Battery system and electric vehicle

Abstract

The invention relates to a battery system and an electric vehicle. The battery ECU updates frequency data of a region in which the temperature and SOC of the battery are used as parameters, and estimates the degree of deterioration (deterioration amount) on the basis of a deterioration coefficient that increases as the frequency data and the temperature increase. When the battery is replaced, the battery ECU acquires the full charge capacity estimation value of the replaced battery, and calculates the degradation degree of the replaced battery on the basis of the difference between the full charge capacity estimation value and the full charge capacity of the new battery. Then, on the basis of the deterioration degree, new frequency data is created. The new frequency data is created as frequency data for a region having a high temperature and a large SOC, and other regions are set to an empty state.

Description

Technical Field

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

[0002] In Japanese Unexamined Patent Application Publication No. 2023-109010, a technique for restoring the deterioration amount of a battery when a battery ECU that calculates the cumulative damage amount of a battery mounted on a vehicle is replaced is disclosed. In 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 the information received from the EFI ECU. Summary of the Invention

[0003] For a battery, the higher the battery temperature, the more the deterioration progresses. Therefore, sometimes the frequency distribution (history) of the battery temperature is used, and the deterioration degree (damage amount, deterioration amount) of the battery is estimated using the Arrhenius law. In this case, the higher the frequency of being in a high temperature state, the greater the deterioration degree of the battery (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. The amount of frequency data increases as the use period of the battery becomes longer.

[0005] Sometimes the battery is replaced without replacing the control device (the battery ECU in Japanese Unexamined Patent Application Publication No. 2023-109010) that estimates the deterioration degree. In this case, the frequency data stored in the memory of the control device is the frequency data of the battery before replacement, so it is impossible to use this frequency data to estimate the deterioration degree of the battery after replacement.

[0006] The present disclosure can estimate the deterioration degree of the battery after replacement using the frequency data when 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, and a control device that estimates the deterioration degree of the battery. The control device is configured to estimate the deterioration degree using the frequency data of the battery temperature and a deterioration coefficient set in such a way that the higher the battery temperature, the faster the deterioration speed, and the frequency data is stored in the memory of the control device. The control device is configured to: when the battery is replaced, obtain an estimated value of the full charge capacity of the battery after replacement, and calculate the deterioration degree of the battery after replacement based on the full charge capacity of the battery when it is new and the estimated value of the full charge capacity. New frequency data is created in such a way that the frequency data becomes the deterioration degree of the battery after replacement, and the deterioration degree is estimated using the new frequency data and the deterioration coefficient.

[0008] According to this structure, the control device estimates the degree of deterioration using the frequency data of the battery temperature and the deterioration coefficient set in such a way that the higher the battery temperature, the faster the deterioration rate. The frequency data is stored in the memory of the control device.

[0009] When replacing the battery, it is not possible to use the frequency data stored in the memory to estimate the degree of deterioration of the replaced battery.

[0010] According to this structure, when the battery is replaced, the control device obtains an estimated value of the full charge capacity of the replaced battery. Then, the control device calculates the degree of deterioration of the replaced battery based on the full charge capacity of the new battery and the estimated value of the full charge capacity. The control device creates new frequency data in such a way that the frequency data becomes the degree of deterioration of the replaced battery. Then, the control device uses the new frequency data and the deterioration coefficient to estimate the degree of deterioration. Since the new frequency data is created as data corresponding to the degree of deterioration of the replaced battery, it is possible to use the new frequency data and the deterioration coefficient to estimate the degree of deterioration of the replaced battery.

[0011] Preferably, the control device may also create new frequency data in such a way 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 of the replaced battery.

[0012] According to this structure, the new frequency data is created in such a way 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 of the replaced battery. The deterioration rate is set in such a way that the higher the battery temperature, the faster it is, so the region for creating the new frequency data is, for example, a high temperature region above a predetermined temperature. Generally, the battery is used less frequently on the low temperature side lower than the normal use temperature region and on the high temperature side higher than the normal use temperature region. Therefore, the usage frequency in the high temperature region for creating the new frequency data is low, so in the control device after replacement, memory area overflow can be suppressed. In addition, the deterioration coefficient is set in such a way that the higher the battery temperature, the faster the deterioration rate. When creating frequency data in such a way that it becomes the degree of deterioration of the replaced battery, compared with creating frequency data in the low temperature region (region with slow deterioration rate) of the battery temperature, when creating frequency data in the high temperature region (region where the deterioration rate is equal to or higher than a predetermined value), the amount of data becomes smaller. Therefore, it is possible to suppress memory area overflow in the control device after battery replacement.

