Battery system

Abstract

Improve the accuracy of calculating the internal pressure of the battery. [Solution] The battery ECU calculates the amount of gas generated inside the case, Vgo (S12), and calculates the amount of gas permeation, Vgp, which corresponds to the amount of gas that has leaked out of the case (S13). Subtracting the amount of gas permeation, Vgp from the amount of gas generated, Vgo, calculates the amount of internal gas, Vg, which is the amount of gas inside the battery (S14). Calculating the amount of electrolyte permeation, Vep, which corresponds to the amount of electrolyte that has leaked out of the case (S15), and adding the amount of electrolyte permeation, Vep, and the initial void volume, Vc0, calculates the internal void volume, Vc, which is the void volume inside the battery (S16). Based on the amount of internal gas, Vg, and the internal void volume, Vc, the internal battery pressure, P, which is the pressure inside the case, is calculated (S17).

Description

[Technical Field]

[0001] This disclosure relates to a battery system. [Background technology]

[0002] Japanese Patent Publication No. 2015-141790 (Patent Document 1) discloses a method for determining the deterioration of battery components over time using the internal pressure of the battery. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-141790 [Overview of the project] [Problems that the invention aims to solve]

[0004] Patent Document 1 calculates the amount of gas generated within a battery (gas generation amount) from the battery's temperature and State of Charge (SOC) history. Then, it calculates the internal pressure of the battery based on the gas generation amount and determines the amount of internal pressure damage from the internal pressure.

[0005] Some gas and electrolyte from inside the battery leak out through seals and other parts. Patent Document 1 does not take into account the leakage of gas and electrolyte, so there is a concern that the accuracy of calculating the internal pressure of the battery will deteriorate.

[0006] The purpose of this disclosure is to improve the accuracy of calculating the internal pressure of a battery. [Means for solving the problem]

[0007] The battery system of the present disclosure is a battery system including a battery that houses an electrode body and an electrolyte in a case, and a control device. The control device subtracts a gas permeation amount Vgp corresponding to the amount of gas leaked outside the case from the generation amount Vgo of gas generated inside the case to calculate an internal gas amount Vg that is the amount of gas inside the battery, adds an electrolyte permeation amount Vep corresponding to the amount of electrolyte leaked outside the case to the initial void volume Vc0 inside the case to calculate an internal void volume Vc that is the void volume inside the battery, and calculates a battery internal pressure P that is the pressure inside the case based on the internal gas amount Vg and the internal void volume Vc.

[0008] According to this configuration, the control device calculates the battery internal pressure P based on the internal gas amount Vg and the internal void volume Vc. The internal gas amount Vg is calculated by subtracting a gas permeation amount Vgp corresponding to the amount of gas leaked outside the case from the generation amount Vgo of gas generated inside the case. The internal void volume Vc is calculated by adding an electrolyte permeation amount Vep corresponding to the amount of electrolyte leaked outside the case to the initial void volume Vc0 inside the case. Since the battery internal pressure P is calculated in consideration of the gas and electrolyte leaking from the battery case, the calculation accuracy of the battery internal pressure P can be improved.

[0009] Preferably, the control device may calculate the internal gas amount Vg by subtracting a gas absorption amount Vga and a gas permeation amount Vgp, by which the gas is absorbed by the electrolyte, from the generation amount Vgo.

[0010] According to this configuration, since the internal gas amount Vg is calculated taking into account the gas absorption amount Vga by which the gas is absorbed by the electrolyte, the calculation accuracy of the battery internal pressure P can be further improved.

[0011] Preferably, the control device may calculate the gas permeation amount Vgp based on the battery internal pressure P.

[0012] The amount of gas leaking outside the case correlates with the magnitude of the battery internal pressure P. According to this configuration, since the gas permeation amount Vgp is calculated based on the battery internal pressure P, the gas permeation amount Vgp can be accurately calculated.

[0013] Preferably, the control device may calculate a gas permeation rate A2, which is the amount of pre-gas leaking out of the case per unit time, based on an index value representing the airtightness of the battery and the battery internal pressure P, and calculate a gas permeation amount Vgp based on the gas permeation rate A2.

