Battery system and electric vehicle

Abstract

To enable estimation of the degree of deterioration using frequency data and restraint of overflow of a memory area of a control device for estimating the degree of deterioration of a battery when the control device is replaced.SOLUTION: A battery ECU updates frequency data (Fig. 3(B)) for an area including battery temperature TB and SOC as parameters, and estimates the degree of deterioration (amount of deterioration) from the frequency data and a deterioration coefficient (Fig. 3(A)) which increases as the temperature TB increases. The degree of deterioration is stored in a control ECU. When the battery ECU is replaced, the battery ECU obtains the degree of deterioration from the control ECU, and creates new frequency data (Fig. 3(C)) based on the degree of deterioration. The new frequency data is created as frequency data F for an area where the temperature TB is high and the SOC is large, and the other areas are set to null (NULL).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a battery system and an electric vehicle.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2023-109010 (Patent Document 1) discloses a technique for restoring the deterioration amount of a battery when a battery ECU that calculates the integrated damage amount of a battery mounted on a vehicle is replaced. In this Patent Document 1, it is said that the deterioration amount of the battery can be appropriately restored without being affected by the communication time of the information received from the EFI ECU.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The higher the battery temperature, the more the battery deteriorates. Therefore, in some cases, the Arrhenius law is used to estimate the degree of battery deterioration (damage amount, deterioration amount) using the frequency distribution (history) of the battery temperature. In this case, the higher the frequency of the high-temperature state, the greater the degree of battery deterioration (the deterioration of the battery is promoted).

[0005] The frequency distribution of the battery temperature is the history of the battery temperature during the use period of the battery. Hereinafter, the data of this history is also referred to as frequency data. As the use period of the battery becomes longer, the amount of this data increases.

[0006] When a control device (battery ECU in Patent Document 1) for estimating the degree of deterioration is replaced, there is no frequency data in the memory of the control device after replacement. In order to estimate the degree of deterioration with the control device after replacement, it is conceivable to write (read) the frequency data stored in the memory of another control device (EFI ECU in Patent Document 1) into the memory of the control device after replacement. However, after that (after replacement of the control device), when the usage period of the battery becomes long, there is a concern that the memory area of the frequency data will overflow.

[0007] An object of the present disclosure is to enable estimation of the degree of deterioration using frequency data and to suppress overflow of the memory area of the control device when a control device for estimating the degree of deterioration of a battery is replaced.

Means for Solving the Problems

[0008] The battery system of the present disclosure is a battery system including a battery, a temperature sensor that detects the battery temperature which is the temperature of the battery, a first control device that estimates the degree of deterioration of the battery, and a second control device that can communicate with the first control device. The first control device is configured to estimate the degree of deterioration using the frequency data of the battery temperature and a deterioration coefficient set such that the higher the battery temperature, the faster the deterioration rate. The second control device is configured to store the degree of deterioration estimated by the first control device in the memory. When the first control device is replaced, the first control device after replacement acquires the degree of deterioration from the second control device. The first control device after replacement creates new frequency data such that the frequency data in the region where the deterioration rate is equal to or higher than a predetermined value becomes the degree of deterioration acquired from the second control device, and is configured to estimate the degree of deterioration using the new frequency data and the deterioration coefficient.

[0009] According to this configuration, the first control device estimates the degree of deterioration using the frequency data of the battery temperature and the deterioration coefficient set such that the higher the battery temperature, the faster the deterioration rate. The degree of deterioration estimated by the first control device is stored in the memory of the second control device.

[0010] When the first control device is replaced, the replaced first control device does not have frequency data regarding the battery. Therefore, the degree of deterioration of the battery cannot be estimated using the frequency data.

[0011] According to this configuration, when the first control device is replaced, the replaced first control device acquires the degree of deterioration from the second control device, and creates new frequency data such that the frequency data in the region where the deterioration rate is equal to or higher than a predetermined value becomes the degree of deterioration acquired from the second control device. Then, the replaced first control device estimates the degree of deterioration using the new frequency data and the deterioration coefficient. Therefore, the replaced first control device can estimate the degree of deterioration of the battery using the new frequency data and the deterioration coefficient.

