Battery system

Abstract

To improve the accuracy of calculating battery SOC.SOLUTION: A battery system 2 includes a battery 10 and an ECU 100. The ECU 100 executes polarization elimination control for eliminating the polarization of the battery 10, and a calculation process for calculating the SOC of the battery 10 after the polarization elimination control. When the polarization elimination control is executed after the battery 10 is discharged, the polarization elimination control is a charging control for charging the battery 10. When the polarization elimination control is executed after the battery 10 is charged, the polarization elimination control is a discharge control that discharges the battery 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Japanese Patent Application Laid-Open Publication No. 2019-160721 (Patent Document 1) discloses a battery system including a secondary battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-160721 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is important to calculate the SOC (State Of Charge) of a power storage device such as a secondary battery with high accuracy in order to properly protect the power storage device and to fully use the device. Therefore, a technique for improving the accuracy of SOC calculation is desired.

[0005] The present disclosure has been made to solve the above problems, and has an object to provide a battery system capable of improving the accuracy of calculating the SOC. [Means for solving the problem]

[0006] The battery system of the present disclosure includes a power storage device and a control device. The control device executes polarization elimination control for eliminating polarization of the power storage device, and a calculation process for calculating the SOC of the power storage device after the polarization elimination control. When the polarization elimination control is executed after the power storage device is discharged, the polarization elimination control is a charge control for charging the power storage device. When the polarization elimination control is executed after the power storage device is charged, the polarization elimination control is a discharge control for discharging the power storage device.

[0007] The polarization of the power storage device changes the voltage of the power storage device, and may affect the calculation result of the SOC. The polarization of the power storage device is eliminated by applying a voltage having the opposite polarity to the polarity of the power storage device. Specifically, the polarization after discharging the power storage device is eliminated by charging the power storage device, and the polarization after charging is eliminated by discharging. With the above configuration, even if polarization occurs, the SOC is calculated after the polarization is eliminated by the polarization elimination control. This makes it possible to avoid a situation in which the calculation result of the SOC is affected by the polarization. As a result, the SOC can be calculated with high accuracy. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic overall configuration of a vehicle equipped with a battery system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating the configuration of each cell of a battery. [Diagram 3] FIG. 2 is a diagram showing an example of a curve representing the SOC-OCV (Open Circuit Voltage) characteristics of a battery. [Figure 4] FIG. 2 is a diagram for explaining that polarization of the battery 10 can affect the accuracy of calculating the SOC. [Diagram 5] 2 is a diagram for specifically explaining the process of calculating the SOC when the full charge capacity of the battery 10 is estimated by an ECU (Electronic Control Unit). FIG. [Figure 6] 4 is a flowchart illustrating a process executed by an ECU in relation to a process of calculating an SOC. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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 designated by the same reference characters and their description will not be repeated.

[0010] Fig. 1 is a diagram showing a schematic overall configuration of a vehicle equipped with a battery system according to an embodiment. With reference to Fig. 1, vehicle 1 is an electric vehicle (BEV: Battery Electric Vehicle) and is configured to be capable of performing external charging for charging a battery 10 using power supplied from power equipment 90 external to vehicle 1.

[0011] The vehicle 1 includes a battery 10, a voltage sensor 21, a current sensor 22, a system main relay (SMR) 25, a power control unit (PCU) 30, and a motor 35. The vehicle 1 further includes an inlet 40, an AC / DC converter 50, a DC-DC converter 65, an auxiliary battery 70, a communication device 75, and an ECU 100. The battery 10, the voltage sensor 21, the current sensor 22, the SMR 25, the AC / DC converter 50, the DC-DC converter 65, the auxiliary battery 70, the communication device 75, and the ECU 100 configure a battery system 2.

[0012] The battery 10 is an example of a power storage device, and stores power for running the vehicle 1. The battery 10 is an assembled battery including a plurality of cells. Each cell is a secondary battery, and in this example, is an all-solid-state battery. An all-solid-state battery is a battery that includes a solid electrolyte layer.

