Battery system and electric vehicle

Abstract

The invention provides a battery system and an electric vehicle. The battery ECU updates the frequency data of a region in which the temperature TB and SOC of the battery are parameters, and estimates the degree of degradation (degradation amount) on the basis of a degradation coefficient that increases as the frequency data and the temperature TB increase. The degradation degree is stored in the control ECU. When the battery ECU is replaced, the battery ECU acquires the degradation degree from the control ECU and creates new frequency data on the basis of the degradation degree. The new frequency data is created as frequency data F for a region having a high temperature TB and a large SOC, and other regions are set to a null state (NULL).

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 discloses a technique for restoring the deterioration amount of a battery when replacing a battery ECU that calculates the cumulative damage amount of a battery mounted on a vehicle. In this Japanese Unexamined Patent Application Publication No. 2023-109010, the deterioration amount of the battery can be appropriately restored without being affected by the communication time of information received from the EFI ECU. Summary of the Invention

[0003] The higher the battery temperature, the more serious the deterioration of the battery. Therefore, there are cases where the frequency distribution (history) of the battery temperature is used and the Arrhenius law is used to estimate the degree of battery deterioration (damage amount, deterioration amount). In this case, the higher the frequency of the high-temperature state, the greater the degree of battery deterioration (promoting the deterioration of the battery).

[0004] 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 will also be referred to as frequency data. As the use period of the battery becomes longer, the amount of frequency data also increases.

[0005] When the control device for estimating the degree of deterioration (the battery ECU in Japanese Patent Application Laid-Open No. 2023-109010) is replaced, the frequency data does not exist in the memory of the replaced control device. In order to estimate the degree of deterioration in the replaced control device, it is considered to write (read in) the frequency data stored in the memory of another control device (the EFI ECU in Japanese Unexamined Patent Application Publication No. 2023-109010) into the memory of the replaced control device. However, when the use period of the battery becomes longer after that (after the control device is replaced), the storage area of the frequency data may overflow.

[0006] An object of the present disclosure is to be able to use frequency data to estimate the degree of deterioration and suppress the overflow of the memory area of the control device when the control device for estimating the degree of deterioration of the battery is replaced.

[0007] The battery system of the present disclosure is a battery system including a battery, a temperature sensor that detects the temperature of the battery, i.e., the battery temperature, 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 in such a manner 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 replaced first control device acquires the degree of deterioration from the second control device. The replaced first control device is configured to create new frequency data such that the frequency data in the region where the deterioration rate is equal to or higher than a specified value becomes the degree of deterioration acquired from the second control device, and estimate the degree of deterioration using the new frequency data and the deterioration coefficient.

[0008] According to this configuration, the first control device estimates the degree of deterioration using the frequency data of the battery temperature and a deterioration coefficient set in such a manner 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.

[0009] If the first control device is replaced, there is no frequency data related to the battery in the replaced first control device. Therefore, it is not possible to use this frequency data to estimate the degree of deterioration of the battery.

[0010] 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, 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. Moreover, 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.

[0011] New frequency data is created in such a way that the frequency data in the region where the degradation rate is equal to or higher than the specified value becomes the degradation degree obtained from the second control device. Since the degradation rate is set such that the higher the battery temperature, the faster the degradation rate, the region for creating the new frequency data is, for example, the high-temperature region above the specified temperature. Batteries are generally used less frequently on the side lower than the normal operating temperature range and on the side higher than the normal operating temperature range. Therefore, since the usage frequency in the high-temperature region where the new frequency data is created is low, in the first control device after replacement, storage area overflow can be suppressed. In addition, the degradation coefficient is set such that the higher the battery temperature, the faster the degradation rate. Therefore, compared with creating frequency data in the low-temperature region of the battery temperature (the region where the degradation rate is slow) in such a way that it becomes the degradation degree obtained from the second control device, when creating frequency data in the high-temperature region (the region where the degradation rate is equal to or higher than the specified value) in such a way that it becomes the degradation degree obtained from the second control device, the amount of data becomes smaller. Therefore, in the first control device after replacement, storage area overflow can be suppressed.

[0012] Preferably, the frequency data can be the history of the battery temperature and the SOC (State Of Charge) of the battery.