[0012] The new frequency data is created such that the frequency data in the region where the deterioration rate is equal to or higher than a predetermined value becomes the degree of deterioration acquired from the second control device. Since the deterioration rate is set to increase as the battery temperature becomes higher, the region where the new frequency data is created is, for example, a high temperature region of a predetermined temperature or higher. Generally, the battery is used less frequently on the lower temperature side and the higher temperature side than in the normal use temperature region. For this reason, since the usage frequency in the high temperature region where the new frequency data is created is low, it is possible to suppress the memory area from overflowing in the replaced first control device. Further, the deterioration coefficient is set such that the deterioration rate increases as the battery temperature becomes higher. For this reason, in the low temperature region of the battery temperature (the region where the deterioration rate is slow), rather than creating frequency data such that it becomes the degree of deterioration acquired from the second control device, in the high temperature region (the region where the deterioration rate is equal to or higher than a predetermined value), creating frequency data such that it becomes the degree of deterioration acquired from the second control device results in a smaller data amount. Therefore, it is possible to suppress the memory area from overflowing in the replaced first control device.

[0013] Preferably, the frequency data may be the history of the battery temperature and the SOC (State Of Charge) of the battery.

[0014] The deterioration rate of the battery varies depending on the SOC. For example, deterioration is likely to be promoted in the high SOC region. According to this configuration, the frequency data is the history of the battery temperature and the SOC of the battery, and since the degree of deterioration is estimated in consideration of the SOC, the estimation accuracy of the degree of deterioration can be improved.

[0015] Preferably, the second control device may be configured to store the degree of deterioration in a memory when the battery system stops, and the first control device may be configured to store the frequency data in the non-volatile memory of the first control device when the system stops.

[0016] According to this configuration, when the battery system stops, the second control device stores the degree of deterioration in a memory. Since the replacement of the first control device is performed after the system stops, the degree of deterioration can surely be read from the second control device when the first control device is replaced. Further, since the frequency data is stored in the non-volatile memory of the first control device when the system stops, it is possible to suppress the frequency data from being erased even when the power of the first control device is lost.

[0017] Preferably, the degree of deterioration may be the amount of capacity reduction of the battery.

[0018] According to this configuration, using the amount of capacity reduction, the current fully charged capacity can be easily estimated, and for example, overcharging of the battery can be suppressed.

[0019] The electric vehicle of the present disclosure is an electric vehicle equipped with the above battery system.

[0020] According to this configuration, even after the first control device is replaced, the degree of deterioration of the battery mounted on the vehicle can be estimated.

Advantages of the Invention

[0021] According to the present disclosure, when the control device for estimating the degree of deterioration of the battery is replaced, the degree of deterioration can be estimated using the frequency data, and it is possible to suppress the memory area of the control device from overflowing.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0023] 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.

[0024] FIG. 1 is an overall configuration diagram of an electric vehicle 1 equipped with a battery system S according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, an electric vehicle. The electric vehicle 1 may be a hybrid vehicle equipped with an internal combustion engine and a battery. The electric vehicle 1 includes a motor generator (MG) 10 that 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 which is an example of a first control device, and a control ECU 500 which is an example of a second control device.

[0025] MG10 is, for example, an embedded 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 speed reducer, a differential device, and the like.

[0026] During braking of the electric vehicle 1, MG10 is driven by the drive wheels 30, and MG10 operates as a generator. Thereby, MG10 also functions as a braking device that performs regenerative braking to convert the kinetic energy of the electric vehicle 1 into electric power. The regenerative electric power generated by the regenerative braking force in MG10 is stored in the battery 100.

[0027] The PCU 40 is a power conversion device that converts power bidirectionally between MG10 and the battery 100. The PCU 40 includes, for example, an inverter and a converter that operate based on a control signal from the control ECU 500.

