Battery control system and battery control method

Abstract

A battery control system (1) comprises: a pressure application means (16) that applies pressure to a battery module (2) by pressing the battery module (2) along the lamination direction of battery cells (21) each having a negative electrode including lithium and a solid electrolyte; a controller (10) that adjusts the value of pressure by controlling the pressure application means (16); and a discharging means (15) that performs balancing of remaining discharge capacities among the battery cells (21) in the battery module (2). The controller (10) starts a first pressure application control in which pressure is increased to a prescribed pressure or higher, by the pressure application means (16), before the balancing is started.

Description

Battery control system and battery control method

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

[0002] A lithium-ion secondary battery is known that includes an electrode assembly including a positive electrode and a negative electrode containing a Si-containing negative electrode active material, and a surface pressure control unit that controls the surface pressure applied to the electrode assembly in a predetermined direction (see, for example, Patent Document 1). The surface pressure control unit of this lithium-ion secondary battery controls the fluctuation of the surface pressure that varies with charge and discharge to 3.8 MPa or less. Specifically, this fluctuation is the difference between the maximum and minimum surface pressure values ​​observed when charging and discharging from 0% to 100% SOC (see, for example, Patent Document 1, paragraph

[0014] ).

[0003] JP 2019-61749 A

[0004] However, in the prior art, no consideration is given to pressure control of the secondary battery when balancing the secondary battery. Note that balancing is performed, for example, when the vehicle control system is stopped and then started up, and the vehicle control system is stopped, for example, when the vehicle is parked.

[0005] Even when the control system is stopped, the secondary battery self-discharges, causing it to shrink. This shrinkage can prevent the application of appropriate pressure to the secondary battery, causing the secondary battery's electrical resistance to fall outside the range suitable for charging and discharging. This can lead to a problem of reduced accuracy in balancing the secondary battery.

[0006] An object of the present invention is to provide a battery control system and a battery control method that can improve the accuracy of balancing of battery cells.

[0007] The present invention solves the above problem by discharging the battery cells to balance the remaining discharge capacity between the battery cells, and by increasing the pressure applied to the battery module to a predetermined pressure or higher by pressing the battery module along the stacking direction of the battery cells before balancing begins.

[0008] According to the present invention, the accuracy of balancing of battery cells can be improved.

[0009] Fig. 1 is a block diagram showing a battery control system according to an embodiment of the present invention. Fig. 2 is a flowchart showing the steps of a battery control method according to an embodiment of the present invention. Fig. 3 is a graph showing the relationship between the pressure applied to a battery cell and the resistance value of the battery cell. Fig. 4 is a graph showing changes in pressure over time in the battery control method according to an embodiment of the present invention. Fig. 5 is a graph showing changes in pressure over time in a battery control method according to a modified example of the present invention.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram showing a battery control system 1 according to the present embodiment.

[0011] 1, the battery control system 1 includes a controller 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, a DC-DC converter 14, a discharge means 15, a pressure application mechanism 16, and a pressure sensor 17. The controller 10 in this embodiment corresponds to an example of the "control means," the "remaining discharge capacity estimation means," and the "determination means" in the present invention. The pressure sensor 17 in this embodiment corresponds to an example of the "pressure acquisition means" in the present invention.

[0012] The controller 10 is a battery control unit (BCU) that includes 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 a voltage sensor 11, the detected current detected by a current sensor 12, the detected temperature detected by a temperature sensor 13, and the like, and determines the SOC usage range of the battery module 2 according to the state of the battery module 2.

[0013] The controller 10 also controls the discharge means 15 and the pressure application mechanism 16, as will be described later.

[0014] 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 wiring 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.

[0015] The DC-DC converter 14 is a power conversion device that converts the voltage input from the battery module 2 to a predetermined voltage and outputs power to a load such as a motor. The DC-DC converter 14 is also a power conversion device that converts the voltage input from a load such as a motor or a charging device to a predetermined voltage and outputs power to the battery module 2. The DC-DC converter 14 is controlled by the controller 10. The battery module 2 is connected to the input side of the DC-DC converter 14, and a load is connected to the output side of the DC-DC converter 14. The load is a power grid or the like that includes a motor inverter or the like. In other words, the battery module 2 is connected to the load via the DC-DC converter 14.

