Battery deterioration determination device, and storage battery deterioration determination method

Abstract

To accomplish a highly accurate deterioration determination of a storage battery.SOLUTION: A battery deterioration determination device (100), which is connected to a storage battery (2), comprises: an acquisition unit (101) that acquires a current value and voltage value of the storage battery; an internal resistance calculation unit (111) that calculates an actual measurement value of internal resistance of the storage battery on the basis of the current value and voltage value; an internal resistance determination unit (112) that determines whether to adopt the actual measurement value from any time point of the time-sequence actual measurement values; an approximation expression derivation unit (113) that derives an approximation expression approximating the internal resistance of the storage battery in the time-sequence on the basis of the actual measurement value having the adoption determined by the internal resistance determination unit; an approximate value calculation unit (114) that calculates an approximate value of the internal resistance of the storage battery, using the approximation expression; and a deterioration determination unit (115) that determines deterioration of the storage battery on the basis of the approximate value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery degradation determination device and a method for determining the degradation of a storage battery.

Background Art

[0002] It has been considered to determine the degradation of a storage battery based on the internal resistance of the storage battery. Patent Document 1 discloses a technique for measuring the internal resistance as the storage battery is operated and determining the degradation based on the time-series data of the measured internal resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Depending on the characteristics of the storage battery, the internal resistance does not always monotonically increase after the start of operation. In this case, it has been found that the accuracy of degradation determination is not always sufficient with the method of Patent Document 1. One aspect of the present invention aims to achieve highly accurate determination of the degradation of a storage battery.

Means for Solving the Problems

[0005] In order to solve the above problems, a battery deterioration determination device according to the present invention includes an acquisition unit that acquires a current value and a voltage value of a storage battery, an internal resistance calculation unit that calculates an actually measured value of the internal resistance of the storage battery based on the current value and the voltage value, an internal resistance determination unit that determines which of the actually measured values of the internal resistance in the time series calculated by the internal resistance calculation unit is to be adopted, an approximate expression derivation unit that derives an approximate expression for approximating the internal resistance of the storage battery in the time series based on the actually measured value of the internal resistance determined to be adopted by the internal resistance determination unit, an approximate value calculation unit that calculates an approximate value of the internal resistance of the storage battery using the approximate expression, and a deterioration determination unit that determines the deterioration of the storage battery based on the approximate value.

[0006] In order to solve the above problems, a method for determining deterioration of a storage battery according to the present invention includes an acquisition step of acquiring a current value and a voltage value of the storage battery, an internal resistance calculation step of calculating an actually measured value of the internal resistance of the storage battery based on the current value and the voltage value, an internal resistance determination step of determining which of the actually measured values of the internal resistance in the time series calculated in the internal resistance calculation step is to be adopted, an approximate expression derivation step of deriving an approximate expression for approximating the internal resistance of the storage battery in the time series based on the actually measured value of the internal resistance determined to be adopted in the internal resistance determination step, an approximate value calculation step of calculating an approximate value of the internal resistance of the storage battery using the approximate expression, and a deterioration determination step of determining the deterioration of the storage battery based on the approximate value.

Advantages of the Invention

[0007] According to the present invention, it is possible to accurately determine the deterioration of the storage battery.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0009] 〔Embodiment 1〕 Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "this embodiment") will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0010] (Configuration of the battery storage system 1) FIG. 1 is a block diagram showing the configuration of the main part of the battery storage system 1 according to Embodiment 1. The battery storage system 1 includes a storage battery 2, an ammeter 3, a voltmeter 4, an RTC (Real Time Clock) 5, and a battery deterioration determination device 100.

[0011] The storage battery 2 is a charging device that can store electricity, and is, for example, a lithium-ion battery or the like. The ammeter 3 measures the current value of the charge and discharge of the storage battery 2. The voltmeter 4 measures the voltage value of the charge and discharge of the storage battery 2. The ammeter 3 and the voltmeter 4 output the current value and the voltage value to the battery deterioration determination device 100, respectively. Further, the RTC 5 outputs the current time to the battery deterioration determination device 100. The RTC 5 may output the current time in response to a request from the battery deterioration determination device 100.

[0012] (Configuration of the battery deterioration determination device 100) The battery degradation determination device 100 includes an acquisition unit 101, an operation time measurement unit 102, a stop time measurement unit 103, a charge-discharge cycle count measurement unit 104, an internal resistance calculation unit 111, an internal resistance determination unit 112, an approximation formula derivation unit 113, an approximate value calculation unit 114, a degradation determination unit 115, a diagnosis availability determination unit 116, and a storage unit 120.

