Battery system

Abstract

The present invention provides a battery system capable of quickly reducing polarization even if polarization occurs in a battery. This battery system is mounted on an electric vehicle and supplies power for traveling. The battery system comprises: a battery including a plurality of battery cells; a pressurization element capable of pressurizing the plurality of battery cells; and a controller for performing first drive control of the pressurization element. The first drive control is control for performing driving to increase the amount of pressurization by the pressurization element and driving to reduce the amount of pressurization, such driving performed in one set or in a plurality of sets and in the given order or in the reverse order.

Description

Battery System

[0001] The present invention relates to a battery system that is mounted on an electric vehicle to supply electric power for running the vehicle.

[0002] Patent Document 1 describes a battery assembly having a drive unit that applies pressure to a plurality of pouch-type battery cells. The pouch-type battery cells are filled with electrolyte and are held in a pressurized state. The battery assembly of Patent Document 1 allows the pouch-type battery cells to be pressurized even while the battery cells are in operation.

[0003] Special Publication No. 2021-516429

[0004] Polarization may occur in a battery, which may cause various problems, such as a decrease in the accuracy of estimating the state of charge (SOC).

[0005] An object of the present invention is to provide a battery system that can quickly reduce polarization even if polarization occurs in the battery.

[0006] The battery system of the present invention is a battery system that is mounted on an electric vehicle to supply power for driving, and comprises: a battery including a plurality of battery cells; a pressure applying element capable of applying pressure to the plurality of battery cells; and a controller that performs first drive control of the pressure applying element, wherein the first drive control is a control that performs one or more sets of drive to increase and drive to decrease the amount of pressure applied by the pressure applying element in that order or in the reverse order.

[0007] According to the present invention, when polarization occurs in the battery, the polarization can be quickly reduced by the first drive control of the pressure element.

[0008] 5B is a flowchart showing the details of the polarization reduction process of step S3 of FIG. 5A and step S13 of FIG. 5B. FIG. 6 is a diagram showing an example of a pressure reduction pattern by a first drive control of a pressure element.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0010] Fig. 1 is a block diagram showing an electric vehicle equipped with a battery system according to this embodiment. Fig. 2A is a perspective view showing the internal structure of the battery. Fig. 2B is a perspective view showing a part of the internal structure of the battery in an exploded state.

[0011] The electric vehicle 1 includes drive wheels 2, a traction motor 3 that drives the drive wheels 2, a battery system 40 according to this embodiment, an inverter 5 that converts power between a battery 41 of the battery system 40 and the traction motor 3, a drive operation unit 6 that can perform drive operations, a vehicle controller 9 that controls drive, and a relay 11 that opens and closes a power line L1 between the battery 41 and an electrical device (such as the inverter 5). The drive operation unit 6 includes a steering operation unit 6a such as a steering wheel, an accelerator operation unit 6b such as an accelerator pedal, and a brake operation unit 6c such as a brake pedal. The traction motor 3 is an electric motor. The relay 11 is, for example, a contactor and may be referred to as a system main relay.

[0012] The vehicle controller 9 is an ECU (Electronic Control Unit) and operates according to a control program stored in a memory unit 9a. The vehicle controller 9 receives an operation signal from the driving operation unit 6 and controls the inverter 5 in accordance with the operation signal to drive the driving motor 3. The vehicle controller 9 also controls the opening and closing of a relay 11. Specifically, the vehicle controller 9 switches the relay 11 to a closed state when starting up the system of the electric vehicle 1, and switches the relay 11 to an open state when shutting down the system of the electric vehicle 1.

[0013] The battery system 40 includes a battery 41 that supplies power for driving, and a controller 42 that manages the state of the battery 41 .

[0014] The battery 41 is configured by housing a plurality of battery modules 411. As shown in Figures 2A and 2B, each battery module 411 is configured by modularizing a plurality of battery cells 412. Each battery cell 412 of the battery 41 is, for example, a lithium-ion secondary battery cell and contains an electrolyte. The battery cells 412 are not limited to lithium-ion secondary battery cells, and various battery cells may be used as long as they contain an electrolyte.

[0015] In the battery module 411, multiple battery cells 412 are arranged in parallel in the thickness direction. The thickness direction is the direction in which the dimension of the battery cell 412 is smallest among the three directions of the height, width, and depth directions. The battery cell 412 includes a strip-shaped separator A1 and strip-shaped internal electrodes A2 and A3 (see FIG. 5 ), and the separator A1 and the internal electrodes A2 and A3 extend in two directions intersecting the thickness direction (e.g., two perpendicular directions). The battery cell 412 may also be called a laminated battery cell.