[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 according to the SOC. For example, deterioration is easily promoted in the high SOC region. According to this structure, the frequency data is set as the history of the battery temperature and the SOC of the battery, and the degree of deterioration is estimated considering the SOC, so the estimation accuracy of the degree of deterioration can be improved.

[0015] Preferably, the control device can be configured to store the frequency data in the non-volatile memory of the control device when the battery system stops operating.

[0016] According to this configuration, when the system stops operating, the frequency data is stored in the non-volatile memory of the control device. Therefore, even when the power supply of the control device is lost, the deletion of the frequency data can be suppressed.

[0017] The electric vehicle of the present disclosure is an electric vehicle equipped with the above-described battery system.

[0018] According to this configuration, even after the battery is replaced, the degree of deterioration of the battery mounted on the vehicle can be estimated.

[0019] According to the present disclosure, when the battery is replaced, the frequency data can be used to estimate the degree of deterioration of the replaced battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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 like reference numerals denote like elements, and wherein:

[0021] Figure 1 is an overall structural diagram of an electric vehicle equipped with the battery system of the present embodiment;

[0022] Figure 2 is a flowchart showing an example of battery deterioration estimation processing executed in the battery ECU;

[0023] Figure 3A is a diagram for explaining the deterioration coefficient and the frequency data in the present embodiment;

[0024] Figure 3B is a diagram for explaining the deterioration coefficient and the frequency data in the present embodiment;

[0025] Figure 3C is a diagram for explaining the deterioration coefficient and the frequency data in the present embodiment;

[0026] Figure 4 is a flowchart showing an example of processing at the time of battery replacement executed by the battery ECU; and

[0027] Figure 5 is a diagram showing the relationship between the temperature TB and the frequency (cumulative time). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. It should be noted that the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0029] Figure 1 This is an overall structural diagram of the electric vehicle 1 equipped with the battery system S of 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 plug-in 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 rotating electric machine, a power transmission gear 20, drive wheels 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 control device, and a control ECU 500.

[0030] The MG 10 is, for example, an interior permanent magnet synchronous motor (IPM motor), and has a function as a motor and a function as a generator. The output torque of the MG 10 is transmitted to the drive wheels 30 via the power transmission gear 20 configured to include a speed reducer and a differential device, etc.

[0031] When the electric vehicle 1 brakes, the drive wheels 30 drive the MG 10, 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.

[0032] 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.

[0033] The SMR 50 is electrically connected to the power line connecting the battery 100 and the PCU 40. When the SMR 50 is closed (turned on) according 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 (turned 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.

[0034] 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 connecting a plurality of single cells (battery units) 100a in series. The battery 100 corresponds to the "battery" of the present disclosure. The single cell 100a can be constituted by a lithium ion battery, for example.

[0035] 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. It should be noted that when the battery 100 discharges, the current IB is a negative (-) value, and when the battery 100 charges, the current IB is a positive (+) value. The temperature sensor 230 detects the temperature TB of the battery 100. The temperature TB is an example of the "battery temperature" of the present disclosure. Each sensor outputs its detection result to the battery ECU 300.

[0036] The electric vehicle 1 is provided with an access port 60, and the battery 100 can be externally charged using a charging device (EVSE: Electric Vehicle Supply Equipment). The access port 60 is configured to be connectable to a connector 420 provided at the front end of a charging cable 410 of the EVSE 400. The access port 60 is electrically connected to a power line connected to the battery 100 via a charging circuit 70. In the present embodiment, when the SMR 50 is closed, the access port 60 is connected to the battery 100 and external charging can be performed. It should be noted that the charging circuit 70 may also include a charging relay. Alternatively, it may be configured such that the access port 60 (charging circuit 70) is connected to the power line between the battery 100 and the SMR 50 via a charging relay, and external charging of the battery 100 can be performed by closing the charging relay.

