Battery control system and battery control method

Abstract

A battery control system (1) is provided with: a pressure applying means (16) that applies pressure to a battery module (2) by pressing the battery module (2) in the stacking direction of battery cells (21) having a solid electrolyte and a negative electrode containing lithium; a controller (10) that adjusts the value of the pressure by controlling the pressure applying unit (16); and a discharge unit (15) that performs balancing of the remaining discharge capacity between the battery cells (21) in the battery module (2), in which the controller (10) starts a first pressurization control in which the pressure is increased to a predetermined pressure or more by the pressure application unit (16) before the balancing is started.

Description

Technical Field

[0001] The present invention relates to a battery control system and a battery control method. Background Art

[0002] A known lithium-ion secondary battery includes an electrode body and a surface pressure control unit. The electrode body includes a positive electrode and a negative electrode containing a Si-containing negative electrode active material, and the surface pressure control unit controls the surface pressure applied to the electrode body in a specified direction (for example, refer to Patent Document 1). The surface pressure control unit of the lithium-ion secondary battery controls the amplitude of the surface pressure that varies with charge and discharge to 3.8 MPa or less. Specifically, this amplitude refers to the difference between the maximum value and the minimum value of the surface pressure observed during charge and discharge from a state of 0% SOC to 100% SOC (for example, refer to Patent Document 1 (paragraph

[0014] )).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-61749 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, in the prior art, no consideration has been given to the pressure control of the secondary battery during the balancing of the secondary battery. In addition, balancing is performed, for example, when starting the vehicle control system after stopping the vehicle control system, and the vehicle control system stops, for example, when the vehicle is parked.

[0008] Even when the control system stops, the secondary battery undergoes self-discharge, and thus the secondary battery contracts due to this self-discharge. There are cases where it is impossible to apply an appropriate pressure to the secondary battery due to this contraction, resulting in the resistance of the secondary battery deviating from the range suitable for charge and discharge. In this case, there is a problem of a decrease in the accuracy of the balancing of the secondary battery.

[0009] The problem to be solved by the present invention is to provide a battery control system and a battery control method capable of improving the accuracy of balancing of battery cells.

[0010] Solutions to the Problems

[0011] The present invention solves the above problems by discharging the battery cells to balance the remaining discharge capacities between the battery cells, and before starting the balancing, pressing the battery module in the stacking direction of the battery cells to increase the pressure applied to the battery module to a value above a specified pressure.

[0012] Effects of the Invention

[0013] According to the present invention, the accuracy of balancing battery cells can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a block diagram showing a battery control system according to an embodiment of the present invention.

[0015] Figure 2 is a flowchart showing the process of a battery control method according to an embodiment of the present invention.

[0016] Figure 3 is a graph showing the relationship between the pressure applied to a battery cell and the resistance value of the battery cell.

[0017] Figure 4 is a graph showing the change over time of the pressure in the battery control method according to an embodiment of the present invention.

[0018] Figure 5 is a graph showing the change over time of the pressure in the battery control method according to a modified example of the present invention. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing the battery control system 1 of the present embodiment.

[0020] As Figure 1 shown, the battery control system 1 includes a controller 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, a DCDC converter 14, a discharge unit 15, a pressure application mechanism 16, and a pressure sensor 17. In addition, the controller 10 in the present embodiment corresponds to an example of the "control unit", "remaining discharge capacity estimation unit", and "determination unit" in the present invention. Further, the pressure sensor 17 in the present embodiment corresponds to an example of the "pressure acquisition unit" in the present invention.

[0021] The controller 10 is a battery control unit (BCU). The controller 10 is composed of a memory such as a ROM or a RAM, and a processor such as a CPU. The controller 10 manages the state of the battery module 2 based on the detected voltage detected by the voltage sensor 11, the detected current detected by the current sensor 12, the detected temperature detected by the temperature sensor 13, etc., and determines the SOC usage range of the battery module 2 according to the state of the battery module 2.

[0022] In addition, as described later, the controller 10 controls the discharge unit 15 and the pressure application mechanism 16.

