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 Art

[0002] Japanese Unexamined Patent Application Publication No. 2019-160721 (Patent Document 1) discloses a battery system including a secondary battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Calculating the SOC (State Of Charge) of a power storage device such as a secondary battery with high accuracy is important when appropriately protecting or sufficiently using the power storage device. Therefore, a technique for improving the calculation accuracy of SOC is desired.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a battery system capable of improving the calculation accuracy of SOC.

Means for Solving the Problems

[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 the 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 charging 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 discharge control for discharging the power storage device.

[0007] Polarization in an energy storage device can affect the State of Charge (SOC) calculation because it changes the voltage of the device. Polarization in an energy storage device can be resolved by applying a voltage with the opposite polarity. Specifically, polarization after discharge is resolved by charging the device, and polarization after charging is resolved by discharging. With this configuration, even if polarization occurs, the SOC is calculated after the polarization is resolved by the polarization resolution control. This avoids the situation where the SOC calculation result is affected by polarization. As a result, the SOC can be calculated with high accuracy. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram schematically shows the overall configuration of a vehicle equipped with a battery system according to the embodiment. [Figure 2] This diagram schematically shows the configuration of each cell in a battery. [Figure 3] This figure shows an example of a curve representing the SOC-OCV (Open Circuit Voltage) characteristics of a battery. [Figure 4] This diagram illustrates how the polarization of battery 10 can affect the accuracy of the SOC calculation. [Figure 5] This diagram illustrates the process by which the ECU (Electronic Control Unit) calculates the State of Charge (SOC) when estimating the full charge capacity of battery 10. [Figure 6] This flowchart illustrates the processes performed by the ECU in relation to the SOC calculation process. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described in detail below with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and their descriptions will not be repeated.

[0010] Figure 1 is a schematic diagram showing the overall configuration of a vehicle equipped with a battery system according to an embodiment. Referring to Figure 1, the vehicle 1 is an electric vehicle (BEV: Battery Electric Vehicle) and is configured to perform external charging, which charges the battery 10 using power supplied from an external power facility 90 outside the vehicle 1.

[0011] Vehicle 1 comprises a battery 10, a voltage sensor 21, a current sensor 22, an SMR (System Main Relay) 25, a PCU (Power Control Unit) 30, and a motor 35. Vehicle 1 further comprises 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, voltage sensor 21, current sensor 22, SMR 25, AC / DC converter 50, DC-DC converter 65, auxiliary battery 70, communication device 75, and ECU 100 constitute a battery system 2.

[0012] Battery 10 is an example of an energy storage device that stores power for the vehicle 1 to run. Battery 10 is a battery pack containing multiple cells. Each cell is a secondary battery, and in this example, it is a solid-state battery. A solid-state battery is a battery that has a solid electrolyte layer.

[0013] Polarization may occur in battery 10 after charging or discharging. Polarization is a phenomenon in which an electromotive force (polarization voltage) in the opposite direction to the current is temporarily generated when an electric current flows through battery 10. In other words, polarization is a phenomenon in which the voltage VB of battery 10 temporarily rises when charging, or temporarily falls when discharging. Polarization will resolve naturally after a sufficiently long time has passed since charging or discharging, or it will resolve when a voltage in the opposite direction to the polarization voltage is applied to 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 the current IB is negative during discharging.

[0015] The SMR25 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 that generates the driving force for the vehicle 1 when it is powered. The motor 35 can also perform regenerative power generation when the vehicle 1 is braking or when acceleration is reduced on a downhill slope. When the motor 35 performs regenerative power generation, the generated power is supplied to the battery 10 through the PCU 30 and the battery 10 is charged.

[0016] The inlet 40 is configured to accept the connector 95 of the power equipment 90 and receives power from the power equipment 90. In this example, the power supplied is alternating current (AC). The AC / DC converter 50 converts the power received through the inlet 40 into direct current (DC) power for charging the battery 10. The AC / DC converter 50 can also convert the power from the battery 10 into AC power and supply it to the power equipment 90 via the inlet 40. The power supply 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 the auxiliary battery 70. The auxiliary battery 70 stores power to operate various auxiliary equipment (not shown) of the vehicle 1. The communication device 75 exchanges various information with the power equipment 90, for example, via CAN (Controller Area Network) communication. This information includes the amount of power transmitted between the vehicle 1 and the power equipment 90 during external charging or external power supply, and information indicating the start / stop of external charging or the start / stop of external power supply.

