Estimation device, power storage device, estimation method, and computer program

Abstract

To provide an estimation device, a power storage device, an estimation method, and a computer program.SOLUTION: An estimation device for estimating a post-deterioration performance value, which is a value indicating performance at a predetermined deterioration time point of an energy storage device, includes an acquisition unit that acquires a voltage change amount, which is a difference between an open circuit voltage before current application and a post-deterioration open circuit voltage of the energy storage device, and a DC resistance value, which is a value obtained by dividing a difference between an open circuit voltage before current application and a closed circuit voltage during current application of the energy storage device by a current value, and an estimation unit that estimates the post-deterioration performance value of the energy storage device at the deterioration time point based on the voltage change amount and the DC resistance value acquired by the acquisition unit using a correlation between the voltage change amount and the DC resistance value and the post-deterioration performance value.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to an estimation device, a power storage device, an estimation method, and a computer program. [Background technology]

[0002] Secondary batteries such as lithium-ion batteries are widely used. For example, secondary batteries are installed in vehicles such as automobiles and are used as a power source for a starter when starting the engine, a power source for various electrical components, and the like.

[0003] In recent years, social demands such as legal regulations have led to calls for the reuse and recycling of secondary batteries. Information on secondary batteries eligible for secondary use is managed on a server and provided to businesses as needed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-99726 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to determine whether a secondary battery can be reused, it is necessary to know the post-degradation performance value of the secondary battery. However, it is difficult to accurately determine the post-degradation performance value of a secondary battery whose usage history is unknown.

[0006] The present disclosure aims to provide an estimation device, an energy storage device, an estimation method, and a computer program that can accurately estimate the post-degradation performance value of an energy storage element even when the usage history is unknown. [Means for solving the problem]

[0007] The estimation device according to the present disclosure is an estimation device that estimates a post-degradation performance value, which is a value indicating the performance of a storage element at a predetermined time point of degradation, and includes an acquisition unit that acquires a voltage change amount, which is the difference between the open-circuit voltage of the storage element before current application and the open-circuit voltage after rest, and a DC resistance value, which is the value obtained by dividing the difference between the open-circuit voltage of the storage element before current application and the closed-circuit voltage during current application by a current value, and an estimation unit that estimates the post-degradation performance value of the storage element at the time point of degradation based on the voltage change amount and current resistance value acquired by the acquisition unit, using a correlation that holds between the voltage change amount, the DC resistance value, and the post-degradation performance value. [Effects of the Invention]

[0008] According to the above aspect, even if the usage history is unknown, the post-degradation performance value of the energy storage element can be accurately estimated. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing the configuration of a vehicle and a server according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the internal configuration of a BMU. [Figure 3] 10 is a graph showing the temperature dependency in deterioration diagnosis using ΔOCV. [Figure 4] 10 is a graph showing temperature dependency in deterioration diagnosis using DCR. [Figure 5] 10 is a graph showing temperature dependency in deterioration diagnosis using DCR×ΔOCR. [Figure 6] 10 is a graph illustrating the estimation accuracy of each method. [Figure 7] 10 is a flowchart showing a procedure for estimating a capacity maintenance rate by a BMU. DETAILED DESCRIPTION OF THE INVENTION

[0010] (1) The estimation device disclosed herein is an estimation device that estimates a post-degradation performance value, which is a value indicating the performance of a storage element at a predetermined time point of degradation, and includes an acquisition unit that acquires a voltage change amount, which is the difference between the open-circuit voltage of the storage element before current application and the open-circuit voltage after rest, and a DC resistance value, which is the value obtained by dividing the difference between the open-circuit voltage of the storage element before current application and the closed-circuit voltage during current application by a current value; and an estimation unit that estimates the post-degradation performance value of the storage element at the time point of degradation based on the voltage change amount and current resistance value acquired by the acquisition unit, using a correlation that holds between the voltage change amount, the DC resistance value, and the post-degradation performance value.

[0011] The energy storage element of the present disclosure is a rechargeable secondary battery such as a lithium-ion secondary battery that is mounted on, for example, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc. Since secondary batteries are expected to be reused or used for other purposes, it is important to understand the performance values ​​of the secondary battery when it is reused.

