Battery system

Abstract

Provided is a battery system capable of quickly reducing polarization even when polarization occurs in a battery. This battery system is mounted on an electric vehicle and supplies power for travel, and is provided with: a battery including a plurality of battery cells; a pressurizing element capable of pressurizing the plurality of battery cells; and a controller that performs first drive control of the pressurizing element. In the first drive control, one or more sets of drive for increasing the amount of pressure applied by the pressure applying element and drive for decreasing the amount of pressure applied by the pressure applying element are controlled in this order or in the reverse order.

Description

Technical Field

[0001] The present invention relates to a battery system mounted on an electric vehicle and supplying driving power. Background Art

[0002] In Patent Document 1, a battery assembly having a driving unit that pressurizes a plurality of pouch-type battery cells is described. The pouch-type battery cells filled with electrolytic solution are held in a pressurized state. The battery assembly of Patent Document 1 can pressurize the pouch-type battery cells even while the battery cells are operating.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-516429 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] Polarization may occur in a battery. When polarization occurs, various problems may arise, such as a decrease in the estimation accuracy of the SOC (state of charge).

[0008] An object of the present invention is to provide a battery system that can rapidly reduce polarization even when polarization occurs in the battery.

[0009] Technical Solution for Solving the Technical Problem

[0010] The battery system of the present invention is a battery system mounted on an electric vehicle and supplying driving power, and the battery system includes:

[0011] a battery including a plurality of battery cells;

[0012] a pressurizing element capable of pressurizing the plurality of battery cells; and

[0013] a controller that performs first drive control on the pressurizing element,

[0014] wherein the first drive control is control in which a drive for increasing the pressurizing amount of the pressurizing element and a drive for decreasing the pressurizing amount of the pressurizing element are performed in one or more sets in this order or in the reverse order of this order.

[0015] Advantages of the Invention

[0016] According to the present invention, when polarization occurs in the battery, polarization can be rapidly reduced by the first drive control of the pressurizing element. Brief Description of the Drawings

[0017] Figure 1 is a block diagram showing an electric vehicle equipped with the battery system of the present embodiment.

[0018] Figure 2A is a perspective view showing the internal structure of the battery.

[0019] Figure 2B is a perspective view showing a part of the internal structure of the battery in an exploded manner.

[0020] Figure 3 is a chart explaining the influence on battery polarization.

[0021] Figure 4 is a diagram explaining the effect of the increase or decrease in the pressing amount on the battery cell.

[0022] Figure 5A is a flowchart showing the start-up process of the battery system executed by the controller.

[0023] Figure 5B is a flowchart showing the end process of the battery system executed by the controller.

[0024] Figure 6 is showing Figure 5A step S3 of Figure 5B and a flowchart showing the details of the polarization reduction process of step S13 of

[0025] Figure 7 is a diagram showing an example of the pressing mode of the first drive control of the pressing element. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0027] Figure 1 is a block diagram showing an electric vehicle equipped with the battery system of the present embodiment. Figure 2A is a perspective view showing the internal structure of the battery. Figure 2B is a perspective view showing a part of the internal structure of the battery in an exploded manner.

[0028] The electric vehicle 1 includes: drive wheels 2; a traveling motor 3 that drives the drive wheels 2; the battery system 40 of the present embodiment; an inverter 5 that converts electric power between the battery 41 of the battery system 40 and the traveling motor 3; a traveling operation unit 6 that can perform traveling operations; a vehicle controller 9 that performs traveling control; and a relay 11 that opens and closes the power line L1 between the battery 41 and electrical devices (such as the inverter 5). The traveling operation unit 6 includes a steering operation unit 6a such as a steering handle, an acceleration operation unit 6b such as an accelerator pedal, and a braking operation unit 6c such as a brake pedal. The traveling motor 3 is an electric motor. The relay 11 is, for example, a contactor and can also be referred to as a system main relay.

