Estimation system, calculation device, estimation method, and program

Abstract

To provide an estimation system that can estimate a cycle life of a lithium-ion battery.SOLUTION: An estimation system 1 estimates a cycle life of a power storage device B1 (e.g., lithium-ion battery). The estimation system 1 comprises a measurement unit 4, a calculation unit 5 and a life estimation unit 6. The measurement unit 4 measures a first charging time and a second charging time. The calculation unit 5 calculates a value of a ratio obtained by dividing the first charging time by the second charging time. The life estimation unit 6 calculates a difference obtained by subtracting a first cycle number when a minimum point appears from a second cycle number when a maximal point appears after the minimum point appears in a curve along an upper end of a graph representing the behavior of the value of the ratio following the transition of the cycle numbers. The life estimation unit 6 sets a third cycle number obtained by adding the difference to the second cycle number as an estimation value of the cycle life.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure generally relates to an estimation system, a calculation device, an estimation method, and a program, and more particularly to an estimation system that estimates the cycle life of a lithium-ion battery, and a calculation device, an estimation method, and a program used in the estimation system. [Background technology]

[0002] The storage battery management system (estimation system) described in Patent Document 1 includes a temperature detection unit, an internal resistance measurement unit, and a remaining life estimation unit. The temperature detection unit detects the temperature of a cell of a storage battery. The internal resistance measurement unit measures the internal resistance of the cell connected to a load. The remaining life estimation unit estimates the remaining life of the cell based on the temperature detected by the temperature detection unit and the internal resistance measured by the internal resistance measurement unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-81218 Summary of the Invention [Problem to be solved by the invention]

[0004] In the battery management system described in Patent Document 1, the remaining life (cycle life) of a lithium ion battery is estimated based on the cell temperature and the internal resistance of the cell connected to a load. However, with this estimation means, it is difficult to estimate the cycle life when the lithium ion battery rapidly deteriorates at the end of its life.

[0005] An object of the present disclosure is to provide an estimation system, a calculation device, an estimation method, and a program capable of estimating the cycle life of a lithium ion battery when the lithium ion battery rapidly deteriorates toward the end of its life. [Means for solving the problem]

[0006] An estimation system according to an embodiment of the present disclosure is an estimation system for estimating a cycle life of a lithium ion battery. The lithium ion battery is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum. The estimation system includes a measurement unit, a calculation unit, and a life estimation unit. The measurement unit measures a first charging time and a second charging time for each cycle of the lithium ion battery. The first charging time is the charging time of the lithium ion battery when the lithium ion battery is charged by the constant current constant voltage control. The second charging time is the charging time of the lithium ion battery when the lithium ion battery is charged by the constant voltage control. The calculation unit calculates a ratio obtained by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured by the measurement unit. The life estimation unit calculates a difference by subtracting a first cycle number, which is the number of cycles when a minimum point appears, from a second cycle number, which is the number of cycles when a maximum point appears after the minimum point appears, in a curve along the upper end of a graph showing the behavior of the value of the ratio with the change in the number of cycles of the lithium ion battery over time. The life estimation unit calculates a third cycle number by adding the difference to the second cycle number, and sets the third cycle number as the estimated value of the cycle life.

[0007] An estimation system according to an embodiment of the present disclosure is an estimation system for estimating a cycle life of a lithium ion battery. The lithium ion battery is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum. The estimation system includes a measurement unit, a calculation unit, and a life estimation unit. The measurement unit measures a first charging time and a second charging time for each cycle of the lithium ion battery. The first charging time is the charging time of the lithium ion battery when the lithium ion battery is charged by the constant current constant voltage control. The second charging time is the charging time of the lithium ion battery when the lithium ion battery is charged by the constant voltage control. The calculation unit calculates a ratio obtained by dividing the second charging time by the first charging time based on the first charging time and the second charging time measured by the measurement unit. The life estimation unit calculates a difference by subtracting a first cycle number, which is the number of cycles when a maximum point appears, from a second cycle number, which is the number of cycles when a minimum point appears after the maximum point appears, in a curve along the upper end of a graph showing the behavior of the value of the ratio with the change in the number of cycles of the lithium ion battery over time. The life estimation unit calculates a third cycle number by adding the difference to the second cycle number, and sets the third cycle number as the estimated value of the cycle life.

[0008] An estimation system according to an embodiment of the present disclosure is an estimation system for estimating the cycle life of a lithium ion battery. The lithium ion battery is charged by constant current and constant voltage control for each cycle. In the constant current and constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum. The estimation system includes a measurement unit, a calculation unit, and a life estimation unit. The measurement unit measures a first charge capacity and a second charge capacity for each cycle of the lithium ion battery. The first charge capacity is the charge capacity of the lithium ion battery when it is charged by the constant current and constant voltage control. The second charge capacity is the charge capacity of the lithium ion battery when it is charged by the constant voltage control. The calculation unit calculates a ratio obtained by dividing the first charge capacity by the second charge capacity based on the first charge capacity and the second charge capacity measured by the measurement unit. The life estimation unit calculates a difference by subtracting a first cycle number, which is the number of cycles when a minimum point appears, from a second cycle number, which is the number of cycles when a maximum point appears after the minimum point appears, in a curve along the upper end of a graph showing the behavior of the value of the ratio with the change in the number of cycles of the lithium ion battery over time. The life estimation unit calculates a third cycle number by adding the difference to the second cycle number, and sets the third cycle number as the estimated value of the cycle life.