[0013] The acquisition unit 101 acquires the current value at which the storage battery 2 charges and discharges from the ammeter 3 and the voltage value at which the storage battery 2 charges and discharges from the voltmeter 4, respectively. The storage unit 120 may store the acquired current value and voltage value. The acquisition unit 101 outputs the acquired current value and voltage value to the internal resistance calculation unit 111.

[0014] The operation time measurement unit 102 acquires the current time from the RTC 5. The operation time measurement unit 102 monitors the operation state of the storage battery system 1, calculates the total operation time, and sequentially stores it in the storage unit 120 together with the actually measured value of the internal resistance (internal resistance actually measured value). Here, the operation time is the total time of the time when the storage battery 2 is charging and the time when the storage battery 2 is discharging.

[0015] The stop time measurement unit 103 acquires the current time from the RTC 5. The stop time measurement unit 103 monitors the stop state of the storage battery system 1, calculates the total stop time, and sequentially stores it in the storage unit 120 together with the actually measured value of the internal resistance. Here, the stop time is the time when the storage battery 2 is neither charging nor discharging, and this value is also the time obtained by subtracting the operation time from the total time.

[0016] The charge-discharge cycle count measurement unit 104 counts the charge-discharge cycle count of the storage battery 2 and stores the charge-discharge cycle count in the storage unit 120 together with the actually measured value of the internal resistance. The charge-discharge cycle count measurement unit 104, for example, starts charging when the SOC (State Of Charge) of the storage battery 2 is 10% or less and counts it as 1 cycle when the SOC becomes 90% or more. Note that the method of counting the charge-discharge cycles is not limited to this.

[0017] Here, the SOC of the storage battery 2 is calculated from the current capacity (unit: Ah) charged and discharged to the storage battery 2 after the storage battery 2 reaches the fully charged state (SOC 100%) or the fully discharged state (SOC 0%). Further, the storage battery 2 may be set to a stopped state where charging and discharging are not performed, and the SOC of the storage battery 2 may be calculated based on the current capacity charged and discharged to the storage battery 2 from the stopped state.

[0018] The internal resistance calculation unit 111 calculates the measured value of the internal resistance of the storage battery 2 based on the current value and the voltage value acquired by the acquisition unit 101. The internal resistance calculation unit 111 stores the measured value in the storage unit 120. The calculation of the measured value of the internal resistance in the internal resistance calculation unit 111 may use various conventional methods. For example, it may be calculated using the voltage value obtained by charging for a predetermined time at a constant current value from the standby state where charging and discharging are not performed.

[0019] The internal resistance determination unit 112 determines which measured value of the internal resistance at any time point among the time-series measured values of the internal resistance calculated by the internal resistance calculation unit 111 is to be adopted. The details of the operation of the internal resistance determination unit 112 will be described later.

[0020] The approximation formula derivation unit 113 derives an approximation formula for approximating the internal resistance of the storage battery 2 in time series based on the measured value of the internal resistance determined to be adopted by the internal resistance determination unit 112. The details of the approximation formula derivation unit 113 will be described later. Note that the approximation formula derivation unit 113 may use the operation time, the stop time, and the number of charge and discharge cycles.

[0021] For example, the following formula can be cited as an approximation formula: R1 = R0 + a×t1 α + b×t2 β + c×n γ ···(Equation 1) Here, R1 is the internal resistance of the storage battery 2 calculated using the approximation formula (Equation 1), and is the value used when performing the deterioration determination. When deriving the approximation formula, the measured value of the internal resistance is substituted into R1.

[0022] R0 is the initial value of the internal resistance of the storage battery 2 before or immediately after the start of operation. It is preferable that this initial value R0 is calculated by the internal resistance calculation unit 111 immediately after operation. Alternatively, it may be calculated before operation.

[0023] a is a coefficient obtained by approximating the internal resistance calculated a plurality of times over time for the storage battery 2 during operation. b is a coefficient obtained by approximating the internal resistance calculated a plurality of times over time for the storage battery 2 during the stopped state. c is a coefficient obtained by approximating the internal resistance calculated a plurality of times according to the number of charge / discharge cycles for the storage battery 2 during operation.