[0013] Polarization of the battery 10 may occur after charging or discharging the battery 10. Polarization is a phenomenon in which, when a current flows through the battery 10, an electromotive force (polarization voltage) is temporarily generated in the opposite direction to the current. In other words, polarization is a phenomenon in which the voltage VB temporarily increases when the battery 10 is charged, or the voltage VB temporarily decreases when the battery 10 is discharged. The polarization is naturally eliminated if a sufficiently long time has passed after charging or discharging, or is eliminated when a voltage in the opposite direction to the polarization voltage is applied to the battery 10 (the polarization voltage becomes zero and the voltage VB stabilizes).

[0014] The voltage sensor 21 detects the voltage VB of the battery 10. The current sensor 22 detects the current IB flowing through the battery 10. The current IB is positive during charging, and negative during discharging.

[0015] The SMR 25 is connected between the battery 10 and the PCU 30. The PCU 30 performs bidirectional power conversion between the battery 10 and the motor 35. The motor 35 is an AC rotating electric machine, and generates driving force for the vehicle 1 to travel when it is powered. The motor 35 can also perform regenerative power generation when the vehicle 1 is braked or when the acceleration is reduced on a downhill slope. During regenerative power generation by the motor 35, the generated power is supplied to the battery 10 via the PCU 30, and the battery 10 is charged.

[0016] The inlet 40 is configured to allow a connector 95 of the power equipment 90 to be inserted therein, and receives supply power from the power equipment 90. In this example, the supply power is AC power. The AC / DC converter 50 converts the power received by the inlet 40 into DC power for charging the battery 10. The AC / DC converter 50 can also convert the power of the battery 10 into AC power and supply it to the power equipment 90 via the inlet 40. The supply of power from the vehicle 1 to the power equipment 90 is also referred to as "external power supply." During external power supply, the battery 10 is discharged.

[0017] The DC-DC converter 65 is connected to an auxiliary battery 70. The auxiliary battery 70 stores power for operating various auxiliaries (not shown) of the vehicle 1. The communication device 75 exchanges various information with the power equipment 90, for example, by CAN (Controller Area Network) communication. This information includes information indicating the amount of power transmitted between the vehicle 1 and the power equipment 90 during external charging or external power feeding, and information indicating start / stop of external charging, or start / stop of external power feeding.

[0018] The ECU 100 includes a CPU (Central Processing Unit) 102, a memory 104, and a storage device 105. The CPU 102 executes various arithmetic operations. The memory 104 includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM stores programs executed by the CPU 102 and various data. The data includes information indicating a characteristic that represents the relationship between the SOC and OCV of the battery 10. This characteristic is also called an SOC-OCV characteristic. This characteristic is used to calculate the SOC according to the OCV, and is influenced by the charge / discharge history (hysteresis) of the battery 10. The OCV is determined as the voltage VB when the SMR 25 is turned off. The storage device 105 stores a charge / discharge history 110 that represents the history of the voltage VB and the current IB.

[0019] The ECU 100 controls various devices of the vehicle 1 and calculates the SOC of the battery 10 based on signals received from each sensor of the monitoring unit 20 and programs and maps stored in the memory 104. The devices include the SMR 25, the PCU 30, the AC / DC converter 50, the DC / DC converter 65, and the communication device 75. When the SMR 25 is turned on, the ECU 100 uses the PCU 30 to control charging and discharging of the battery 10. The ECU 100 drives the motor 35 by controlling the PCU 30. The ECU 100 is configured to be capable of executing control (pumping charge control) to control the DC-DC converter 65 so as to supply power from the auxiliary battery 70 to the battery 10.

[0020] The ECU 100 is configured to be capable of executing external charging control for controlling external charging and external power supply control for controlling external power supply. These controls are executed using the AC / DC converter 50 and the communication device 75. The ECU 100 is configured to be capable of estimating the full charge capacity of the battery 10 by dividing the charge amount of the battery 10 by an increment (ΔSOC) of SOC during charging of the battery 10. The charge amount of the battery 10 is determined based on an integrated value of the current IB.