[0009] An estimation system according to an embodiment of the present disclosure is an estimation system for estimating a cycle life of a lithium ion battery. The lithium ion battery is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum. The estimation system includes a measurement unit, a calculation unit, and a life estimation unit. The measurement unit measures a first charge capacity and a second charge capacity for each cycle of the lithium ion battery. The first charge capacity is the charge capacity of the lithium ion battery when it is charged by the constant current constant voltage control. The second charge capacity is the charge capacity of the lithium ion battery when it is charged by the constant voltage control. The calculation unit calculates a ratio obtained by dividing the second charge capacity by the first charge capacity based on the first charge capacity and the second charge capacity measured by the measurement unit. The life estimation unit calculates a difference by subtracting a first cycle number, which is the number of cycles when a maximum point appears, from a second cycle number, which is the number of cycles when a minimum point appears after the maximum point appears, in a curve along the upper end of a graph showing the behavior of the value of the ratio with the change in the number of cycles of the lithium ion battery over time. The life estimation unit calculates a third cycle number by adding the difference to the second cycle number, and sets the third cycle number as the estimated value of the cycle life.

[0010] A calculation device according to an aspect of the present disclosure is a calculation device used in the estimation system. The calculation device includes the measurement unit, the calculation unit, and a communication unit. The communication unit transmits information regarding the value of the ratio calculated by the calculation unit to a predetermined device.

[0011] An estimation method according to an embodiment of the present disclosure is a method for estimating a cycle life of a lithium ion battery. The lithium ion battery is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum. The estimation method includes a measurement step, a calculation step, and a life estimation step. In the measurement step, a first charging time and a second charging time are measured for each cycle of the lithium ion battery. The first charging time is the charging time of the lithium ion battery when the lithium ion battery is charged by the constant current constant voltage control. The second charging time is the charging time of the lithium ion battery when the lithium ion battery is charged by the constant voltage control. In the calculation step, a ratio value obtained by dividing the first charging time by the second charging time is calculated based on the first charging time and the second charging time measured in the measurement step. In the life estimation step, a difference is calculated by subtracting a first cycle number, which is the number of cycles when a minimum point appears on a curve along the upper end of a graph showing the behavior of the value of the ratio with the transition of the number of cycles of the lithium ion battery, from a second cycle number, which is the number of cycles when a maximum point appears after the minimum point appears. In the life estimation step, a third cycle number, which is the second cycle number plus the difference, is set as the estimated value of the cycle life.

[0012] A program according to one aspect of the present disclosure causes a computer to execute the estimation method. Effect of the Invention

[0013] The estimation system, calculation device, estimation method, and program disclosed herein have the advantage of being able to estimate the cycle life of a lithium ion battery when the lithium ion battery rapidly deteriorates toward the end of its life. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 is a diagram illustrating the rapid deterioration that occurs in a lithium ion battery toward the end of its life. [Diagram 2] FIG. 2 is a diagram for explaining the behavior of the ratio value γ with the change in the number of cycles. [Diagram 3] FIG. 3 is an explanatory diagram for explaining the behavior of the OCV after cycle discharge with the change in the number of cycles. [Figure 4] FIG. 4 is a block diagram of the estimation system according to the first embodiment. [Diagram 5] FIG. 5 is a flowchart illustrating the operation of the estimation system. [Figure 6] FIG. 6 is a graph showing an example of the function f(DS1,i,T). [Figure 7] FIG. 7 is a block diagram of an estimation system according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (1) Embodiment 1 Hereinafter, an estimation system according to an embodiment will be described with reference to the drawings.

[0016] (1-1) Overview The estimation system 1 according to the first embodiment estimates the cycle life of the power storage device B1 (e.g., a lithium ion battery). The power storage device B1 is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the power storage device B1 is charged by constant current control until the battery voltage of the power storage device B1 reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the power storage device B1 is charged by constant voltage control until the plate resistance of the power storage device B1 reaches a maximum. The estimation system 1 includes a measurement unit 4, a calculation unit 5, and a life estimation unit 6. The measurement unit 4 measures a first charging time and a second charging time for each cycle of the power storage device B1. The first charging time is the charging time of the power storage device B1 when it is charged by constant current constant voltage control. The second charging time is the charging time of the power storage device B1 when it is charged by constant voltage control. The calculation unit 5 calculates a ratio value γ obtained by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured by the measurement unit 4. The value γ is a function f(I, T) with parameters of the current I flowing through the power storage device B1 during charging and discharging and the atmospheric temperature T of the power storage device B1, and is based on values ​​under constant conditions of the current I and temperature T. When these parameters fluctuate, the efficiency at the time of the fluctuation is obtained. The efficiency at the time of the fluctuation is a value obtained by multiplying the ratio (Coulomb efficiency) of the charging current amount (discharging current amount) at the reference charging current to the charging current amount (discharging current amount) at the fluctuated charging current by the ratio of the charging current amount (discharging current amount) under the reference temperature atmosphere to the charging current amount (discharging current amount) under the fluctuated temperature atmosphere.