[0024] t1 is the elapsed time during the operation of the storage battery 2. Here, the operation time measured by the operation time measurement unit 102 and stored in the storage unit 120 is used. t2 is the elapsed time during the stopped state of the storage battery 2. Here, the stop time measured by the stop time measurement unit 103 and stored in the storage unit 120 is used. n is the number of charge / discharge cycles during the operation of the storage battery 2. Here, the number of charge / discharge cycles measured by the charge / discharge cycle number measurement unit 104 and stored in the storage unit 120 is used.

[0025] It is desirable that α, β, and γ be constants that minimize the error with respect to the change in the internal resistance of the storage battery 2. However, it is known that the decrease in the discharge capacity of a lithium-ion battery is proportional to the square root of the operation time, so-called the square root law. Therefore, these power constants may be set to 1 / 2. Also, since the DC internal resistance of a lithium-ion battery is said to be proportional to the operation time, these power constants may be set to 1.

[0026] Note that the storage battery 2 deteriorates even in a stopped state where no current is being charged or discharged. Therefore, by managing the operation time, stop time, and number of charge / discharge cycles, and calculating the internal resistance of the storage battery 2 using (Equation 1), a highly accurate approximation becomes possible. Note that when the stop time and the number of charge / discharge cycles cannot be measured, the coefficients b and c may be set to 0, and the internal resistance of the storage battery 2 may be approximated using only the operation time.

[0027] That is, the approximate formula derivation unit 113 derives an approximate formula for the internal resistance from the measured value of the internal resistance after the boundary time, the operation time, the stop time, and the number of charge and discharge cycles. As the approximate formula, a regression line (solid line in FIG. 2) between the measured value of the internal resistance after the boundary time and the operation time may be derived. Note that the regression line may be a regression curve, which is not a straight line but a curve. In addition, in order to derive the approximate formula, it is preferable that there are a predetermined number or more of measured values. Therefore, when the number of measured values is less than the predetermined number, the approximate formula derivation unit 113 may not derive the approximate formula. The predetermined number is, for example, 3.

[0028] The approximate value calculation unit 114 substitutes the latest operation time, stop time, and number of charge and discharge cycles into the approximate formula derived by the approximate formula derivation unit 113, and calculates an approximate value of the internal resistance of the storage battery 2.

[0029] The degradation determination unit 115 determines the degradation of the storage battery 2 by comparing the approximate value of the internal resistance of the storage battery 2 calculated by the approximate value calculation unit 114 with a determination value. The degradation determination unit 115 determines whether or not the approximate value of the internal resistance exceeds the determination value. The determination value is a threshold value determined by the user. The determination value is, for example, a value twice the initial value R0, and the degradation determination unit 115 may determine that the storage battery 2 is degraded when the approximate value of the internal resistance of the storage battery 2 calculated by the approximate value calculation unit 114 exceeds 2×R0.

[0030] The diagnosis permission determination unit 116 controls whether or not to perform the determinations in the approximate formula derivation unit 113, the approximate value calculation unit 114, and the degradation determination unit 115. The diagnosis permission determination unit 116 permits the diagnosis of the storage battery (determines whether the diagnosis is possible) when there are a predetermined number or more of measured values of the internal resistance.

[0031] When the number of measured values is small, it is considered that the accuracy of the approximate formula is low and sufficient reliability cannot be obtained. Therefore, the calculation of the approximate value by the approximate value calculation unit 114 and the diagnosis in the deterioration determination unit 115 are not permitted. That is, the approximate value calculation unit 114 and the deterioration determination unit 115 derive the approximate formula and perform the determination of deterioration when it is determined by the diagnosis permission determination unit 116 that the diagnosis of the storage battery is possible.

[0032] The storage unit 120 stores programs, parameters, and data used in each part of the battery deterioration determination device 100. For example, the storage unit 120 stores measured values of the internal resistance in time series, approximate formulas, operation time, stop time, number of charge and discharge cycles, and the like.

[0033] (Operation of the battery deterioration determination device 100) FIG. 2 is a flowchart showing the operation of the battery deterioration determination device 100 according to Embodiment 1. The processing of the flowchart is executed periodically.

[0034] The internal resistance calculation unit 111 calculates the measured value R of the internal resistance using the current value and voltage value acquired by the acquisition unit 101 (S1). real (S1).