[0016] In the battery module 411, the multiple battery cells 412 are restrained with pressure being applied in the thickness direction by a restraining body 414. The restraining body 414 may have any structure, but may, for example, have two restraining plates 414a, 414b and a connecting member 414c, and the connecting member 414c connects the two restraining plates 414a, 414b with a predetermined gap between them.

[0017] A plurality of electrodes are provided on the top of the plurality of battery cells 412, and the plurality of electrodes are electrically connected by a predetermined wiring pattern. The wiring 413 connecting the plurality of electrodes may be a bus bar or a flexible conductor. The spacing between the electrodes does not change significantly even if the pressure applied to the plurality of battery cells 412 changes. The plurality of battery cells 412 constrained as described above may be housed in a housing to form a single battery module 411.

[0018] The battery module 411 further includes a pressure element 415 that applies pressure to the multiple battery cells 412. The pressure element 415 may have any configuration as long as it can apply pressure to the multiple battery cells 412 and increase or decrease the pressure. As an example, FIGS. 2A and 2B show an example in which a plate-shaped piezoelectric element is used as the pressure element 415. The thickness of the pressure element 415 changes when a voltage is applied. The pressure element 415 is located between a pair of adjacent first and second battery cells 412a and 412b among the multiple battery cells 412 restrained by the restraining body 414. Therefore, when the pressure element 415 is activated to increase its thickness, the pressure in the thickness direction of the multiple battery cells 412 increases. When the pressure element 415 is activated to decrease its thickness, the pressure in the thickness direction of the multiple battery cells 412 decreases.

[0019] In the example shown in FIGS. 2A and 2B , the pressure element 415 has dimensions in the height and width directions that are approximately the same as those of one battery cell 412 (within a ±10% range), allowing it to apply uniform pressure to the battery cell 412 in the height and width directions. This configuration reduces unevenness in the pressure applied to the battery cell 412 by the pressure element 415. The pressure element 415 may also be configured to apply pressure to a partial range in the height direction or a partial range in the width direction of the battery cell 412. Applying pressure to a partial range causes the electrolyte to move from that range to another range within the battery cell 412, thereby enhancing the stirring effect of the electrolyte. The number of pressure elements 415 is not limited to one per battery module 411; multiple pressure elements 415 may be arranged between multiple battery cells 412 included in one battery module 411.

[0020] The battery module 411 is further provided with a pressure sensor 416 that detects the pressure applied to the multiple battery cells 412. As an example, the pressure sensor 416 is a piezoelectric element, and is disposed between the pressure element 415 and the second battery cell 412b, or between a pair of adjacent battery cells 412. The pressure sensor 416 detects the pressure of the battery cells 412, which is increased or decreased by the pressure element 415.

[0021] The battery module 411 is further provided with a temperature sensor 417. The temperature sensor 417 is disposed in the battery module 411 and detects the temperature of the battery cells 412. The temperature sensor 417 may detect the temperature of any one of the battery cells 412 in the battery module 411 as a representative temperature.

[0022] The controller 42 is an ECU and operates according to a control program in a storage unit 42a. The controller 42 performs a first drive control of the pressure element 415. The first drive control is a control that performs one or more sets of increasing and decreasing the amount of pressure applied by the pressure element 415 in that order or in the reverse order. The outputs of the pressure sensor 416 and the temperature sensor 417 are sent to the controller 42. In Fig. 2A, a wire d415 that outputs a voltage to drive the pressure element 415 and wires d416 and d417 that send sensor signals from the pressure sensor 416 and the temperature sensor 417 are omitted.

[0023] The controller 42 may be configured to perform the function of a BCU (Battery Control Unit) that manages the state of the battery 41. The controller 42 as a BCU receives measured values ​​of the current, voltage, and temperature of the battery 41 and manages the SOC (State Of Charge), dischargeable power Wout, chargeable power Win, and the like of the battery 41. The battery 41 is provided with a sensor 418 that measures the current, voltage, and temperature, and the output of the sensor 418 is sent to the controller 42. The controller 42 manages the SOC of the battery 41 by integrating the current of the battery 41. The controller 42 also has a data table or a formula that represents the relationship between the voltage (e.g., OCV: Open Circuit Voltage) and the SOC, and estimates the SOC from the data table or formula and the voltage.