[0017] The life estimation unit 6 calculates a difference Δc by subtracting a first cycle number c1, which is the cycle number when the minimum point P1 appears, from a second cycle number c2, which is the cycle number when the maximum point P2 appears after the minimum point P1 appears, in a curve G4 along the upper end of the graph G2 that shows the behavior of the ratio value γ with the change in the number of cycles of the power storage device B1. The life estimation unit 6 estimates the cycle life by adding the absolute value of the difference Δc to the second cycle number c2 to obtain a cycle number c3 (third cycle number).

[0018] According to this configuration, the cycle life of the power storage device B1 is estimated using the ratio value γ calculated for each cycle, so that the cycle life of the power storage device B1 can be estimated in the event that the power storage device B1 rapidly deteriorates toward the end of its life.

[0019] (1-2) Characteristics of time transition of the state of health (SOH) of lithium-ion batteries Graph G1 in Fig. 1 shows the time progression of the degradation state of a lithium-ion battery. As shown in Fig. 1, the degradation state of a lithium-ion battery progresses in the following order: a first period T1 in which primary degradation occurs, a second period T2 in which secondary degradation occurs, and a third period T3 in which tertiary degradation occurs.

[0020] Primary degradation is degradation that occurs due to factors such as the collapse of crystals in the positive electrode of a lithium-ion battery caused by charging. Due to this primary degradation, the degradation state of a lithium-ion battery drops sharply in the early stages (i.e., it deteriorates rapidly).

[0021] Secondary degradation occurs when time continues to progress after the primary degradation due to a decrease in reversible lithium ions caused by liquid decomposition at the negative electrode of the lithium ion battery. This secondary degradation causes the degradation state of the lithium ion battery to decrease relatively slowly (i.e., deteriorate relatively slowly).

[0022] Tertiary degradation occurs after secondary degradation due to the sudden deposition of lithium ions on the negative electrode of a lithium-ion battery caused by charging. This tertiary degradation causes the degradation state of the lithium-ion battery to suddenly decrease (i.e., to suddenly deteriorate).

[0023] In FIG. 1, a certain time t1 in the second period T2 is the current time. That is, in FIG. 1, the left side of the time t1 is the past, and the right side of the time t1 is the future. In the graph G1, the left side of the time t1 is the actually measured part, and the right side of the time t1 is the predicted (estimated) part. Conventionally, the life or remaining life of a lithium ion battery is estimated by extrapolation using information on the deterioration state of the lithium ion battery in a certain period (second period T2) until the current time t1. For example, in the above extrapolation, the change rate (decrease rate) of the deterioration state of the lithium ion battery in a certain period (second period T2) until the current time t1 is obtained, and as shown by the dotted line R1 in FIG. 1, the time when the deterioration state at the current time t1 continues to deteriorate at the obtained change rate and reaches a predetermined deterioration state (for example, 60%) is set to t2. At this time, the time from the current time t1 to the time t2 is estimated as the remaining life. Or, the time from the time t0 when the deterioration state of the lithium ion battery is 100% to the time t2 is estimated as the life.

[0024] However, this extrapolation method for estimating the lifespan of a lithium-ion battery makes it difficult to estimate the lifespan when the tertiary deterioration of the third period T3 occurs. For this reason, it is necessary to consider a new deterioration index for estimating the time when the tertiary deterioration occurs (i.e., the start time of the third period T3).

[0025] (1-3) New Deterioration Indicators In the first embodiment, the lithium ion battery is charged and discharged by constant current and constant voltage control. In the constant current and constant voltage control, the lithium ion battery is first charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage. When the battery voltage of the lithium ion battery reaches the predetermined voltage, the constant current control is switched to constant voltage control. The lithium ion battery is then charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum. One cycle of a lithium ion battery is the flow from charging once to discharging the lithium ion battery.

[0026] In such constant current constant voltage control, for each cycle of the lithium ion battery, a ratio value γ (=first charging time / second charging time) between a first charging time, which is the charging time of the lithium ion battery when it is charged by the above-mentioned constant current constant voltage control, and a second charging time, which is the charging time of the lithium ion battery when it is charged by the above-mentioned constant voltage control, is considered. Then, the behavior of the ratio value γ with the transition of the number of cycles is considered. Note that the second charging time is the time that the charging time by constant voltage control occupies within the charging time by constant current constant voltage control (first charging time).

[0027] Graph G2 shown in FIG. 2 is a graph in the case of using a lithium-ion battery with a rate of 0.7C under a temperature of 10°C. The rate (also called "C rate") is a value obtained by dividing the nominal capacity [Ah] of the battery by the output current [A] of the battery, and indicates the current load per active material in the battery. Graph G2 shows the behavior of the ratio value γ with the transition of the cycle number. Graph G3 shown in FIG. 2 shows the behavior of the deterioration state of the lithium-ion battery with the transition of the cycle number. Graph G3 is a graph in which the horizontal axis of graph G1 in FIG. 1 is converted to the cycle number, and is substantially the same as graph G1. Therefore, like graph G1, graph G3 also drops sharply in the third period T3 corresponding to the end of the lithium-ion battery. Graph G4 shown in FIG. 2 is a curve along the upper end of graph G2. More specifically, graph G4 is a curve approximating the upper end of graph G2 with a smooth curve. In FIG. 2, the left vertical axis indicates the ratio value γ, the right vertical axis indicates the deterioration state of the lithium ion battery, and the horizontal axis indicates the number of cycles.