[0028] The SMR 50 is electrically connected to a power line connecting the battery 100 and the PCU 40. When the SMR 50 is closed (ON) in response to a control signal from the control ECU 500, power can be exchanged between the battery 100 and the PCU 40. On the other hand, when the SMR 50 is opened (OFF) in response to a control signal from the control ECU 500, the electrical connection between the battery 100 and the PCU 40 is interrupted.

[0029] The battery 100 stores electric power for driving MG10. The battery 100 is a rechargeable DC power source (secondary battery), and is a battery pack in which a plurality of single cells (battery cells) 100a are electrically connected in series. The single cell 100a may be composed of, for example, a lithium ion battery. The battery 100 corresponds to the "battery" of the present disclosure. The electric vehicle 1 is provided with an inlet (not shown), and external charging of the battery 100 is enabled by connecting a plug (charging cable) of a charging facility to the inlet.

[0030] 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 battery 100. The current sensor 220 detects the current IB input to and output from the battery 100. The temperature sensor 230 detects the temperature TB of the battery 100. The temperature TB corresponds to the "battery temperature" of the present disclosure. Each sensor outputs its detection result to the battery ECU 300.

[0031] The battery ECU 300 includes a CPU (Central Processing Unit) 301 and a memory 302. The memory 302 includes a RAM (e.g., SRAM (Static Random Access Memory)) and a non-volatile memory (e.g., EEROM (Electrically Erasable Programmable Read-Only Memory)). When the power supply to the RAM stops (when the power of the battery ECU 300 is lost), the stored data disappears. The non-volatile memory does not lose the stored data even when the power supply stops (even when the power of the battery ECU 300 is lost). The battery ECU 300 estimates the SOC of the battery 100 using the signal received from the monitoring unit 200 and outputs it to the control ECU 500. Further, the battery ECU 300 estimates the degree of deterioration of the battery 100 and outputs it to the control ECU 500. The battery ECU 300 and the control ECU 500 may be connected, for example, by a CAN (Controller Area Network). In the present embodiment, the battery system S is composed of the battery 100, the monitoring unit 200, the battery ECU 300, the control ECU 500, etc.

[0032] The control ECU 500 includes a CPU 501 and a memory 502. The memory 502 includes a RAM and a non-volatile memory, similar to the memory 302. The control ECU 500 controls each device so that the electric vehicle 1 is in a desired state based on the signal 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.

[0033] Figure 2 is a flowchart showing an example of battery degradation estimation processing executed in the battery ECU 300. This flowchart is executed when the power switch (ignition switch) 250 is turned ON and the battery system S is in the ON state. When the power switch 250 is turned ON and the battery system S is in the ON state, at step (hereinafter, step is abbreviated as "S") 10, the temperature TB and SOC of the battery 100 are acquired. The temperature TB may be a detection signal of the temperature sensor 230. The SOC may be calculated and acquired from the SOC-OCV (Open Circuit Voltage) of the battery 100 using the voltage VB detected by the voltage sensor 210.

[0034] In S11, the frequency data is updated based on the temperature TB and SOC acquired in S10. Figure 3 is a diagram for explaining the degradation coefficient and frequency data in the present embodiment. Figure 3(A) is a diagram for explaining the degradation coefficient described later, and Figure 3(B) is a diagram for explaining the frequency data updated in S11. In Figure 3(B), the vertical axis is the temperature TB [°C], and the horizontal axis is the SOC [%]. In the present embodiment, the frequency data is the cumulative time of the time when the battery 100 exists in each region in a two-dimensional map with the temperature TB and SOC as parameters. For example, the temperature TB may be in the range of -40°C to +60°C, and the SOC may be in the range of 1% to 100%. Also, in each region, the interval of the temperature TB may be 1°C, or 2°C, or 5°C, and the interval of the SOC may be 1%, or 2%, or 5%. Also, the cumulative time may be, for example, in units of 1 minute. In S11, the time in the region corresponding to the temperature TB and SOC acquired in S10 is integrated (accumulated), and the frequency data is updated. The frequency data is stored in the SRAM of the memory 302 and is updated at any time when S11 is processed.