[0021] Fig. 2 is a diagram illustrating a schematic configuration of each cell of the battery 10. Referring to Fig. 2, the cell 15 includes a positive electrode layer 15a, a negative electrode layer 15b, and a solid electrolyte layer 15c.

[0022] The positive electrode layer 15a includes a positive electrode active material layer 15d and a positive electrode current collector 15e. The positive electrode active material layer 15d includes lithium cobalt oxide, lithium nickel oxide, or lithium iron phosphate. The positive electrode active material layer 15d is bonded to the solid electrolyte layer 15c, and in the example of FIG. 2(A), they are in close contact with each other. The region 16 is a bonding region of these layers. The negative electrode layer 15b includes a negative electrode active material layer 15f and a negative electrode current collector 15g. The negative electrode active material layer 15f includes a metal active material or a carbon active material. The negative electrode active material layer 15f is bonded to the solid electrolyte layer 15c, and in this example, they are in close contact with each other. The solid electrolyte layer 15c is interposed between the positive electrode layer 15a and the negative electrode layer 15b. The positive electrode layer 15a, the solid electrolyte layer 15c, and the negative electrode layer 15b are stacked in the direction in which the multiple cells 15 are stacked (Y direction).

[0023] When the all-solid-state battery is repeatedly charged and discharged, a part of the bond between the electrode layer, such as the positive electrode layer 15a, and the solid electrolyte layer 15c may peel off (FIG. 2(B)). Such a phenomenon is also called delamination. Regions 17 and 18 are the non-bonded region and bonded region between the electrode layer (in this example, the positive electrode layer 15a) and the solid electrolyte layer, respectively, during delamination. During delamination, the electrical resistance of region 17 is high, and the electrical resistance of region 18 is low. Such non-uniformity of electrical resistance affects the diffusion of charge carriers and is likely to cause non-uniformity in electron density. As a result, in the all-solid-state battery, lithium salts and the like are likely to diffuse and polarization is likely to occur. Furthermore, during delamination, a large current is likely to flow in the all-solid-state battery due to the low electrical resistance of region 18. When the all-solid-state battery is charged (overcharged) with a large current and then immediately discharged, a large amount of discharge current flows into region 18. As a result, the all-solid-state battery is discharged with a large current, and the polarization after charging is immediately eliminated.

[0024] Fig. 3 is a diagram showing an example of a curve showing the SOC-OCV characteristics of the battery 10. Fig. 4 is a diagram for explaining that the polarization of the battery 10 can affect the calculation accuracy of the SOC.

[0025] Referring to FIG. 3, a line 200 illustrates the SOC-OCV characteristic when the battery 10 is charged. In this example, the characteristic corresponds to the SOC-OCV characteristic when the battery 10 is charged from a fully discharged state to a fully charged state. The line 200 is also referred to as a "charging curve." A line 220 illustrates the SOC-OCV characteristic when the battery 10 is discharged. In this example, the characteristic corresponds to the SOC-OCV characteristic when the battery 10 is discharged from a fully charged state to a fully discharged state. The line 220 is also referred to as a "discharging curve." In this way, the SOC-OCV characteristic differs depending on the charge / discharge history (hysteresis). Each of the lines 200 and 220 shows the SOC-OCV characteristic under a situation where the polarization of the battery 10 does not occur (or is eliminated).

[0026] Line 240 illustrates the SOC-OCV characteristic when battery 10 is charged from a fully discharged state to a fully charged state, but differs from line 200 in that the characteristic is in a state where polarization occurs. Line 260 illustrates the SOC-OCV characteristic when battery 10 is charged from a fully charged state to a fully discharged state, but differs from line 220 in that the characteristic is in a state where polarization occurs. Thus, the SOC-OCV characteristic changes due to the influence of polarization in addition to the influence of hysteresis. In this example, each of lines 200 and 220 is stored in memory 104, but each of lines 240 and 260 is not stored in memory 104.