[0028] As shown in Fig. 2, in graph G4, as the number of cycles changes (i.e., moving from left to right), a minimum point P1 appears when the number of cycles is, for example, 1020 [cyc], then it rises, and a maximum point P2 appears when the number of cycles is, for example, 1735 [cyc], and then it drops sharply. Note that [cyc] is the unit of the number of cycles. It can also be seen that the sudden drop after the maximum point P2 in graph G4 coincides in timing with the sudden drop (i.e., tertiary degradation) in the third period T3 in graph G3.

[0029] That is, it is understood that it is possible to estimate the number of cycles c3 at the start of occurrence of the tertiary deterioration of the graph G3 (i.e., the start of the third period T3) by using the graph G4 obtained from the graph G2 (i.e., the ratio value γ). That is, it is understood that the ratio value γ can be used as a new deterioration index.

[0030] (1-4) Method for estimating the number of cycles c3 using a new deterioration index (ratio value γ) The number of cycles c3 is the start point of the third period T3 at which the tertiary deterioration occurs. As shown in FIG. 2, in the graph G4 obtained from the ratio value γ (i.e., the graph G2), as the number of cycles changes, first, a minimum point P1 appears, then it rises and a maximum point P2 appears, and then it suddenly drops. That is, in the graph G4, the minimum point P1 and the maximum point P2 appear before the sudden drop. In this behavior, the number of cycles at the minimum point P1 is c1, the number of cycles at the maximum point P2 is c2, and the difference (c2-c1) in the number of cycles from the minimum point P1 to the maximum point P2 is Δc. At this time, it can be seen that the number of cycles c3 at the start of the third period T3 can be approximated by the number of cycles (c2+Δc) obtained by adding the difference Δc to the number of cycles c2. That is, it can be seen that the number of cycles c3 at the start of the third period T3 is given by Equation 1.

[0031]

number

[0032] Then, the number of cycles c1 calculated by Equation 1 is compared with the reference cycle life c4. The reference cycle life c4 is the cycle life of the lithium-ion battery estimated by extrapolation. More specifically, the reference cycle life c4 is the number of cycles when the state of charge (SOC) of the lithium-ion battery reaches a predetermined state of charge (e.g., 60%) when the extension line L1 extends the graph G3 from near point P3 of the graph G3 at the number of cycles c2 at a predetermined rate of change (i.e., the rate of change when the graph G3 is decreasing relatively slowly in the second period T2) (see FIG. 2).

[0033] As a result of the above comparison, when the cycle number c3 obtained by the formula 1 is larger than the reference cycle life c4, the reference cycle life c4 of the lithium ion battery comes before the tertiary deterioration of the third period T3, so the tertiary deterioration of the third period T3 does not actually occur. On the other hand, when the cycle number c3 obtained by the formula 1 is smaller than the reference cycle life c4, the tertiary deterioration of the third period T3 occurs before the reference cycle life c4 of the lithium ion battery, so in this case, it is possible to predict the occurrence of the tertiary deterioration of the third period T3. In other words, it is possible to predict whether the tertiary deterioration of the third period T3 occurs depending on whether the cycle number c3 obtained by the formula 1 is smaller than the reference cycle life c4. In the first embodiment, this cycle number c3 is used as an estimated value of the cycle life of the lithium ion battery when the tertiary deterioration occurs.

[0034] [Table 1]

[0035] Table 1 shows the calculated values ​​(Equation 1) of the cycle number c1, the cycle number c2, and the cycle number c3, the measured value of the cycle number c3, and the reference cycle life c4 when a lithium-ion battery is used with a rate of 0.7C and a battery temperature of 10°C. From Table 1, it can be seen that in a lithium-ion battery with a rate of 0.7C and a battery temperature of 10°C, the calculated value and the measured value of the cycle number c3 almost match. In addition, since the calculated value of the cycle number c3 is smaller than the reference cycle life c4, it is predicted that tertiary deterioration will occur in the third period T3. In this case, the cycle life of the lithium-ion battery is estimated to be the number of cycles (2450 [cyc]) given by the calculated value of the cycle number c3.

[0036] [Table 2]

[0037] Table 2 shows the calculated values ​​(Equation 1) of the cycle number c1, the cycle number c2, and the cycle number c3, the measured value of the cycle number c3, and the reference cycle life c4 when a lithium-ion battery is used with a rate of 1.0C and a battery temperature of 10°C and 20°C. From Table 2, it can be seen that the calculated value and the measured value of the cycle number c3 almost match even when the lithium-ion battery is used with a rate of 1.0C and a battery temperature of 10°C or 20°C. In addition, since the calculated value of the cycle number c3 is smaller than the reference cycle life c4, it is predicted that tertiary deterioration will occur in the third period T3. In this case, the cycle life of the lithium-ion battery when the battery temperature is 20°C is estimated to be 3004 [cyc] given by the calculation formula. In addition, the cycle life of the lithium-ion battery when the battery temperature is 10°C is estimated to be 1378 [cyc] given by the calculation formula.