[0024] Note that the controller 42 that performs the first drive control of the pressure element 415 may not have the function of the BCU, and the controller 42 and the BCU may be provided as separate ECUs. In this case, the controller 42 and the BCU may communicate with each other and cooperate with each other. Also, the controller 42 that performs the first drive control of the pressure element 415 may be integrated into the vehicle controller 9, and the vehicle controller 9 may perform the function of the controller 42. Below, a configuration in which the controller 42 also performs the function of the BCU will be described.

[0025] <Battery Properties> Fig. 3 is a graph illustrating the influence of battery polarization, and Fig. 4 is a diagram illustrating the effect of increasing or decreasing the amount of pressure on the battery cell.

[0026] The degree of polarization of the battery 41 may increase with current flow. Polarization corresponds to a phenomenon in which the actual voltage of the battery 41 deviates from the voltage at equilibrium of the battery 41. The voltage V0 in FIG. 3 represents the voltage at equilibrium of the battery 41. The relationship curve f in FIG. 3 represents the relationship between the voltage at equilibrium and the SOC of the battery 41. If the voltage V0 at equilibrium is known, the actual SOC_U0 can be estimated with high accuracy by using a data table or a calculation formula that represents the relationship between the voltage and the SOC of the battery 41. However, if polarization ΔV occurs, the voltage V1 obtained from the output of the sensor 418 deviates from the voltage V0 at equilibrium. Therefore, when the SOC is calculated using a data table or a calculation formula, the calculated SOC_U1 includes an error ΔU corresponding to the polarization ΔV from the accurate SOC_U0.

[0027] One of the causes of polarization is the occurrence of a bias in the concentration of ions contained in the electrolyte near the internal electrodes A2 and A3 of the battery cell 412. As shown in Figure 4, the internal electrodes A2 and A3 included in the battery cell 412 are provided with a large number of pores b, and the internal electrodes A2 and A3 are impregnated with the electrolyte. This bias in the ion concentration of the electrolyte in the pores b can increase the degree of polarization.

[0028] When the degree of polarization increases as described above, the volume of the pores b in the internal electrodes A2 and A3 can be decreased and then increased by applying pressure to the battery cell 412 in the thickness direction and increasing or decreasing the pressure. This action generates an agitation effect on the electrolyte, reduces the imbalance in the ion concentration of the electrolyte near the internal electrodes A2 and A3, and quickly alleviates polarization.

[0029] <Start-up process and shutdown process of battery system> Fig. 5A is a flowchart showing the startup process of the battery system executed by the controller. Fig. 5B is a flowchart showing the shutdown process of the battery system executed by the controller. Fig. 6 is a flowchart showing details of the polarization reduction process of step S3 in Fig. 5A and step S13 in Fig. 5B.

[0030] When the system of the electric vehicle 1 enters a hibernation state, the controller 42 starts the start-up process of Fig. 5A. In the start-up process, the controller 42 first repeats a process (step S1) of determining whether a system start-up request has been made for the electric vehicle 1 until a YES result is obtained. The system start-up request is generated when the user turns on the power button of the electric vehicle 1, for example.

[0031] If a YES result is obtained in step S1, the controller 42 first communicates with the vehicle controller 9 to confirm that the relay 11 is in the open state (step S2). When a system startup request for the electric vehicle 1 is made, the relay 11 is normally in the open state, and it is confirmed in step S2 that the relay 11 is in the open state. Note that if the controller 42 cannot confirm that the relay 11 is in the open state in step S2 due to a special situation, the controller 42 may send an open request for the relay 11 to the vehicle controller 9 and temporarily control the relay 11 to be in the open state. Alternatively, if the controller 42 cannot confirm that the relay 11 is in the open state in step S2, the controller 42 may skip step S3 and proceed to step S4, or may skip steps S3 and S4 and end the start processing.

[0032] If the open state is confirmed in step S2, the controller 42 executes a polarization reduction process (step S3). In the polarization reduction process, as shown in Fig. 6, the controller 42 first measures the current value of the battery 41 (step S21). Even when the relay 11 is in the open state, the current of the battery 41 may not become completely zero, and so in step S21, the controller 42 measures this current value. Note that the current value measured in step S21 may not be the current value between the two terminals of the battery 41, but may be the value of an internal current flowing between the multiple battery modules 411 or the multiple battery cells 412.

[0033] Next, the controller 42 determines whether the current value measured in step S21 is smaller than a threshold value (step S22). The threshold value is preferably set to a value that ensures that the performance degradation of the battery cell 412 is within an acceptable range even if the amount of pressure applied to the battery cell 412 changes.