[0037] 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 is stopped (when the power of the battery ECU 300 is lost), the data stored in the RAM disappears. Even when the power supply is stopped (even when the power of the battery ECU 300 is lost), the data stored in the non-volatile memory does not disappear. The battery ECU 300 uses the signal 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 via, for example, 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.

[0038] The control ECU 500 includes a CPU 501 and a memory 502. Similar to the memory 302, the memory 502 includes a RAM and a non-volatile memory. The control ECU 500 controls each device in such a way that the electric vehicle 1 becomes 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.), maps and programs stored in the memory 502, and other information.

[0039] Figure 2 It is a flowchart showing an example of the battery deterioration estimation process 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 becomes the on state. When the power switch 250 is turned on and the battery system S becomes the on state, in step (hereinafter, step is abbreviated 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 calculated and acquired based on the voltage VB detected by the voltage sensor 210 according to the SOC-OCV (Open Circuit Voltage) characteristic of the battery 100.

[0040] In S11, the frequency data is updated based on the temperature TB and SOC acquired in S10. Figure 3A 、 Figure 3B, Figure 3C This is a diagram illustrating the degradation coefficient and frequency data in the present embodiment. Figure 3A This is a diagram illustrating the degradation coefficient described later. Figure 3B This is a diagram illustrating the frequency data updated in S11. In Figure 3B , 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 the 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 or 2°C or 5°C, and the interval of the SOC can be 1% or 2% or 5%. In addition, the cumulative time can be in units of 1 minute, for example. In S11, the time of the region corresponding to the temperature TB and the SOC obtained 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 through the process of S11.

[0041] In the subsequent S12, the degradation amount ΔQ of the battery 100 is calculated. The degradation amount ΔQ is the degradation amount of the capacity [Ah] of the battery 100 (capacity degradation amount), 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 3A This is a diagram illustrating the degradation coefficient. The vertical axis is the temperature TB, and the horizontal axis is the SOC. In the present embodiment, the degradation coefficient is the capacity degradation rate [% / Hr]. The higher the temperature TB, and in addition, the higher (larger) the SOC, the more the degradation of the battery 100 is promoted. Therefore, the degradation coefficient is set such that the higher the temperature TB and the higher the SOC, the faster the capacity degradation rate. In S12, the frequency data (cumulative time) in each region is multiplied by the degradation coefficient (capacity degradation rate) to obtain the capacity degradation amount in each region, and their sum is calculated as the degradation amount ΔQ. It should be noted that it is known that the capacity degradation of the battery 100 (battery) follows the root law (capacity degradation is proportional to the 1 / 2 power of time and the number of cycles), and the degradation capacity of each region can be obtained using the root law based on the frequency data (cumulative time) and the degradation coefficient.

[0042] In S13, it is determined whether the battery system S changes from on to off. If 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 predetermined intervals.

[0043] In S14, after writing the frequency data updated in S11 into the non-volatile memory of the memory 302, it proceeds to S15. It should be noted that when the frequency data disappears, etc., the frequency data stored in the non-volatile memory of the memory 302 is used for the recovery of the frequency data. When the frequency data disappears, for example, it is generally considered to be when the power line is disconnected 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, when the frequency data stored in the SRAM of the memory 302 disappears, and so on.

[0044] In S15, after sending the deterioration amount ΔQ calculated in S12 to the control ECU 500, this routine ends. The control ECU 500 writes (stores) the received deterioration amount ΔQ into the non-volatile memory of the memory 502.

[0045] In the battery system S, the battery 100 is sometimes replaced. The frequency data stored in the memory 302 (SRAM, non-volatile memory) of the battery ECU 300 is the frequency data of the battery 100 before replacement. Therefore, if the battery 100 is replaced, the frequency data stored in the memory 302 cannot be used to calculate the deterioration amount ΔQ of the replaced battery 100. In the present embodiment, when the battery 100 is replaced, by creating new frequency data, the deterioration amount ΔQ of the replaced battery 100 can be calculated.

