Battery system

Abstract

Improve the accuracy of calculating the internal pressure of the battery. [Solution] The battery ECU obtains the internal void volume Vc0, which is the volume in which gas can be retained within the case of a single cell (S11), calculates the amount of gas generated in the case Vgo (S12), and calculates the gas pressure Pg inside the case from the amount of gas generated Vgo and the internal void volume Vco (S13). The electrolyte vapor pressure Pe is calculated from the battery temperature (S14), and the internal battery pressure P, which is the pressure inside the case, is calculated by adding the electrolyte vapor pressure Pe to the gas pressure Pg (S15).

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 Initiative] [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] Patent Document 1 does not take into account the vapor pressure of the electrolyte when calculating the internal pressure of the battery. Therefore, there is a concern that the accuracy of the calculation of 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 this disclosure comprises a battery containing electrodes and an electrolyte in a case, and a control device. The control device calculates the internal battery pressure P, which is the pressure inside the case, based on the amount of gas generated in the case Vgo, the internal void volume Vc0, which is the volume in the case where gas can be retained, and the electrolyte vapor pressure Pe, which is the vapor pressure of the electrolyte.

[0008] This configuration allows for the calculation of the battery internal pressure P by considering the electrolyte vapor pressure Pe, thereby improving the accuracy of the battery internal pressure P calculation.

[0009] Preferably, the control device may calculate the electrolyte vapor pressure Pe based on the battery temperature TB.

[0010] With this configuration, the electrolyte vapor pressure Pe is calculated from the battery temperature TB, making it easy to determine the electrolyte vapor pressure Pe.

[0011] Preferably, the control device may calculate the gas pressure Pg inside the case based on the amount of gas generated Vgo and the internal void volume Vc0, and then calculate the internal battery pressure P by adding the electrolyte vapor pressure Pe to the gas pressure Pg.

[0012] With this configuration, the internal battery pressure P can be calculated accurately by adding the electrolyte vapor pressure Pe to the gas pressure P inside the case.

[0013] Preferably, the control device calculates a cumulative damage amount ΣDp, which corresponds to an indicator of the deterioration of the components constituting the battery over time, based on the internal pressure P of the battery, and may issue an alarm when the cumulative damage amount ΣDp exceeds a threshold.

[0014] With this configuration, the cumulative damage ΣDp is calculated based on the accurately calculated internal battery pressure P, allowing for a proper estimation of the degradation of the battery components over time and enabling effective alarms. [Effects of the Invention]

[0015] According to this disclosure, the accuracy of calculating the internal pressure P of the battery can be improved. [Brief explanation of the drawing]

[0016] [Figure 1] This is an overall configuration diagram of an electric vehicle equipped with the battery system according to this embodiment. [Figure 2]It is a flowchart showing an example of battery internal pressure calculation processing executed in a battery ECU. [Figure 3] (A) and (B) are diagrams for explaining a method of calculating the gas generation rate A1. [Figure 4] It is a diagram showing the relationship between the electrolyte vapor pressure Pe and the temperature TB. [Figure 5] It is a flowchart showing an example of damage estimation processing executed in a control ECU.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0018] FIG. 1 is an overall configuration diagram of an electric vehicle 1 equipped with a battery system B according to the present embodiment. In the present embodiment, the electric vehicle 1 is, for example, an electric vehicle. The electric vehicle 1 may be a plug-in hybrid vehicle equipped with an internal combustion engine and a battery. The electric vehicle 1 includes a motor generator (MG) 10 that is a rotary 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 an example of the "control device" of the present disclosure.

[0019] MG10 is, for example, an embedded structure permanent magnet synchronous motor (IPM motor), and has functions as a motor and as a generator. The output torque of MG10 is transmitted to the drive wheels 30 via a power transmission gear 20 configured to include a reduction gear and a differential device.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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).

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In S11, the internal void volume Vc0 is obtained. The internal void volume Vc0 is the volume in the case of the single cell 110 in which gas can be retained. The internal void volume Vc0 is the volume obtained by subtracting the volume of the electrode body and the electrolyte volume Ve0 from the volume inside the case of the single cell 110. The electrolyte volume Ve0 is the amount of electrolyte injected into the case of the single cell 110 during the electrolyte injection process.

[0032] 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 internal void volume Vc0 may be read from this two-dimensional code and stored in memory 302. In this case, in S11, the internal void volume Vc0 is 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 internal void volume Vc0 may be obtained from the server through communication between the electric vehicle 1 (battery ECU 300) and the server.

[0033] In step S12, the amount of gas generated, Vgo, is calculated. During the charging and discharging of the single cell 110, gas is generated due to the decomposition reaction of the electrolyte, etc. In step 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 (ln(gas generation rate A1)) of the gas generation rate A1 [cc / √time] in a single cell 110 and the reciprocal of the temperature TB (1000 / TB in this embodiment). Figure 3(A) is known as the Arrhenius plot (Anireus equation) and can be obtained through experiments and simulations using a single cell 110. As shown in Figure 3(A), the gas generation rate A1 can be approximated by a straight line that increases as the temperature TB increases (as the reciprocal of temperature TB decreases) and as the SOC increases for each SOC. For example, the gas generation rate A1 can be calculated from the relationship in Figure 3(A) using the following equation (1).

[0034] 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.

[0035] 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.