[0012] According to the estimation device of (1) above, a performance value at a predetermined degradation point (post-degradation performance value) can be estimated by acquiring a voltage change amount, which is the difference between the open-circuit voltage of the energy storage element before current application and the open-circuit voltage after current application is stopped, and a DC resistance value, which is the difference between the open-circuit voltage of the energy storage element before current application and the closed-circuit voltage during current application, divided by a current value. The predetermined degradation point refers to any point in time after the energy storage element has started to be used. The post-degradation performance value is, for example, a capacity maintenance rate. Alternatively, the post-degradation performance value may be a discharge capacity, a remaining service life, the number of times that the element can be charged, an internal resistance value, or the like. The estimation device of (1) above can estimate the post-degradation performance value at a degradation point in time by measuring the voltage change amount and DC resistance even for an energy storage element whose usage history is unknown.

[0013] (2) In the estimation device described above in (1), the correlation may be expressed by a function having a product of the voltage change amount and the DC resistance value as an input value and the degraded performance value as an output value.

[0014] According to the estimation device of (2) above, the post-degradation performance value can be estimated using a function in which the product of the voltage change amount and the DC resistance value is the input value and the post-degradation performance value is the output value.

[0015] (3) The estimation device according to (1) or (2) above further includes a correction unit that corrects the correlation in accordance with an environmental temperature of the storage element.

[0016] According to the estimation device of (3) above, the correlation is corrected using the environmental temperature at the time when the voltage change amount and the DC resistance are measured, so that the post-degradation performance value can be estimated with higher accuracy.

[0017] (4) A power storage device according to the present disclosure includes a power storage element and the estimation device according to any one of (1) to (3) above.

[0018] According to the power storage device of (4) above, the post-degradation performance value can be estimated within the power storage device.

[0019] (5) The estimation method disclosed herein is a method for estimating a post-degradation performance value, which is a value indicating the performance of a storage element at a predetermined time point of degradation, by acquiring a voltage change amount, which is the difference between the open-circuit voltage of the storage element before current application and the open-circuit voltage after rest, and a DC resistance value, which is the value obtained by dividing the difference between the open-circuit voltage of the storage element before current application and the closed-circuit voltage during current application by a current value, and using a correlation between the voltage change amount, the DC resistance value, and the post-degradation performance value, a process is performed by a computer to estimate the post-degradation performance value of the storage element at the time point of degradation based on the voltage change amount and the current resistance value acquired by the acquisition unit.

[0020] According to the estimation method (5) above, even for an energy storage element whose usage history is unknown, the post-degradation performance value at that time can be estimated by measuring the voltage change amount and DC resistance at that time.

[0021] (6) A computer program disclosed herein is a computer program for estimating a post-degradation performance value, which is a value indicating the performance of a storage element at a predetermined time point of degradation. The computer program acquires a voltage change amount, which is the difference between the open-circuit voltage of the storage element before current application and the open-circuit voltage after rest, and a DC resistance value, which is the difference between the open-circuit voltage of the storage element before current application and the closed-circuit voltage during current application, divided by a current value, and uses a correlation between the voltage change amount, the DC resistance value, and the post-degradation performance value to cause a computer to execute a process of estimating the post-degradation performance value of the storage element at the time point of degradation based on the voltage change amount and the current resistance value acquired by the acquisition unit.

[0022] According to the computer program of (6) above, even for a storage element whose usage history is unknown, the post-degradation performance value at that time can be estimated by measuring the voltage change amount and DC resistance at that time.

[0023] Hereinafter, an application example of the present disclosure will be described using an electric storage device mounted on a vehicle. (Embodiment 1) 1 is a block diagram showing the configurations of a vehicle 1 and a server 2 according to embodiment 1. Vehicle 1 includes a power storage element 11 consisting of a plurality of battery cells 10, a BMU (Battery Management Unit) 12, a load 13, an integrated ECU (Electronic Control Unit) 14, a communication unit 15, a voltage sensor 16, and a current sensor 17.

[0024] The vehicle 1 may be an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or the like. The vehicle 1 is equipped with a high-voltage battery for driving an electric motor for driving the vehicle, a 12V battery for starting the vehicle, and an auxiliary battery. The vehicle 1 may also be equipped with a 12V battery as a backup power source. Reusable secondary batteries such as lithium-ion batteries are used for the high-voltage battery and the 12V battery.