[0046] Figure 4 It is a flowchart showing an example of the process at the time of battery replacement executed in the battery ECU 300. This flowchart is executed when the IG switch (power switch) 250 is turned on and the battery ECU 300 is started. In S20, it is determined whether a battery replacement has occurred. For example, when the control ECU 500 receives a replacement signal from the service tool ST used by the operator who replaces the battery 100, it can be determined that a battery replacement has occurred. In addition, when the identification number (ID) of the battery 100 stored in the non-volatile memory of the memory 302 or the memory 502 is different from the identification number of the battery 100, it can be determined that a battery replacement has occurred. Or, when the SOC at the time of the IG switch disconnection operation stored in the non-volatile memory of the memory 302 or the memory 502 differs from the SOC at the time of the IG switch 250 turn-on operation by a predetermined value or more, it can be determined that a battery replacement has occurred. When a battery replacement occurs, it proceeds to S21, and in the case where no battery replacement has occurred, this routine ends.

[0047] In S21, the frequency data stored in the memory 302 is reset. In the present embodiment, the frequency data stored in the SRAM and the non-volatile memory of the memory 302 is reset. The reset of the frequency data can be set to a state where the frequency data is empty (NULL), for example. Alternatively, frequency data such as the amount of deterioration ΔQ when the battery 100 is used for 10 years as if it were a new product can be prepared in advance, and this frequency data can be used as the reset frequency data.

[0048] In the subsequent S22, an estimated full charge capacity Ca of the replaced battery 100 is obtained. The method for obtaining the estimated full charge capacity Ca can also be any method. For example, when the operator of the battery 100 notifies the end of the battery replacement operation by operating the service tool ST, the battery ECU 300 discharges the battery 100 so that the SOC of the replaced battery 100 becomes equal to or less than a predetermined value (e.g., 3%). When the SCO becomes equal to or less than the predetermined value, the discharge is stopped. When the time required to eliminate the polarization of the battery 100 has elapsed, external charging is started using the EVSE 400, and the charging current is integrated. The external charging can be CCCV (Constant Current Constant Voltage) charging or CC (Constant Current) charging. Then, when the battery 100 is fully charged (when the charging termination current or charging termination voltage is reached), the charging is stopped. Then, after a predetermined time has elapsed, based on the SOC at the start of charging, the SOC at full charge, the amount of charging power, etc., obtained from the SOC-OCV characteristics, the estimated full charge capacity Ca of the replaced battery 100 is calculated. In S22, the estimated full charge capacity Ca calculated in this way can be obtained.

[0049] In S23, the amount of deterioration ΔQ of the replaced battery 100 is calculated. The full charge capacity Cs of the battery 100 when it is new (at the time of manufacture, when shipped from the factory) is stored in advance in the memory 302 of the battery ECU 300. For example, the full charge capacity Cs can be the specification value (design value) of the battery 100. In S23, the amount of deterioration ΔQ is calculated as the difference between the full charge capacity Cs and the estimated full charge capacity Qa (ΔQ = Cs - Ca). (It should be noted that when the amount of deterioration ΔQ is processed as a negative value, it can also be calculated according to ΔQ = Ca - Cs.)

[0050] In the subsequent S24, frequency data is created based on the amount of deterioration ΔQ calculated in S23, and this example routine ends. In the present embodiment, the frequency data is created such that the frequency data in the region with the largest deterioration coefficient (capacity deterioration rate) becomes the amount of deterioration ΔQ. For example, when the frequency data in the region where the temperature TB is the highest and the SOC is the largest (the region with the largest deterioration coefficient) is set as F and the deterioration coefficient in this region is set as S, the calculation is F = ΔQ / S. Then, as Figure 3C shown, the frequency data for this region is set as F, and the frequency data for other regions is set as 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 may also be stored in the non-volatile memory of the memory 302.) After that, the new frequency data is updated in S11 of the battery deterioration estimation process ( Figure 2 ).