[0013] The degradation rate of the battery varies according to the SOC. For example, degradation is likely to be promoted in the high-SOC region. According to this configuration, the frequency data is set as the history of the battery temperature and the SOC of the battery, and the degradation degree is estimated considering the SOC, so the estimation accuracy of the degradation degree can be improved.

[0014] Preferably, it can also be configured such that the second control device stores the degradation degree in the memory when the battery system stops, and the first control device stores the frequency data in the non-volatile memory of the first control device when the system stops.

[0015] According to this configuration, when the battery system stops, the second control device stores the degradation degree in the memory. Since the first control device is replaced after the system stops, the degradation degree can be reliably read from the second control device when the first control device is replaced. In addition, when the system stops, the frequency data is stored in the non-volatile memory of the first control device, so even when the power supply of the first control device is lost, the frequency data can be prevented from being erased.

[0016] Preferably, the degradation degree can be the amount of reduction in the battery capacity.

[0017] According to this configuration, the current full charge capacity can be easily estimated using the amount of reduction in the capacity, and overcharging of the battery, for example, can be suppressed.

[0018] The electric vehicle of the present disclosure is an electric vehicle equipped with the above battery system.

[0019] According to this structure, even after the first control device is replaced, it is possible to estimate the degree of deterioration of the battery mounted on the vehicle.

[0020] According to the present disclosure, when replacing the control device for estimating the degree of deterioration of the battery, it is possible to estimate the degree of deterioration using frequency data and suppress the overflow of the storage area of the control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the drawings, in which the same reference numerals denote the same elements, and in which: Figure 1 is an overall structural diagram of an electric vehicle equipped with the battery system according to the present embodiment; Figure 2 is a flowchart showing an example of battery deterioration estimation processing executed in the battery ECU; Figure 3A is a diagram for explaining the deterioration coefficient and frequency data in the present embodiment; Figure 3B is a diagram for explaining the deterioration coefficient and frequency data in the present embodiment; Figure 3C is a diagram for explaining the deterioration coefficient and frequency data in the present embodiment; Figure 4 is a flowchart showing an example of processing at the time of battery ECU replacement executed by the replaced battery ECU; Figure 5 is a diagram showing the relationship between temperature TB and frequency (cumulative time). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0023] Figure 1It is an overall structure diagram of the electric vehicle 1 equipped with the battery system S according to the present embodiment. In the present embodiment, the electric vehicle 1 is, for example, a battery electric vehicle. The electric vehicle 1 may also be a hybrid electric vehicle equipped with an internal combustion engine and a battery. The electric vehicle 1 includes an electric generator (MG: Motor Generator) 10 as a rotary electric machine, a power transmission gear 20, a drive wheel 30, a power control unit (PCU: Power Control Unit) 40, a system main relay (SMR: System Main Relay) 50, a battery 100, a monitoring unit 200, a battery ECU (Electronic Control Unit) 300 as an example of a first control device, and a control ECU 500 as an example of a second control device.

[0024] The MG 10 is, for example, an embedded permanent magnet synchronous motor (IPM motor) and has a function as a motor (electric machine) and a function as a generator (Generator). The output torque of the MG 10 is transmitted to the drive wheel 30 via the power transmission gear 20 including a speed reducer and a differential device, etc.

[0025] When the electric vehicle 1 brakes, the MG 10 is driven by the drive wheel 30 and the MG 10 operates as a generator. Thus, the MG 10 also functions as a braking device that performs regenerative braking for converting the kinetic energy of the electric vehicle 1 into electric power. The regenerative electric power generated by the regenerative braking force in the MG 10 is stored in the battery 100.

[0026] The PCU 40 is a power conversion device that converts electric power bidirectionally between the MG 10 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.

[0027] The SMR 50 is electrically connected to the power line connecting the battery 100 and the PCU 40. When the SMR 50 is closed (ON) according to a control signal from the control ECU 500, power can be transmitted and received between the battery 100 and the PCU 40. On the other hand, when the SMR 50 is opened (OFF) according to a control signal from the control ECU 500, the electrical connection between the battery 100 and the PCU 40 is cut off.

[0028] The battery 100 stores electric power for driving the MG 10. The battery 100 is a rechargeable DC power source (secondary battery), and is a battery pack formed by electrically connecting a plurality of single cells (battery monomers) 100a in series. The single cell 100a can be formed 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 a socket (not shown), and external charging of the battery 100 can be performed by connecting the plug (charging cable) of a charging device to the socket.