[0035] In the subsequent S12, the amount of deterioration ΔQ of the battery 100 is calculated. The amount of deterioration ΔQ is the amount of deterioration of the capacity [Ah] of the battery 100 (capacity deterioration amount), and corresponds to an example of the "degree of deterioration" in the present disclosure. The amount of deterioration ΔQ is calculated based on the frequency data updated in S11 and the deterioration coefficient. FIG. 3(A) is a diagram for explaining the deterioration coefficient, where the vertical axis is the temperature TB and the horizontal axis is the SOC. In the present embodiment, the deterioration coefficient is the capacity deterioration rate [% / Hr]. Since the higher the temperature TB and the higher (larger) the SOC, the more the deterioration of the battery 100 is promoted, the deterioration coefficient is set such that the higher the temperature TB and the higher the SOC, the faster the capacity deterioration rate. In S12, the frequency data (cumulative time) in each region is multiplied by the deterioration coefficient (capacity deterioration rate) to obtain the capacity deterioration amount in each region, and the sum thereof is calculated as the amount of deterioration ΔQ. Note that it is known that the capacity deterioration of the battery 100 (battery) follows the square root rule (capacity deterioration is proportional to the square root of time or the number of cycles), and the deteriorated capacity in each region may be obtained using the square root rule from the frequency data (cumulative time) and the deterioration coefficient.

[0036] In S13, it is determined whether the battery system S has changed from ON to OFF. When the power switch 250 is operated from ON to OFF, it is determined that the battery system S has changed from ON to OFF, and the process proceeds to S14. If there is no operation of the power switch 250, a negative determination is made and the process returns to S10, and the processes from S10 to S13 are repeatedly executed. The processes from S10 to S13 may be performed at predetermined intervals.

[0037] In S14, after writing the frequency data updated in S11 into the non-volatile memory of the memory 302, the process proceeds to S15. Note that the frequency data stored in the non-volatile memory of the memory 302 is used for the return of the frequency data, for example, when the power line is removed from the output terminal of the auxiliary battery that is the power source of the battery ECU 300 during the maintenance of the electric vehicle 1 or the like, and the frequency data stored in the SRAM of the memory 302 is lost.

[0038] In S15, after writing the amount of deterioration ΔQ calculated in S12 to the non-volatile memory of the memory 502 of the control ECU 500, this routine is terminated.

[0039] The battery ECU 300 may be replaced. In the memory 302 (SRAM and non-volatile memory) of the replaced battery ECU 300 (new battery ECU 300), there is no frequency data (the area where the frequency data of the SRAM and non-volatile memory is stored is null). Note that the deterioration coefficient is stored in advance in the memory 302 according to the specifications of the battery 100. Therefore, in the battery ECU 300 after replacement, the degree of deterioration (amount of deterioration ΔQ) cannot be estimated using the frequency data.

[0040] In the present embodiment, when the battery ECU 300 is replaced, new frequency data is created using the degree of deterioration ΔQ stored in the control ECU 500, so that the amount of deterioration ΔQ can be calculated. FIG. 4 is a flowchart showing an example of the process at the time of battery ECU replacement executed by the battery ECU 300 after replacement. This flowchart is executed when the battery ECU 300 is replaced. For example, the integrated mileage of the electric vehicle 1 stored in the non-volatile memory of the memory 302 of the battery ECU 300 is compared with the integrated mileage stored in the non-volatile memory of the control ECU 500. When the respective integrated mileages are different, it may be determined that the battery ECU 300 has been replaced, and this flowchart may be executed. The detection of the replacement of the battery ECU 300 may be in any form.