[0023] The voltage sensor 11 is a sensor for detecting the voltage between the terminals of the battery module 2. The voltage sensor 11 is connected between the wirings connected to the positive and negative electrodes of the battery module 2. The current sensor 12 is a sensor for detecting the input / output current of the battery module 2. The current sensor 12 is connected to the wiring connected to the positive or negative electrode of the battery module 2. The temperature sensor 13 is provided in the battery module 2. The temperature sensor 13 is a sensor for detecting the temperature of the battery module 2.

[0024] The DCDC converter 14 is a power conversion device that converts the voltage input from the battery module 2 into a specified voltage and outputs power to a load such as a motor. In addition, the DCDC converter 14 is also a power conversion device that converts the voltage input from a load such as a motor or a charging device into a specified voltage and outputs power to the battery module 2. The DCDC converter 14 is controlled by the controller 10. The battery module 2 is connected to the input side of the DCDC converter 14, and a load is connected to the output side of the DCDC converter 14. The load is a power grid including a motor inverter or the like. That is, the battery module 2 is connected to the load via the DCDC converter 14.

[0025] The discharge unit 15 is a circuit for individually discharging the plurality of battery cells 21 included in the battery module 2. The discharge unit 15 is electrically connected to the positive and negative electrodes of the battery cell 21, and one discharge unit 15 is electrically connected to one battery cell 21. The discharge unit 15 may be a general discharge unit for balancing the discharge of the battery cell 21 having a remaining discharge capacity larger than that of the other battery cells 21. In the present embodiment, as this balance, passive balancing is performed in such a manner that the remaining discharge capacity of the other battery cells 21 is made to coincide with the remaining discharge capacity of the battery cell 21 having the smallest remaining discharge capacity. However, as the balance, active balancing may also be performed.

[0026] There is no particular limitation on the discharge unit 15 in the present embodiment. For example, it has at least a resistor body and a switch electrically connected in series with the resistor body. The switch is controlled to be turned on and off by the controller 10, and the battery cell 21 is discharged by turning on the switch by the controller 10.

[0027] The pressure applying mechanism 16 applies pressure to the battery module 2 by pressing the battery module 2 along the stacking direction of the battery cells 21 in the battery module 2. The pressure applying mechanism 16 in the present embodiment includes a motor drive circuit 161, a motor 162, a gearbox 163, a pressure transmission body 164, a fixed end plate 165, a movable end plate 166, and a plurality of shafts 167. The movable end plate 166 in the present embodiment corresponds to an example of the "pressure applying unit" in the present invention.

[0028] The motor drive circuit 161 operates the motor 162. The motor drive circuit 161 controls the drive for operating the motor 162 based on a control signal from the controller 10.

[0029] The motor 162 has a first drive shaft 162a. The motor 162 rotationally drives the first drive shaft 162a according to the output from the motor drive circuit 161.

[0030] The gearbox 163 is connected to the first drive shaft 162a and converts the rotational drive of the first drive shaft 162a into a drive of the pressure transmission body 164 in the stacking direction described above.

[0031] The pressure transmission body 164 moves up and down by the driving force transmitted via the gearbox 163. The pressure transmission body 164 includes a second drive shaft 164a and a pressure transmission plate 164b. The second drive shaft 164a is connected to the gearbox 163, and the rotational drive of the first drive shaft 162a of the motor 162 is transmitted through the gearbox 163. The pressure transmission plate 164b is a plate that moves along the stacking direction as the second drive shaft 164a rotates. In the present embodiment, by moving the pressure transmission plate 164b downward in the figure, the pressure applied to the battery module 2 can be controlled in the increasing direction, and by moving the pressure transmission plate 164b upward in the figure, the pressure applied to the battery module 2 can be controlled in the decreasing direction.