[0016] The discharge means 15 is a circuit for individually discharging the multiple battery cells 21 included in the battery module 2. The discharge means 15 is electrically connected to the positive and negative electrodes of the battery cells 21, and one discharge means 15 is electrically connected to one battery cell 21. This discharge means 15 may be a general discharge means used for balancing, which discharges a battery cell 21 having a larger remaining discharge capacity than the remaining discharge capacity of the other battery cells 21. In this embodiment, this balancing is performed as passive balancing, in which the remaining discharge capacity of the other battery cells 21 is matched to the remaining discharge capacity of the battery cell 21 with the smallest remaining discharge capacity. However, active balancing may also be performed as balancing.

[0017] The discharge means 15 in this embodiment is not particularly limited, but may include, for example, at least a resistor and a switch electrically connected in series to the resistor. The switch is on / off controlled by the controller 10, and when the controller 10 turns on the switch, the battery cell 21 is discharged.

[0018] The pressure application 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 application mechanism 16 in this embodiment has a motor driver circuit 161, a motor 162, a gear box 163, a pressure transmitter 164, a fixed end plate 165, a movable end plate 166, and multiple shafts 167. The movable end plate 166 in this embodiment corresponds to an example of the "pressure application means" in the present invention.

[0019] The motor driver circuit 161 operates the motor 162. The motor driver circuit 161 controls the driving of the motor 162 based on a control signal from the controller 10.

[0020] The motor 162 has a first drive shaft 162 a. The motor 162 drives and rotates the first drive shaft 162 a in response to an output from the motor driver circuit 161 .

[0021] The gear box 163 is connected to the first drive shaft 162a and converts the rotational drive of the first drive shaft 162a into drive of the pressure transmission body 164 in the stacking direction.

[0022] The pressure transmission body 164 moves up and down by the driving force transmitted via the gear box 163. This 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 gear box 163, and the gear box 163 transmits the rotational drive of the first drive shaft 162a of the motor 162 to the pressure transmission body 164a. The pressure transmission plate 164b is a plate that moves in the stacking direction as the second drive shaft 164a rotates. In this embodiment, the pressure applied to the battery modules 2 can be controlled to increase by moving the pressure transmission plate 164b downward in the figure, and the pressure applied to the battery modules 2 can be controlled to decrease by moving the pressure transmission plate 164b upward in the figure.

[0023] The fixed end plate 165 and the movable end plate 166 are a pair of plate-like members 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 modules 2. On the other hand, the movable end plate 166 is not fixed to the shaft 167 and is movable along the extension direction of the shaft 167, applying pressure to the battery modules 2 from above in response to the force transmitted from the pressure transmitter 164. Furthermore, the movable end plate 166 can move along the stacking direction in response to the expansion and contraction of the battery modules 2 due to charging and discharging, and the expansion and contraction of the battery modules 2 in response to changes in the pressure applied to the battery modules 2 by the movable end plate 166.

[0024] 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.

[0025] The battery module 2 is electrically connected to a charging device. The charging device connected to the battery cells 21 is, for example, a device for charging the battery module 2 mounted on an electric vehicle or a hybrid vehicle. Charging the mounted battery module 2 is performed by removing the charging cable from the charging device, attaching the charging gun at the end of the charging cable to the connector of the vehicle's charging port, and then operating the charging start switch. The controller 10 manages the state of charge (SOC) of the battery cells 21 included in the battery module 2, and controls the DCDC converter 14 and the charging device so that the state of charge of the battery module 2 reaches a target state of charge.

[0026] As described above, the battery module 2 is electrically connected to a load such as a motor. The load is a device that operates using the power of the battery module 2, such as a motor that serves as a drive source for the vehicle, or auxiliary devices such as an air conditioner or lights. Discharge of the battery module 2 is executed under the control of the controller 10 in response to a system request or an external power request. The system request corresponds to a command from an on-board computer such as an ECU while the vehicle is running. With regard to an external power request, for example, when an external device such as a mobile terminal is used to operate an air conditioner by timer setting before the vehicle starts running so that the interior temperature of the vehicle is appropriate when the vehicle starts running, the command from the external device corresponds to an external power request.