[0035] The internal resistance determination unit 112 determines whether the measured value R real is greater than or equal to the threshold value R x1 (S2). If the measured value R real is less than the threshold value R x1 (No in S2), the internal resistance determination unit 112 determines that the storage battery 2 is not deteriorated (S3). Then, the process ends.

[0036] If the measured value R real is greater than or equal to the threshold value R x1 (Yes in S2), the internal resistance determination unit 112 determines whether the measured value R real is greater than or equal to the threshold value R x1The operation time when the above is satisfied is calculated as the boundary time (S4). That is, the internal resistance determination unit 112 determines which measured value in the time-series measured values to adopt. This determination criterion may be determined based on whether the measured values of the time-series internal resistance calculated by the internal resistance calculation unit 111 are increasing.

[0037] FIG. 3 is a diagram showing the time change of the internal resistance related to the operation of the battery deterioration determination device 100 according to Embodiment 1. In FIG. 3, the horizontal axis shows the value t1 when the operation time of the storage battery is t1. α (However, α is a constant of 0.1 to 1.5), and the vertical axis shows the internal resistance. In FIG. 3, α = 0.5.

[0038] As shown in FIG. 3, it can be seen that the internal resistance does not change much over time initially and has a tendency to increase after a certain period of time. In the former period, the internal resistance may not increase but may decrease. Thus, it has been found that depending on the storage battery, the temporal tendency of the internal resistance shows a different aspect in the initial stage of operation from other periods. Here, in FIG. 3, the horizontal axis is not the operation time t1 but t1 α because the internal resistance is often approximated by the square root of the operation time.

[0039] The internal resistance determination unit 112 calculates the boundary time when the increase in the measured value starts when a predetermined condition is satisfied. For example, the internal resistance determination unit 112 determines whether the measured value of the internal resistance has an increasing tendency and calculates the boundary time when the increase in the measured value starts. A predetermined condition is used to determine whether the measured value of the internal resistance has an increasing tendency.

[0040] The predetermined condition in Embodiment 1 is that the measured value becomes equal to or greater than a predetermined threshold value, and the operation time at this time is calculated as the boundary time. The predetermined threshold value may be a threshold value R obtained by adding a predetermined offset to the measured value R0 of the initial internal resistance of the storage battery 2. x1 That is, the internal resistance determination unit 112 determines that the measured value of the internal resistance is the threshold value R x1The operation time at this point is calculated as the boundary time. As a result, before the boundary time, it is the period during which the internal resistance does not increase, and after the boundary time, it is the period during which the internal resistance increases.

[0041] The diagnosis feasibility determination unit 116 determines whether the number of accumulated data, which is a combination of the measured value R real and the operation time, is equal to or greater than a predetermined number (S5). If the number of accumulated data is less than the predetermined number (No in S5), the diagnosis feasibility determination unit 116 determines that the data is insufficient (S6). Then, the process ends.

[0042] If the number of accumulated data is equal to or greater than the predetermined number (Yes in S5), the approximate formula derivation unit 113 derives an approximate formula using all the data after the boundary time (S7). Here, as a specific example, regarding FIG. 2, the approximate formula in Embodiment 1 is compared with the approximate formula when the approximate formula is derived based on all the measured values from the operation start point, which is a comparative example. In each approximate formula, a = 1, b = 0, c = 0, and α = 0.5.

[0043] The value of R 2 in FIG. 3 is the coefficient of determination, and the closer the coefficient of determination is to 1, the more accurately it can be approximated. The coefficient of determination of the comparative example is 0.6230, while the coefficient of determination of Embodiment 1 is 0.9558. That is, it can be seen that Embodiment 1 can approximate with higher accuracy than the comparative example. This is because by approximating only with the data after the boundary time without using the data before the boundary time with different trends, the trend can be faithfully represented.

[0044] The approximate value calculation unit 114 calculates the approximate value R ana of the internal resistance at the time of determining deterioration using the approximate formula (S8).

[0045] The deterioration determination unit 115 determines whether the approximate value R ana is equal to or greater than the determination value R x2 (S9). Whether the approximate value R ana is equal to or greater than the determination value R x2If it is less (No in S9), the deterioration determination unit 115 determines that the storage battery 2 has not deteriorated (S10). Then, the process ends. Approximation value R ana is the determination value R x2 If it is greater than or equal (Yes in S9), the deterioration determination unit 115 determines that the storage battery 2 has deteriorated (S11). Then, the process ends.