[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 battery 100. The current sensor 220 detects the current IB input to the battery 100 and the current IB 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.

[0030] The battery ECU 300 includes a central processing unit (CPU) 301 and a memory 302. The memory 302 includes a RAM (for example, a static random access memory (Static Random Access Memory)) and a non-volatile memory (for example, an EEROM (Electrically Erasable Programmable Read-Only Memory)). The data stored in the RAM is lost when the power supply to the RAM is stopped (when the power supply of the battery ECU 300 is lost). The non-volatile memory does not lose the stored data even when the power supply is stopped (when the power supply of the battery ECU 300 is lost). The battery ECU 300 uses the signals received from the monitoring unit 200 to estimate the SOC of the battery 100 and outputs it to the control ECU 500. In addition, 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 can be connected by, for example, 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, and the like.

[0031] The control ECU 500 includes a CPU 501 and a memory 502. The memory 502, like the memory 302, includes a RAM and a non-volatile memory. The control ECU 500 controls each device based on the signals received from the battery ECU 300, signals from various sensors (not shown) (for example, an accelerator opening signal, a vehicle speed signal, etc.), and information such as maps and programs stored in the memory 502 so that the electric vehicle 1 is in a desired state.

[0032] Figure 2 It is a flowchart showing an example of the battery degradation estimation process executed by the battery ECU 300. This flowchart is executed when the power switch (ignition switch) 250 is turned ON and the battery system S becomes the ON state. When the power switch 250 becomes ON and the battery system S becomes the ON state, in step (hereinafter referred to as "S") 10, the temperature TB and SOC of the battery 100 are acquired. The temperature TB can be the detection signal of the temperature sensor 230. The SOC can be acquired by calculating from the SOC-OCV (open circuit voltage) of the battery 100 using the voltage VB detected by the voltage sensor 210.

[0033] In S11, based on the temperature TB and SOC acquired in S10, the frequency data is updated. Figure 3A , Figure 3B , Figure 3C It is a diagram for explaining the degradation coefficient and the frequency data in the present embodiment. Figure 3A It is a diagram for explaining the degradation coefficient described later, Figure 3B It is a diagram for explaining the frequency data updated in S11. In Figure 3B , the vertical axis represents the temperature TB [°C], and the horizontal axis represents 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 can be in the range of -40°C to +60°C, and the SOC can be in the range of 1% to 100%. In addition, in each region, the interval of the temperature TB can be 1°C, 2°C, or 5°C, and the interval of the SOC can be 1%, 2%, or 5%. Further, the cumulative time can be, for example, in units of 1 minute. In S11, the time of the region corresponding to the temperature TB and SOC acquired in S10 is accumulated (cumulated), and the frequency data is updated. The frequency data is stored in the SRAM of the memory 302 and is updated at any time by the process S11.

[0034] In the following S12, the degradation amount ΔQ of the battery 100 is calculated. The degradation amount ΔQ is the degradation amount (capacity degradation amount) of the capacity [Ah] of the battery 100, which is an example of the "degree of degradation" of the present disclosure. The degradation amount ΔQ is calculated based on the frequency data updated in S11 and the degradation coefficient. Figure 3AIt is a graph showing the deterioration coefficient, with the vertical axis being the temperature TB and the horizontal axis being the SOC. In the present embodiment, the deterioration coefficient is the capacity deterioration rate [% / Hr]. The higher the temperature TB and the higher the SOC, the more the deterioration of the battery 100 is promoted. Therefore, 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 (accumulated time) in each region is multiplied by the deterioration coefficient (capacity deterioration rate) to obtain the capacity deterioration amount in each region, and their sum is calculated as the deterioration amount ΔQ. In addition, it is known that the capacity deterioration of the battery 100 (battery) follows the square root law (capacity deterioration is proportional to the square root of time and the number of cycles), and the deteriorated capacity of each region can be obtained using the square root law based on the frequency data (accumulated time) and the deterioration coefficient.

[0035] In S13, it is determined whether the battery system S changes from ON to OFF. When the power switch 250 is operated from ON to OFF, it is determined that the battery system S changes from ON to OFF, and the process proceeds to S14. In the case where there is no operation of the power switch 250, a negative determination is made and the process returns to S10, and the processes of S10 to S13 are repeatedly executed. The processes of S10 to S13 can be performed at regular intervals.