[0029] The vehicle controller 9 is an ECU (electronic control unit) that operates according to a control program stored in a storage unit 9a. The vehicle controller 9 receives an operation signal from the traveling operation unit 6 and controls the inverter 5 according to this operation signal, thereby driving the traveling motor 3. The vehicle controller 9 also performs opening and closing control of the relay 11. Specifically, when starting the system of the electric vehicle 1, the vehicle controller 9 switches the relay 11 to a closed state, and when ending the system of the electric vehicle 1, the vehicle controller 9 switches the relay 11 to an open state.

[0030] The battery system 40 includes a battery 41 that supplies traveling electric power and a controller 42 that manages the state of the battery 41.

[0031] The battery 41 is configured to accommodate a plurality of battery modules 411 in a housing. As Figure 2A and Figure 2B shown, each battery module 411 is formed by modularizing a plurality of battery cells 412. Each battery cell 412 of the battery 41 is, for example, a battery cell of a lithium-ion secondary battery and contains an electrolyte. The battery cell 412 is not limited to being a battery cell of a lithium-ion secondary battery, and various battery cells can be used as long as they contain an electrolyte.

[0032] In the battery module 411, the plurality of battery cells 412 are arranged in parallel in the thickness direction. The thickness direction refers to the direction with the smallest dimension among the three directions of the height direction, width direction, and depth direction of the battery cell 412. The battery cell 412 is a structure including a strip-shaped separator A1 and strip-shaped internal electrodes A2 and A3 (refer to FIG. 5), and the separator A1 and the internal electrodes A2 and A3 extend along two directions (for example, two orthogonal directions) intersecting the thickness direction. The battery cell 412 can also be referred to as a laminated battery cell.

[0033] In the battery module 411, a plurality of battery cells 412 are constrained in a state where pressure is applied in the thickness direction by a constraining body 414. The constraining body 414 can have any structure, for example, having two constraining plates 414a, 414b and a connecting member 414c, and the connecting member 414c connects the two constraining plates 414a, 414b while keeping a predetermined interval therebetween.

[0034] A plurality of electrodes are provided on the upper part of the plurality of battery cells 412, and the plurality of electrodes are electrically connected in a predetermined wiring pattern. The wiring 413 connecting the plurality of electrodes can be a bus bar or a flexible conductor. Even if the pressure applied to the plurality of battery cells 412 changes, the interval between the electrodes does not change significantly. The plurality of battery cells 412 constrained as described above can also be accommodated in a housing to constitute a battery module 411.

[0035] The battery module 411 further includes a pressurizing element 415 that applies pressure to the plurality of battery cells 412. The structure of the pressurizing element 415 can be arbitrary as long as it is a structure that applies pressure to the plurality of battery cells 412 and can increase or decrease the pressure. As an example, in Figure 2A and Figure 2B , an example is shown in which a plate-shaped piezoelectric element is used as the pressurizing element 415. The pressurizing element 415 changes its thickness by applying a voltage. The pressurizing element 415 is located between a pair of adjacent first battery cells 412a and second battery cells 412b among the plurality of battery cells 412 constrained by the constraining body 414. Therefore, if the pressurizing element 415 is driven to increase its thickness, the pressure in the thickness direction of the plurality of battery cells 412 increases. If the pressurizing element 415 is driven to decrease its thickness, the pressure in the thickness direction of the plurality of battery cells 412 decreases.

[0036] In Figure 2A and 2B 's example, the pressurizing element 415 has dimensions substantially the same (within ±10%) as one battery cell 412 in the height direction and the width direction, and can apply uniform pressure to the battery cell 412 in the height direction and the width direction. With this structure, the non-uniformity of the pressure applied by the pressurizing element 415 to the battery cell 412 can be reduced. In addition, the pressurizing element 415 can also be a structure that applies pressure to a partial range in the height direction or a partial range in the width direction of the battery cell 412. By applying pressure to a partial range, the electrolyte moves from this range to other ranges inside the battery cell 412, and the stirring effect of the electrolyte can be further obtained. For one battery module 411, the number of the pressurizing elements 415 is not limited to one, and a plurality of pressurizing elements 415 can be respectively arranged between multiple battery cells 412 included in one battery module 411.