[0014] The amount of gas leaking out of the case is also correlated with the airtightness of the case. According to this configuration, the gas permeation rate A2 is calculated based on an index value representing the airtightness of the battery and the battery internal pressure P. Since the gas permeation amount Vgp is calculated based on the gas permeation rate A2, the gas permeation amount Vgp can be accurately calculated.

[0015] Preferably, the control device may calculate an electrolyte permeation amount Vep based on the temperature of the battery.

[0016] The amount of electrolyte leaking out of the case is correlated with the temperature of the battery. According to this configuration, since the electrolyte permeation amount Vep is calculated based on the temperature of the battery, the electrolyte permeation amount Vep can be accurately calculated.

[0017] Preferably, the control device may calculate a cumulative damage amount ΣDp corresponding to an index of the deterioration over time of the members constituting the battery based on the battery internal pressure P, and issue an alarm when the cumulative damage amount ΣDp exceeds a threshold value.

[0018] According to this configuration, since the cumulative damage ΣDp is calculated based on the accurately calculated battery internal pressure P, the deterioration over time of the members constituting the battery can be appropriately estimated, and an alarm can be preferably issued. [[ID=​​​​​​​​​​​​​​​This flowchart shows an example of the battery internal pressure calculation process performed in the battery ECU. [Figure 3] (A) and (B) are diagrams illustrating the method for calculating the gas generation rate A1. [Figure 4] (A) and (B) are diagrams illustrating the method for calculating the gas permeation rate Vgp. [Figure 5] This figure shows the relationship between the electrolyte permeation rate A3 and temperature TB. [Figure 6] This flowchart shows an example of the damage estimation process performed by the control ECU. [Figure 7] This figure shows the calculation map for the gas absorption rate A4. [Modes for carrying out the invention]

[0021] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0022] Figure 1 is an overall configuration diagram of an electric vehicle 1 equipped with a battery system B according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, an electric vehicle. The electric vehicle 1 may also be a plug-in hybrid vehicle equipped with an internal combustion engine and a battery. The electric vehicle 1 comprises a motor generator (MG) 10 which is a rotating electric machine, a power transmission gear 20, drive wheels 30, a power control unit (PCU) 40, a system main relay (SMR) 50, a battery 100, a monitoring unit 200, a battery ECU (Electronic Control Unit) 300, and a control ECU 500. The battery ECU 300 and the control ECU 500 correspond to examples of "control devices" in this disclosure.

[0023] MG10 is, for example, an embedded permanent magnet synchronous motor (IPM motor) that has both the function of a motor and the function of a generator. The output torque of MG10 is transmitted to the drive wheels 30 via a power transmission gear 20 which includes a reduction gear and a differential gear.

[0024] When the electric vehicle 1 is braked, the MG10 is driven by the drive wheels 30, and the MG10 operates as a generator. As a result, the MG10 also functions as a braking device that performs regenerative braking, converting the kinetic energy of the electric vehicle 1 into electricity. The regenerative power generated by the regenerative braking force in the MG10 is stored in the battery 100.

[0025] The PCU40 is a power converter that converts power bidirectionally between the MG10 and the battery 100. The PCU40 includes, for example, an inverter and a converter that operate based on control signals from the control ECU500.

[0026] The SMR50 is electrically connected to the power line connecting the battery 100 and the PCU40. When the SMR50 is closed (ON) in response to a control signal from the control ECU500, power can be exchanged between the battery 100 and the PCU40. On the other hand, when the SMR50 is opened (OFF) in response to a control signal from the control ECU500, the electrical connection between the battery 100 and the PCU40 is interrupted.

[0027] Battery 100 stores power to drive MG10. Battery 100 is a rechargeable DC power source (secondary battery) and is a battery pack in which multiple single cells 110 are electrically connected in series. A single cell 110 corresponds to the “battery” in this disclosure. A single cell 110 may be composed of, for example, a lithium-ion battery.