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

[0019] Based on the signals received from each sensor of the monitoring unit 20 and the programs and maps stored in the memory 104, the ECU 100 controls various devices of the vehicle 1 and calculates the SOC of the battery 10. 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 controls the charge and discharge of the battery 10 using the PCU 30. The ECU 100 drives the motor 35 by controlling the PCU 30. The ECU 100 is configured to be able to execute control (boost charging control) to control the DC-DC converter 65 to supply the power of the auxiliary battery 70 to the battery 10.

[0020] The ECU 100 is configured to be able to execute external charge 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 able to estimate the full charge capacity of the battery 10 by dividing the charge amount of the battery 10 by the increment (ΔSOC) of the SOC during charging of the battery 10. The charge amount of the battery 10 is determined based on the integrated value of the current IB.

[0021] FIG. 2 is a diagram schematically showing the 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 contains lithium cobaltate, lithium nickelate, or lithium iron phosphate. The positive electrode active material layer 15d is joined to the solid electrolyte layer 15c and is in close contact in the example of FIG. 2(A). Region 16 is the joining 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 contains a metal active material or a carbon active material. The negative electrode active material layer 15f is joined to the solid electrolyte layer 15c and is in close contact in this example. 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 (Y direction) in which a plurality of cells 15 are stacked.

[0023] When the charge and discharge of the all-solid-state battery are repeated, a part of the joining of 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-joining region and the joining region of the electrode layer (in this example, the positive electrode layer 15a) and the solid electrolyte layer during delamination, respectively. 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 tends to cause non-uniformity of electron density. As a result, in the all-solid-state battery, lithium salts and the like are easily diffused and polarization is likely to occur. Further, during delamination, a large current easily flows in the all-solid-state battery because the electrical resistance of region 18 is low. When the all-solid-state battery is discharged immediately after being charged (overcharged) with a large current, 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] Figure 3 shows an example of a curve representing the SOC-OCV characteristics of battery 10. Figure 4 is a diagram illustrating how the polarization of battery 10 can affect the accuracy of SOC calculation.

[0025] Referring to Figure 3, line 200 illustrates the SOC-OCV characteristics when battery 10 is being charged. In this example, this characteristic corresponds to the SOC-OCV characteristics when battery 10 is charged from a fully discharged state to a fully charged state. Line 200 is also referred to as the "charging curve". Line 220 illustrates the SOC-OCV characteristics when battery 10 is being discharged. In this example, this characteristic corresponds to the SOC-OCV characteristics when battery 10 is discharged from a fully charged state to a fully discharged state. Line 220 is also referred to as the "discharge curve". Thus, the SOC-OCV characteristics differ depending on the charge-discharge history (hysteresis). Lines 200 and 220, respectively, show the SOC-OCV characteristics under the condition that polarization of battery 10 has not occurred (or has been resolved).

[0026] Line 240 illustrates the SOC-OCV characteristics when the battery 10 is charged from a completely discharged state to a fully charged state, but differs from line 200 in that these characteristics occur under conditions of polarization. Line 260 illustrates the SOC-OCV characteristics when the battery 10 is charged from a fully charged state to a completely discharged state, but differs from line 220 in that these characteristics occur under conditions of polarization. Thus, SOC-OCV characteristics change under the influence of polarization in addition to the influence of hysteresis. In this example, lines 200 and 220 are stored in memory 104, but lines 240 and 260 are not stored in memory 104.

[0027] Points P1 and P2 are points on lines 240 and 260, respectively, corresponding to V1. Each of points P1 and P2 corresponds to the operating point when OCV is V1 and polarization is occurring.