[0025] The energy storage element 11 is the above-mentioned high-voltage battery or a 12V battery. The energy storage element 11 is configured by connecting a plurality of battery cells 10 in series. An example of the battery cells 10 is a lithium-ion battery cell. Alternatively, the battery cells 10 may be chargeable and dischargeable battery cells such as all-solid-state batteries, lead batteries, redox flow batteries, zinc-air batteries, alkaline manganese batteries, lithium-sulfur batteries, sodium-sulfur batteries, silver-zinc oxide batteries, nickel-metal hydride batteries, and molten salt thermal batteries.

[0026] BMU 12 is a device for managing the state of energy storage element 11. BMU 12 acquires time-series measurement data obtained from various sensors such as voltage sensor 16 and current sensor 17, and stores the acquired measurement data as history in storage unit 122 (see FIG. 2). The measurement data includes the voltage value of energy storage element 11, the value of current flowing through energy storage element 11, etc. The measurement data may also include temperature (also referred to as ambient temperature or environmental temperature) measured by a temperature sensor disposed around energy storage element 11. BMU 12 may count the number of charge / discharge cycles and store the counted number of cycles as history in storage unit 122.

[0027] The BMU 12 may estimate a performance value indicating the performance of the energy storage element 11 based on the acquired measurement data, and store the estimated performance value in the storage unit 122. An example of the performance value is a full charge capacity. The full charge capacity is estimated using an existing method, such as a method of estimating by combining an open circuit voltage (OCV) and an integrated current value, or a method of estimating by using measured values ​​of a current, a voltage, etc. when discharging at a constant current to a set voltage.

[0028] In this embodiment, when the difference between the OCV of the storage element 11 before current application and the OCV after the application is taken as ΔOCV and the value obtained by dividing the difference between the OCV of the storage element 11 before current application and the CCV (Closed Circuit Voltage) during current application by the current value is taken as DCR (Direct Current Resistance), the BMU 12 estimates a post-degradation performance value indicating the performance of the storage element 11 at a predetermined degradation point in time based on ΔOCV and DCR. Here, the predetermined degradation point in time refers to any point in time after the storage element 11 is mounted on the vehicle 1 and use of the storage element 11 begins. A method for estimating the post-degradation performance value will be described in detail later.

[0029] The load 13 is an electric motor that generates a driving torque for driving the vehicle 1. The load 13 may include various accessories that the vehicle 1 is equipped with, such as headlights, turn signals, interior lights, and power windows.

[0030] The manager ECU 14 is a control device that performs overall control of the vehicle 1, and performs charge / discharge control of the storage element 11, drive control of the load 13, etc. The manager ECU 14 is connected to the BMU 12 and a communication unit 15 so as to be able to communicate with them. CAN (Controller Area Network), LIN (Local Interconnect Network), ECHONET (registered trademark), ECHONET Light (registered trademark), etc. are used for communication within the vehicle 1. The manager ECU 14 acquires data of the storage element 11 managed by the BMU 12 at appropriate times, and uploads the acquired data of the storage element 11 to the server 2 via the communication unit 15. The manager ECU 14 receives various types of data transmitted from the server 2 via the communication unit 15, and performs processing according to the received data.

[0031] The communication unit 15 includes an in-vehicle communication interface for communicating with the supervisory ECU 14 and an external communication interface for communicating with the server 2 via the communication network NW. The external communication interface may be a communication interface for wireless communication such as WiFi (registered trademark), 3G, 4G, 5G, or LTE (Long Term Evolution). The communication unit 15 communicates with the supervisory ECU 14 via the in-vehicle communication network described above, and transmits and receives various data to and from the server 2 via the communication network NW.

[0032] The voltage sensor 16 is an existing voltage sensor and is connected in parallel to the energy storage element 11. The voltage sensor 16 measures the voltage of the energy storage element 11 in time series and outputs the measurement results to the BMU 12. The voltage sensor 16 may be connected in parallel to each battery cell 10. In this case, the sum of the cell voltages measured for each battery cell 10 may be output to the BMU 12 as the voltage value of the energy storage element 11.

[0033] Current sensor 17 is an existing current sensor such as a Hall sensor, and is connected in series to power storage element 11. Current sensor 17 measures the current flowing through power storage element 11 in time series and outputs the measurement result to BMU 12.

[0034] The server 2 includes a control unit 21, a storage unit 22, a communication unit 23, etc. The control unit 21 of the server 2 includes a CPU (Central Processing Unit) and executes overall control of the server. The storage unit 22 includes a storage device such as an HDD (Hard Disk Drive) and stores data on the energy storage elements 11 received from the vehicle 1 via the communication network NW. The communication unit 23 includes a wired or wireless communication interface for communicating with the vehicle 1 via the communication network NW.