[0028] The single cell 110 may be, for example, a rectangular cell 110a. In a rectangular cell 110a, an electrode body 112a is housed inside a case 111a made of a rectangular prism housing, and an electrolyte is sealed inside. Alternatively, the single cell 110 may be a laminated cell (pouch cell) 110b. In a laminated cell 110b, an electrode body 112b and an electrolyte are sealed inside a case 111b made of laminate film. Both the rectangular cell 110a and the laminated cell 110b are equipped with components such as a discharge valve (safety valve) for releasing gas to the outside when the internal pressure of the battery rises due to gas generated inside the battery (inside the case), and a current interruption mechanism for interrupting the current when the battery overheats abnormally.

[0029] The monitoring unit 200 includes a voltage sensor 210, a current sensor 220, and a temperature sensor 230. The voltage sensor 210 detects the voltage VB of the single cell 110. The current sensor 220 detects the current IB that is input to and output from the battery 100 (single cell 110). Note that when the battery 100 is discharging, the current IB is a negative (-) value, and when the battery 100 is charging, the current IB is a positive (+) value. The temperature sensor 230 detects the temperature TB of the battery 100 (single cell 110).

[0030] The electric vehicle 1 is equipped with an inlet 60, and the battery 100 can be externally charged using an electric vehicle supply equipment (EVSE) 400. The inlet 60 is configured to be connectable to a connector 420 provided at the end of the charging cable 410 of the EVSE 400. The inlet 60 is electrically connected to a power line connected to the battery 100 via a charging circuit 70. In this embodiment, when the SMR 50 is closed, the inlet 60 and the battery 100 are connected, enabling external charging. The charging circuit 70 may include a charging relay. Alternatively, the inlet 60 (charging circuit 70) may be connected to the power line between the battery 100 and the SMR 50 via a charging relay, and the battery 100 may be configured to be externally charged when the charging relay is closed.

[0031] The battery ECU 300 includes a CPU (Central Processing Unit) 301 and a memory 302. The memory 302 includes RAM (e.g., SRAM (Static Random Access Memory)) and non-volatile memory (e.g., EEROM (Electrically Erasable Programmable Read-Only Memory)). If power to the RAM is cut off (if the battery ECU 300 loses power), the data stored in the RAM is lost. Even if power is cut off (if the battery ECU 300 loses power), the data stored in the non-volatile memory is not lost. The battery ECU 300 uses signals received from the monitoring unit 200 to estimate the State of Charge (SOC) of the battery 100 (single cell 110) and outputs this to the control ECU 500. The battery ECU 300 also estimates the degree of degradation of the battery 100 and outputs this to the control ECU 500. The battery ECU 300 and the control ECU 500 are connected, for example, via CAN (Controller Area Network). It may be connected via a network. In this embodiment, the battery system B consists of a battery 100, a monitoring unit 200, a battery ECU 300, a control ECU 500, and the like.

[0032] The control ECU 500 includes a CPU 501 and a memory 502. The memory 502, like the memory 302, includes RAM and non-volatile memory. Based on signals received from the battery ECU 300, signals from various sensors (not shown) (e.g., accelerator opening signal, vehicle speed signal, etc.), and information such as maps and programs stored in the memory 502, the control ECU 500 controls each device so that the electric vehicle 1 reaches a desired state.

[0033] Figure 2 is a flowchart showing an example of the battery internal pressure calculation process performed in the battery ECU 300. This flowchart is executed at predetermined intervals for each individual cell 110 when the power switch (ignition switch) 250 is turned ON and the battery system B is in the ON state, and when the battery 100 is being externally charged by the EVSE 400.

[0034] In step 10 (hereinafter, steps will be abbreviated as "S"), it is determined whether flag F is 1 or not. Flag F is set to "0" when the electric vehicle 1 is shipped and when the battery 100 is replaced. If flag F is 0 and the result is negative, proceed to S11; if flag F is 1 and the result is positive, proceed to S12.

[0035] In S11, the initial void volume Vc0 and the leak amount KHe are obtained. The initial void volume Vc0 is the volume in the case of the single cell 110 in which gas can be retained. The initial void volume Vc0 is the volume obtained by subtracting the volume of the electrode body and the initial electrolyte amount Ve0 from the volume in the case of the single cell 110. The initial electrolyte amount Ve0 is the amount of electrolyte injected into the case of the single cell 110 during the electrolyte injection process. The leak amount KHe is an index value representing the airtightness of the single cell 110 obtained in the airtightness test process of the single cell 110. For example, the leak amount KHe may be the amount of leak obtained in a leak test using helium gas.