[0034] If the result of step S22 is NO, the controller 42 performs a timing process (step S23) and determines whether the total time measured in step S23 has exceeded a threshold time (step S24). If the total time has not exceeded a threshold time, the controller 42 returns the process to step S21. On the other hand, if the threshold time has passed, the polarization reduction drive is omitted, so the controller 42 ends the polarization reduction process and proceeds to the next step S4 in FIG. 5.

[0035] On the other hand, if the result of the determination in step S22 is YES, the controller 42 acquires the temperature of the battery cell 412 (hereinafter referred to as "cell temperature"), the voltage and SOC of the battery 41 (step S25). The SOC acquired here does not have to be a value that represents the current SOC with high accuracy, such as an SOC converted from the voltage of the battery 41 or a current SOC calculated based on the SOC previously acquired in the battery system 40.

[0036] Next, the controller 42 determines a pressure application pattern for the first drive control of the pressure element 415 based on the cell temperature, voltage, and SOC acquired in step S25 (step S26).

[0037] 7 is a diagram showing an example of a pressure pattern according to the first drive control of the pressure element. As described above, the first drive control is a control that performs one or more sets of increasing and decreasing the amount of pressure applied by the pressure element 415, in that order or in the reverse order. Even when performing the first drive control, the controller 42 can employ multiple pressure patterns. For example, as shown in the multiple pressure patterns P1 to P3 in FIG. 7, the controller 42 can create multiple pressure patterns by varying the absolute value of the pressure amount (such as the maximum and minimum values), the number of times the pressure amount is increased or decreased, the rate of change of the pressure amount, or several of these.

[0038] In the battery 41, when the cell temperature is high, the degree of polarization of the battery cells 412 tends to be small, and when the cell temperature is low, the degree of polarization of the battery cells 412 tends to be large. Therefore, if there are no differences in other parameters, it is advisable to select a pressurization pattern in which the maximum amount of pressurization is lower the higher the cell temperature is, and the maximum amount of pressurization is higher the lower the cell temperature is.

[0039] Furthermore, when the SOC is high, the amount of expansion of the battery cell 412 tends to be large, and when the SOC is low, the amount of expansion of the battery cell 412 tends to be small. Furthermore, when the SOC is within a specific range, there may be a characteristic in which the slope of the relationship curve between the SOC and the amount of expansion of the battery cell 412 is reversed. Therefore, if there is no difference in other parameters, it is advisable to select a pressurization pattern in which the maximum amount of pressurization is relatively low for an SOC with a large amount of expansion, and the maximum amount of pressurization is relatively high for an SOC with a small amount of expansion.

[0040] Furthermore, a high voltage tends to increase the amount of expansion of the battery cell 412, while a low voltage tends to decrease the amount of expansion of the battery cell 412. Therefore, if there are no differences in other parameters, it is advisable to select a pressure pattern that lowers the maximum amount of pressure the higher the voltage and increases the maximum amount of pressure the lower the voltage.

[0041] In addition, when the degree of polarization is large due to a low cell temperature, but the maximum amount of applied pressure cannot be increased based on the voltage or SOC, a pressurization pattern may be selected in which the maximum amount of applied pressure is reduced while the number of increases and decreases is increased. Alternatively, a pressurization pattern may be selected in which the maximum amount of applied pressure is increased to a medium level while the rate of change of the amount of applied pressure is slowed.

[0042] By selecting the above-described pressurization pattern, it is possible to suppress deterioration of the battery cells 412, while stirring the electrolyte and reducing polarization of the battery 41. The memory unit 42a of the controller 42 is provided with a data table that allows the above-described selection of the pressurization pattern.

[0043] In step S26, the controller 42 determines a pressure application pattern of the pressure element 415 according to the state information of the battery 41 by referring to the data table for the state information of the battery 41, such as the cell temperature, SOC, and voltage.

[0044] After the pressure pattern is determined in step S26, the controller 42 executes a first drive control to drive the pressure element 415 so as to generate a pressure force according to the pressure pattern (step S27).

[0045] 4, the first drive control in step S27 applies pressure to the battery cell 412 in the thickness direction, and the applied pressure increases and decreases. The applied pressure causes the volume of the pores b in the internal electrodes A2 and A3 to decrease and then increase, or vice versa, stirring the electrolyte. This stirring of the electrolyte reduces the bias in the ion concentration of the electrolyte near the internal electrodes A2 and A3, quickly reducing polarization in the battery cell 412.