[0046] Depending on the characteristics and usage of the storage battery 2, the determination value R for determining deterioration x2 is different. Therefore, it is difficult to determine the determination value unconditionally. For example, the determination value R x2 is set to a value twice that of the initial value R0, and the deterioration determination unit 115 determines the deterioration of the storage battery 2 when the approximation value R x2 is greater than or equal to ana .

[0047] (Differences in the frequency of each process) Note that the processes of the approximation value calculation unit 114 and the deterioration determination unit 115 may be processed more frequently than the processes of the acquisition unit 101, the internal resistance calculation unit 111, the internal resistance determination unit 112, and the approximation formula derivation unit 113. The acquisition of the measured value may be performed only a limited number of times. In this case, naturally, the derivation of the approximation formula can also be performed only a limited number of times (frequency).

[0048] However, it is not always the case that deterioration determination needs to be performed only at the timing when the approximation formula is derived. Therefore, the processes of the approximation value calculation unit 114 and the deterioration determination unit 115 may be performed more frequently than the processes of the acquisition unit 101, the internal resistance calculation unit 111, the internal resistance determination unit 112, and the approximation formula derivation unit 113, which are performed a limited number of times. That is, by performing low-frequency processes, an approximation formula can be derived to model the trend of the internal resistance of the storage battery 2, and by performing high-frequency processes, the deterioration determination of the storage battery 2 can be performed in real time. Therefore, it is possible to prevent the storage battery 2 from being mistakenly used continuously after it has deteriorated.

[0049] When an approximate formula has been derived, the approximate formula may be output to a device (not shown) that directly controls the storage battery 2, and in this device, the processes of the approximate value calculation unit 114 and the deterioration determination unit 115 may be performed. In this case, there is an advantage that edge processing for deterioration determination of the storage battery 2 becomes possible.

[0050] 〔Embodiment 2〕 Another embodiment of the present invention will be described below. For convenience of explanation, members having the same functions as those described in the above embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

[0051] FIG. 4 is a flowchart showing the operation of the battery deterioration determination device 100 according to Embodiment 2. Instead of S2, the processes of S21 to S22 are performed. Instead of S4, the process of S23 is performed.

[0052] The internal resistance determination unit 112 calculates the slope S of the regression line between the measured value R real stored in the storage unit 120 and time (S21). The internal resistance determination unit 112 determines whether or not the slope S has been continuously positive for a predetermined number of times (S22). If the slope S has not been continuously positive for a predetermined number of times (No in S22), the process of S3 is performed.

[0053] FIG. 5 is a diagram showing the time change of the internal resistance related to the operation of the battery deterioration determination device 100 according to Embodiment 2. In FIG. 5, the value t1 when the operating time of the storage battery is t1 is taken on the horizontal axis α (where α is a constant of 0.1 to 1.5), the slope of the regression line described later is taken on the first vertical axis, and the internal resistance is taken on the second vertical axis. In FIG. 5, α = 0.5.

[0054] The slope of the regression line may be obtained by drawing a regression line based on all the data up to that time. Alternatively, a regression line in the process of changing from the previous measured value to the current measured value may be drawn for each span. That is, the slope of the regression line for all the data may be used, or the slope (slope of the regression line) obtained by linearly interpolating for each span between the measurement intervals may be used.

[0055] As a predetermined condition in Embodiment 2, when the slope of the regression line has been positive for a predetermined number of consecutive times, or when the slope of the regression line has been positive for a predetermined number of consecutive times, the first time the slope of the regression line becomes positive. That is, among the measured values of the internal resistance in time series calculated by the internal resistance calculation unit 111, the measured values of the internal resistance from the initial time to each time point at which the measured value of the internal resistance is calculated are used, and the operation time of the storage battery is set as t1, and the value t1 α (where α is a constant of 0.1 to 1.5), a regression line approximating the internal resistance of the storage battery 2 is sequentially calculated.

[0056] Then, when the slope of the regression line has been positive for a predetermined number of consecutive times, it is calculated as the boundary time, or when the slope of the regression line has been positive for a predetermined number of consecutive times, the first time the slope of the regression line becomes positive is calculated as the boundary time. Thereby, it is possible to surely detect that the period in which the internal resistance increases has been entered. Note that the regression line may be a regression curve.

[0057] When the slope S has been positive for a predetermined number of consecutive times (Yes in S22), the operation time when the slope S has been positive for a predetermined number of consecutive times is calculated as the boundary time (S23).