[0036] 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 n This is the gas generation amount Vgo (current value) calculated this time, and Vgon-1 is the gas generation amount Vgo (previous value) calculated last time. dt is the elapsed time from the previous time to the current time, and corresponds to the calculation period of the flowchart in FIG. 2. When the gas generation amount Vgo is calculated in S12, the current value is set as the previous value (Vgo n-1 ), stored in the non-volatile memory of the memory 302, and proceeds to S13. The initial value of Vgo n-1 may be "0", or a predetermined value may be set.

[0037] In S*13*, the gas pressure Pg is calculated. The gas pressure Pg is the pressure of the gas generated in the single cell 110 (case). The gas pressure Pg is calculated using the following formula (3).

[0038] Pg = Vgo / Vc0 ···· (3) Vgo is the gas generation amount Vgo (current value Vgo n ) calculated in S12, and currently corresponds to the amount of gas present inside the case. Vc0 is the internal void volume Vc0 obtained in S11.

[0039] In the subsequent S14, the electrolyte vapor pressure Pe is calculated. FIG. 4 is a diagram showing the relationship between the electrolyte vapor pressure Pe and the temperature TB. As shown in FIG. 4, the electrolyte vapor pressure Pe is proportional to the exponential function of the temperature TB. The electrolyte vapor pressure Pe is calculated using the following formula (4). [[ID=2,2]]

[0040] Pe = k3 × exp(k4 × TB) ···· (4) k3 and k4 are constants. k3 and k4 are obtained by experiments or the like using the electrolyte enclosed in the single cell 110, and are set based on the graph in FIG. 4.

[0041] In S15, the battery internal pressure P is calculated. The battery internal pressure P is calculated using the following formula (5).

[0042] P = Pg + Pe ···· (5) Pg is the gas pressure Pg calculated in S13, and Pe is the electrolyte vapor pressure Pe calculated in S14. The battery internal pressure P is the value obtained by adding the electrolyte vapor pressure Pe to the gas pressure Pg. When S15 is processed, this routine ends.

[0043] Figure 5 is a flowchart showing an example of damage estimation processing executed by the control ECU 500. This flowchart is executed for each unit cell 110 at regular intervals when the power switch 250 is turned ON and the battery system B is in the ON state, and when the battery 100 is externally charged by the EVSE 400. In S20, the damage amount Dp of the unit cell 110 is calculated. The calculation of the damage amount Dp is substantially the same as the calculation method described in Patent Document 1. The damage amount Dp is calculated from the temperature TB and the battery internal pressure P calculated in the battery internal pressure calculation process of FIG. 2. In the present embodiment, the damage amount Dp is a factor that affects the creep fracture of the members (constituent members) constituting the unit cell 110, and for example, the current interruption mechanism is targeted as a component.

[0044] The damage amount Dp is stored in the memory 502 as a map with the temperature TB and the battery internal pressure P as parameters. For example, the larger the temperature TB and the larger the battery internal pressure P, the larger the value is set. In S20, the damage amount Dp is calculated from the temperature TB and the battery internal pressure P.

[0045] 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).

[0046] In S22, it is determined whether or not 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), this routine ends.

[0047] In S23, the MIL (Malfunction Indicator Lamp) 260 is illuminated, an alarm is triggered, and the routine ends.

[0048] According to this embodiment, the internal battery pressure P, which is the pressure inside the case, is calculated based on the amount of gas generated Vgo inside the case of the single cell 110, the internal void volume Vc0 which is the volume in which gas can be retained inside the case, and the electrolyte vapor pressure Pe, which is the vapor pressure of the electrolyte. Since the internal battery pressure P is calculated taking into account the electrolyte vapor pressure Pe, the accuracy of calculating the internal battery pressure P can be improved.

[0049] According to this embodiment, the electrolyte vapor pressure Pe is calculated from the battery temperature TB based on the relationship shown in Figure 4, making it easy to determine the electrolyte vapor pressure Pe.

[0050] According to this embodiment, the gas pressure Pg inside the case is calculated based on the gas generation amount Vgo and the internal void volume Vc0, and the internal battery pressure P is determined by adding the electrolyte vapor pressure Pe to the gas pressure Pg. Since the electrolyte vapor pressure Pe is added to the gas pressure P inside the case, the internal battery pressure P can be calculated with high accuracy.

[0051] In this embodiment, the cumulative damage amount ΣDp is calculated based on the internal battery pressure P, and the MIL260 is illuminated when the cumulative damage amount ΣDp exceeds the threshold S. Since the cumulative damage ΣDp is calculated based on the internal battery pressure P which is calculated with high accuracy, the deterioration of the components constituting the single cell 110 over time can be appropriately estimated, and an alarm can be provided effectively.

[0052] 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 5). 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.

[0053] 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]

[0054] 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 A battery system that calculates the internal pressure of the battery, which is the pressure inside the case, based on the amount of gas generated inside the case, the internal void volume which is the volume in which the gas can be retained inside the case, and the electrolyte vapor pressure which is the vapor pressure of the electrolyte.

2. The battery system according to claim 1, wherein the control device calculates the electrolyte vapor pressure based on the temperature of the battery.

3. The battery system according to claim 2, wherein the control device calculates the gas pressure inside the case based on the amount of gas generated and the internal void volume, and calculates the internal pressure of the battery by adding the electrolyte vapor pressure to the gas pressure.

4. 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 3, wherein an alarm is issued when the cumulative amount of damage exceeds a threshold.

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