[0036] Process history information is recorded in a two-dimensional code printed on the surface of the single cell 110 case. When assembling the battery 100 (battery pack), the initial void volume Vc0 and leak amount KHe may be read from this two-dimensional code and stored in memory 302. In this case, in S11, the initial void volume Vc0 and leak amount KHe are read from memory 302. Alternatively, the process history information of the single cell 110 may be stored on a server (not shown), and when the electric vehicle 1 is started, the initial void volume Vc0 and leak amount KHe may be obtained from the server through communication between the electric vehicle 1 (battery ECU 300) and the server.

[0037] In S12, the amount of gas generated, Vgo, is calculated. During charging and discharging of the single cell 110, gas is generated due to the decomposition reaction of the electrolyte, etc. In S12, this amount of gas generated is calculated as the amount of gas generated, Vgo. In this embodiment, the amount of gas generated, Vgo, is calculated based on the gas generation rate, A1. Figure 3 is a diagram illustrating the method for calculating the gas generation rate, A1. Figure 3(A) shows the relationship between the natural logarithm of the gas generation rate, A1 [cc / √time] (ln(gas generation rate A1)), and the reciprocal of the temperature TB (1000 / TB in this embodiment) in the single cell 110. Figure 3(A) is known as the Arrhenius plot (Anireus equation) and can be obtained by experiments and simulations using the single cell 110. As shown in Figure 3(A), the gas generation rate, A1, can be approximated as a straight line that increases as the temperature TB is large (as the reciprocal of the temperature TB is small) and as the SOC is large, for each SOC. For example, the gas generation rate A1 can be calculated using the following equation (1) from the relationship shown in Figure 3(A).

[0038] A1=ln(k1×exp(k2×1000 / TB)) (1) k1 is the value of the intercept on the vertical axis in Figure 3(A), and k2 is the slope of the line, which is set for each SOC. Temperature TB is the value detected by temperature sensor 230, and SOC is the current SOC.

[0039] Figure 3(B) shows the calculation map for the gas generation rate A1. Figure 3(B) maps the gas generation rate A1 based on the relationship between the gas generation rate A1, temperature TB, and state of temperature (SOC) shown in Figure 3(A). The gas generation rate A1 may also be calculated from the map in Figure 3(B) using temperature TB and SOC as parameters.

[0040] The gas generation amount Vgo is calculated from the gas generation rate A1 using the following equation (2). Vgo n =Vgo n-1 +(A1 2 / (2×Vgo n-1 ))×dt····(2) Vgo nis the gas generation amount Vgo (current value) calculated this time, and Vgo n-1 is the gas generation amount Vgo (previous value) calculated last time. dt is the elapsed time from last time to this time, and corresponds to the operation cycle of the flowchart in FIG. 2. When the gas generation amount Vgo is calculated in S12, the current value is used as the previous value (Vgo n-1 ), stored in the non-volatile memory of the memory 302, and proceed to S13. The initial value of Vgo n-1 may be "0", or a predetermined value may be set.

[0041] In S13, the gas permeation amount Vgp is calculated. The gas in the single cell 110 leaks to the outside from the seal part or the like. The gas permeation amount Vgp is the amount of gas leaking from the single cell 110 (case) to the outside. In the present embodiment, the gas permeation amount Vgp is calculated based on the gas permeation rate A2. FIG. 4 is a diagram for explaining the calculation method of the gas permeation amount Vgp. FIG. 4(A) shows the relationship between the gas permeation rate A2 [cc / time] and the battery internal pressure P in the single cell 110. As shown in FIG. 4(A), the gas permeation rate A2 is proportional to the battery internal pressure P. From the relationship in FIG. 4(A), the gas permeation rate A2 is calculated using the following formula (3).