[0032] The fixed end plate 165 and the movable end plate 166 are a pair of plate-like members and are connected to each other by a plurality of shafts 167. The fixed end plate 165 is fixed to the shaft 167 and supports the battery module 2. On the other hand, the movable end plate 166 is not fixed to the shaft 167 and is movable along the extending direction of the shaft 167. The movable end plate 166 presses the battery module 2 from above according to the force transmitted from the pressure transmission body 164. In addition, the movable end plate 166 can move along the stacking direction according to the expansion and contraction of the battery module 2 caused by charging and discharging and the expansion and contraction of the battery module 2 caused by the change in the pressure applied to the battery module 2 by the movable end plate 166.

[0033] The pressure sensor 17 is a sensor that can measure the pressure applied to the battery module 2. The pressure sensor 17 can output the detected pressure to the controller 10.

[0034] The battery module 2 is electrically connected to the charging device. The charging device connected to the battery cell 21 is, for example, a device for charging the battery module 2 mounted on an electric vehicle or a hybrid vehicle. Charging of the in-vehicle battery module 2 is performed by operating the charging start switch after removing the charging cable of the charging device and attaching the charging gun at the front end of the charging cable to the connector of the vehicle's charging port. The controller 10 controls the DCDC converter 14 and the charging device respectively to manage the charging state (SOC) of the battery cell 21 included in the battery module 2, and to make the charging state of the battery module 2 the target charging state.

[0035] As described above, the battery module 2 is electrically connected to loads such as a motor. The load is a device that operates using the power of the battery module 2, and is a motor, an air conditioner, a lamp, or other auxiliary devices that are the driving sources of the vehicle. Discharge of the battery module 2 is performed under the control of the controller 10 according to a system request or an external power request. The system request corresponds to an instruction from an in-vehicle computer such as an ECU during vehicle travel. Regarding the external power request, for example, when the air conditioner is set to operate before vehicle travel by a timer instruction from an external device such as a portable terminal so that the interior of the vehicle becomes a suitable temperature when the vehicle starts to travel, the instruction from the external device corresponds to the external power request.

[0036] In addition, the battery module 2 mounted on an electric vehicle or a hybrid vehicle can also be used for Vehicle Grid Integration (VGI). VGI is a technology for system-connecting an electric vehicle or a hybrid vehicle equipped with the battery module 2 and supplying the power stored in the battery module 2 to the system (load) via the power grid.

[0037] The battery cell 21 included in the battery module 2 has at least a positive electrode, a solid electrolyte, and a negative electrode. The positive electrode contains at least a positive electrode active material capable of releasing and absorbing alkali metals such as lithium (Li), sodium (Na), or potassium (K), and although not particularly limited, it is preferably a positive electrode active material containing sulfur. As the solid electrolyte, for example, a sulfide solid electrolyte or an oxide solid electrolyte can be used, but a sulfide solid electrolyte is preferably used. The negative electrode only needs to contain lithium, and preferably contains lithium metal, for example.

[0038] Next, a battery control method for the battery module 2 using such a battery control system 1 will be described. Figure 2 It is a flowchart showing the process of the battery control method of the present embodiment. Regarding the battery control method of the present embodiment, it is repeatedly executed at regular intervals, especially when the vehicle starts and the balance of the battery cell 21 needs to be performed.

[0039] First, in step S1, the controller 10 estimates the SOC of each battery cell 21 based on the open-circuit voltage of each battery cell 21. The SOC can be estimated by a general method using the open-circuit voltage of each battery cell 21 and the cumulative value of the charge and discharge charge.

[0040] In step S2, the controller 10 calculates the difference between the maximum value (highest SOC) and the minimum value (lowest SOC) among the SOCs of each battery cell 21. Then, the calculated difference is compared with a specified difference threshold.

[0041] When the difference calculated in step S2 is equal to or greater than the difference threshold, balancing (capacity adjustment) needs to be performed. Therefore, in step S3, based on the difference between the SOC of each battery cell 21 and the lowest SOC, the discharge amount at balance in each battery cell 21 is calculated so that the remaining discharge capacity of each battery cell 21 is approximately equal. For example, in a battery with a capacity of Q max [Ah] at an SOC of 100%, if the remaining discharge capacity of the battery cell 21 with the lowest SOC is Q min [Ah], and if the remaining capacity of a specific battery cell 21 included in the battery module 2 is Q 1 [Ah], then the discharge amount at balance of this battery cell 21 is Q 1 -Q min [Ah].