[0046] The pressure application patterns in steps S26 and S27 are not limited to the above examples, and various pressure application patterns may be adopted as long as the pressure application patterns increase and decrease over time.

[0047] When the first drive control in step S27 is completed, the controller 42 ends the polarization reduction process and proceeds to the next step in Fig. 5. Then, the controller 42 performs an SOC estimation process (step S4). In step S4, the controller 42 measures the OCV of the battery 41 using the sensor 418 and obtains an estimated SOC value by applying the OCV to a data table or a calculation formula.

[0048] Then, the controller 42 ends the start-up process of the battery system 40. After that, when the system of the electric vehicle 1 starts up, the controller 42 shifts the process to the battery management process. In the battery management process, the highly accurate SOC acquired by the controller 42 in the start-up process is added to the amount of change in SOC based on the subsequent current integrated value, thereby managing the SOC while the electric vehicle 1 is running. Therefore, highly accurate SOC management can be achieved even in the battery management process.

[0049] When the system of the electric vehicle 1 is started and the start processing of the battery system 40 is completed, the controller 42 starts the shutdown processing of the battery system 40 shown in Fig. 5B. Then, in parallel with the battery management processing, the controller 42 repeats the processing of determining the timing for the system of the electric vehicle 1 to transition to a hibernation state (step S11) until a YES result is obtained. The timing for the system of the electric vehicle 1 to transition to a hibernation state comes based on, for example, a system shutdown operation of the electric vehicle 1 by the user.

[0050] As a result, when it is time for the system to transition to the hibernation state and a YES result is obtained in the determination process of step S11, the controller 42 first communicates with the vehicle controller 9 to confirm that the relay 11 is in the open state (step S12). Normally, the relay 11 is set to the open state when the system of the electric vehicle 1 transitions to the hibernation state, so the controller 42 confirms that the relay 11 is in the open state in step S12. If the controller 42 cannot confirm that the relay 11 is in the open state in step S12, the controller 42 may wait for a predetermined time and then perform a process to confirm again whether the relay 11 has been set to the open state. Alternatively, if the controller 42 cannot confirm that the relay 11 is in the open state in step S12, the controller 42 may skip step S13 and proceed to step S14, or may skip steps S13 and S14 and proceed to step S15.

[0051] If the open state is confirmed in step S12, the controller 42 executes a polarization reduction process (step S13). The polarization reduction process in step S13 is the same as the polarization reduction process in step S3 in FIG. 5A.

[0052] Next, the controller 42 performs an SOC estimation process (step S14). In step S14, the controller 42 measures the OCV of the battery 41 using the sensor 418 and calculates an estimated SOC value by applying the OCV to a data table or a calculation formula. Then, the controller 42 performs its own shutdown process (step S15) and ends the shutdown process of the battery system 40. This shutdown process allows the controller 42 to obtain the SOC of the battery 41 with high accuracy even when the traveling of the electric vehicle 1 ends.

[0053] The programs for the start-up process and shutdown process of the battery system 40 described above are stored in a non-transitory computer readable medium, such as the storage unit 42a of the controller 42. The controller 42 may be configured to read and execute the programs stored in a portable non-transitory recording medium. The portable non-transitory recording medium may store the programs for the start-up process and shutdown process of the battery system 40 described above.

[0054] As described above, the battery system 40 of this embodiment includes a battery 41 including a plurality of battery cells 412, a pressure element 415 capable of applying pressure to the plurality of battery cells 412, and a controller 42 that performs a first drive control of the pressure element 415. The first drive control is a control that performs one or more sets of increasing and decreasing the amount of pressure applied by the pressure element 415, in that order or in the reverse order. With this configuration, if polarization occurs in the battery 41 due to an imbalance in the ion concentration of the electrolyte, the first drive control agitates the electrolyte, thereby quickly reducing the polarization. Therefore, various issues caused by polarization, such as a deterioration in the accuracy of SOC estimation due to polarization, can be quickly resolved.

[0055] Furthermore, according to the battery system 40 of this embodiment, the electric vehicle 1 is provided with a relay 11 that opens and closes the power line L1 between the battery 41 and the electric device, and the controller 42 executes a first drive control of the pressure element 415 when the relay 11 is in an open state. When the pressure on the battery cell 412 is increased or decreased by the first drive control, if a current flows through the battery cell 412, this may accelerate deterioration of the battery cell 412. Therefore, such deterioration can be suppressed.