[0038] (1-5) Correlation between the new deterioration index (ratio value γ) and the third deterioration in the third period T3 3 shows the behavior of the OCV (Open Circuit Voltage) of a lithium-ion battery after cyclic discharge with respect to the number of cycles before the occurrence of tertiary deterioration (i.e., a rapid drop) in the third period T3. The cyclic discharge is the discharge that the lithium-ion battery performs in each cycle.

[0039] As shown in Figure 3, the OCV after cycle discharge changes with the number of cycles of the lithium-ion battery, reaching a maximum M1 at a certain number of cycles (e.g., around 1000 [cyc]), reaching a minimum M2 at a certain number of cycles thereafter (e.g., around 1300 [cyc]), and then showing a rapid increase (behavior 1).

[0040] This is believed to be due to the following phenomenon. When the number of cycles changes over a certain period W1 (period including maximum M1), the capacity of the negative electrode changes due to the formation of a coating of irreversible reaction on the negative electrode of the lithium-ion battery under the influence of constant voltage control when charging the lithium-ion battery. As a result, the OCV after cycle discharge takes on maximum M1. As the number of cycles continues to change, during the period W2 until the OCV after cycle discharge reaches minimum M2, the resistance of the positive electrode decreases due to the progression of deterioration of the active material of the positive electrode of the lithium-ion battery. As a result, the OCV after cycle discharge drops from maximum M1 to minimum M2. As the number of cycles continues to change over the period W3 after minimum M2, the capacity of the negative electrode decreases while the deterioration of the active material of the positive electrode further progresses, causing the OCV after cycle discharge to drop to minimum M2 and then to rise sharply.

[0041] In this way, it is believed that the capacity of the negative electrode changes due to the influence of constant voltage control when charging a lithium-ion battery, and then the resistance of the positive electrode is initially small and then increases suddenly, resulting in the above-mentioned behavior 1. It is believed that if a new deterioration index (ratio value γ) that reflects the influence of constant voltage control related to such behavior 1 is used, it is possible to predict the tertiary deterioration (i.e., a rapid decrease) in the third period T3.

[0042] (1-6) Configuration of the estimation system of embodiment 1 The estimation system 1 of the first embodiment estimates the cycle life of the power storage device B1 to be estimated by using the formula 1 (i.e., by using the ratio value γ). As shown in Fig. 4, the estimation system 1 includes a charge / discharge control unit 2, a storage unit 3, a measurement unit 4, a calculation unit 5, a life estimation unit 6, and an operation panel unit 7. Note that the operation panel unit 7 may not be included in the configuration of the estimation system 1, and may be connected to the estimation system 1 as an external device.

[0043] The power storage device B1 to be estimated is a secondary battery capable of repeatedly charging and discharging, such as a lithium ion battery. The power storage device B1 is, for example, a power storage device used in a house or a facility. The power storage device B1 supplies power to an electrical device (load) used in the house or facility. The power storage device B1 is not limited to a power storage device installed in a house or a facility, and may be a power storage device mounted on a moving body (for example, an automobile).

[0044] The charge / discharge control unit 2 controls charging and discharging of the power storage device B1. More specifically, the charge / discharge control unit 2 charges the power storage device B1 using power supplied from an external power source GB1, and controls discharging (i.e., power supply) from the power storage device B1 to a load (electrical device). The external power source GB1 may be an AC power source, or may be a DC power source using renewable energy (for example, a solar panel, wind power generation, or hydroelectric power generation). When the external power source GB1 is a DC power source, the charge / discharge control unit 2 transforms the voltage of the DC power supplied from the external power source GB1 to a predetermined voltage, and charges the power storage device B1 with the transformed DC voltage. When the external power source GB1 is an AC power source, the charge / discharge control unit 2 converts the AC power supplied from the AC power source to DC power, transforms the voltage of the converted DC power to a predetermined voltage, and charges the power storage device B1 with the transformed DC voltage.

[0045] The charge / discharge control unit 2 charges the power storage device B1 by constant current / constant voltage control. In the constant current / constant voltage control, first, the charge / discharge control unit 2 charges the power storage device B1 by constant current control until the battery voltage of the power storage device B1 reaches a predetermined voltage. The constant current control is a charge control that charges the power storage device B1 by controlling the current flowing through the power storage device B1 to be constant. Then, when the battery voltage of the power storage device B1 reaches the above-mentioned predetermined voltage, the charge / discharge control unit 2 switches the charge control method from constant current control to constant voltage control. The constant voltage control is a charge control that charges the power storage device B1 by controlling the voltage applied to the power storage device B1 to be constant. Then, the charge / discharge control unit 2 charges the power storage device B1 by constant voltage control until the electrode resistance of the power storage device B1 becomes maximum. Then, when the electrode resistance of the power storage device B1 becomes maximum, the charge / discharge control unit 2 ends the charging of the power storage device B1.