[0042] In step S4, the discharge time T of each battery cell is calculated based on the calculated discharge amount dis，x (x = 1, 2,..., n) (n is the number of battery cells 21). The discharge time T can be calculated for each battery cell 21 dis，x , for example, when the discharge amount of a specific battery cell 21 is Q 1 -Q min [Ah], using the resistance value R [Ω] of the resistor of the discharge unit 15 connected to each battery cell 21 and the current battery voltage V [V], the discharge time becomes (Q 1 -Q min ) × R ÷ V [h].

[0043] In step S5, the controller 10 turns on the power supply of the pressure application mechanism 16. That is, in the present embodiment, the controller 10 outputs an on signal to the motor drive circuit 161. The pressure application control of the battery module by the pressure application mechanism 16 performed during the period from step S5 to step S13 corresponds to an example of the "first pressure application control" in the present invention.

[0044] In step S6, the controller 10 increases the pressure applied to the battery module 2 to a specified pressure. That is, the controller 10 moves the movable end plate 166 in the downward direction (the contraction direction of the battery module 2) before starting the balancing to increase the pressure applied to the battery module 2. As a result, the resistance of the battery cell 21 decreases.

[0045] In step S7, the controller 10 determines whether the pressure applied to the battery module 2 has reached the specified pressure based on the detection value of the pressure sensor 17. The specified pressure in this embodiment is the performance requirement pressure P 1 . In addition, the pressure applied to the battery cell 21 is a value substantially equal to the pressure applied to the battery module 2.

[0046] Figure 3 is a graph showing the relationship between the pressure applied to the battery cell 21 and the resistance value of the battery cell 21. As Figure 3 shown, the greater the pressure applied to the battery module 2, the smaller the resistance value of the battery cell 21. Here, the performance requirement pressure P 1 is the pressure that makes the resistance of the battery cell 21 equal to a specified threshold value, and this threshold value is the maximum value of the resistance within the range of the resistance at which the battery cell 21 can input and output the charge and discharge power required for the vehicle's control system to operate.

[0047] The performance requirement pressure P can be obtained through experiments as follows 1 . The greater the resistance of the battery cell, the smaller the charge and discharge power of the battery cell. Therefore, pressure is applied to the battery cell to reduce the resistance of the battery cell to at least the level where it can output the power required for the vehicle's control system (including the system for balancing) to operate. Based on the relationship between pressure and power, the minimum value of the pressure at which the power required for the control system to operate can be output in this case is obtained through experiments, and thus the performance requirement pressure P 1 can be obtained.

[0048] In addition, this performance requirement pressure P 1 is greater than the earthquake resistance requirement pressure P 0 . The earthquake resistance requirement pressure P 0 refers to the minimum value of the pressure at which the battery module 2 will not fall off between the fixed end plate 165 and the movable end plate 166 even when an external force due to impact, vibration, etc. is applied to the battery module 2.

[0049] In addition, the specified pressure can be a pressure greater than the performance requirement pressure P 1 , or when the specified pressure is small enough not to cause problems due to adverse effects on the balance accuracy, it can also be a pressure slightly smaller than the performance requirement pressure P 1 .

[0050] Further, in the present embodiment, the pressure applied to the battery module 2 (the pressure applied to the battery cell 21) is detected by the pressure sensor 17, but it is not limited thereto. The pressure may be estimated without using the pressure sensor 17.

[0051] Specifically, for example, when the negative electrode is a Li metal negative electrode, the thickness of the battery cell changes in a manner substantially proportional to the SOC. Therefore, the thickness of the battery module changes in a manner substantially proportional to the charge / discharge amount of the battery module. In addition, the amount of change in the thickness of the battery module caused by operating the motor is determined by the gear ratio, pitch, etc. within the pressure applying mechanism and the operation amount of the motor. Therefore, as long as the relationship between the difference between the amount of change in the thickness of the battery module caused by the charge / discharge amount and the amount of change in the thickness of the battery module caused by the motor operation and the pressure is obtained through experiments, the pressure can be estimated based on this relationship according to the time series changes of the motor command value and the SOC.