[0028] Referring to Figure 4, the polarization of battery 10 can affect the accuracy of calculating the State of Charge (SOC) of battery 10. For example, if the OCV is V1 during charging, polarization may actually occur, so the actual operating point may be point P1 and the actual SOC may be X1 (Figure 4(A)). However, since the charging curve stored in memory 104 is line 200 and not line 240, the operating point may be incorrectly determined to be point P1f based on line 200, and the SOC may be calculated as X1f. As a result, the calculated SOC may contain an error of ΔE1. ​​Similarly, if polarization occurs during discharge, even though the actual operating point is point P2 (SOC is X2), the operating point may be incorrectly determined to be point P2f based on line 220, and the SOC may be calculated as X2f (Figure 4(B)). As a result, the calculated SOC may contain an error of ΔE2. Thus, polarization is likely to lead to a decrease in the accuracy of SOC calculation. In particular, in all-solid-state batteries, polarization is likely to occur due to delamination (Figure 2), so there is a need for technologies to avoid the decrease in the accuracy of SOC calculation caused by polarization.

[0029] The inventors focused on the fact that if polarization occurs, the accuracy of SOC calculation can be improved by eliminating the polarization and then calculating the SOC after the polarization has been eliminated. Polarization is eliminated by applying a voltage with the opposite polarity. Specifically, polarization after discharge is eliminated by charging, and polarization after charging is eliminated by discharging.

[0030] In this embodiment, the ECU 100 performs polarization depolarization control to eliminate the polarization of the battery 10, and a calculation process to calculate the State of Charge (SOC) of the battery 10 after the polarization depolarization control. If the polarization depolarization control is performed after the battery 10 has been charged, the polarization depolarization control is a discharge control to discharge the battery 10. This control may be performed using the PCU 30 when the vehicle 1 is running, or it may be an external power supply control. If the polarization depolarization control is performed after the battery 10 has been discharged, the polarization depolarization control is a charge control to charge the battery 10. This control may be performed using the PCU 30 when the vehicle 1 is running, or it may be an external charge control.

[0031] According to the calculation process described above, even if polarization occurs, the polarization is resolved by the polarization depolarization control, and then the State of Charge (SOC) is calculated. This prevents the SOC calculation result from being affected by polarization. Furthermore, since the polarization is resolved by the polarization depolarization control before a sufficiently long time has elapsed for the polarization to resolve naturally, the SOC can be calculated earlier.

[0032] The ECU 100 uses the SOC-OCV characteristics (lines 200, 220) stored in memory 104 to calculate the State of Charge (SOC) according to the OCV of the battery 10. For example, if discharge control is performed as depolarization control after the battery 10 has been charged, the above calculation process corresponds to the process of calculating the SOC using line 220 (discharge curve). For example, if 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 line 250 due to the discharge control (the OCV decreases from V1 to V1a), and then changes along line 220 (Figure 4(A)). Line 250 is not stored in memory 104. After the discharge control, the ECU 100 calculates the SOC according to the OCV using line 220. For example, if the OCV after the discharge control is V1a, the calculated SOC is Xa. Xa is lower than X1 by ΔXa.

[0033] When charging control is performed as a depolarization control after the battery 10 has been discharged, the above calculation process corresponds to the process of calculating the SOC using line 200 (charging curve). For example, if the OCV at the start of this charging control is V1, the operating point changes from point P2 to point P2a via line 270 due to the charging control (the OCV rises from V1 to V1b), and then changes along line 200 (Figure 4(B)). Line 270 is not stored in memory 104. After the charging control, the ECU 100 calculates the SOC according to the OCV using line 200. For example, if the OCV after the charging control is V1b, the calculated SOC is Xb. Xb is ΔXb higher than X2.

[0034] According to the polarization depolarization control described above, the battery 10 is discharged after charging, or charged after discharging, thereby depolarizing the battery. As a result, the SOC is calculated in a depolarized state (when the operating point is on line 200 or 220), thus avoiding a decrease in the accuracy of the SOC calculation caused by polarization.

[0035] Furthermore, the period during which the depolarization control is performed (hereinafter also referred to as the "depolarization period") is preferably moderately short. This is to avoid a situation in which a new polarization voltage opposite to the original polarization voltage is generated as a result of this control.