[0035] 2 is a block diagram showing the internal configuration of the BMU 12. The BMU 12 includes a control unit 121, a storage unit 122, a connection unit 123, a communication unit 124, and the like.

[0036] The control unit 121 is an arithmetic circuit or processing circuit including a CPU, a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The CPU included in the control unit 121 reads and executes a computer program stored in the ROM or the storage unit 122, thereby controlling each hardware unit and causing the entire device to function as the estimation device of the present disclosure.

[0037] Alternatively, the control unit 121 may be any arithmetic circuit or processing circuit including multiple CPUs, a multi-core CPU, a GPU (Graphics Processing Unit), a microcomputer, a volatile or non-volatile memory, etc. The control unit 121 may also have functions such as a timer that measures the elapsed time from when an instruction to start measurement is given to when an instruction to end measurement is given, a counter that counts numbers, and a clock that outputs date and time information.

[0038] The storage unit 122 includes a storage device such as a flash memory or a hard disk. Various computer programs and data are stored in the storage unit 122. The computer programs stored in the storage unit 122 include an estimation program PG for causing a computer to execute a process of estimating a post-degradation performance value indicating the performance of the energy storage element 11 at a predetermined degradation point, based on the ΔOCV and DCR of the energy storage element 11. The storage unit 122 includes a history database DB for storing measurement data such as the voltage, current, and temperature of the energy storage element 11.

[0039] A computer program (program product) including the estimation program PG is provided by a non-transitory recording medium RM on which the computer program is readably recorded. The recording medium RM is a portable memory such as a CD-ROM, a USB memory, or an SD (Secure Digital) card. The control unit 121 reads a desired computer program from the recording medium RM using a reading device (not shown) and stores the read computer program in the storage unit 122. Alternatively, the computer program including the estimation program PG may be provided via communication.

[0040] The estimation program PG may be a single computer program or a group of programs consisting of multiple computer programs. The estimation program PG may be executed by multiple computers working together. The estimation program PG may partially use an existing library.

[0041] The connection unit 123 includes connection terminals for connecting various sensors such as the voltage sensor 16 and the current sensor 17. The control unit 121 acquires, via the connection unit 123, various measurement data measured by the sensors connected to the connection unit 123.

[0042] The communication unit 124 includes a communication interface for transmitting and receiving various types of data. The communication interface included in the communication unit 124 may be a communication interface conforming to the above-mentioned CAN, LIN, ECHONET (registered trademark), ECHONET Light (registered trademark), etc. The communication unit 124 transmits and receives necessary data to and from the supervisory ECU 14.

[0043] In the deterioration diagnosis using ΔOCV or DCR of the energy storage element 11, variations occur depending on the temperature at which the energy storage element 11 is used. FIG. 3 is a graph showing the temperature dependency in the deterioration diagnosis using ΔOCV. In this embodiment, cycle tests were performed on the energy storage element 11 at various temperatures (15 to 55°C), and during each temperature cycle, a 1C discharge capacity measurement at 25°C and a pulse discharge test at 50% SOC (1C discharge for 60 seconds, followed by a 600-second rest) were performed. The horizontal axis of the graph shown in FIG. 3 is the capacity retention rate (%), and the vertical axis is ΔOCV (arbitrary unit). The capacity retention rate is given as the ratio of the capacity after aging, assuming the initial capacity to be 100%. ΔOCV is given as the difference between the OCV of the energy storage element 11 before current application and the OCV after the rest. As shown in the graph in Figure 3, although there is a certain correlation between ΔOCV and capacity retention rate, there is variation depending on the temperature at which the storage element 11 is used, and the ΔOCV that achieves the same capacity retention rate tends to be higher as the temperature of the storage element 11 used is lower.

[0044] FIG. 4 is a graph showing the temperature dependence of degradation diagnosis using DCR. As described above, a cycle test was performed on the energy storage element 11 at various temperatures (15 to 55°C). During each temperature cycle, a 1C discharge capacity measurement at 25°C and a pulse discharge test (1C discharge for 60 seconds, followed by a 600-second rest) at 50% SOC were performed. The horizontal axis of the graph shown in FIG. 4 represents the capacity retention rate (%), and the vertical axis represents ΔOCV (arbitrary unit). The capacity retention rate is given as the percentage of the capacity after aging, assuming the initial capacity to be 100%. The DCR is given by the difference between the OCV of the energy storage element 11 before current application and the CCV during current application for 1 second, divided by the current value. As shown in FIG. 4, although a certain correlation is observed between the DCR and the capacity retention rate, there is variation depending on the temperature at which the energy storage element 11 is used. The DCR that achieves the same capacity retention rate tends to increase as the temperature at which the energy storage element 11 is used increases.