[0041] When the battery ECU 300 is replaced, the new battery ECU 300 acquires the amount of deterioration ΔQ stored in the non-volatile memory of the memory 502 of the control ECU 500 in S20. For example, at the request of the battery ECU 300, the amount of deterioration ΔQ may be transmitted from the control ECU 500 to the battery ECU 300.

[0042] In subsequent S21, frequency data is created based on the acquired deterioration amount ΔQ, and this routine ends. In the present embodiment, the frequency data is created such that the frequency data in the region where the deterioration coefficient (capacity deterioration rate) is the largest becomes the deterioration amount ΔQ acquired from the control ECU500. For example, when the temperature TB is the highest and the frequency data F in the region where the SOC is the largest (the region where the deterioration coefficient is the largest) is calculated as F = ΔQ / S, where S is the deterioration coefficient of the region. Then, as shown in Fig. 3(C), the frequency data of the region is set to F, the frequency data of other regions is maintained as NULL, and new frequency data is created. The new frequency data is stored in the SRAM of the memory 302. (At this time, the new frequency data may also be stored in the non-volatile memory of the memory 302.) Thereafter, the new frequency data is updated in S11 of the battery deterioration estimation process (Fig. 2).

[0043] According to the present embodiment, the battery ECU300 estimates the deterioration amount ΔQ using the frequency data of the temperature TB and the SOC and the deterioration coefficient set such that the higher the temperature TB, the faster the deterioration rate (capacity deterioration rate). The control ECU500 stores the deterioration amount ΔQ estimated by the battery ECU300 in the memory 502. When the battery ECU300 is replaced, the battery ECU300 after replacement acquires the deterioration amount ΔQ from the control ECU500. The battery ECU300 after replacement creates new frequency data such that the frequency data in the region where the temperature TB is the highest and the SOC is the largest (the region where the deterioration coefficient is the largest) becomes the deterioration amount ΔQ acquired from the control ECU500. Then, the battery ECU300 after replacement estimates the deterioration amount ΔQ using the new frequency data and the deterioration coefficient.

[0044] Fig. 5 is a diagram showing the relationship between the temperature TB and the frequency (cumulative time). In Fig. 5, the vertical axis represents the frequency (cumulative time), and the horizontal axis represents the temperature TB. As shown in Fig. 5, the battery 100 is generally used less frequently on the lower temperature side and the higher temperature side than the normal use temperature range.

[0045] In the present embodiment, new frequency data is created such that the frequency data in the region where the temperature TB is high and the deterioration coefficient is the largest (the region where the capacity deterioration rate is the largest) becomes the deterioration amount ΔQ. When the deterioration coefficient of this region is S, the frequency data F of this region is F = ΔQ / S, and the frequency data of other regions maintains NULL. Since the larger the deterioration coefficient, the smaller the frequency data F, the data volume becomes smaller than creating frequency data from the deterioration amount ΔQ in a region where the deterioration coefficient is small (the region where the capacity deterioration rate is slow). Also, after that (after replacing the battery ECU 300), the temperature TB becomes high, and the frequency existing in the region where the deterioration coefficient is the largest is small. Thereby, it is possible to suppress the frequency data from overflowing after replacing the battery ECU 300.

[0046] In the above embodiment, in S21 (FIG. 4), the frequency data F in the region where the temperature TB is the highest and the SOC is the largest (the region where the deterioration coefficient is the largest) was calculated based on the deterioration amount ΔQ, and new frequency data was created. However, the frequency data created based on the deterioration amount ΔQ does not necessarily have to be in the region where the temperature TB is the highest and the SOC is the largest (the region where the deterioration coefficient is the largest). For example, in the region where the temperature TB is the second highest and the SOC is the second largest, the frequency data f calculated based on the deterioration amount ΔQ is calculated, and as shown in FIG. 3(C), the frequency data of this region is set to f, and the frequency data of other regions is maintained as NULL.