[0027] Points P1 and P2 are points on lines 240 and 260, respectively, that correspond to V1. Points P1 and P2 each correspond to an operating point when the OCV is V1 and polarization is occurring.

[0028] With reference to FIG. 4, the polarization of the battery 10 may affect the calculation accuracy of the SOC of the battery 10. For example, when the OCV is V1 during charging, polarization may actually occur, so that the actual operating point may be point P1 and the actual SOC may be X1 (FIG. 4(A)). However, since the charging curve stored in the memory 104 is line 200, not line 240, the operating point may be erroneously determined to be point P1f based on line 200, and the SOC may be calculated as X1f. As a result, the calculation result of the SOC may include an error of ΔE1. ​​Similarly, when polarization occurs during discharging, even though the actual operating point is point P2 (SOC is X2), the operating point may be erroneously determined to be point P2f based on line 220, and the SOC may be calculated as X2f (FIG. 4(B)). As a result, the calculation result of the SOC may include an error of ΔE2. In this way, polarization is likely to cause a decrease in the calculation accuracy of the SOC. In particular, in all-solid-state batteries, polarization is likely to occur due to delamination between layers (Figure 2), so there is a demand for technology to avoid a decrease in the accuracy of SOC calculations due to polarization.

[0029] The inventors have noticed that when polarization occurs, the accuracy of SOC calculation can be improved by eliminating the polarization and calculating the SOC after the polarization is eliminated. The polarization is eliminated by applying a voltage having the opposite polarity to the polarity of the polarization. Specifically, the polarization after discharge is eliminated by charging, and the polarization after charging is eliminated by discharging.

[0030] In the embodiment, the ECU 100 executes polarization elimination control for eliminating the polarization of the battery 10, and a calculation process for calculating the SOC of the battery 10 after the polarization elimination control. When the polarization elimination control is executed after the battery 10 is charged, the polarization elimination control is a discharge control for discharging the battery 10. This control may be a control executed using the PCU 30 while the vehicle 1 is running, or may be an external power supply control. When the polarization elimination control is executed after the battery 10 is discharged, the polarization elimination control is a charge control for charging the battery 10. This control may be a control executed using the PCU 30 while the vehicle 1 is running, or may be an external charge control.

[0031] According to the above calculation process, even if polarization occurs, the polarization is eliminated by the polarization elimination control, and the SOC is then calculated. This makes it possible to avoid a situation in which the SOC calculation result is affected by the polarization. Furthermore, since the polarization is eliminated by the polarization elimination control before the polarization is naturally eliminated after a sufficiently long time has passed, the SOC can be calculated early.

[0032] The ECU 100 executes a calculation process of the SOC according to the OCV of the battery 10 using the SOC-OCV characteristics (lines 200, 220) stored in the memory 104. For example, when the discharge control is executed as the polarization elimination control after the battery 10 is charged, the above calculation process corresponds to a process of calculating the SOC using the line 220 (discharge curve). For example, when the OCV at the start of this discharge control is V1, the operating point of the battery 10 changes from point P1 to point P1a via the line 250 due to the discharge control (OCV drops from V1 to V1a), and then changes on the line 220 ((A) of FIG. 4). The line 250 is not stored in the memory 104. After the discharge control, the ECU 100 calculates the SOC according to the OCV using the line 220. For example, when the OCV after the discharge control is V1a, the calculation result of the SOC is Xa. Xa is lower than X1 by ΔXa.

[0033] When charging control is executed as polarization elimination control after the battery 10 is discharged, the above calculation process corresponds to a process of calculating the SOC using the line 200 (charging curve). For example, when the OCV at the start of this charging control is V1, the operating point changes from point P2 to point P2a via the line 270 due to the charging control (OCV rises from V1 to V1b), and then changes on the line 200 (FIG. 4B). The line 270 is not stored in the memory 104. After the charging control, the ECU 100 calculates the SOC according to the OCV using the line 200. For example, when the OCV after the charging control is V1b, the calculation result of the SOC is Xb. Xb is higher than X2 by ΔXb.