[0027] The battery module 2 mounted on an electric vehicle or a hybrid vehicle may also be used for vehicle grid integration (VGI), which is a technology for connecting an electric vehicle or a hybrid vehicle equipped with a battery module 2 to a power grid and supplying power stored in the battery module 2 to a power grid (load) via the power grid.

[0028] The battery cells 21 included in the battery module 2 have 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 absorbing and releasing an alkali metal such as lithium (Li), sodium (Na), or potassium (K), and preferably contains a positive electrode active material containing sulfur, although this is not particularly limited. As the solid electrolyte, for example, a sulfide solid electrolyte or an oxide solid electrolyte can be used, but it is preferable to use a sulfide solid electrolyte. The negative electrode may contain lithium, and preferably contains, for example, lithium metal.

[0029] The following describes a battery control method for the battery module 2 using the battery control system 1. Fig. 2 is a flowchart showing the steps of the battery control method of this embodiment. The battery control method of this embodiment is repeatedly executed at predetermined intervals, particularly when the vehicle is started and balancing of the battery cells 21 is performed.

[0030] 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 that uses the open circuit voltage of each battery cell 21 or an integrated value of the charge and discharge charge.

[0031] In step S2, the controller 10 calculates the difference between the maximum value (highest SOC) and the minimum value (lowest SOC) of the SOC of each battery cell 21. Then, the controller 10 compares the calculated difference with a predetermined difference threshold value.

[0032] If 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, the discharge amount at the time of balancing for each battery cell 21 is calculated from the difference between the SOC of each battery cell 21 and the minimum SOC, so that the remaining discharge capacity of each battery cell 21 can be made approximately equal. For example, if the capacity at 100% SOC is Q ｍａｘ [Ah], the remaining discharge capacity of the battery cell 21 with the lowest SOC is Q ｍｉｎ [Ah], the remaining capacity of a specific battery cell 21 included in the battery module 2 is Q １[Ah], the discharge amount of the battery cell 21 during balancing is Q １ -Q ｍｉｎ [Ah].

[0033] In step S4, the discharge time T of each battery cell is calculated from the calculated discharge amount. ｄｉｓ，ｘ (x=1, 2, ..., n) (n is the number of battery cells 21). Discharge time T ｄｉｓ，ｘ can be calculated for each battery cell 21. For example, the discharge amount of a specific battery cell 21 is Q １ -Q ｍｉｎ [Ah], the discharge time is calculated by using the resistance value R [Ω] of the resistor of the discharge means 15 connected to each battery cell 21 and the current battery voltage V [V]. １ -Q ｍｉｎ ) × R ÷ V [h].

[0034] In step S5, the controller 10 turns on the power supply of the pressure application mechanism 16. That is, in this embodiment, the controller 10 outputs an ON signal to the motor driver circuit 161. The pressure application control of the battery module by the pressure application mechanism 16 executed in steps S5 to S13 corresponds to an example of the "first pressure application control" in the present invention.

[0035] In step S6, the controller 10 increases the pressure applied to the battery module 2 to a predetermined pressure. That is, before balancing starts, the controller 10 moves the movable end plate 166 downward (in the direction in which the battery module 2 contracts) to increase the pressure applied to the battery module 2. This reduces the electrical resistance of the battery cells 21.

[0036] In step S7, the controller 10 determines whether the pressure applied to the battery module 2 has reached a predetermined pressure based on the detected value of the pressure sensor 17. The predetermined pressure in this embodiment is the performance required pressure P １ The pressure applied to the battery cells 21 is approximately equal to the pressure applied to the battery module 2.

[0037] 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 shown in FIG. 3, the resistance value of the battery cell 21 decreases as the pressure applied to the battery module 2 increases. Here, the performance required pressure P １ is the pressure at which the electrical resistance of the battery cell 21 becomes equal to a predetermined threshold value, and this threshold value is the maximum value of the electrical resistance within the range of electrical resistance at which the battery cell 21 can input and output the charging and discharging power required to operate the vehicle's control system.

[0038] Performance required pressure P １ can be experimentally determined as follows: The higher the resistance of the battery cell, the less power the battery cell can charge and discharge. Therefore, pressure is applied to the battery cell to reduce its resistance until it can output at least the power required to operate the vehicle's control system (including the balancing system). In this case, the minimum pressure at which the power required to operate the control system can be output can be experimentally determined from the relationship between pressure and power to determine the performance required pressure P １ can be obtained.