[0042] A2 = k3 × P n-1 × kj ····(3) P n-1 is the battery internal pressure P calculated last time. k3 is a constant and is the slope of the straight line shown in FIG. 4(A). kj is a correction coefficient.

[0043] Figure 4(B) is a diagram illustrating the correction coefficient kj. The relationship between the gas permeation rate A2 and the internal pressure P of the cell shown in Figure 4(A) is the relationship (experimental value) when the leak amount KHe of the cell 110 (an index value representing the airtightness of the cell) is the reference value Sd. When the leak amount KHe of the cell 110 is greater than the reference value Sd, the slope of the line shown in Figure 4(A) becomes steeper, and when the leak amount KHe of the cell 110 is less than the reference value Sd, the slope of the line shown in Figure 4(A) becomes shallower. Therefore, as shown in Figure 4(B), the correction coefficient kj is "1" when the leak amount KHe of the cell 110 is the reference value Sd. When the leak amount KHe is less than the reference value Sd, the correction coefficient kj is a value less than 1, and when the leak amount KHe is greater than the reference value Sd, the correction coefficient kj is a value greater than 1. Using the leak amount KHe obtained in S11, the correction coefficient kj can be determined from Figure 4(B).

[0044] The gas permeation rate Vgp is calculated from the gas permeation rate A2 using the following equation (4). VGP n =A2×dt+Vgp n-1 ...(4) VGP n This is the gas permeation rate Vgp (current value) calculated this time, and Vgp n-1 is the gas permeation rate Vgp (previous value) calculated last time. dt is the elapsed time from last time to this time, and corresponds to the calculation period in the flowchart in Figure 2. In S13, when the gas permeation rate Vgp is calculated, the current value is the previous value (Vgp n-1 ) is stored in the non-volatile memory of memory 302, and the process proceeds to S14. Vgp n-1 The initial value of may be "0", or a predetermined value may be set.

[0045] In S14, the amount of internal gas Vg is calculated. The amount of internal gas Vg is calculated using the following equation (5). Vg=Vgo n -Vgp n ...(5) Vgo n This is the amount of gas generated Vgo calculated in S12, and Vgp nThis is the gas permeation rate Vgp calculated in S13.

[0046] In the following step S15, the electrolyte permeation amount Vep is calculated. The electrolyte inside the single cell 110 leaks to the outside through the seal, etc. The electrolyte permeation amount Vep is the amount of electrolyte leaking from the single cell 110 (case) to the outside. In this embodiment, the electrolyte permeation amount Vep is calculated based on the electrolyte permeation rate A3. Figure 5 shows the relationship between the natural logarithm of the electrolyte permeation rate A3 (ln(electrolyte permeation rate A3)) and the reciprocal of the temperature TB (1000 / TB in this embodiment). The electrolyte permeation rate A3 [cc / time] increases as the temperature TB increases (as the reciprocal of the temperature TB decreases). The electrolyte permeation rate A3 is calculated from the relationship in Figure 5 using the following equation (6).

[0047] A3=ln(k4×exp(k5×1000 / TB)) (6) k4 and k5 are constants, and temperature TB is the value detected by temperature sensor 230. The constants k4 and k5 are determined according to the composition of the electrolyte (viscosity, vapor pressure, etc.) and the structure of the electrolyte seal.

[0048] The electrolyte permeation rate Vep is calculated from the electrolyte permeation rate A3 using the following equation (7). Vep n =A2×dt+Vep n-1 ...(7) Vep n This is the electrolyte permeation amount Vep (current value) calculated this time, and Vep n-1 is the electrolyte permeation amount Vep (previous value) calculated last time. dt is the elapsed time from last time to this time, and corresponds to the calculation period in the flowchart in Figure 2. In S15, when the electrolyte permeation amount Vep is calculated, the current value is the previous value (Vep n-1 ) is stored in the non-volatile memory of memory 302, and the process proceeds to S16. n-1 The initial value of may be "0", or a predetermined value may be set.