[0034] According to the above polarization elimination control, the battery 10 is discharged after charging, or charged after discharging, thereby eliminating the polarization. As a result, the SOC is calculated in a state where the polarization is eliminated (a state where the operating point is on the line 200 or 220), so that it is possible to avoid a decrease in the calculation accuracy of the SOC due to polarization.

[0035] It is preferable that the period during which the polarization elimination control is executed (hereinafter also referred to as the "polarization elimination period") is appropriately short in order to avoid a situation in which a new polarization voltage opposite to the original polarization voltage is generated due to this control.

[0036] When the battery 10 is discharged immediately before the polarization elimination period (specifically, the start time thereof), the period during which the battery 10 is discharged is also referred to as the “immediately preceding discharge period”. When the battery 10 is charged immediately before the polarization elimination period, the period during which the battery 10 is charged is also referred to as the “immediately preceding charge period”. “Immediately before the polarization elimination period” basically refers to the period (when it is shorter than a predetermined upper limit described later) that is closest to the current time among the charge period (when the battery 10 is charged) and the discharge period (when the battery 10 is discharged) before the start of this control. This period corresponds to the period from the time when the charge / discharge of the battery 10 was last switched (the time when the positive and negative of the current IB were last switched) to the current time. When the length of this period is longer than a predetermined upper limit (e.g., 3 minutes), “immediately before the polarization elimination period” (the immediately preceding charge period or the immediately preceding discharge period) is determined as a period having the length of the predetermined upper limit. Information on the charge period and the discharge period is generated based on the current IB and stored in the memory 104.

[0037] The polarization elimination period after charging is shorter than the immediately preceding charging period. Similarly, the polarization elimination period after discharging is shorter than the immediately preceding discharging period. If the polarization elimination period is too long, a new polarization voltage opposite to the original polarization voltage may be generated. However, in the embodiment, the polarization elimination period is short, so that the above situation can be avoided.

[0038] Furthermore, since the SOC calculation process is performed after the polarization elimination control, the shorter the polarization elimination period, the earlier the calculation process starts. In the embodiment, since the polarization elimination period is short, the polarization elimination control during this period is completed in a short time. As a result, the SOC can be calculated quickly.

[0039] It is also undesirable that the polarization elimination period is too short. In this case, the polarization may not be sufficiently eliminated. In addition, the SOC may be calculated before the operating point changes from point P1 (FIG. 4) to a point on line 220 (e.g., point P1a) or before the operating point changes from point P2 to a point on line 200 (e.g., point P2a) (i.e., while the operating point is moving on line 250 or 270). Since the memory 104 stores lines 200 and 220 but not lines 250 and 270, the SOC calculated at the above timing may be inaccurate.

[0040] The inventors have experimentally found that if the length of the polarization elimination period is 1 / 11 or more and 1 / 9 or less (hereinafter also referred to as "about 1 / 10") of the length of the previous discharge period or the previous charge period, the polarization is easily eliminated and a polarization voltage opposite to the original polarization voltage is unlikely to be generated. Specifically, by setting the length of the polarization elimination period in this manner, the operating points can be changed from points P1 and P2 to points on lines 220 and 200, respectively (specifically, points P1a and P2a or points in the vicinity thereof). Thus, in the embodiment, when the polarization elimination control (charging control) is executed after the battery 10 is discharged, the length of the polarization elimination period is set to about 1 / 10 of the length of the previous discharge period. Similarly, when the polarization elimination control (discharging control) is executed after the battery 10 is charged, the length of the polarization elimination period is set to about 1 / 10 of the length of the previous charge period. In this way, the length of the polarization elimination period is basically longer as the previous charge period or the previous discharge period is longer.