[0045] The present inventors have found that, in the deterioration diagnosis of energy storage element 11, the ΔOCV that achieves the same capacity retention rate increases as the temperature of used energy storage element 11 decreases, and the DCR that achieves the same capacity retention rate increases as the temperature of used energy storage element 11 increases, showing an opposite trend. Based on this finding, the present inventors have carefully investigated the relationship between the product of ΔOCV and DCR and the capacity retention rate.

[0046] FIG. 5 is a graph showing temperature dependency in degradation diagnosis using DCR×ΔOCR. The horizontal axis of the graph shown in FIG. 5 represents the capacity maintenance rate, and the vertical axis represents DCR×ΔOCV. The capacity maintenance rate is given as a percentage of the capacity after aging when the initial capacity is set to 100%. DCR×ΔOCV is given as the integrated value between the above-mentioned DCR and ΔOCV. As shown in FIG. 5, by multiplying DCR and ΔOCV, their temperature dependencies can be canceled out, and it was found that the capacity maintenance rate can be estimated independently of temperature. As shown in the comparative examples of FIGS. 3 and 4, estimating the capacity maintenance rate from ΔOCV or DCR requires information on the temperature at which the storage element 11 was used. Without this temperature information, it was difficult to accurately estimate the capacity maintenance rate. In contrast, in the present embodiment, the temperature dependency is eliminated. Therefore, even when information on the temperature at which the storage element 11 was used is unknown (for example, when the storage element 11 is removed from the vehicle 1 and its usage history is unknown), it is possible to accurately estimate the capacity maintenance rate by calculating DCR×ΔOCV. Moreover, in the present embodiment, the parameters (ΔOCV and DCR) required for estimating the capacity retention ratio can be obtained by a pulse discharge test (1C discharge for 60 seconds, followed by a 600-second rest period), so that the capacity retention ratio can be estimated in a shorter time than with the conventional method using a cycle test.

[0047] FIG. 6 is a graph illustrating the estimation accuracy of each method. The horizontal axis of the graph represents the capacity retention rate, and the vertical axis represents ΔOCV, DCR, or DCR×ΔOCV. The inventors obtained an approximation curve for estimating the capacity retention rate from each of the ΔOCV, DCR, and DCR×ΔOCV graphs, and calculated an index value (R-squared value in the example of FIG. 6) representing the deviation of each value from the approximation curve. When ΔOCV or DCR was used, the R-squared value was approximately 0.94 due to large variations with temperature, whereas when DCR×ΔOCV was used, the R-squared value was improved to 0.98.

[0048] 5 is derived in advance, and a function form representing the derived approximate curve or a table showing the relationship between the input and output of the approximate curve is stored, for example, in the storage unit 122. When the control unit 121 of the BMU 12 acquires new ΔOCV and DCR for the storage element 11 mounted on the vehicle 1, the control unit 121 estimates the capacity maintenance rate of the storage element 11 using the function form or the table stored in the storage unit 122.

[0049] The function form or table of the approximation curve may be stored in the storage unit 22 of the server 2. In this case, the server 2 can estimate the capacity maintenance rate of the storage element 11 by acquiring, via the communication network NW, the ΔOCV and DCR measured for the storage element 11 in a state where it is mounted on the vehicle 1. The server 2 may also acquire the ΔOCV and DCR measured for the storage element 11 in a state where it is removed from the vehicle 1, and estimate the capacity maintenance rate of the storage element 11 based on the acquired ΔOCV and DCR. In the latter case, even if the usage history of the storage element 11 is unknown, the server 2 can estimate the capacity maintenance rate of the storage element 11 with high accuracy in a short time.

[0050] 7 is a flowchart showing the procedure for estimating the capacity maintenance rate by the BMU 12. It is assumed that the memory unit 122 of the BMU 12 stores the function form of an approximation curve that approximates each point in FIG. 5. The control unit 121 of the BMU 12 measures the 1C discharge capacity of the storage element 11 (step S101) and performs a pulse discharge test at SOC 50% (1C discharge for 60 seconds, followed by a 600-second pause) (step S102).