[0058] 〔Summary〕 The battery deterioration determination device according to Aspect 1 of the present invention includes an acquisition unit that acquires a current value and a voltage value of a storage battery, an internal resistance calculation unit that calculates a measured value of the internal resistance of the storage battery based on the current value and the voltage value, and among the measured values of the internal resistance in time series calculated by the internal resistance calculation unit, an internal resistance determination unit that determines which time point's measured value of the internal resistance to adopt, and based on the measured value of the internal resistance determined to be adopted by the internal resistance determination unit, an approximate expression derivation unit that derives an approximate expression approximating the internal resistance of the storage battery in time series, an approximate value calculation unit that calculates an approximate value of the internal resistance of the storage battery using the approximate expression, and a deterioration determination unit that determines the deterioration of the storage battery based on the approximate value.

[0059] According to the above configuration, it is possible to accurately determine the deterioration of the storage battery.

[0060] In the battery deterioration determination device according to Embodiment 2 of the present invention, in the above Embodiment 1, the internal resistance determination unit calculates a boundary time at which an increase starts in the time-series internal resistance measured values calculated by the internal resistance calculation unit, and determines the internal resistance measured values after the boundary time as the internal resistance measured values to be adopted.

[0061] According to the above configuration, it is possible to appropriately model the change in the behavior of the characteristics of the storage battery before and after the boundary time, and to accurately determine the deterioration state of the storage battery.

[0062] In the battery deterioration determination device according to Embodiment 3 of the present invention, in the above Embodiment 2, it may be configured to calculate the time when the internal resistance measured value becomes equal to or greater than a predetermined threshold value as the boundary time.

[0063] According to the above configuration, the boundary time can be appropriately calculated.

[0064] In the battery deterioration determination device according to Embodiment 4 of the present invention, the internal resistance determination unit uses the internal resistance measured values from the initial time to each time point at which the internal resistance measured value is calculated among the time-series internal resistance measured values calculated by the internal resistance calculation unit, and sets the operation time of the storage battery as t. For the value t α (where α is a constant of 0.1 to 1.5), a regression line approximating the internal resistance of the storage battery is sequentially calculated, and the time when the slope of the regression line becomes positive for a predetermined number of consecutive times is calculated as the boundary time.

[0065] According to the above configuration, the boundary time can be appropriately calculated.

[0066] In the battery deterioration determination device according to Embodiment 5 of the present invention, the internal resistance determination unit uses the internal resistance measured values from the initial time to each time point at which the internal resistance measured value is calculated among the time-series internal resistance measured values calculated by the internal resistance calculation unit, and sets the operation time of the storage battery as t. For the value tα For (where α is a constant between 0.1 and 1.5), a regression line approximating the internal resistance of the storage battery is sequentially calculated, and when the slope of the regression line remains positive for a predetermined number of consecutive times, the time when the slope of the regression line first becomes positive may be calculated as the boundary time.

[0067] According to the above configuration, the boundary time can be appropriately calculated.

[0068] The battery deterioration determination device according to Aspect 6 of the present invention further includes a diagnosis availability determination unit that determines the availability of diagnosis of the storage battery based on whether there are a predetermined number or more of the actually measured internal resistance values after the boundary time in any of the above Aspects 2 to 5. The approximate expression derivation unit may be configured to derive the approximate expression when the diagnosis availability determination unit determines that the diagnosis of the storage battery is possible.

[0069] According to the above configuration, it is possible to perform the diagnosis of the storage battery only when the deterioration can be determined with sufficient accuracy.

[0070] The battery deterioration determination device according to Aspect 7 of the present invention may be configured to further include a storage unit that stores the time-series actually measured internal resistance values calculated by the internal resistance calculation unit over time in any of the above Aspects 1 to 6.

[0071] According to the above configuration, based on the past data of the actually measured values, the deterioration determination can be performed by the storage unit.

[0072] The method for determining the deterioration of a storage battery according to Aspect 8 of the present invention includes an acquisition step of acquiring the current value and voltage value of the storage battery, an internal resistance calculation step of calculating the actually measured internal resistance value of the storage battery based on the current value and the voltage value, an internal resistance determination step of determining which of the actually measured internal resistance values in the time series calculated in the internal resistance calculation step to adopt, an approximate expression derivation step of deriving an approximate expression for approximating the internal resistance of the storage battery in time series based on the actually measured internal resistance value determined to be adopted in the internal resistance determination step, an approximate value calculation step of calculating an approximate value of the internal resistance of the storage battery using the approximate expression, and a deterioration determination step of determining the deterioration of the storage battery based on the approximate value.