[0037] A pressure sensor 416 is also provided in the battery module 411. The pressure sensor 416 detects the pressing force applied to the plurality of battery cells 412. As an example, the pressure sensor 416 is, for example, a piezoelectric element, and is arranged between the pressing 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 cell 412 increased or decreased by the pressing element 415.

[0038] A temperature sensor 417 is also provided in the battery module 411. The temperature sensor 417 is arranged inside the battery module 411 and detects the temperature of the battery cell 412. The temperature sensor 417 only needs to detect the temperature of any one of the battery cells 412 inside the battery module 411 as a representative temperature.

[0039] The controller 42 is an ECU and operates according to the control program in the storage unit 42a. The controller 42 performs the first drive control of the pressing element 415. The first drive control is to perform one or more sets of controls on the drive to increase the pressing amount of the pressing element 415 and the drive to decrease the pressing amount of the pressing element 415 in this order or in the reverse order of this order. The outputs of the pressure sensor 416 and the temperature sensor 417 are transmitted to the controller 42. In Figure 2A it, the wiring d415 for outputting the voltage to drive the pressing element 415, and the wirings d416 and d417 for transmitting the sensor signals from the pressure sensor 416 and the temperature sensor 417 are omitted.

[0040] The controller 42 may also be configured to undertake the BCU (Battery Control Unit) function of managing the state of the battery 41. The controller 42 as the BCU receives the measured values of the current, voltage and temperature of the battery 41, and manages the SOC (State of Charge), the dischargeable power Wout, the rechargeable power Win, etc. of the battery 41. A sensor 418 for measuring the current, voltage and temperature is provided in the battery 41, and the output of the sensor 418 is transmitted to the controller 42. The controller 42 manages the SOC of the battery 41 by integrating the current of the battery 41. In addition, the controller 42 has a data table or a calculation formula indicating the relationship between the voltage (for example, OCV: Open Circuit Voltage) and the SOC, and estimates the SOC based on this data table or calculation formula and the voltage.

[0041] In addition, the controller 42 that performs the first drive control of the pressurizing element 415 may not undertake the functions of the BCU, and the controller 42 and the BCU may be separately provided as individual ECUs. In this case, the controller 42 and the BCU may be configured to communicate and cooperate. In addition, the controller 42 that performs the first drive control of the pressurizing element 415 may also be integrated in the vehicle controller 9, and the vehicle controller 9 undertakes the functions of the controller 42. The structure in which the controller 42 also undertakes the functions of the BCU will be described below.

[0042] <Battery characteristics>

[0043] Figure 3 It is a graph for explaining the influence on battery polarization. Figure 4 It is a diagram for explaining the effect of the increase or decrease in the pressurizing amount on the battery cells.

[0044] The degree of polarization of the battery 41 may increase due to energization. Polarization is a phenomenon in which the actual voltage deviates from the voltage of the battery 41 in the balanced state. Figure 3 The voltage V0 represents the voltage of the battery 41 in the balanced state. Figure 3 The relationship curve f represents the relationship between the voltage of the battery 41 in the balanced state and the SOC. If the voltage V0 in the balanced state is known, the actual SOC_U0 can be accurately estimated by using a data table or a calculation formula representing the relationship between the voltage of the battery 41 and the SOC. However, if polarization ΔV occurs, the voltage V1 obtained from the output of the sensor 418 will deviate from the voltage V0 in the balanced state. Therefore, when the SOC is calculated using a data table or a calculation formula, the calculated SOC_U1 will include an error ΔU deviating from the accurate SOC_U0 by the polarization ΔV amount.

[0045] One of the main causes of polarization is the imbalance in the concentration of ions contained in the electrolyte near the internal electrodes A2 and A3 of the battery cell 412. As Figure 4 shown, a plurality of fine holes b are provided on the internal electrodes A2 and A3 included in the battery cell 412, and the internal electrodes A2 and A3 are impregnated with the electrolyte. Sometimes, the degree of polarization increases due to the imbalance in the ion concentration in the electrolyte in the fine holes b.