[0051] Control unit 121 obtains the OCV of power storage element 11 before current application and the OCV after the current is stopped via voltage sensor 16, and measures ΔOCV given as the difference between them (step S103).

[0052] Control unit 121 measures DCR, which is given by dividing the difference between OCV of power storage element 11 before current application and CCV during current application for one second by the current value (step S104).

[0053] The control unit 121 inputs the ΔOCV measured in step S103 and the DCR measured in step S104 into a function or table stored in the storage unit 122 to estimate the capacity maintenance ratio (step S105). Since the 1C discharge capacity measured in step S101 is measured at a reference temperature of 25°C, the control unit 121 may correct the capacity maintenance ratio in accordance with the temperature of the energy storage element 11 measured by the temperature sensor. The correction coefficient is determined in advance, for example, so that the capacity maintenance ratio decreases when the temperature is high and increases when the temperature is low.

[0054] As described above, in the embodiment, the capacity maintenance ratio can be accurately estimated by using ΔOCV and DCR even when the usage history of energy storage element 11 is unknown. Of course, the method for estimating the capacity maintenance ratio according to the embodiment can also be applied to energy storage element 11 whose usage history is known.

[0055] The disclosed embodiments are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims.

[0056] In the embodiment, the capacity maintenance rate is estimated as the post-degradation performance value at a predetermined degradation point of the storage element 11. However, it is also possible to estimate the discharge capacity that can be discharged from the storage element 11 at the predetermined degradation point, and to estimate the performance value as the post-degradation performance value by converting the discharge capacity into a performance value such as the remaining usage period, the number of times that the storage element 11 can be charged, the distance that the storage element 11 can travel, or the internal resistance value. [Explanation of symbols]

[0057] 1 vehicle 2 Server 10 battery cells 11 Energy storage element 12 BMU 13 Load 14 Control ECU 15 Communications Department 121 Control Unit 122 Storage section 123 Connection 124 Communications Department PG Estimation Program RM recording medium

Claims

1. An estimation device that estimates a post-degradation performance value that is a value indicating performance of a storage element at a predetermined degradation point, an acquisition unit that acquires a voltage change amount, which is the difference between an open circuit voltage of the storage element before current application and an open circuit voltage after current application has stopped, and a DC resistance value, which is the value obtained by dividing the difference between the open circuit voltage of the storage element before current application and a closed circuit voltage during current application by a current value; an estimation unit that estimates a post-degradation performance value of the energy storage element at the time of degradation based on the voltage change amount and the DC resistance value acquired by the acquisition unit, using a correlation that holds between the voltage change amount, the DC resistance value, and the post-degradation performance value; An estimation device comprising:

2. The estimation device according to claim 1 , wherein the correlation is expressed by a function having a product of the voltage change amount and the DC resistance value as an input value and the degraded performance value as an output value.

3. a correction unit that corrects the correlation in accordance with an environmental temperature of the storage element; The estimation device according to claim 1 , comprising:

4. A storage element; The estimation device according to any one of claims 1 to 3; A power storage device comprising:

5. A method for estimating a post-degradation performance value that is a value indicating performance of a storage element at a predetermined degradation point, comprising: a voltage change amount, which is the difference between the open circuit voltage of the storage element before the application of current and the open circuit voltage after the application of current is stopped, and a DC resistance value, which is the value obtained by dividing the difference between the open circuit voltage of the storage element before the application of current and the closed circuit voltage during the application of current by the current value; Using a correlation established between the voltage change amount, the DC resistance value, and the post-degradation performance value, the post-degradation performance value of the storage element at the time of degradation is estimated based on the voltage change amount and the current resistance value acquired by the acquisition unit. An estimation method in which the processing is performed by a computer.

6. A computer program for estimating a post-degradation performance value, which is a value indicating the performance of a storage element at a predetermined degradation point, a voltage change amount, which is the difference between the open circuit voltage of the storage element before the application of current and the open circuit voltage after the application of current is stopped, and a DC resistance value, which is the value obtained by dividing the difference between the open circuit voltage of the storage element before the application of current and the closed circuit voltage during the application of current by the current value; Using a correlation established between the voltage change amount, the DC resistance value, and the post-degradation performance value, the post-degradation performance value of the storage element at the time of degradation is estimated based on the voltage change amount and the current resistance value acquired by the acquisition unit. A computer program that causes a computer to execute a process.

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