[0052] Return Figure 2 , when it is determined that the pressure applied to the battery module 2 has reached the specified pressure, in step S8, the controller 10 allows the charge / discharge based on balancing of each battery cell 21 of the battery module 2. That is, the controller 10 uses the discharge unit 15 to discharge each battery cell 21 through the discharge unit 15 to achieve balance. At this time, the first pressure application control has not been completed, and the pressure application operation for the battery module 2 is still continuing. That is, in the present embodiment, the discharge unit 15 starts balancing before the completion of the first pressure application control based on an instruction from the controller 10. The discharge of the battery cell 21 performed by the discharge unit 15 during the period from step S8 to step S13 in the present embodiment corresponds to an example of "balancing" in the present invention.

[0053] Figure 4 is a graph showing the change over time of the pressure in the battery control method of the present embodiment. In addition, the solid line in the graph shows the change over time of the pressure. As Figure 4 shown, after starting the first pressure application control, the pressure applied to the battery module 2 is gradually increased, and then, balancing starts at the time point when the pressure reaches the performance requirement pressure P 1 . In addition, in Figure 4 , after starting balancing, the pressure becomes fixed, which is due to the shrinkage of the battery module 2 caused by balancing. As will be described below, in fact, the pressure application based on the first pressure application control continues even after starting balancing.

[0054] In addition, when it is determined in step S7 that the pressure applied to the battery module 2 has not reached the specified pressure, the present battery control is ended, and the battery control is restarted from step S1 after a specified period.

[0055] Return Figure 2 , in step S9, if the cumulative discharge time based on the balance of each battery cell 21 has not reached T dis，x , the controller 10 continues to discharge until the cumulative discharge time based on the balance of each battery cell 21 reaches T dis，x .

[0056] In step S10, the controller 10 calculates the shrinkage amount (thickness reduction amount) of the battery module 2 per unit time based on the total value of the discharge currents of each battery cell 21 calculated in step S3. The shrinkage amount of the battery module 2 per unit time can be obtained through experiments. For example, the amount of discharge current of a single battery cell 21 and the thickness reduction amount per unit time of a single battery cell 21 corresponding to the amount of discharge current are measured in advance to obtain the relationship between the amount of discharge current and the thickness reduction amount per unit time of a single battery cell 21. Moreover, the controller 10 calculates the thickness reduction amount per unit time of each battery cell 21 based on the amount of discharge current of each battery cell 21 included in the battery module 2, and calculates the total of the thickness reduction amounts per unit time of each battery cell 21. This total value is the shrinkage amount of the battery module 2 per unit time.

[0057] In step S11, the controller 10 moves the movable end plate 166 of the pressure applying mechanism 16 in the shrinking direction of the battery module 2 ( Figure 1 the downward direction in Figure 4 ) at the same speed as the thickness reduction amount of the battery per unit time. Thus, as 1 shown, the pressure applied to the battery module 2 from the movable end plate 166 during the balancing period is maintained substantially constant and does not drop significantly below the performance requirement P 1 . In addition, the moving amount of the movable end plate 166 can also be larger than the shrinkage amount of the battery module 2. In this case, the pressure applied to the battery module 2 is larger than the performance requirement pressure P

[0058] In step S12, the controller 10 determines whether the cumulative discharge time based on the balance of all battery cells 21 has reached T dis，x so that the SOC of all battery cells 21 has become a value equivalent to the above-mentioned minimum SOC.

[0059] In the case where the controller 10 determines in step S12 that the SOC of all battery cells 21 has become a value equivalent to the above-mentioned minimum SOC, in step S13, the controller 10 determines that the balancing of all battery cells 21 is completed.

[0060] In addition, when it is determined in step S12 that the balancing of all the battery cells 21 is not completed, the current battery control is ended, and after a prescribed period, the battery control is restarted from step S1.