[0046] When the number of cycles c3 (estimated value) obtained by Equation 1 is determined as the cycle life of the power storage device B1, the charge / discharge control unit 2 performs a life extension process for extending the cycle life of the power storage device B1 in the determined cycle. More specifically, the charge / discharge control unit 2 changes at least one set value of the charging voltage, charging current, discharging voltage, and discharging current when charging / discharging the power storage device B1 to a smaller set value, and charges / discharges the power storage device B1. That is, when charging / discharging the power storage device B1, the charge / discharge control unit 2 charges / discharges the power storage device B1 with the charging voltage, charging current, discharging voltage, and discharging current of preset set values ​​(for example, rated values). Then, when the number of cycles c3 (estimated value) obtained by Equation 1 is determined as the cycle life of the power storage device B1, the charge / discharge control unit 2 charges / discharges the power storage device B1 with the charging voltage, charging current, discharging voltage, and discharging current of values ​​smaller than the rated values. This reduces the load on power storage device B1 during charging and discharging, and as a result, the cycle life of power storage device B1 can be extended beyond the number of cycles c3 (estimated value) calculated using equation (1).

[0047] The storage unit 3 is a non-volatile storage device, and is configured, for example, with an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The storage unit 3 stores various information used in each process of the estimation system 1. The above-mentioned various information includes the measurement results of the measurement unit 4, the calculation results of the calculation unit 5, the estimation results of the life estimation unit 6, etc. Furthermore, the above-mentioned various information includes various programs for operating the estimation system 1.

[0048] The measurement unit 4 measures a first charging time and a second charging time for each cycle of the power storage device B1 while the charge / discharge control unit 2 is charging the power storage device B1 under constant current / constant voltage control. The first charging time is the charging time of the power storage device B1 when it is charged under constant current / constant voltage control. The second charging time is the charging time of the power storage device B1 when it is charged under constant voltage control under constant current / constant voltage control.

[0049] The measurement unit 4 also measures the maximum state of charge SOC11 and the minimum state of charge SOC12 of the power storage device B1 for each cycle of the power storage device B1. The maximum state of charge SOC11 is the maximum value of the state of charge of the power storage device B1 in each cycle. The minimum state of charge SOC12 is the minimum value of the state of charge of the power storage device B1 in each cycle.

[0050] Calculation unit 5 calculates a ratio value γ for each cycle of power storage device B1 based on the measurement result of measurement unit 4. More specifically, calculation unit 5 calculates a ratio value γ (=first charging time / second charging time) obtained by dividing the first charging time by the second charging time for the first charging time and the second charging time measured in each cycle.

[0051] Further, the calculation unit 5 calculates the deterioration state of the power storage device B1 in each cycle of the power storage device B1 based on the measurement result of the measurement unit 4. More specifically, the calculation unit 5 first calculates the differential state of charge ΔSOC1 and the central state of charge SOCm1 in each cycle based on the maximum state of charge SOC11 and the minimum state of charge SOC12 measured by the measurement unit 4. The differential state of charge ΔSOC1 is the difference (SOC11-SOC12) obtained by subtracting the minimum state of charge SOC12 from the maximum state of charge SOC11. The central state of charge SOCm1 is the sum of the maximum state of charge SOC11 and the minimum state of charge SOC12 divided by 2 ((SOC11+SOC12) / 2). Then, the calculation unit 5 integrates the differential state of charge ΔSOC1 and the central state of charge SOCm1 in each cycle to calculate an integrated value DS1 (=ΔSOC1×SOCm1). Then, calculation unit 5 calculates the state of health (SOH) of power storage device B1 in each cycle based on information (Equation 2 below) that defines the relationship between integrated value DS1 in each cycle and the state of health of power storage device B1 in each cycle.

[0052] More specifically, calculation unit 5 calculates the state of health (SOH) of power storage device B1 in each cycle based on Equation 2.

[0053]

number

[0054] The function f(DS1,i,T) in Equation 2 is a function with the integrated value DS1, the current i, and the temperature T as variables. The integrated value DS1 is a value calculated for each cycle as described above. The current i is the charging current or discharging current of the power storage device B1 in each cycle. The temperature T is the temperature of the power storage device B1 in each cycle. The function f(DS1,i,T) is given by, for example, graph G5 shown in FIG. 6. Graph G5 in FIG. 6 is a graph in the case where the current i is a certain current value and the temperature T is a certain temperature. The first term on the right side of Equation 2 is a function that expresses the charge current from 0 (the first cycle) to cyc curr This means accumulating the function f(DS1,i,T) over each cycle up to (the current cycle).

[0055] The function ZB(T, SOC) is a function with the temperature T and the state of charge SOC as variables. The temperature T is the temperature of the power storage device B1 in each cycle, as described above. The state of charge SOC is the state of charge of the power storage device B1 during a pause in charging and discharging in each cycle. The function ZB(T, SOC) is a conservation coefficient obtained from the Arrhenius law. The second term on the right side of Equation 2 varies from 0 to t rest This means integrating the function ZB(T,SOC) over the time t rest is the rest time of each charge / discharge cycle.

[0056] Based on the calculation results of calculation unit 5, life estimation unit 6 estimates the cycle life of power storage device B1.