[0036] If the battery 10 is discharged immediately before the depolarization period (specifically, its start time), the period during which the battery 10 is discharged in this manner is also referred to as the "immediate discharge period." If the battery 10 is charged immediately before the depolarization period, the period during which the battery 10 is charged in this manner is also referred to as the "immediate charging period." "Immediately before the depolarization period" basically refers to the charging period (the period during which the battery 10 was charged) and the discharging period (the period during which the battery 10 was discharged) prior to the start of this control, which are the periods closest to the present time (if shorter than the predetermined upper limit described later). This period corresponds to the period from the time when the charging / discharging of the battery 10 last switched (the time when the positive and negative of the current IB last switched) to the present time. If the length of this period is longer than the predetermined upper limit (for example, 3 minutes), the "immediately before the depolarization period" (immediate charging period or immediate discharge period) is defined as a period having the length of the predetermined upper limit. Information on the charging period and the discharging period is generated based on the current IB and stored in the memory 104.

[0037] The depolarization period after charging is shorter than the preceding charging period. Similarly, the depolarization period after discharge is shorter than the preceding discharge period. If the depolarization period is excessively long, it is conceivable that a new polarization voltage opposite to the original polarization voltage may be generated. However, in this embodiment, since the depolarization period is short, the above situation can be avoided.

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

[0039] The polarization depolarization period should not be excessively short. In this case, polarization may not be sufficiently depolarized. In addition, the SOC may be calculated before the operating point changes from point P1 (Figure 4) to a point on line 220 (e.g., point P1a), or before it changes from point P2 to a point on line 200 (e.g., point P2a) (i.e., while the operating point is moving along line 250 or 270). Since 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 experimentally found that if the length of the depolarization period is between 1 / 11 and 1 / 9 (hereinafter also referred to as "approximately 1 / 10") the length of the preceding discharge period or preceding charge period, polarization is easily resolved, and a polarization voltage opposite to the original polarization voltage is unlikely to be generated. Specifically, by setting the length of the depolarization period in this way, the operating point could be changed from points P1 and P2 to points on lines 220 and 200, respectively (more specifically, points P1a, P2a, or points in their vicinity). Therefore, in the embodiment, when depolarization control (charge control) is performed after the battery 10 has been discharged, the length of the depolarization period is set to approximately 1 / 10 of the length of the preceding discharge period. Similarly, when depolarization control (discharge control) is performed after the battery 10 has been charged, the length of the depolarization period is set to approximately 1 / 10 of the length of the preceding charge period. Thus, the length of the depolarization period is basically longer the longer the preceding charge period or preceding discharge period is.

[0041] If the depolarization period is shorter than one-eleventh of the length of the preceding charging or discharging period, polarization may not be sufficiently depolarized, or the SOC calculation accuracy may be reduced because the operating point is calculated while moving along line 250 or 270. If the depolarization period is longer than one-ninth of the length of the preceding charging or discharging period, a new polarization voltage opposite to the original polarization voltage may be generated, thereby reducing the SOC calculation accuracy. In contrast, the embodiment can avoid such problems.

[0042] If the preceding charging period or preceding discharge period is defined as having the aforementioned upper limit length, the length of the depolarization period is set (restricted) to approximately one-tenth of that upper limit. Otherwise, the length of the depolarization period is set to approximately one-tenth of the length of the preceding charging period or preceding discharge period. This prevents the depolarization period from becoming excessively long and delaying the calculation of the State of Charge (SOC), even if the battery 10 has been charged or discharged for a long period of time before depolarization control.

[0043] Figure 5 is a diagram illustrating the process by which the ECU 100 calculates the State of Charge (SOC) when estimating the full charge capacity of the battery 10. Referring to Figure 5, line 300 represents an example of the SOC progression.

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

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

[0046] At time t2, the ECU 100 stops the external charging control, which is performing at a low power level, and calculates the State of Charge (SOC). Subsequently, during the period from time t2 to time t3 (period P23), the external charging control is performed so that the charging power is greater than the charging power during period P12.