[0039] In addition, this performance required pressure P １ is the earthquake resistance required pressure P ０ The earthquake resistance required pressure P ０ This is the minimum pressure at which the battery module 2 will not fall out from between the fixed end plate 165 and the movable end plate 166 even if an external force such as an impact or vibration is applied to the battery module 2 .

[0040] The predetermined pressure is the performance required pressure P １ The pressure may be larger, or may be small enough so that the adverse effect on the balancing accuracy does not cause any problems. １ A slightly lower pressure may also be used.

[0041] In addition, in this embodiment, the pressure applied to the battery module 2 (the pressure applied to the battery cells 21) is detected by the pressure sensor 17, but this is not limiting. The pressure may be estimated without using the pressure sensor 17.

[0042] Specifically, for example, when the negative electrode is a Li metal negative electrode, the thickness of the battery cell changes approximately in proportion to the SOC. Therefore, the thickness of the battery module changes approximately in proportion to the charge / discharge amount of the battery module. Furthermore, the amount of change in the thickness of the battery module due to motor operation is determined by the gear ratio, screw pitch, etc., within the pressure application mechanism and the amount of motor operation. Therefore, if the relationship between the difference between the amount of change in the thickness of the battery module due to the charge / discharge amount and the amount of change in the thickness of the battery module due to motor operation and the pressure is experimentally obtained, the pressure can be estimated from the time-series changes in the motor command value and the SOC based on this relationship.

[0043] Returning to FIG. 2 , if it is determined that the pressure applied to the battery module 2 has reached the predetermined pressure, in step S8, the controller 10 permits charging and discharging of each battery cell 21 of the battery module 2 through balancing. That is, the controller 10 uses the discharging means 15 to discharge each battery cell 21 for balancing. At this time, the first pressurization control has not yet been completed, and the pressurization operation on the battery module 2 is continuing. That is, in this embodiment, the discharging means 15 starts balancing based on an instruction from the controller 10 before the first pressurization control is completed. The discharge of the battery cells 21 by the discharging means 15, which is executed in steps S8 to S13 in this embodiment, corresponds to an example of "balancing" in the present invention.

[0044] 4 is a graph showing the change in pressure over time in the battery control method of this embodiment. The solid line in the graph shows the change in pressure over time. As shown in FIG. 4, after the first pressurization control is started, the pressure applied to the battery module 2 is gradually increased until the pressure reaches the performance required pressure P １ In Fig. 4, the pressure remains constant after the start of balancing, but this is due to contraction of the battery module 2 caused by balancing. As will be explained below, pressurization by the first pressurization control actually continues even after the start of balancing.

[0045] If it is determined in step S7 that the pressure applied to the battery module 2 has not reached the predetermined pressure, the current battery control is terminated, and after a predetermined period, the battery control is restarted from step S1.

[0046] Returning to FIG. 2, in step S9, the controller 10 determines whether the cumulative discharge time due to balancing of each battery cell 21 is T ｄｉｓ，ｘ If the cumulative discharge time due to balancing of each battery cell 21 has not reached T ｄｉｓ，ｘ Discharge is continued until it reaches

[0047] In step S10, the controller 10 calculates the amount of shrinkage (thickness reduction) of the battery module 2 per unit time based on the total value of the discharge current of each battery cell 21 calculated in step S3. The amount of shrinkage of the battery module 2 per unit time can be determined experimentally. For example, the amount of discharge current of each battery cell 21 and the amount of thickness reduction of the battery cell 21 per unit time relative to the amount of discharge current are measured in advance, and the relationship between the amount of discharge current and the amount of thickness reduction of the battery cell 21 per unit time is determined. Then, the controller 10 calculates the amount of thickness reduction of each battery cell 21 per unit time based on the amount of discharge current of each battery cell 21 included in the battery module 2, and calculates the sum of the amounts of thickness reduction of the battery cells 21 per unit time. This sum is the amount of shrinkage of the battery module 2 per unit time.