[0036] 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 when the frequency data stored in the SRAM of the memory 302 disappears, etc., the frequency data stored in the non-volatile memory of the memory 302 is used to restore the frequency data. For example, when maintaining the electric vehicle 1 or the like, when the power line is removed from the output terminal of the auxiliary battery that is the power source of the battery ECU 300, the frequency data may disappear.

[0037] In S15, after writing the deterioration amount ΔQ calculated in S12 into the non-volatile memory of the memory 502 of the control ECU 500, the present routine ends.

[0038] Sometimes the battery ECU 300 is 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 regions of the SRAM and non-volatile memory for storing the frequency data are empty (NULL)). In addition, the deterioration coefficient is pre-stored in the memory 302 according to the specifications of the battery 100. Therefore, in the replaced battery ECU 300, the frequency data cannot be used to estimate the degree of deterioration (deterioration amount ΔQ).

[0039] 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, whereby the deterioration amount ΔQ can be calculated. Figure 4FIG. is a flowchart showing an example of a process at the time of replacing the battery ECU 300, which is executed when the battery ECU 300 is replaced. For example, the cumulative driving distance of the electric vehicle 1 stored in the non-volatile memory of the memory 302 of the battery ECU 300 is compared with the cumulative driving distance stored in the non-volatile memory of the control ECU 500. Then, when the cumulative driving distances are different from each other, this flowchart can be executed to determine that the battery ECU 300 has been replaced. The detection of the replacement of the battery ECU 300 can be in any manner.

[0040] When replacing the battery ECU 300, the new battery ECU 300 acquires the deterioration amount ΔQ stored in the non-volatile memory of the memory 502 of the control ECU 500 in S20. For example, according to the request of the battery ECU 300, the deterioration amount ΔQ can be sent from the control ECU 500 to the battery ECU 300.

[0041] In the next S21, frequency data is created based on the acquired deterioration amount ΔQ, and this example routine ends. In the present embodiment, the frequency data is created such that the frequency data in the region with the maximum deterioration coefficient (capacity deterioration rate) becomes the deterioration amount ΔQ acquired from the control ECU 500. For example, when the deterioration coefficient in the region where the temperature TB is the highest temperature and the SOC is the maximum (the region with the largest deterioration coefficient) is set to S, the frequency data F in this region is calculated as F = ΔQ / S. Then, as Figure 3C shown, the frequency data in this region is set to F, and the frequency data in other regions remains empty (NULL) to create new frequency data. The new frequency data is stored in the SRAM of the memory 302. (At this time, the new frequency data can also be stored in the non-volatile memory of the memory 302). Then, in step S11 of the battery deterioration estimation process ( Figure 2 ), the new frequency data is updated.

[0042] According to the present embodiment, the battery ECU 300 estimates the deterioration amount ΔQ by using the frequency data of the temperature TB, SOC, and the deterioration coefficient, where the deterioration coefficient is set such that the higher the temperature TB, the faster the deterioration rate (capacity deterioration rate). The control ECU 500 stores the deterioration amount ΔQ estimated by the battery ECU 300 in the memory 502. When the battery ECU 300 is replaced, the replaced battery ECU 300 acquires the deterioration amount ΔQ from the control ECU 500. The replaced battery ECU 300 creates new frequency data such that the frequency data in the region where the temperature TB is the highest temperature and the SOC is the maximum (the region with the largest deterioration coefficient) becomes the deterioration amount ΔQ acquired from the control ECU 500. Moreover, the replaced battery ECU 300 estimates the deterioration amount ΔQ by using the new frequency data and the deterioration coefficient.

[0043] Figure 5 is a graph showing the relationship between the temperature TB and the frequency (cumulative time). In Figure 5 , the vertical axis is the frequency (cumulative time), and the horizontal axis is the temperature TB. As Figure 5 shown, the battery 100 generally has a low usage frequency on the side lower than the normal usage temperature range and on the side higher than the normal usage temperature range.

[0044] 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 degradation coefficient is the largest (the region where the capacity degradation speed is the largest) becomes the degradation amount ΔQ. When S represents the degradation coefficient of this region, the frequency data F of this region is F = ΔQ / S, and the frequency data of other regions remains empty (NULL). The larger the degradation coefficient, the smaller the frequency data F becomes. Therefore, compared with creating frequency data based on the degradation amount ΔQ in a region with a small degradation coefficient (a region with a slow capacity degradation speed), the amount of data becomes smaller. In addition, after that (after replacing the battery ECU 300), the frequency in the region where the temperature TB becomes high and the degradation coefficient is the largest is also small. Thus, it is possible to suppress frequency data overflow after replacing the battery ECU 300.

