expansion index of the battery stack 20 are associated with each other. Note that the above expansion index is an example of the "expansion index" in the claims. In addition, although the specific expansion index is omitted from the expansion index map shown in FIG. 3, an expansion index is actually set for each open cell.

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 in detail later, 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 (early use and late 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 early use, map A is used.

The expansion index of the expansion index map corresponding to the battery stack 20 with a higher degree of use is smaller. Specifically, the expansion index of the expansion index map corresponding to the battery stack 20 at the end of use is larger than the expansion index of the expansion index map corresponding to the battery stack 20 at the beginning of use. The expansion index maps may be divided into three or more types of degrees of use (for example, early use, middle use, and late use).

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). Note that the number of expansion index maps stored in 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).

As shown in FIG. 5, the memory 12 of the battery ECU 10 stores a table showing 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 of initial restraint load between 2 kN and 24 kN (i.e., 2 kN, 4 kN, . . . 22 kN, 24 kN). The larger the initial restraint load, the smaller the correction coefficient in the table. The expansion index is corrected using the correction coefficient. This correction will be described in detail later. In the table shown in FIG. 5, specific correction coefficients are omitted, but in reality, a correction coefficient is set for each open cell. The initial restraint load is an example of the "load" in the claims.

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

First, in step S1, it is determined whether 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.

Next, in step S2, a start SOC (see _S1 in FIG. 7B) is detected, which is the SOC at time t1 when discharge starts. Also, a temperature Tmax (see FIG. 7B) is detected, 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).

Next, in step S3, it is determined whether the current i is 0 or not. 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.

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.

Here, the amount of expansion of the battery stack 20 changes depending on the degree of deterioration of the battery stack 20. In other words, if the degree of deterioration of the battery stack 20 varies from one battery stack 20 to another, it may be difficult to accurately estimate the amount of expansion of the battery stack 20. Therefore, in this 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 used when quantifying the expansion of the battery stack 20 is changed depending on the degree of use of the battery stack 20.

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, which is the maximum temperature of the battery stack 20. Then, the processor 11 obtains the expansion index corresponding to the start SOC and the end SOC in the selected expansion index map.

Specifically, in step S5, it is determined whether or not the total discharge amount of the cells 21 (battery stack 20) from the early stage of use is smaller than a predetermined threshold value Th _A. If the total discharge amount is smaller than the threshold value Th _A (Yes in S5), it is determined that the degree of use of the battery stack 20 is small (i.e., in the early stage of use), and the process proceeds to step S6. If the total discharge amount is equal to or larger than the threshold value Th _A (No in S5), it is determined that the degree of use of the battery stack 20 is large (i.e., in the final stage of use), and the process proceeds to step S7.

In step S6, the expansion index SW is obtained (calculated) based on the expansion index maps (maps A to C) for the initial 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 obtained (calculated) using map C in FIG. 4. In this case, the expansion index SW corresponding to the starting SOC obtained in step S2 and the ending SOC obtained in step S4 is obtained (calculated) based on map C.

In addition, in step S7, the expansion index SW is obtained (calculated) based on the expansion index map (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 in step S7, so a detailed description of step S7 will not be repeated.

Here, the amount of expansion of the battery stack 20 (cells 21) changes depending on the load (weight) on the battery stack 20, in addition to the degree of use of the battery stack 20 described above. In other words, if the load (weight) on the battery stack 20 varies from one battery stack 20 to another, it may be difficult to accurately estimate the amount of expansion of the battery stack 20. Therefore, in this embodiment, the processor 11 is configured to obtain the expansion index of the battery stack 20 based on the load on the battery stack 20 (between the multiple cells 21).

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.

In detail, 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.

Next, in step S9, the expansion indexes are accumulated to calculate an accumulated value SWsum. Specifically, the corrected expansion index _SWB calculated in step S8 is added to the accumulated value SWsum accumulated from the beginning of charging and discharging the battery stack 20 (for example, at the time of shipping the vehicle 1).