[0048] In step S11, the controller 10 moves the movable end plate 166 of the pressure application mechanism 16 in the contraction direction of the battery module 2 (downward in FIG. 1) at a speed equal to the amount of reduction in battery thickness per unit time. As a result, as shown in FIG. 4, the pressure applied from the movable end plate 166 to the battery module 2 during balancing is kept almost constant and the performance requirement P １ The amount of movement of the movable end plate 166 may be larger than the amount of contraction of the battery module 2. In this case, the pressure applied to the battery module 2 is not greater than the performance required pressure P １ becomes larger than

[0049] In step S12, the controller 10 determines whether the cumulative discharge time due to balancing of all the battery cells 21 is T ｄｉｓ，ｘ , and it is determined whether the SOC of all the battery cells 21 has reached a value equivalent to the minimum SOC.

[0050] If the controller 10 determines in step S12 that the SOC of all the battery cells 21 has reached a value equivalent to the above-mentioned minimum SOC, then in step S13, the controller 10 determines that balancing of all the battery cells 21 has been completed.

[0051] If it is determined in step S12 that balancing of all battery cells 21 has not been completed, the current battery control is ended, and after a predetermined period, the battery control is restarted from step S1.

[0052] If the controller 10 determines in step S2 that the calculated difference is less than the difference threshold, the controller 10 sets the pressure of the battery cell 21 to a predetermined pressure (performance required pressure P １ The pressurization control executed in step S14 corresponds to an example of the "second pressurization control" of the present invention.

[0053] In step S15, the controller 10 determines from the detection value of the pressure sensor 17 whether the pressure applied to the battery module 2 has reached a predetermined pressure.

[0054] In step S15, if the controller 10 determines that the pressure applied to the battery module 2 has reached the predetermined pressure, the controller 10 permits charging and discharging of the battery cells 21. In this case, balancing of the battery cells 21 is not required, and therefore charging and discharging of the battery cells 21 refers to charging and discharging of a load such as a vehicle drive motor.

[0055] If the controller 10 determines in step S15 that the pressure applied to the battery module 2 has not reached the predetermined pressure, the current battery control is terminated, and after a predetermined period, the battery control is restarted from step S1.

[0056] In the past, due to the pressure application mechanism, control method, and self-discharge during long-term stoppage, there were cases where the appropriate pressure for charging and discharging could not be applied to the battery module when the vehicle's control system started up. Also, in the conventional control system, the BMS adjusted the capacity of the battery cells immediately after startup to make the battery cells ready for charging and discharging as quickly as possible. However, charging and discharging occurred outside the appropriate pressure range, and even if discharging was performed within the specified time, the amount of discharge deviated due to resistance loss, and the desired amount was not achieved, which reduced the accuracy of balancing.

[0057] In contrast, with the battery control system and battery control method of this embodiment, the first pressure control is initiated before balancing begins, which increases the pressure applied to the battery module 2 by the movable end plate 166 to a predetermined pressure or higher to reduce the electrical resistance of the battery cells 21, allowing charging and discharging to occur within an appropriate pressure range, thereby improving balancing accuracy.

[0058] In this embodiment, the predetermined pressure is the performance required pressure P １ By setting the resistance of the battery cell 21 at this value, the electrical resistance of the battery cell 21 can be made more suitable for balancing, thereby improving the accuracy of balancing.

[0059] Furthermore, in this embodiment, the discharge means 15 starts balancing before the first pressurization control is completed, so that the time required for the start-up process of the vehicle can be shortened.

[0060] Furthermore, in this embodiment, if balancing is started before the first pressurization control is completed, the amount of movement of the movable end plate 166 during the first pressurization control is set to the same amount of contraction of the battery module 2 due to balancing, thereby suppressing an increase in the electrical resistance of the battery cells 21 and suppressing an increase in resistance loss during balancing. This not only shortens the startup time, but also improves the accuracy of balancing.

[0061] Furthermore, in this embodiment, even if it is determined that balancing is not necessary, the second pressure control (see step S14 in Figure 2) is executed to increase the pressure applied to the battery module 2 to a predetermined pressure or higher, so that the resistance value of the battery module 2 can be set to an appropriate value before the vehicle control system is operated.

[0062] In the above embodiment, balancing is started before the first pressurization control is completed, but this is not limiting, and balancing may be started after the first pressurization control is completed.

[0063] 5 is a graph showing the change in pressure over time in a battery control method according to a modification of the present embodiment. As shown in FIG. 5, in this modification, the pressure applied to the battery module 2 is set to the performance required pressure P １ A first pressure P ２ Increase to.