[0047] At time t3, ECU100 stops external charging control. The period from time t23 to time t3 (period P23a) is the previous charging period. In this example, since the length of the period from the time when the charging / discharging of battery 10 last switched to the current time is longer than the upper limit, period P23a (previous charging period) is the period with the length of that upper limit. Polarization is assumed to be occurring at time t3.

[0048] Based on the charge / discharge history 110, ECU 100 determines that the battery 10 was charged during period P23a. Based on this determination, ECU 100 executes discharge control as depolarization control during the period from time t3 to time t4 (period P34). This control is external power supply control. Period P34 is the depolarization period when depolarization control is executed after the battery 10 has been charged. In this example, the length of period P34 is one-tenth the length of period P23a. At time t4, ECU 100 stops the external power supply control and calculates the State of Charge (SOC).

[0049] The ECU100 calculates ΔSOC as the absolute value of the difference between the SOC calculated at time t2 and the SOC calculated at time t4, and estimates the full charge capacity based on this.

[0050] Figure 6 is a flowchart illustrating the processes performed by the ECU 100 in relation to the SOC calculation process. This flowchart starts when vehicle 1 is plugged in.

[0051] Referring to Figure 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 charged immediately before (YES in S107), the ECU 100 sets the length of the depolarization period to, for example, one-tenth of the length of the previous charging period (S110). The ECU 100 performs discharge control as depolarization control over the set period (S115). This discharge control corresponds, for example, to external power supply control during period P34. After S115, the ECU 100 determines the OCV of the battery 10 (for example, V1a in Figure 4) and calculates the SOC according to the OCV using line 220 (discharge curve) (S117). In this example, the SOC is calculated as Xa (Figure 4).

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

[0054] The ECU 100 may execute S105 to S127 while the vehicle 1 is running (while the motor 35 is running). In this case, the charge control and discharge control are performed using the PCU 30. Alternatively, the charge control may be the aforementioned pump-charge control.

[0055] As described above, according to this embodiment, it is possible to avoid situations where the SOC calculation result is affected by polarization. As a result, the SOC can be calculated with high accuracy.

[0056] <Modified Example of Embodiment> In this modified example, we assume a case where, while the vehicle 1 is in motion, the motor 35 is powered or regeneratively generated for a relatively long period of time (when the preceding discharge period or preceding charge period is long), and the ECU 100 then performs charge control or discharge control using the PCU 30.

[0057] If one-eleventh of the length of the preceding discharge period is less than 0.1 seconds, and one-ninth of the length of the preceding discharge period is 0.1 seconds or more, the length of the depolarization period (charge control period) may be less than 0.1 seconds when set to one-eleventh or more and one-ninth or less of the length of the preceding discharge period. The inventors have found that when the length of this depolarization period is less than 0.1 seconds, polarization is not always sufficiently resolved even by polarization polarity control (charge control). On the other hand, the inventors have found that when the length of this depolarization period is 0.1 seconds or more, polarization is particularly easily resolved. Therefore, if one-eleventh of the length of the preceding discharge period is less than 0.1 seconds, and one-ninth of the length of the preceding discharge period is 0.1 seconds or more, the ECU100 may set the length of the depolarization period to 0.1 seconds or more and one-ninth or less of the length of the preceding discharge period.

[0058] If one-eleventh of the length of the preceding charging period is less than 0.1 seconds, and one-ninth of the length of the preceding charging period is 0.1 seconds or more, the length of the depolarization period (discharge control period) may be less than 0.1 seconds when set to one-eleventh or more and one-ninth or less of the length of the preceding charging period. The inventors have found that when the length of this depolarization period is less than 0.1 seconds, polarization is not always sufficiently resolved even by depolarization control (discharge control). On the other hand, the inventors have found that when the length of this depolarization period is 0.1 seconds or more, polarization is particularly easily resolved. Therefore, if one-eleventh of the length of the preceding charging period is less than 0.1 seconds, and one-ninth of the length of the preceding charging period is 0.1 seconds or more, the ECU100 may set the length of the depolarization period to 0.1 seconds or more and one-ninth or less of the length of the preceding charging period.