[0041] If the length of the polarization elimination period is shorter than 1 / 11 of the length of the previous charging period or the previous discharging period, the polarization may not be sufficiently eliminated, or the SOC may be calculated while the operating point is moving on line 250 or 270, which may reduce the accuracy of the SOC calculation. If the length of the polarization elimination period is longer than 1 / 9 of the length of the previous charging period or the previous discharging period, a new polarization voltage in the opposite direction to the original polarization voltage may be generated, which may reduce the accuracy of the SOC calculation. In contrast, the embodiment can avoid such problems.

[0042] If the immediately preceding charge period or the immediately preceding discharge period is defined as a period having the aforementioned upper limit length, the length of the polarization elimination period is set (limited) to be about one-tenth of the upper limit. If not, the length of the polarization elimination period is set to about one-tenth of the length of the immediately preceding charge period or the immediately preceding discharge period. This makes it possible to avoid a situation in which the polarization elimination period becomes excessively long and the calculation of the SOC is delayed, even if the battery 10 is charged or discharged for a long period of time before the polarization elimination control.

[0043] Fig. 5 is a diagram for specifically explaining the process of calculating the SOC when estimating the full charge capacity of the battery 10 by the ECU 100. Referring to Fig. 5, a line 300 represents an example of a transition of the SOC.

[0044] During the period from time t0 to time t1 (period P01), the vehicle 1 is traveling and the battery 10 is charged and discharged. At time t1, the vehicle 1 is connected (plugged in) to the power equipment 90 via the inlet 40. The period from time t01 to time t1 (period P01a) is the previous discharge period. It is assumed that polarization is occurring at time t1.

[0045] At time t1, the ECU 100 determines based on the charge / discharge history 110 that the battery 10 was discharged during the period P01a. Based on this determination result, the ECU 100 executes charging control as polarization elimination control during the period from time t1 to time t2 (period P12). This control is external charging control. The period P12 is a polarization elimination period when polarization elimination control is executed after the battery 10 is discharged. During the period P12, the ECU 100 executes external charging control so that the charging power of the battery 10 becomes minute. In this example, the length of the period P12 is one tenth of the period P01a (the previous discharge period).

[0046] At time t2, the ECU 100 stops the external charging control in which the charging power is minute, and calculates the SOC. After that, during the period from time t2 to time t3 (period P23), the external charging control is executed so that the charging power is higher than the charging power during period P12.

[0047] At time t3, the ECU 100 stops the external charging control. The period from time t23 to time t3 (period P23a) is the previous charging period. In this example, the length of the period from the time when charging / discharging of the battery 10 was last switched to the current time is longer than the upper limit, so period P23a (the previous charging period) is a period having the upper limit length. It is assumed that polarization occurs at time t3.

[0048] The ECU 100 determines, based on the charge / discharge history 110, that the battery 10 was charged during the period P23a. Based on this determination result, the ECU 100 executes discharge control as polarization elimination control during the period from time t3 to time t4 (period P34). This control is external power supply control. The period P34 is a polarization elimination period in which polarization elimination control is executed after the battery 10 is charged. In this example, the length of the period P34 is one-tenth the length of the period P23a. At time t4, the ECU 100 stops the external power supply control and calculates the SOC.

[0049] The ECU 100 calculates the absolute value of the difference between the SOC calculated at time t2 and the SOC calculated at time t4 as ΔSOC, and estimates the full charge capacity based on the calculated difference.

[0050] 6 is a flowchart illustrating a process related to the calculation of the SOC and executed by the ECU 100. This flowchart starts when the vehicle 1 is plugged in.

[0051] 6, the ECU 100 reads the charge / discharge history 110 (S105), and determines whether the battery 10 was charged or discharged immediately before the current time (S107).