[0057] More specifically, the life estimation unit 6 monitors the behavior of the ratio value γ calculated by the calculation unit 5 in accordance with the transition of cycles.

[0058] 2, the life estimation unit 6 plots the ratio value γ for each cycle calculated by the calculation unit 5 on a coordinate system with the ratio value γ on the vertical axis and the number of cycles on the horizontal axis to generate a graph G2 (graph G2 up to the current number of cycles) showing the behavior of the ratio value γ with the number of cycles. Then, the life estimation unit 6 generates a graph G3 (graph G3 up to the current number of cycles) which is an approximation curve along the upper end of the graph G2 (more specifically, the general shape of the upper end). Then, the life estimation unit 6 determines whether or not the maximum point P2 has appeared in the graph G4 (more specifically, whether or not the maximum point P2 has appeared after the minimum point P1 has appeared).

[0059] When the life estimation unit 6 determines that the local maximum point P2 appears after the local minimum point P1 appears, it calculates a difference Δc (=c2-c1) by subtracting the number of cycles c1 when the local minimum point P1 appears from the number of cycles c2 when the local maximum point P2 appears. Then, the life estimation unit 6 sets the number of cycles c3 obtained by adding the difference Δc to the number of cycles c2 (i.e., the number of charging cycles at the start of the third period T3) as a candidate for an estimate of the cycle life of the power storage device B1. Note that the number of cycles c3 is the number of cycles calculated by Equation 1.

[0060] Further, the life estimation unit 6 calculates a reference cycle life c4 (see FIG. 2) based on the calculation result of the calculation unit 5. More specifically, the life estimation unit 6 calculates a rate of change (i.e., a slope in the second period T2 of the graph G3 in FIG. 2) of the degradation state of the power storage device B1 in a period of a predetermined number of cycles up to the cycle number c2 (e.g., a period up to the current cycle number in the second period T2) based on the degradation state of the power storage device B1 in each cycle calculated by the calculation unit 5. Then, the life estimation unit 6 calculates the number of cycles at which the degradation state of the power storage device B1 reaches a predetermined state of charge (e.g., 60%) when the degradation state of the power storage device B1 changes (i.e., decreases) at the calculated rate of change from the degradation state of the power storage device B1 in the cycle number c2 (i.e., point P3 in FIG. 2). That is, as shown in FIG. 2, the life estimation unit 6 draws an extension line L1 with a slope equal to the calculated rate of change from the point P3, and calculates the number of cycles at which the extension line L1 reaches the predetermined state of charge (e.g., 60%) as the reference cycle life c4.

[0061] Furthermore, the life estimation unit 6 compares the calculated cycle number c3 with the reference cycle life c4. If the cycle number c3 is smaller than the reference cycle life c4, the life estimation unit 6 determines the cycle number c3 (estimated value) as the cycle life of the power storage device B1. On the other hand, if the cycle number c3 is larger than the reference cycle life c4, the life estimation unit 6 determines the reference cycle life c4 as the cycle life of the power storage device B1.

[0062] When the life estimation unit 6 receives a display request signal from the operation panel unit 7, which will be described later, it outputs the determined cycle life to the operation panel unit 7, and causes the operation panel unit 7 to display the cycle life.

[0063] The operation panel unit 7 receives operation inputs for the estimation system 1 and displays the estimation results of the lifespan estimation unit 6. The operation panel unit 7 includes an operation input unit 71 that receives operation inputs for the estimation system 1, and a display unit 72 that displays the estimation results of the lifespan estimation unit 6. The display unit 72 is configured, for example, from a liquid crystal display panel, and is capable of displaying various types of information. The operation input unit 71 is configured, for example, from mechanical buttons.

[0064] The operation input unit 71 may be configured as a touch sensor disposed on the display screen of the display unit 72 and detecting a touch operation on the display screen. In this case, an operation input screen is displayed on the display screen of the display unit 72, and the touch sensor detects a touch operation on the operation input screen, thereby accepting an operation input to the estimation system 1.

[0065] When operation panel unit 7 receives input of an operation (display operation) requesting the display of the cycle life of power storage device B1, it outputs a display request signal to life estimation unit 6 to notify that a display operation has been input to operation panel unit 7.

[0066] In the first embodiment, the charge / discharge control unit 2, the measurement unit 4, the calculation unit 5, and the life estimation unit 6 constitute a processing unit. The processing unit is mainly configured as a computer system having a processor and a memory. The processing unit realizes the charge / discharge control unit 2, the measurement unit 4, the calculation unit 5, and the life estimation unit 6 of the processing unit by the processor executing a program recorded in the memory. The program may be pre-recorded in the memory, or may be provided through a telecommunication line such as the Internet, or may be recorded and provided on a non-transitory recording medium such as a memory card.

[0067] (1-7) Explanation of the operation of the estimation system The operation of the estimation system 1 will be described with reference to Fig. 5. In the following description, an argument n indicates the ordinal number of the current cycle.