[0046] When the degree of polarization increases as described above, by pressurizing the battery cell 412 in the thickness direction and changing the applied pressure to increase and decrease, the volume of the fine holes b of the internal electrodes A2 and A3 can be reduced and then increased. Such an effect causes the electrolyte to be agitated, and the imbalance in the ion concentration of the electrolyte near the internal electrodes A2 and A3 can be reduced, and the polarization can be quickly reduced.

[0047] <Start-up process and shutdown process of the battery system>

[0048] Figure 5A is a flowchart showing the start-up process of the battery system executed by the controller. Figure 5B is a flowchart showing the end process of the battery system executed by the controller. Figure 6 is showing Figure 5A step S3 of Figure 5B and a flowchart showing the details of the polarization mitigation process of step S13 of

[0049] When the system of the electric vehicle 1 becomes a stopped state, the controller 42 starts Figure 5A the start-up process. In the start-up process, first, the controller 42 repeatedly performs the process of determining whether there is a system start-up request for the electric vehicle 1 (step S1) until a "yes" result is obtained. The above system start-up request occurs when the user turns on the power button of the electric vehicle 1 or the like.

[0050] 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 there is a system start-up request for the electric vehicle 1, usually, the relay 11 is in the open state, so it is confirmed to be in the open state in step S2. In addition, if the relay 11 cannot be confirmed to be in the open state due to special circumstances in step S2, the controller 42 can also send a request to the vehicle controller 9 to open the relay 11, and control the relay 11 to temporarily become open. Or, if the relay 11 cannot be confirmed to be in the open state in step S2, the controller 42 can skip step S3 and make the process enter step S4, or can skip steps S3 and S4 and end the start-up process.

[0051] After being confirmed to be in the open state in step S2, the controller 42 executes the polarization mitigation process (step S3). In the polarization mitigation process, as Figure 6 shown, first, the controller 42 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 be completely zero. In step S21, the controller 42 measures this current value. In addition, the current value measured in step S21 may not be the current value between the two terminals of the battery 41, but the value of the internal current flowing between multiple battery modules 411 or between multiple battery cells 412.

[0052] Next, the controller 42 determines whether the current value measured in step S21 is less than the threshold value (step S22). This threshold value can be set to a value that can ensure that the performance degradation of the battery cell 412 is within the allowable range even when the applied voltage of the battery cell 412 changes.

[0053] If the result of step S22 is "No", the controller 42 performs a timing process (step S23), and determines whether the total elapsed time of step S23 has reached a threshold time (step S24). If not, the controller 42 returns the process to step S21 again. If the threshold time has been reached, since the polarization mitigation drive is omitted, the controller 42 ends the polarization mitigation process and advances the process to the next step S4 in FIG. 5.

[0054] On the other hand, if the determination result of step S22 is "Yes", the controller 42 acquires the temperature of the battery cell 412 (hereinafter referred to as "cell temperature"), the voltage of the battery 41, and the SOC (step S25). The SOC acquired here may not be the SOC converted from the voltage of the battery 41, or a value that accurately shows the current SOC such as the current SOC calculated based on the SOC acquired last in the battery system 40.

[0055] Next, the controller 42 determines the pressurization mode of the first drive control of the pressurizing element 415 based on the cell temperature, voltage, and SOC acquired in step S25 (step S26).

[0056] Figure 7 FIG. is an example of a pressurization mode showing the first drive control of the pressurizing element. As described above, the first drive control means performing one or more sets of controls in which the drive to increase the pressurization amount of the pressurizing element 415 and the drive to decrease the pressurization amount of the pressurizing element 415 are performed in this order or in the reverse order. When performing the first drive control, the controller 42 can adopt multiple pressurization modes. For example, as Figure 7 shown by the multiple pressurization modes P1 to P3, the controller 42 can formulate multiple pressurization modes by making the absolute value of the pressurization amount (such as the maximum value and the minimum value), the number of increases and decreases of the pressurization amount, the change speed of the pressurization amount, or a plurality of them different.

[0057] In the battery 41, when the battery cell temperature is high, the degree of polarization of the battery cell 412 tends to decrease, and when the battery cell temperature is low, the degree of polarization of the battery cell 412 tends to increase. Therefore, if there is no difference in other parameters, a pressurization mode can be selected in which the maximum value of the pressurization amount is lower when the cell temperature is higher and the maximum value of the pressurization amount is higher when the cell temperature is lower.