[0051] According to the present embodiment, the battery ECU 300 estimates the amount of deterioration 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). When the battery 100 is replaced, the battery ECU 300 acquires the full charge capacity estimated value Ca of the replaced battery 100. Then, the battery ECU 300 calculates the amount of deterioration ΔQ of the replaced battery 100 based on the full charge capacity Cs when the battery 100 is new and the full charge capacity estimated value Ca. Then, the battery ECU 300 creates new frequency data such that the frequency data becomes the amount of deterioration ΔQ of the replaced battery 100. Then, the battery ECU 300 uses the new frequency data and the deterioration coefficient to estimate the amount of deterioration ΔQ (degree of deterioration). Since the new frequency data is created as data corresponding to the amount of deterioration ΔQ of the replaced battery 100, the amount of deterioration ΔQ of the replaced battery 100 can be estimated using the new frequency data and the deterioration coefficient.

[0052] 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 is generally used less frequently on the low-temperature side lower than the normal use temperature region and on the high-temperature side higher than the normal use temperature region.

[0053] 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 rate is the largest) becomes the degradation amount ΔQ. When the degradation coefficient in this region is set to S, the frequency data F in this region is F = ΔQ / S, and the frequency data in other regions is set to NULL. The larger the degradation coefficient, the smaller the value of the frequency data F. Therefore, compared with creating frequency data based on the degradation amount ΔQ in a region where the degradation coefficient is small (the region where the capacity degradation rate is slow), the amount of data becomes smaller. Additionally, after that (after replacing the battery 100), the temperature TB becomes high, and the frequency in the region where the degradation coefficient is the largest is also small. Thus, it is possible to suppress frequency data overflow after replacing the battery 100.

[0054] In the above embodiment, in S24( Figure 4 ), the frequency data F 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) 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 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 region from the highest temperature and the SOC is the second largest, the frequency data f calculated based on the degradation amount ΔQ is calculated. As Figure 3C shown, the frequency data in this region may be set to f, and the frequency data in other regions may be set to NULL.

[0055] Additionally, the frequency data f1 and f2 are calculated such that the value obtained by adding the degradation amount calculated from the frequency data f1 in 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 in the region where the temperature TB is the second region from the highest temperature and the SOC is the largest becomes the degradation amount ΔQ. As Figure 3C shown, the frequency data in this region may be set to f1 and f2, and the frequency data in other regions may be set to NULL. In the present disclosure, the "region where the degradation rate is equal to or higher than a predetermined value" may be any region among the top 10% regions with a fast capacity degradation rate (a large degradation coefficient).

[0056] In the above embodiment, the frequency data is set to the cumulative time of the time when 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 also be the cumulative time with only the temperature TB as a parameter. Additionally, as long as the frequency data is equivalent to the history of the time when the battery 100 exists in this region, it may not be the cumulative time.

[0057] It should be noted that if the root law is used to calculate the degradation degree (degradation amount ΔQ) of the battery 100, the capacity degradation speed becomes slower as the usage time of the battery 100 passes and the degradation degree increases. According to this embodiment, the degradation amount ΔQ of the replaced battery 100 is calculated, and new frequency data is created based on this degradation amount ΔQ. Therefore, the new frequency data is created as data that takes into account the usage time of the battery 100 (the usage time from when it was new to the current time). Thus, even after replacement, the battery ECU 300 can accurately estimate the degradation degree (degradation amount ΔQ).

[0058] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is represented not by the description of the above embodiments but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A battery system comprising a battery, a temperature sensor for detecting a temperature of the battery, i.e., a battery temperature, and a control device for estimating a degree of degradation of the battery, wherein: The control device is configured to estimate the degree of degradation using frequency data of the battery temperature and a degradation coefficient set such that the higher the battery temperature, the faster the degradation rate, and the frequency data is stored in a memory of the control device. The control device is composed of: When the battery is replaced, obtaining an estimated value of the full charge capacity of the replaced battery, calculating the degree of deterioration of the battery after replacement based on the full charge capacity of the battery when it was new and the estimated value of the full charge capacity, creating new frequency data in such a manner that the frequency data corresponds to the degree of degradation of the battery after replacement, The degree of degradation is estimated using the new frequency data and the degradation coefficient.

2. The battery system according to claim 1, wherein: The control device creates new frequency data such that the frequency data in a region where the degradation rate is equal to or greater than a predetermined value corresponds to the degradation degree of the battery after replacement.

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

4. The battery system according to claim 3, wherein: The control device is configured to store the frequency data in a nonvolatile memory of the control device when the battery system is stopped.

5. An electric vehicle equipped with the battery system according to claim 4.

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