[0059] If one-ninth of the length of the preceding discharge period is less than 0.1 seconds, the length of the depolarization period is always less than 0.1 seconds when set to at least one-eleventh and no more than one-ninth of the length of the preceding discharge period. In this case, as described above, polarization is not always sufficiently resolved even by depolarization control (charge control). Therefore, if one-ninth of the length of the preceding discharge period is less than 0.1 seconds, the ECU100 may set the length of the depolarization period to 0.1 seconds or more (for example, 0.1 seconds).

[0060] If one-ninth of the length of the preceding charging period is less than 0.1 seconds, the length of the depolarization period is always less than 0.1 seconds when set to at least one-eleventh and no more than one-ninth of the length of the preceding charging period. In this case, as described above, polarization is not always sufficiently resolved even by depolarization control (discharge control). Therefore, if one-ninth of the length of the preceding charging period is less than 0.1 seconds, the ECU 100 may set the length of the depolarization period to 0.1 seconds or more (for example, 0.1 seconds).

[0061] <Other variations> Each cell of the battery 10 may be a liquid-type battery, such as a liquid-type lithium-ion battery. The polarization depolarization control and SOC calculation processes described above can also be applied to battery systems that include liquid-type batteries instead of all solid-state batteries. [Industrial applicability]

[0062] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0063] 1 Vehicle, 10 Batteries, 21 Voltage Sensors, 22 Current Sensors, 35 Motors, 40 Inlets, 50 AC / DC Converters, 65 Converters, 70 Auxiliary Batteries, 75 Communication Devices, 90 Power Equipment, 95 Connectors, 100 ECUs.

Claims

1. Energy storage device, The system includes a polarization depolarization control for eliminating the polarization of the energy storage device, and a control device that performs a calculation process to calculate the State of Control (SOC) of the energy storage device after the polarization depolarization control. If the depolarization control is performed after the energy storage device has been discharged, the depolarization control is a charging control that charges the energy storage device. If the depolarization control is performed after the energy storage device has been charged, the depolarization control is a discharge control that discharges the energy storage device. The aforementioned calculation process is, If the polarization depolarization control is performed after the energy storage device has been discharged, the process involves calculating the SOC using the SOC-OCV characteristics of the energy storage device when it is being charged. A battery system comprising the process of calculating the State of Control (SOC) using the SOC-OCV characteristics of the energy storage device when the energy storage device is discharged, after the depolarization control has been performed on the energy storage device.

2. The period during which the aforementioned polarization depolarization control is performed is defined as the depolarization period. If the energy storage device was charged immediately before the aforementioned deactivation period, the period during which the energy storage device was charged shall be the immediate preceding charging period. If the energy storage device discharges immediately before the aforementioned discharge period, the period during which the energy storage device discharged is defined as the immediate discharge period. If the polarization depolarization control is performed after the energy storage device has discharged, the depolarization period is shorter than the immediate discharge period. The battery system according to claim 1, wherein, if the depolarization control is performed after the energy storage device has been charged, the depolarization period is shorter than the immediate charging period.

3. If the polarization depolarization control is performed after the energy storage device has been discharged, the length of the depolarization period is at least 1 / 11 and at least 1 / 9 of the length of the preceding discharge period. The battery system according to claim 2, wherein, when the depolarization control is performed after the energy storage device has been charged, the length of the depolarization period is at least one-eleventh and no more than one-ninth of the length of the immediately preceding charging period.

4. If one-eleventh of the length of the preceding discharge period is less than 0.1 seconds, and one-ninth of the length of the preceding discharge period is 0.1 seconds or more, then the length of the elimination period is 0.1 seconds or more, and one-ninth or less of the length of the preceding discharge period. If one-ninth of the length of the preceding discharge period is less than 0.1 seconds, then the length of the elimination period is 0.1 seconds. If one-eleventh of the length of the preceding charging period is less than 0.1 seconds, and one-ninth of the length of the preceding charging period is 0.1 seconds or more, then the length of the release period is 0.1 seconds or more, and one-ninth or less of the length of the preceding charging period. The battery system according to claim 3, wherein if one-ninth of the length of the preceding charging period is less than 0.1 seconds, the length of the discharging period is 0.1 seconds.

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