[0058] In addition, there is a tendency that the larger the SOC, the greater the expansion of the battery cell 412, and the smaller the SOC, the smaller the expansion of the battery cell 412. In addition, there is sometimes a characteristic that when the SOC is within a specific range, the slope of the relationship curve between the SOC and the expansion amount of the battery cell 412 is reversed. Therefore, if there is no difference in other parameters, a pressurization mode can be selected such that the maximum value of the pressurization amount is lower when the SOC is large in terms of expansion amount, and the maximum value of the pressurization amount is higher when the SOC is small in terms of expansion amount.

[0059] In addition, there is a tendency that the larger the voltage, the greater the expansion of the battery cell 412, and the smaller the voltage, the smaller the expansion of the battery cell 412. Therefore, if there is no difference in other parameters, a pressurization mode can be selected such that the higher the voltage, the lower the maximum value of the pressurization amount, and the lower the voltage, the higher the maximum value of the pressurization amount.

[0060] In addition, when on the one hand, due to the low cell temperature, the degree of polarization is large, and on the other hand, due to voltage or SOC, the maximum value of the pressurization amount cannot be increased, a pressurization mode can be selected in which although the maximum value of the pressurization amount is low, the number of increase and decrease times is increased. Alternatively, a pressurization mode can be selected in which the maximum value of the pressurization amount is increased to a medium level on the one hand, and the change speed of the pressurization amount is slowed down on the other hand.

[0061] By selecting the pressurization mode as described above, it is possible to suppress the deterioration of the battery cell 412 while performing an electrolyte stirring action and reducing the polarization of the battery 41. A data table for implementing the selection of the above pressurization mode is set in the storage unit 42a of the controller 42.

[0062] In step S26, the controller 42 determines the pressurization mode of the pressurization element 415 corresponding to the state information of the battery 41 by comparing the state information of the battery 41 such as the cell temperature, SOC, and voltage with the data table.

[0063] After determining the pressurization mode in step S26, the controller 42 performs a first drive control to drive the pressurization element 415 to generate the pressing force of the above pressurization mode (step S27).

[0064] Through the first drive control of step S27, as Figure 4 shown, the battery cell 412 is pressurized in the thickness direction, and the pressing force increases and decreases. This pressing force causes the volume of the pores b of the internal electrodes A2, A3 to decrease and then increase, or vice versa, so that the electrolyte is stirred. Then, through this stirring of the electrolyte, the imbalance of the ion concentration of the electrolyte near the internal electrodes A2, A3 is reduced, and the polarization of the battery cell 412 is rapidly reduced.

[0065] In addition, the pressurization modes in steps S26 and S27 are not limited to the above examples, and various pressurization modes can be adopted, as long as the applied pressure increases and decreases over time.

[0066] After the first drive control in step S27 is completed, the controller 42 ends the polarization mitigation process and enters the process of the next step in FIG. 5. Then, the controller 42 performs the SOC estimation process (step S4). In step S4, the controller 42 measures the OCV of the battery 41 through the sensor 418, and substitutes the OCV into a data table or a calculation formula to obtain an estimated value of the SOC.

[0067] Then, the controller 42 ends the startup process of the battery system 40. Thereafter, when the system of the electric vehicle 1 starts, the controller 42 transfers the process to the battery management process. In the battery management process, to the highly accurate SOC obtained by the controller 42 in the startup process, the SOC change amount based on the subsequent current cumulative value is added to manage the SOC when the electric vehicle 1 is running. Therefore, highly accurate SOC management can also be achieved in terms of the battery management process.

[0068] When the system of the electric vehicle 1 starts and the startup process of the battery system 40 ends, the controller 42 starts Figure 5B the ending process of the battery system 40. Then, the controller 42 repeatedly performs the process of determining the moment when the system of the electric vehicle 1 transfers to the stop state (step S11) in parallel with the battery management process until a "yes" result is obtained. The moment when the system of the electric vehicle 1 transfers to the stop state arrives, for example, based on an end operation performed by the user on the system of the electric vehicle 1.