[0049] In S16, the internal void volume Vc is calculated. The internal void volume Vc is the volume in which gas can currently be retained inside the case of the single cell 110. The internal void volume Vc is calculated from the following equation (8). Vc = Vc0 + Vep n ...(8) Vc0 is the initial void volume Vc0 obtained in S11. n This is the electrolyte permeation rate Vep calculated in S16. The internal void volume Vc is calculated by adding the electrolyte permeation rate Vep to the initial void volume Vc0.

[0050] In S17, the internal battery pressure P is calculated. The internal battery pressure P is calculated using the following equation (9). P = Vg / Vc····(9) Vg is the amount of internal gas Vg calculated in S14, and Vc is the internal void volume Vc calculated in S16. Once S17 is processed, this routine will terminate.

[0051] Figure 6 is a flowchart showing an example of damage estimation processing performed by the control ECU 500. This flowchart is executed at predetermined intervals for each cell 110 when the power switch 250 is turned ON and the battery system B is turned ON, and when the battery 100 is being externally charged by the EVSE 400. In S20, the amount of damage Dp of the cell 110 is calculated. The calculation of the amount of damage Dp is substantially the same as the calculation method described in Patent Document 1. The amount of damage Dp is calculated from the temperature TB and the battery internal pressure P calculated in the battery internal pressure calculation processing in Figure 2. In this embodiment, the amount of damage Dp is a factor that affects creep failure of the components (constituent members) that make up the cell 110, and for example, the current interruption mechanism is targeted as a component.

[0052] The damage amount Dp is stored in memory 502 as a map with temperature TB and battery pressure P as parameters. For example, the larger the temperature TB and the larger the battery pressure P, the larger the value set. In S20, the damage amount Dp is calculated from the temperature TB and battery pressure P.

[0053] In the subsequent S21, the integrated damage ΣDp is calculated by integrating the damage amount Dp calculated in S20 (ΣDp = ΣDp n-1 + Dp: ΣDp n-1 is the previous value of ΣDp).

[0054] In S22, it is determined whether the integrated damage ΣDp is equal to or greater than the threshold value S. If the integrated damage ΣDp is equal to or greater than the threshold value S (ΣDp ≥ S), the process proceeds to S23. If the integrated damage ΣDp is less than the threshold value S (ΣDp < S), the current routine ends.

[0055] In S23, the MIL (Malfunction Indicator Lamp) 260 is lit to give an alarm, and the current routine ends.

[0056] According to the present embodiment, the internal gas amount Vg is calculated by subtracting the gas permeation amount Vgp corresponding to the amount of gas leaked out of the case from the gas generation amount Vgo generated inside the case of the single battery 110. The internal void volume Vc is calculated by adding the electrolyte permeation amount Vep corresponding to the amount of electrolyte leaked out of the case to the initial void volume Vc0 inside the case. Since the battery internal pressure P is calculated from the internal gas amount Vg and the internal void volume Vc, the battery internal pressure P can be calculated in consideration of the gas and electrolyte leaking from the case of the single battery 110, and the calculation accuracy of the battery internal pressure P can be improved.

[0057] According to the present embodiment, the gas permeation amount Vgp is calculated using the gas permeation rate A2 calculated based on the leakage amount KHe and the battery internal pressure P. Therefore, the gas permeation rate A2 related to the airtightness of the case can be accurately calculated, and the calculation accuracy of the battery internal pressure P can be improved.

[0058] In the present embodiment, the cumulative damage amount ΣDp is calculated based on the battery internal pressure P, and when the cumulative damage amount ΣDp exceeds the threshold value S, the MIL 260 is lit. Since the cumulative damage ΣDp is calculated based on the accurately calculated battery internal pressure P, the deterioration over time of the members constituting the single battery 110 can be appropriately estimated, and an alarm can be preferably given.

[0059] In the above embodiment, the battery ECU 300 performed the battery internal pressure calculation process (Figure 2), and the control ECU 500 performed the damage estimation process (Figure 6). However, these processes may be performed by either the battery ECU 300 or the control ECU 500, or they may be performed collaboratively by the battery ECU 300 and the control ECU 500.

[0060] In the above embodiment, when calculating the gas permeation rate A2 using equation (3), the correction coefficient kj was determined from Figure 4(B). The gas permeation rate A2 may also be calculated without using the correction coefficient kj (for example, the gas permeation rate A2 may be calculated by setting the correction coefficient kj = 1).