[0061] When the controller 10 determines in step S2 that the calculated difference is lower than the difference threshold, in step S14, the pressure of the battery cell 21 is increased to a prescribed pressure (performance requirement pressure P 1 ). The pressurization control executed in this step S14 corresponds to an example of the "second pressurization control" in the present invention.

[0062] In step S15, the controller 10 determines whether the pressure applied to the battery module 2 has reached the prescribed pressure based on the detection value of the pressure sensor 17.

[0063] When the controller 10 determines in step S15 that the pressure applied to the battery module 2 has reached the prescribed pressure, the controller 10 permits the charge and discharge of the battery cell 21. In this case, since the balancing of the battery cell 21 is not required, the charge and discharge of the battery cell 21 refers to the charge and discharge for loads such as the drive motor of the vehicle.

[0064] When the controller 10 determines in step S15 that the pressure applied to the battery module 2 has not reached the prescribed pressure, the current battery control is ended, and after a prescribed period, the battery control is restarted from step S1.

[0065] In the past, due to the pressure applying mechanism, control method, and self-discharge during long-term storage, it was sometimes impossible to apply a pressure suitable for charge and discharge to the battery module at the start of the vehicle control system. In addition, in the conventional control system, in order to make the battery cell capable of charge and discharge as early as possible, the capacity adjustment of the battery cell was immediately performed after the BMS was started. Therefore, there was a situation where charge and discharge were performed outside the appropriate pressure range, and even if discharge was performed for a prescribed time, the discharge amount deviated due to resistance loss and did not become the desired discharge amount, resulting in a decrease in the accuracy of balancing.

[0066] In contrast, according to the battery control system and battery control method of the present embodiment, before starting the balancing, the first pressurization control for increasing the pressure applied to the battery module 2 to a value higher than the prescribed pressure by the movable end plate 166 to reduce the resistance of the battery cell 21 is started. Therefore, charge and discharge can be performed within an appropriate pressure range. Therefore, the accuracy of balancing can be improved.

[0067] In addition, in the present embodiment, by setting the prescribed pressure to the performance requirement pressure P 1 , the resistance of the battery cell 21 can be set to a resistance more suitable for balancing, and thus the accuracy of balancing can be improved.

[0068] In addition, in the present embodiment, the discharge unit 15 starts balancing before the first pressure control is completed, so that the time required for the vehicle start-up process can be shortened.

[0069] In addition, in the present embodiment, when balancing starts before the first pressure control is completed, the moving amount of the movable end plate 166 in the first pressure control is set to be the same as the shrinkage amount of the battery module 2 due to balancing. Therefore, an increase in the resistance of the battery cell 21 can be suppressed, and an increase in the resistance loss during balancing can be suppressed. Thus, not only can the start-up time be shortened, but also the accuracy of balancing can be improved.

[0070] In addition, in the present embodiment, even when it is determined that balancing is not required, a second pressure control for increasing the pressure applied to the battery module 2 to a pressure higher than a specified pressure is performed (refer to Figure 2 step S14), so that the vehicle control system can be operated after the resistance value of the battery module 2 becomes an appropriate value.

[0071] In addition, in the above embodiment, balancing starts before the first pressure control is completed, but it is not limited thereto, and balancing may also start after the first pressure control is completed.

[0072] Figure 5 is a graph showing the change over time of the pressure in the battery control method according to a modified example of the present embodiment. As Figure 5 shown, in this modified example, in Figure 2 steps S6 to S7 of the flowchart, the pressure applied to the battery module 2 is increased to a first pressure P 1 greater than the performance requirement pressure P 2 .

[0073] The first pressure P 2 is a pressure considering the shrinkage amount of the battery module 2 caused by the discharge of the battery cell 21 during balancing. Specifically, the larger the total remaining discharge capacity of each battery cell 21, the larger the first pressure P 2 is set. In other words, the larger the reduction amount of the thickness of the battery module 2 due to balancing, the larger the first pressure P 2 is set.