[0069] As a result, if it is the moment when the system transfers to the stop 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). At the moment when the system of the electric vehicle 1 transfers to the stop state, generally, the relay 11 is set to the open state, so it will be confirmed as the open state in step S12. In addition, if it cannot be confirmed in step S12 that the relay 11 is in the open state, the controller 42 can also standby for a specified time and then perform the process of confirming again whether the relay 11 has become in the open state. Or, if it cannot be confirmed in step S12 that the relay 11 is in the open state, the controller 42 can skip step S13 and enter the process of step S14, or can skip steps S13 and S14 and enter the process of step S15.

[0070] If it is confirmed in step S12 that it is in the open state, the controller 42 then executes the polarization mitigation process (step S13). The polarization mitigation process in step S13 is the same as Figure 5Ais the same as the polarization mitigation process in step S3.

[0071] Next, the controller 42 performs SOC estimation processing (step S14). In step S14, the controller 42 measures the OCV of the battery 41 through the sensor 418, and substitutes the OCV into a data table or a calculation formula to calculate an estimated value of the SOC. Then, the controller 42 performs its own shutdown processing (step S15) to end the shutdown processing of the battery system 40. Through this shutdown processing, even when the operation of the electric vehicle 1 ends, the controller 42 can accurately obtain the SOC of the battery 41.

[0072] The programs of the startup processing and the shutdown processing of the battery system 40 described above are stored in a non-temporary storage medium (non-transitory computer-readable medium) such as the storage unit 42a of the controller 42. The controller 42 may also be configured to read a program stored in a portable non-temporary recording medium and execute the program. The above-mentioned portable non-temporary storage medium may also store the programs of the startup processing and the shutdown processing of the battery system 40.

[0073] As described above, according to the battery system 40 of the present embodiment, it includes: a battery 41 including a plurality of battery cells 412; a pressurizing element 415 capable of pressurizing the plurality of battery cells 412; and a controller 42 that performs first drive control of the pressurizing element 415. And the above-mentioned first drive control is to perform one or more sets of controls in which the drive to increase the pressurizing amount of the pressurizing element 415 and the drive to decrease the pressurizing amount of the pressurizing element 415 are in this order or in the reverse order of this order. According to this structure, when polarization occurs in the battery 41 due to an imbalance in the ion concentration of the electrolyte, a stirring effect of the electrolyte can be generated through the first drive control, thereby rapidly reducing the polarization. Therefore, various problems caused by polarization, such as the deterioration of the SOC estimation accuracy due to polarization, can be quickly solved.

[0074] In addition, in the battery system 40 according to the present embodiment, a relay 11 that opens and closes the power line L1 between the battery 41 and the electrical device is provided on the electric vehicle 1. When the relay 11 is in the open state, the controller 42 executes the first drive control of the pressurizing element 415. When the pressing force of the battery cell 412 is increased or decreased by the first drive control, if current flows through the battery cell 412, the degree of deterioration of the battery cell 412 may sometimes progress. Therefore, such deterioration can be suppressed.

[0075] In addition, in the battery system 40 according to the present embodiment, the controller 42 includes a current sensor (the sensor 418 or a sensor that measures the current between the battery cells 412 or between the battery modules 411). When the current value measured by the current sensor is less than or equal to the threshold value, the first drive control of the pressurizing element 415 is executed. Even when the relay 11 is in the open state, there may be current flowing through the battery 41. Therefore, if the first drive control of the pressurizing element 415 is performed while this current is flowing, the degree of deterioration of the battery cells 412 may sometimes progress. Thus, such deterioration can be suppressed.

[0076] In addition, in the battery system 40 according to the present embodiment, a plurality of battery cells 412 are arranged in sequence, and the pressurizing element 415 is disposed between the adjacent first battery cell 412a and second battery cell 412b. With this structure, it is possible to apply pressure to the plurality of battery cells 412 evenly using one pressurizing element 415. Therefore, it is possible to relatively suppress the problem of an increase in the volume of the battery 41 due to the structure for additional pressurization.