[0061] (modified version) During the charging and discharging of the single cell 110, some of the gas generated is absorbed by the electrolyte. Depending on the characteristics (type) of the single cell 110, the amount of gas absorbed by the electrolyte may not be negligible. In the modified example, the amount of gas absorbed by the electrolyte is also taken into account when calculating the internal pressure P of the battery.

[0062] Figure 7 shows the calculation map for the gas absorption rate A4. The gas absorption rate A4 [cc / time] is the absorption rate of gas absorbed into the electrolyte of the single cell 110. The gas absorption rate A4 has been mapped in advance through experiments, etc., with temperature TB and SOC as parameters. For example, after the process in S13 (see Figure 2), the gas absorption rate A4 can be determined from temperature TB and SOC using this gas absorption rate A4 calculation map, and the gas absorption amount Vga can be calculated using the following equation (10). Vga n =A4×dt+Vga n-1 ...(10) Vga n This is the gas absorption amount Vga (this value) calculated this time, and Vga n-1 Vga is the gas absorption amount Vga (previous value) calculated last time. dt is the elapsed time from the previous calculation to the current one, and corresponds to the calculation period in the flowchart in Figure 2.

[0063] In the modified example, in S14, the amount of internal gas Vg is calculated using the following equation (11). Vg=Vgo n -Vgp n -Vga n ...(11) In the modified example, the gas generation amount Vgo calculated this time... n Therefore, the gas permeation amount Vgp calculated this time n And the gas absorption amount Vga calculated this time n Subtracting this, we obtain the amount of internal gas Vg. Then, in S17, we calculate the internal pressure P of the battery using equation (9).

[0064] According to this modified method, the amount of gas absorbed into the electrolyte is also taken into account when calculating the internal battery pressure P, thus improving the accuracy of the calculation of the internal battery pressure P.

[0065] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0066] 1 Electric vehicle, 10 Motor generator (MG), 20 Drive transmission gear, 30 Drive wheel, 40 PCU, 50 SMR, 60 Inlet, 70 Charging circuit, 100 Battery, 110 Single cell, 111a, 111b Case, 112a, 112b Electrode body, 200 Monitoring unit, 210 Voltage sensor, 220 Current sensor, 230 Temperature sensor, 300 Battery ECU, 301 CPU, 302 Memory, 400 EVSE, 420 Connector, 500 Control ECU, 501 CPU, 502 Memory, B Battery system.

Claims

1. A battery containing electrodes and electrolyte inside a case, A battery system comprising a control device, The control device is The amount of gas generated within the case is used to calculate the amount of gas permeation corresponding to the amount of gas that leaks out of the case, thereby determining the amount of gas inside the battery, i.e., the amount of gas inside the battery. The internal void volume, which is the void volume inside the battery, is calculated by adding the amount of electrolyte permeation corresponding to the amount of electrolyte that leaked out of the case to the initial void volume inside the case. A battery system that calculates the internal pressure of the battery, which is the pressure inside the case, based on the amount of internal gas and the volume of internal voids.

2. The battery system according to claim 1, wherein the control device calculates the amount of internal gas by subtracting the amount of gas absorbed by the electrolyte and the amount of gas permeated from the amount of gas generated.

3. The battery system according to claim 1, wherein the control device calculates the amount of gas permeation based on the internal pressure of the battery.

4. The battery system according to claim 3, wherein the control device calculates a gas permeation rate, which is the amount of gas that leaks out of the case per unit time, based on an index value representing the airtightness of the battery and the internal pressure of the battery, and calculates the amount of gas permeation based on the gas permeation rate.

5. The battery system according to any one of claims 1 to 4, wherein the control device calculates the amount of electrolyte permeation based on the temperature of the battery.

6. The control device is Based on the internal pressure of the battery, the cumulative amount of damage corresponding to an indicator of the deterioration of the components constituting the battery over time is calculated. The battery system according to any one of claims 1 to 4, wherein an alarm is issued when the cumulative amount of damage exceeds a threshold.

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