[0047] Also, the frequency data f1 and f2 are calculated such that the value obtained by adding the deterioration amount calculated from the frequency data f1 in the region where the temperature TB is the highest and the SOC is the second largest and the deterioration amount calculated from the frequency data f2 in the region where the temperature TB is the second highest and the SOC is the largest becomes the deterioration amount ΔQ. As shown in FIG. 3(C), the frequency data of this region is set to f1 and f2, and the frequency data of other regions is maintained as NULL. In the present disclosure, the "region where the deterioration rate is equal to or higher than a predetermined value" may be, for example, any one of the upper 10% regions where the capacity deterioration rate is fast (the deterioration coefficient is large).

[0048] In the above embodiment, the frequency data is the cumulative time of the time when the battery 100 existed in each region in the two-dimensional map using the temperature TB and the SOC as parameters. However, the frequency data may be the cumulative time using only the temperature TB as a parameter. Further, the frequency data does not have to be the cumulative time as long as it is a history corresponding to the time when the battery 100 existed in the region.

[0049] In the above embodiment, in S12 (FIG. 2), using the root law, the capacity degradation amount of each region is obtained from the frequency data (cumulative time) and the degradation coefficient (capacity degradation rate) in each region, and the sum thereof is calculated as the degradation amount ΔQ. When the degradation amount Δq due to the charge / discharge current is also calculated using the history data of the charge / discharge current of the battery 100, the added value (ΔQ + Δq) obtained by adding the degradation amount Δq to the degradation amount ΔQ may be stored in the control ECU500 in S15. In this case, in S21 (FIG. 4), the frequency data F may be calculated based on the added value (ΔQ + Δq) to create new frequency data.

[0050] When the root law is used to obtain the degradation degree (degradation amount ΔQ) of the battery 100, the capacity degradation rate decreases as the usage time of the battery 100 elapses. According to the present embodiment, the control ECU500 acquires the degradation amount ΔQ and creates new frequency data from the degradation degree ΔQ. For this reason, since the new frequency data is created as data in which the usage time of the battery 100 (the usage time from when it was new to the present) is considered, the degradation degree (degradation amount ΔQ) can be accurately estimated even after the battery ECU300 is replaced.

[0051] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the description of the above embodiments but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Signs

[0052] 1 Electric vehicle, 10 Motor generator (MG), 20 Drive transmission gear, 30 Drive wheels, 40 PCU, 50 SMR, 100 Battery, 100a Single battery, 200 Monitoring unit, 210 Voltage sensor, 220 Current sensor, 230 Temperature sensor, 300 Battery ECU, 301 CPU, 302 Memory, 500 Control ECU, 501 CPU, 502 Memory, S Battery system.

Claims

1. A battery system comprising a battery, a temperature sensor that detects the battery temperature which is the temperature of the battery, a first control device that estimates the degree of deterioration of the battery, and a second control device that can communicate with the first control device, wherein the first control device is configured to estimate the degree of deterioration using the frequency data of the battery temperature and a deterioration coefficient set such that the higher the battery temperature, the faster the deterioration rate, the second control device is configured to store the degree of deterioration estimated by the first control device in a memory, when the first control device is replaced, the first control device after replacement, acquires the degree of deterioration from the second control device, creates new frequency data such that the frequency data in a region where the deterioration rate is equal to or higher than a predetermined value becomes the degree of deterioration acquired from the second control device, and is configured to estimate the degree of deterioration using the new frequency data and the deterioration coefficient. A battery system.

2. The battery system according to claim 1, wherein the frequency data is a history of the battery temperature and the state of charge (SOC) of the battery.

3. The second control device stores the degree of deterioration in the memory when the battery system stops, The battery system according to claim 1 or claim 2, wherein the first control device is configured to store the frequency data in a non-volatile memory of the first control device when the system stops.

4. The battery system according to claim 1 or claim 2, wherein the degree of deterioration is the amount of decrease in the capacity of the battery.

5. An electric vehicle equipped with the battery system according to claim 3.

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