[0074] The first pressure P 2 and the difference P 1 between the first pressure P 2 -P 1 corresponding to the further applied pressure according to the shrinkage amount of the battery module 2. Regarding this difference P 2 -P 1, the shrinkage amount (thickness reduction amount) of the battery module 2 caused by balancing is calculated based on the total value of the discharge currents of the respective battery cells 21 calculated in step S3. The relationship between this shrinkage amount and the reduction amount of the pressure applied to the battery module 2 can be calculated in advance through experiments, and the calculated reduction amount of the pressure is set as the difference P 2 -P 1 .

[0075] If balancing starts after the pressure reaches the first pressure P set in this way 2 , then it is possible to Figure 5 suppress the pressure from falling below the performance requirement pressure P during balancing as shown 1 . Therefore, according to the battery control system and the battery control method in this modification example, even if the discharge amount based on balancing changes, it is possible to suppress the pressure drop so that the resistance of the battery increases. In addition, even if the pressure drops during balancing, it is possible to prevent the pressure from dropping to an unacceptable level of resistance loss.

[0076] Description of Reference Numerals

[0077] 1: Battery control system; 10: Controller; 11: Voltage sensor; 12: Current sensor; 13: Temperature sensor; 14: DCDC converter; 15: Discharge unit; 16: Pressure application mechanism; 161: Motor drive circuit; 162: Motor; 162a: First drive shaft; 163: Gearbox; 164: Pressure transmission body; 164a: Second drive shaft; 164b: Pressure transmission plate; 165: Fixed end plate; 166: Movable end plate; 167: Shaft; 17: Pressure sensor; 2: Battery module.

Claims

1. A battery control system controls a battery module formed by stacking a plurality of battery cells. Each battery cell has a solid electrolyte and a negative electrode containing lithium. The battery control system includes: A pressure application unit that applies pressure to the battery module by pressing the battery module along the stacking direction of the battery cells; A control unit that adjusts the value of the pressure by controlling the pressure application unit; A remaining discharge capacity calculation unit that calculates the remaining discharge capacity of each battery cell; and A discharge unit that balances the remaining discharge capacities between the battery cells by discharging the battery cells, wherein, Before starting the balance, the control unit starts a first pressurization control that increases the pressure to a pressure higher than a specified pressure by the pressure application unit.

2. The battery control system according to claim 1, wherein, The specified pressure is a performance requirement pressure, The performance requirement pressure is a pressure that makes the resistance of the battery cell become the same value as a threshold value, The threshold value is the maximum value of the resistance within the range of the resistance of the battery cell that can input and output the charge and discharge power required for the control system of the vehicle to operate.

3. The battery control system according to claim 2, wherein, The control unit increases the pressure to a first pressure greater than the performance requirement pressure in the first pressurization control, The greater the total value of the remaining discharge capacities, the greater the first pressure is set.

4. The battery control system according to claim 3, wherein, The greater the reduction amount of the thickness of the battery module caused by the balance, the greater the first pressure is set by the control unit.

5. The battery control system according to claim 2, wherein, The discharge unit starts the balance before the first pressurization control is completed.

6. The battery control system according to claim 5, wherein, Due to the balance, the battery module shrinks in the contraction direction along the stacking direction as the battery cells discharge, The pressure application unit moves along the contraction direction in the first pressurization control, The moving amount of the pressure application unit in the first pressurization control is greater than or equal to the contraction amount of the battery module caused by the balance.

7. The battery control system according to claim 1, wherein, The battery control system further includes a determination unit that determines whether the balance is required. In the case where it is determined that the balance is not required, the control unit completes a second pressurization control that increases the pressure to a pressure higher than the specified pressure to reduce the resistance of the battery cells before the battery module starts the charge and discharge for the control system of the vehicle to operate.

8. A battery control method controls a battery module formed by stacking a plurality of battery cells. Each battery cell has a solid electrolyte and a negative electrode containing lithium. In the battery control method, Calculate the remaining discharge capacity of each battery cell, Balance the remaining discharge capacities between the battery cells by discharging the battery cells, Before starting the above-described balancing, the battery module is pressed along the stacking direction of the battery cells by a pressure applying unit, whereby the pressure applied to the battery module is increased to a value higher than a specified pressure.

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