[0064] First pressure P ２ is a pressure that takes into account the amount of contraction of the battery module 2 that accompanies the discharge of the battery cells 21 during balancing. Specifically, the first pressure P ２ is set to a larger value as the total remaining discharge capacity of each battery cell 21 increases. ２ is set to a larger value as the reduction in thickness of the battery module 2 due to balancing increases.

[0065] First pressure P ２ and performance required pressure P １ Difference P ２ -P １ corresponds to the pressure further applied in accordance with the amount of contraction of the battery module 2. ２ -P １ calculates the amount of shrinkage (amount of thickness reduction) of the battery module 2 due to balancing based on the total value of the discharge current of each battery cell 21 calculated in step S3. The relationship between this amount of shrinkage and the amount of reduction in pressure applied to the battery module 2 can be calculated experimentally in advance, and the calculated amount of reduction in pressure is calculated as the difference P ２ -P １ Let's say.

[0066] The first pressure P ２ If balancing is started after the pressure reaches the performance required pressure P １ Therefore, with the battery control system and battery control method of this modification, even if the discharge amount fluctuates due to balancing, it is possible to prevent the pressure from decreasing and the resistance of the battery from increasing. Furthermore, even if the pressure decreases due to balancing, it is possible to prevent the pressure from decreasing to an extent that the resistance loss cannot be tolerated.

[0067] DESCRIPTION OF SYMBOLS 1...Battery control system 10...Controller 11...Voltage sensor 12...Current sensor 13...Temperature sensor 14...DC-DC converter 15...Discharge means 16...Pressure application mechanism 161...Motor driver circuit 162...Motor 162a...First drive shaft 163...Gear box 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

A battery control system for controlling a battery module in which a plurality of battery cells each having a solid electrolyte and a negative electrode containing lithium are stacked, a pressure applying means for applying pressure to the battery module by pressing the battery module along the stacking direction of the battery cells; a control means for controlling the pressure applying means to adjust the value of the pressure; a remaining discharge capacity calculation means for calculating the remaining discharge capacity of each of the battery cells; a discharging means for discharging the battery cells to balance the remaining discharge capacities of the battery cells; The control means starts a first pressurization control to increase the pressure to a predetermined pressure or higher by the pressure application means before the balancing is started.

2. The battery control system according to claim 1, the predetermined pressure is a performance requirement pressure, the performance requirement pressure is a pressure at which the electrical resistance of the battery cell becomes equal to a threshold value, A battery control system in which the threshold value is the maximum value of the electrical resistance within the range of electrical resistance of the battery cell that allows the battery cell to input and output the charging and discharging power necessary to operate a vehicle control system.

3. The battery control system according to claim 2, the control means increases the pressure to a first pressure that is greater than the performance required pressure in the first pressurization control, The battery control system sets the first pressure to a larger value as the total value of the remaining discharge capacities increases.

4. The battery control system according to claim 3, The control means sets the first pressure to a larger value as the amount of reduction in thickness of the battery module due to the balancing increases.

3. The battery control system according to claim 2, The discharging means starts the balancing before the first pressurization control is completed.

6. The battery control system according to claim 5, the battery module contracts in a contraction direction along the stacking direction as the battery cells discharge due to the balancing; the pressure applying means moves along the contraction direction in the first pressure control, A battery control system in which the movement amount of the pressure application means in the first pressurization control is equal to or greater than the contraction amount of the battery module due to the balancing.

2. The battery control system according to claim 1, The battery control system further includes a determination unit for determining whether the balancing is necessary, When it is determined that the balancing is not necessary, the control means completes a second pressurization control that increases the pressure to a predetermined pressure or higher to reduce the electrical resistance of the battery cells before the battery module starts charging or discharging to operate a vehicle control system. 　 A battery control method for controlling a battery module in which a plurality of battery cells each having a solid electrolyte and a negative electrode containing lithium are stacked, comprising: Calculating the remaining discharge capacity of each of the battery cells; By discharging the battery cells, the remaining discharge capacities of the battery cells are balanced; a pressure application means for applying pressure to the battery module in a stacking direction of the battery cells, before the balancing is started, thereby increasing the pressure applied to the battery module to a predetermined pressure or higher.