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 Th ₁ to Th ₃ described later). The degradation suppression control includes control for notifying an abnormality to the outside 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.

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.

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

In step S12, it is determined whether the cumulative value SWsum is greater than a threshold value _Th2 . 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. If the cumulative value SWsum is equal to or smaller than the threshold value _Th2 (No in S12), the process proceeds to step S13.

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 cell 21 (battery stack 20). This suppresses the charge amount of the battery stack 20, making it possible to suppress the 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.

In step S14, it is determined whether the cumulative value SWsum is greater than a threshold value _Th3 . 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.

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 is within the above-mentioned predetermined range, the cells 21 are less likely to expand than when the SOC is outside the above-mentioned predetermined range. Therefore, by charging the cells 21 so that the SOC falls within the above-mentioned predetermined range, it is possible to suppress the expansion of the battery stack 20.

In addition, instead of the control to suppress the current flowing through the cell 21 (battery stack 20) as in steps S14 and S15, a command to lower the battery cooling target value may be generated.

In addition, 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). In addition, 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 of Fig. 6 will be described. Note that in Fig. 8, the same step numbers are assigned to the parts where the same controls as in Fig. 6 are performed.

First, in step S21, it is determined whether 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.

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.

As shown in FIG. 9, the total discharge amount by the control of this embodiment is greater than the total discharge amount by the comparative example. This result shows that the control of this embodiment allows a greater 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.

As described above, in this embodiment, the processor 11 is configured to obtain the expansion index of the battery stack 20 corresponding to the start SOC and 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 obtain 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 manufacture of the battery stack 20 (manufacturing errors occur), the amount of expansion of each battery stack 20 when the battery stack 20 is discharged (charged) can be accurately estimated.

In addition, in this embodiment, the processor 11 is configured to correct the expansion index corresponding to the start SOC and end SOC in the expansion index map stored in the memory 12 based on the load. This allows the expansion amount of the battery stack 20 to be appropriately corrected 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.

In addition, in this 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 then configured to correct the expansion index 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 (degree of deterioration) of the battery stack 20.

In addition, unlike the case where the expansion state of the battery stack 20 is detected by, for example, sandwiching a sensor, probe, etc. 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, probe, etc. As a result, it is possible to suppress a deterioration in the performance of the battery stack 20.

For example, in the above embodiment, an example was shown in which the expansion index corresponding to the start SOC and end SOC in the expansion index map is 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 multiple initial restraint loads, and the expansion index map to be used may be switched based on the measured initial restraint load.

Specifically, as shown in FIG. 10, the battery ECU 110 according to the 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.

As shown in FIG. 11, in step S36, the processor 111 selects an expansion index map corresponding to the initial restraint load measured when the battery stack 20 is assembled. Then, the processor 111 obtains the expansion index corresponding to the start SOC and the end SOC in the selected 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).

In addition, in the above embodiment, an example was shown in which control was performed to obtain the expansion index based on the load on the battery stack 20, but the present disclosure is not limited to this. In the control to obtain the expansion index, the load on the battery stack 20 does not need 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 discharge 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 degree of use).

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, the degree of use of the battery stack 20 may not be taken into account, and only the initial restraining load may be taken into account. Even in this case, as shown in FIG. 15, the 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).

In addition, in the above embodiment, an example is 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.

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

In addition, in the above embodiment, an example is shown 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.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments above, and is intended to include all modifications within the meaning and scope of the claims.

10,110 Battery ECU (battery management device), 11,111 Processor (control unit), 12,112 Memory (storage unit), 20 Battery stack, 21 Battery.

Claims (9)

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 start SOC and end SOC in the correspondence relationship based on the load information . 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. 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. 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. The battery management device according to claim 3 , wherein the expansion index map corresponding to the battery stack having a greater degree of use among the plurality of expansion index maps has a smaller expansion index. 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. The battery management device according to any one of claims 1 to 6, wherein 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. 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. 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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