[0073] According to the above configuration, it is possible to determine the deterioration of the storage battery with high accuracy.

[0074] 〔Supplementary Notes〕 The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0075] 1 Battery system 2 Storage battery 3 Ammeter 4 Voltmeter 5 RTC 100 Battery deterioration determination device 101 Acquisition unit 102 Operation time measurement unit 103 Stop time measurement unit 104 Charge / discharge cycle count measurement unit 111 Internal resistance calculation unit 112 Internal resistance determination unit 113 Approximate expression derivation unit 114 Approximate value calculation unit 115 Deterioration determination unit 116 Diagnosis availability determination unit 120 Memory unit

Claims

1. An acquisition unit that acquires the current value and voltage value of a storage battery; An internal resistance calculation unit that calculates an actually measured value of the internal resistance of the storage battery based on the current value and the voltage value; An internal resistance determination unit that determines which of the actually measured values of the internal resistance in the time series calculated by the internal resistance calculation unit is to be adopted; An approximate expression derivation unit that derives an approximate expression for approximating the internal resistance of the storage battery in time series based on the actually measured value of the internal resistance determined to be adopted by the internal resistance determination unit; An approximate value calculation unit that calculates an approximate value of the internal resistance of the storage battery using the approximate expression; A battery deterioration determination device comprising a deterioration determination unit that determines the deterioration of the storage battery based on the approximate value.

2. The internal resistance determination unit calculates a boundary time at which an increase starts in the actually measured values of the internal resistance in the time series calculated by the internal resistance calculation unit, and determines the actually measured value of the internal resistance after the boundary time as the actually measured value of the internal resistance to be adopted. The battery deterioration determination device according to claim 1.

3. The internal resistance determination unit calculates the boundary time when the actually measured value of the internal resistance becomes equal to or greater than a predetermined threshold value. The battery deterioration determination device according to claim 2.

4. The internal resistance determination unit uses the actually measured values of the internal resistance in the time series calculated by the internal resistance calculation unit from the initial time to each time point at which the actually measured value of the internal resistance is calculated, and sets the operation time of the storage battery as t. For the value t α (where α is a constant of 0.1 to 1.5), sequentially calculates a regression line for approximating the internal resistance of the storage battery, and calculates the boundary time when the slope of the regression line becomes positive for a predetermined number of consecutive times. The battery deterioration determination device according to claim 2.

5. The internal resistance determination unit uses the measured internal resistance values from the initial time to each time point when the measured internal resistance values are calculated among the time-series measured internal resistance values calculated by the internal resistance calculation unit, and sets the operation time of the storage battery as t, and uses the value t α (where α is a constant of 0.1 to 1.5), sequentially calculates a regression line approximating the internal resistance of the storage battery, and when the slope of the regression line becomes positive for a predetermined number of consecutive times, calculates the time when the slope of the regression line first becomes positive as the boundary time. The battery degradation determination device according to claim 2.

6. Further comprising a diagnosis availability determination unit that determines the availability of diagnosis of the storage battery based on whether there are a predetermined number or more of the measured internal resistance values after the boundary time, The approximate formula derivation unit derives the approximate formula when the diagnosis availability determination unit determines that the diagnosis of the storage battery is possible. The battery degradation determination device according to claim 2.

7. Further comprising a storage unit that stores the time-series measured internal resistance values calculated by the internal resistance calculation unit over time. The battery degradation determination device according to claim 1.

8. An acquisition step of acquiring a current value and a voltage value of a storage battery, An internal resistance calculation step of calculating a measured internal resistance value of the storage battery based on the current value and the voltage value, An internal resistance determination step of determining which time point's measured internal resistance value among the time-series measured internal resistance values calculated in the internal resistance calculation step to adopt, An approximate formula derivation step of deriving an approximate formula approximating the internal resistance of the storage battery in time series based on the measured internal resistance value determined to be adopted in the internal resistance determination step, An approximate value calculation step of calculating an approximate value of the internal resistance of the storage battery using the approximate formula, A degradation determination method for a storage battery, including a degradation determination step of determining the degradation of the storage battery based on the approximate value.

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