[0052] If the battery 10 was previously charged (YES in S107), the ECU 100 sets the length of the polarization elimination period to, for example, one tenth of the length of the previous charging period (S110). The ECU 100 executes discharge control as polarization elimination control over the set period (S115). This discharge control corresponds to, for example, the external power supply control during period P34. After S115, the ECU 100 determines the OCV of the battery 10 (for example, V1a in FIG. 4) and calculates the SOC according to the OCV using the line 220 (discharge curve) (S117). In this example, the SOC is calculated as Xa (FIG. 4).

[0053] If the battery 10 was discharged immediately before (NO in S107), the ECU 100 sets the length of the polarization elimination period to, for example, one tenth of the length of the immediately preceding discharge period (S120). The ECU 100 executes charging control as polarization elimination control over the set period (S125). This charging control corresponds to, for example, the external charging control during period P12. After S125, the ECU 100 determines the OCV of the battery 10 (for example, V1b in FIG. 4) and calculates the SOC according to the OCV using the line 200 (charging curve) (S127). In this example, the SOC is calculated as Xb (FIG. 4).

[0054] The ECU 100 may execute S105 to S127 while the vehicle 1 is traveling (while the motor 35 is being driven). In this case, the charging control and discharging control are executed using the PCU 30. Alternatively, the charging control may be the pumping charging control described above.

[0055] As described above, according to the embodiment, it is possible to prevent the result of SOC calculation from being affected by polarization, and as a result, it is possible to calculate the SOC with high accuracy.

[0056] <Modifications of the embodiment> In this variant, a case is assumed in which ECU 100 performs charging control or discharging control using PCU 30 after motor 35 has been powered or regenerated for a relatively long period of time while vehicle 1 is traveling (when the previous discharging period or previous charging period is long).

[0057] When 1 / 11 of the length of the previous discharge period is less than 0.1 seconds and 1 / 9 of the length of the previous discharge period is 0.1 seconds or more, the length of the polarization elimination period (period of charge control) may be less than 0.1 seconds when it is set to 1 / 11 or more and 1 / 9 or less of the length of the previous discharge period. The inventors have found that when the length of this polarization elimination period is less than 0.1 seconds, the polarization is not always sufficiently eliminated even by the polarization polarity control (charge control). On the other hand, the inventors have found that when the length of this polarization elimination period is 0.1 seconds or more, the polarization is particularly likely to be sufficiently eliminated. Therefore, when 1 / 11 of the length of the previous discharge period is less than 0.1 seconds and 1 / 9 of the length of the previous discharge period is 0.1 seconds or more, the ECU 100 may set the length of the polarization elimination period to 0.1 seconds or more and 1 / 9 or less of the length of the previous discharge period.

[0058] When 1 / 11 of the length of the immediately preceding charging period is less than 0.1 seconds and 1 / 9 of the length of the immediately preceding charging period is 0.1 seconds or more, the length of the polarization elimination period (period of discharge control) may be less than 0.1 seconds when it is set to 1 / 11 or more and 1 / 9 or less of the length of the immediately preceding charging period. The inventors have found that when the length of this polarization elimination period is less than 0.1 seconds, polarization is not always sufficiently eliminated even by polarization elimination control (discharge control). On the other hand, the inventors have found that when the length of this polarization elimination period is 0.1 seconds or more, polarization is particularly likely to be sufficiently eliminated. Therefore, when 1 / 11 of the length of the immediately preceding charging period is less than 0.1 seconds and 1 / 9 of the length of the immediately preceding charging period is 0.1 seconds or more, the ECU 100 may set the length of the polarization elimination period to 0.1 seconds or more and 1 / 9 or less of the length of the immediately preceding charging period.

[0059] When one-ninth of the length of the previous discharge period is less than 0.1 seconds, the length of the polarization elimination period is always less than 0.1 seconds when it is set to be greater than or equal to one-eleventh and less than or equal to one-ninth of the length of the previous discharge period. In this case, as described above, polarization is not always sufficiently eliminated even by polarization elimination control (charging control). Therefore, when one-ninth of the length of the previous discharge period is less than 0.1 seconds, the ECU 100 may set the length of the polarization elimination period to be greater than or equal to 0.1 seconds (for example, 0.1 seconds).