[0056] Furthermore, according to the battery system 40 of this embodiment, the controller 42 has a current sensor (sensor 418, or a sensor that measures the current between the battery cells 412 or the current between the battery modules 411). When the current value measured by the current sensor is equal to or less than a threshold, the controller 42 executes the first drive control of the pressure element 415. Even when the relay 11 is in the open state, current may flow to the battery 41. Therefore, if the first drive control of the pressure element 415 is executed while this current is flowing, the deterioration of the battery cells 412 may progress. Therefore, such deterioration can be suppressed.

[0057] Furthermore, in the battery system 40 of this embodiment, the multiple battery cells 412 are arranged in a row, and the pressure element 415 is arranged between the adjacent first battery cell 412a and second battery cell 412b. This configuration allows the single pressure element 415 to apply pressure evenly to the multiple battery cells 412. Therefore, it is possible to relatively suppress an increase in the volume of the battery 41 due to the addition of a pressure applying configuration.

[0058] Furthermore, according to the battery system 40 of this embodiment, the controller 42 varies the pressure application pattern of the first drive control of the pressure application element 415 in accordance with the status information (temperature, voltage, SOC, etc.) of the battery 41. With this configuration, a pressure application pattern according to the status of the battery 41 can be applied to the battery cell 412 to reduce polarization. Therefore, it is possible to achieve a process for reducing polarization while suppressing the progression of deterioration of the battery cell 412.

[0059] The above describes an embodiment of the present invention. However, the present invention is not limited to the above embodiment. For example, in the above embodiment, the timing of executing the first drive control of the pressure element 415 is the timing before the SOC estimation process. However, the first drive control of the pressure element 415 may be executed before charging starts, after charging ends, while driving is suspended, or at a timing unrelated to the SOC estimation process. By reducing polarization of the battery cell 412, the efficiency of charging and discharging the battery 41 can be improved. Furthermore, in the above embodiment, the first drive control of the pressure element 415 is executed when the system of the electric vehicle 1 is started and when driving ends. However, the SOC estimation process executed after the first drive control may be omitted. By reducing polarization of the battery cell 412, the efficiency of charging and discharging the battery 41 can be improved and the deterioration of the battery 41 during its storage period can be slowed.

[0060] Furthermore, in the above embodiment, the multiple battery cells 412 are constrained by the constraining body 414, and the pressure element 415 expands inside the constraining body 414 to apply pressure to the multiple battery cells 412. However, various forms of the configuration for applying pressure to the multiple battery cells 412 may be adopted, such as a configuration in which the multiple battery cells 412 are sandwiched and the clamping force is changeable. Other details shown in the embodiment may be modified as appropriate without departing from the spirit of the invention.

[0061] The present invention can be used for a battery system that is mounted on an electric vehicle and supplies electric power for running the vehicle.

[0062] REFERENCE SIGNS LIST 1 Electric vehicle 2 Drive wheel 3 Traction motor 5 Inverter 6 Traction operation unit 9 Vehicle controller 9a Memory unit 11 Relay 40 Battery system 41 Battery 411 Battery module 412 Battery cell 412a First battery cell 412b Second battery cell A1 Separator A2, A3 Internal electrode b Pore 413 Wiring 414 Restraint body 414a, 414b Restraint plate 414c Connector 415 Pressurizing element 416 Pressure sensor 417 Temperature sensor 418 Sensor 42 Controller 42a Memory unit L1 Power line

Claims

1. A battery system that is mounted on an electric vehicle to supply power for driving the vehicle, comprising: a battery including a plurality of battery cells; a pressure applying element capable of applying pressure to the plurality of battery cells; and a controller that performs a first drive control of the pressure applying element, wherein the first drive control is a control that performs one or more sets of drives to increase and decrease the amount of pressure applied by the pressure applying element, either in that order or in the reverse order of the aforementioned order.

2. The battery system described in claim 1, characterized in that the electric vehicle is provided with a relay that opens and closes a power line between the battery and an electric device, information indicating an open or closed state of the relay is input to the controller, and the controller performs the first drive control when the relay is in an open state.

3. The battery system according to claim 2, further comprising a current sensor for measuring the current of the battery, wherein the controller performs the first drive control when the relay is open and the current value measured by the current sensor is equal to or lower than a threshold value.

4. The battery system according to claim 1, wherein the plurality of battery cells are arranged in sequence, and the pressure element is arranged between adjacent first and second battery cells among the plurality of battery cells.

5. The battery system according to claim 1, wherein the controller varies a pressurization pattern by the first drive control in accordance with state information of the battery.

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