[0077] In addition, in the battery system 40 according to the present embodiment, the controller 42 makes the pressurization mode of the first drive control of the pressurizing element 415 different according to the state information (temperature, voltage, SOC, etc.) of the battery 41. With this structure, it is possible to apply a pressurization mode corresponding to the state of the battery 41 to the battery cells 412 to reduce polarization. Therefore, it is possible to perform the polarization reduction process while suppressing the progress of deterioration of the battery cells 412.

[0078] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the above embodiments, an example is shown in which the timing of executing the first drive control of the pressurizing element 415 is before the process of estimating the SOC. However, the first drive control of the pressurizing element 415 can be performed before the start of charging, after the end of charging, during a driving interruption, etc., or at a timing unrelated to the process of estimating the SOC. By reducing the polarization of the battery cells 412, it is possible to improve the charging and discharging efficiency of the battery 41. In addition, in the above embodiments, an example is shown in which the first drive control of the pressurizing element 415 is executed when the system of the electric vehicle 1 is started and when the driving ends, but the SOC estimation process performed after the first drive control can also be omitted. By reducing the polarization of the battery cells 412, it is possible to improve the charging and discharging efficiency of the battery 41, and in addition, it is possible to slow down the progress of deterioration during the storage period of the battery 41.

[0079] In addition, in the above-described embodiment, a structure is employed in which a plurality of battery cells 412 are constrained by a constraining body 414, and a pressure is applied to the plurality of battery cells 412 by expanding an inflatable member 415 inside the constraining body 414. However, various other forms of structures for applying a pressing force to the plurality of battery cells 412 may be adopted. For example, a structure in which the plurality of battery cells 412 are clamped and the clamping force can be changed may be adopted. In addition, the details shown in the embodiment may be appropriately changed without departing from the gist of the present invention.

[0080] Industrial Applicability

[0081] The present invention can be used for a battery system mounted on an electric vehicle to supply driving power.

[0082] Reference Signs

[0083] 1... Electric vehicle

[0084] 2... Driving wheel

[0085] 3... Driving motor

[0086] 5... Inverter

[0087] 6... Driving operation unit

[0088] 9... Vehicle controller

[0089] 9a... Storage unit

[0090] 11... Relay

[0091] 40... Battery system

[0092] 41... Battery

[0093] 411... Battery module

[0094] 412... Battery cell

[0095] 412a... First battery cell

[0096] 412b... Second battery cell

[0097] A1... Separator

[0098] A2, A3... Internal electrode

[0099] b... Pore

[0100] 413... Wiring

[0101] 414... Constraining body

[0102] 414a, 414b... Constraining plate

[0103] 414c... Connecting part

[0104] 415... Pressurizing element

[0105] 416... Pressure sensor

[0106] 417... Temperature sensor

[0107] 418... Sensor

[0108] 42... Controller

[0109] 42a... Storage unit

[0110] L1... Power line.

Claims

1. A battery system is mounted on an electric vehicle and supplies driving power, and the battery system comprises: a battery including a plurality of battery cells; a pressurizing element capable of pressurizing the plurality of battery cells; and a controller that performs first drive control on the pressurizing element, wherein the first drive control is to perform one or more sets of control in an order of driving that increases the pressurizing amount of the pressurizing element and driving that decreases the pressurizing amount of the pressurizing element in this order or in the reverse order of this order.

2. The battery system according to claim 1, wherein a relay for opening and closing a power line between the battery and an electrical device is provided on the electric vehicle, the controller is input with information indicating whether the relay is in an open or closed state, and when the relay is in an open state, the controller performs the first drive control.

3. The battery system according to claim 2, further comprises: a current sensor that measures the current of the battery, wherein when the relay is in an open state and the current value measured by the current sensor is less than or equal to a threshold value, the controller performs the first drive control.

4. The battery system according to claim 1, wherein the plurality of battery cells are arranged in sequence, and the pressurizing element is disposed between a first battery cell and a second battery cell adjacent to each other among the plurality of battery cells.

5. The battery system according to claim 1, wherein the controller makes the pressurizing mode of the first drive control different according to the state information of the battery.

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