[0045] In the above embodiment, in S21 ( Figure 4 ), the frequency data F of the region where the temperature TB is the highest temperature and the SOC is the largest (the region where the degradation coefficient is the largest) is calculated based on the degradation amount ΔQ, and new frequency data is created. However, the frequency data created based on the degradation amount ΔQ may not be in the region where the temperature TB is the highest temperature and the SOC is the largest (the region where the degradation coefficient is the largest). For example, in the region where the temperature TB is the second highest temperature from the highest temperature and the SOC is the second largest, the frequency data f is calculated based on the degradation amount ΔQ. Then, as Figure 3C shown, the frequency data of this region can be set to f, and the frequency data of other regions can be kept as zero.

[0046] In addition, the frequency data f1 and f2 are calculated such that the value obtained by adding the degradation amount calculated from the frequency data f1 of the region where the temperature TB is the highest temperature and the SOC is the second largest and the degradation amount calculated from the frequency data f2 of the region where the temperature TB is the second highest temperature from the highest temperature and the SOC is the largest becomes the degradation amount ΔQ. Then, as Figure 3C shown, the frequency data of this region can be set to f1 and f2, and the frequency data of other regions can be kept empty. In the present disclosure, the "region where the degradation speed is equal to or higher than a specified value" means, for example, any region within the top 10% of the regions with a fast capacity degradation speed (a large degradation coefficient).

[0047] In the above-described embodiment, the frequency data is the cumulative time of the time that the battery 100 exists in each region in a two-dimensional map with the temperature TB and the SOC as parameters. However, the frequency data may be the cumulative time with only the temperature TB as a parameter. In addition, as long as the frequency data is a history equivalent to the time that the battery 100 exists in this region, it may not be the cumulative time.

[0048] In the above-described embodiment, in S12( Figure 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 their sum is calculated as the degradation amount ΔQ. If the degradation amount Δq caused by the charge / discharge current is also calculated by using the history data of the charge / discharge current of the battery 100, then the added value (ΔQ + Δq) obtained by adding the degradation amount Δq and the degradation amount ΔQ can be stored in the control ECU500 in step S15. In this case, in S21( Figure 4 ), the frequency data F can be calculated based on the added value (ΔQ + Δq), and new frequency data can be produced.

[0049] In addition, if the root law is used when obtaining the degradation degree (degradation amount ΔQ) of the battery 100, the capacity degradation rate becomes slower as the usage time of the battery 100 elapses. According to the present embodiment, the degradation amount ΔQ is obtained from the control ECU500, and new frequency data is produced based on this degradation degree ΔQ. Therefore, the new frequency data is produced as data that takes into account the usage time of the battery 100 (the usage time from when it was new to the present), so even after the replacement of the battery ECU300, the degradation degree (degradation amount ΔQ) can be estimated with high accuracy.

[0050] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated not by the description of the above embodiments but by the claims, including the meanings equivalent to the claims and all modifications within the scope.

Claims

1. A battery system comprising a battery; a temperature sensor for detecting a battery temperature as a temperature of the battery; a first control device for estimating a degree of degradation of the battery; and a second control device capable of communicating with the first control device, wherein: The first control device is configured to estimate the degree of degradation using the frequency data of the battery temperature and a degradation coefficient set such that the higher the battery temperature, the faster the degradation rate. The second control device is configured to store the degree of degradation estimated by the first control device in a memory, When the first control device is replaced, The replaced first control device is configured to obtain the degree of degradation from the second control device, to create new frequency data in a manner such that the frequency data in the area where the degradation rate is above a specified value becomes the degree of degradation obtained from the second control device, and to estimate the degree of degradation using the new frequency data and the degradation coefficient.

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

3. The battery system according to claim 1 or 2, wherein: The battery system is constructed as follows: the second control device stores the degree of degradation in the memory when the battery system is stopped, The first control device stores the frequency data in a nonvolatile memory of the first control device when the system is stopped.

4. The battery system according to claim 1 or 2, wherein: The degree of degradation is an amount of reduction in capacity of the battery.

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

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