[0060] When one-ninth of the length of the immediately preceding charging period is less than 0.1 seconds, the length of the polarization elimination period is always less than 0.1 seconds when set to be greater than or equal to one-eleventh and less than or equal to one-ninth of the length of the immediately preceding charging period. In this case, as described above, polarization is not always sufficiently eliminated even by polarization elimination control (discharge control). Therefore, when one-ninth of the length of the immediately preceding charging period is less than 0.1 seconds, ECU 100 may set the length of the polarization elimination period to be greater than or equal to 0.1 seconds (for example, 0.1 seconds).

[0061] <Other Modifications> Each cell of the battery 10 may be a liquid battery such as a liquid lithium ion battery. The above-described polarization elimination control and SOC calculation process can also be applied to a battery system including a liquid battery instead of an all-solid-state battery. [Industrial Applicability]

[0062] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] 1 Vehicle, 10 Battery, 21 Voltage sensor, 22 Current sensor, 35 Motor, 40 Inlet, 50 AC / DC converter, 65 Converter, 70 Auxiliary battery, 75 Communication device, 90 Power equipment, 95 Connector, 100 ECU.

Claims

1. A power storage device; a control device that executes a polarization elimination control for eliminating the polarization of the power storage device, and a calculation process for calculating an SOC of the power storage device after the polarization elimination control, When the polarization elimination control is executed after the power storage device is discharged, the polarization elimination control is a charging control for charging the power storage device, A battery system, wherein, when the polarization elimination control is executed after the power storage device is charged, the polarization elimination control is a discharge control for discharging the power storage device.

2. The calculation process includes: a process of calculating the SOC using an SOC-OCV characteristic of the power storage device when the power storage device is charged, when the polarization elimination control is executed after the power storage device is discharged; 2. The battery system according to claim 1, wherein, when the polarization elimination control is executed after the power storage device is charged, the SOC is calculated using an SOC-OCV characteristic of the power storage device when the power storage device is discharged.

3. A period during which the polarization elimination control is executed is defined as an elimination period, If the power storage device is charged immediately before the termination period, the period during which the power storage device is charged is set as a immediately preceding charging period; In the case where the power storage device is discharged immediately before the cancellation period, the period during which the power storage device is discharged is defined as a immediately preceding discharge period, When the polarization elimination control is executed after the power storage device is discharged, the elimination period is shorter than the immediately preceding discharge period, 3. The battery system according to claim 1, wherein when the polarization elimination control is executed after the power storage device is charged, the elimination period is shorter than the immediately preceding charging period.

4. When the polarization elimination control is executed after the power storage device is discharged, the length of the elimination period is equal to or greater than 1 / 11 and equal to or less than 1 / 9 of the length of the immediately preceding discharge period, 4. The battery system according to claim 3, wherein when the polarization elimination control is executed after the power storage device is charged, the length of the elimination period is equal to or greater than 1 / 11 and equal to or less than 1 / 9 of the length of the immediately preceding charging period.

5. When 1 / 11 of the length of the previous discharge period is less than 0.1 seconds and 1 / 9 of the length of the previous discharge period is 0.1 seconds or more, the length of the cancellation period is 0.1 seconds or more and 1 / 9 of the length of the previous discharge period or less, if one-ninth of the length of the preceding discharge period is less than 0.1 seconds, the length of the cancellation period is 0.1 seconds; when 1 / 11 of the length of the immediately preceding charging period is less than 0.1 seconds and 1 / 9 of the length of the immediately preceding charging period is 0.1 seconds or more, the length of the cancellation period is 0.1 seconds or more and 1 / 9 of the length of the immediately preceding charging period or less; 5. The battery system of claim 4, wherein if one-ninth of the length of the immediately preceding charging period is less than 0.1 seconds, the length of the cancellation period is 0.1 seconds.

Images