[0068] In the estimation system 1, an argument n is set to "1" (n=1) (step S1). Then, in the estimation system 1, a charge / discharge process in the nth (=1) cycle is started (step S2). First, the charge / discharge control unit 2 charges the power storage device B1 under constant current / constant voltage control, and then discharges the charged power storage device B1. Then, the measurement unit 4 measures a first charge time and a second charge time of the power storage device B1 in the nth cycle (step S3). The first charge time is a charge time of the power storage device B1 under constant current / constant voltage control, and the second charge time is a charge time of the power storage device B1 under constant voltage control under the constant current / constant voltage control. In addition, the measurement unit 4 measures a maximum state of charge SOC11 and a minimum state of charge SOC12 of the power storage device B1 in the nth cycle (step S3).

[0069] Then, the calculation unit 5 calculates the ratio value γ (=first charging time / second charging time) in the n-th cycle based on the first charging time and the second charging time measured in step S3 (step S4).Then, the calculation unit 5 generates graphs G2 and G4 (see FIG. 2) up to the n-th cycle based on the calculated ratio value γ (step S5).

[0070] The calculation unit 5 also calculates a differential state of charge ΔSOC1 (=SOC11-SOC12) and a median state of charge SOCm1 (=(SOC11+SOC12) / 2) based on the maximum state of charge SOC11 and the minimum state of charge SOC12 measured in step S3. The calculation unit 5 then calculates an integrated value DS1 (=ΔSOC1×SOCm1) by integrating the calculated differential state of charge ΔSOC1 and the median state of charge SOCm1. The calculation unit 5 then calculates the degradation state of the power storage device B1 in the n-th cycle based on the calculated integrated value DS1 and information (Equation 2) that defines the relationship between the calculated integrated value DS1 and the degradation state of the power storage device B1 in the n-th cycle (step S6). The calculation unit 5 then generates a graph G3 (see FIG. 2) up to the n-th cycle based on the calculated degradation state (step S7).

[0071] Then, the life estimation unit 6 judges whether or not the maximum point P2 appears in the graph G3 (step S8). The maximum point P2 is a maximum point that appears after the minimum point P1 appears. Therefore, in step S8, the life estimation unit 6 judges whether or not the maximum point P2 appears after the minimum point P1 appears in the graph G3. Then, if the result of this judgment is that the maximum point P2 does not appear (No in step S8), the argument n is replaced with n+1 (step S9), and the process returns to step S2. Then, the processes of steps S3 to S8 are repeated as the charge / discharge process in the (n+1)th cycle.

[0072] Then, if the determination in step S8 indicates that the local maximum point P2 has appeared (Yes in step S8), the life estimation unit 6 calculates the number of cycles c3 (see FIG. 2) at the start of the third period T3 of the graph G3 based on the above formula 1 (step S10). More specifically, the life estimation unit 6 calculates the number of cycles c3 based on formula 1 from the number of cycles c2 at the local maximum point P2 and the difference Δc (=c2-c1) obtained by subtracting the number of cycles c1 at the local minimum point P1 from the number of cycles c2 at the local maximum point P2.

[0073] Furthermore, life estimation unit 6 calculates reference cycle life c4 of power storage device B1 as described above (step S11). Note that, as described above, reference cycle life c4 is the number of cycles at which extension line L1 reaches a predetermined state of charge (e.g., 60%) when extension line L1 extends graph G3 from near point P3 of graph G3 at a predetermined rate of change (i.e., the rate of change of graph G3 when graph G3 falls relatively gently in second period T2) (see FIG. 2).

[0074] Then, the life estimation unit 6 compares the number of cycles c3 (estimated value) calculated in step S10 with the reference cycle life c4 calculated in step S11 (step S12). If the result of this comparison shows that the number of cycles c3 is smaller than the reference cycle life c4 (Yes in step S12), the number of cycles c3 is determined to be the cycle life of the power storage device B1 (step S13). If this is determined, the charge / discharge control unit 2 performs a life extension process for extending the cycle life of the power storage device B1 when charging / discharging the power storage device B1 in the (n+1)th cycle after the nth cycle (step S14). Then, the process proceeds to step S16. On the other hand, if the result of the comparison in step S12 shows that the number of cycles c3 is equal to or larger than the reference cycle life c4 (No in step S12), the reference cycle life c4 is determined to be the cycle life of the power storage device B1 (step S15). Then, the process proceeds to step S16.

[0075] In step S16, the life estimation unit 6 judges whether or not a display operation has been input to the operation panel unit 7. The display operation is an operation for displaying the cycle life determined in step S13 or step S16 on the operation panel unit 7. If the result of this judgment is that the display operation has been input to the operation panel unit 7 (Yes in step S16), the life estimation unit 6 displays the cycle life determined in step S13 or S15 on the operation panel unit 7 (step S17). Then, the process ends. On the other hand, if the result of the judgment in step S16 is that the display operation has not been input to the operation panel unit 7 (No in step S16), step S17 is not performed (i.e., the cycle life is not displayed on the operation panel unit 7) and the process ends.

[0076] (1-8) Effects The estimation system 1 according to the embodiment is an estimation system that estimates the cycle life of the power storage device B1. The power storage device B1 is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the power storage device B1 is charged by constant current control until the battery voltage of the power storage device B1 reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the power storage device B1 is charged by constant voltage control until the plate resistance of the power storage device B1 reaches a maximum. The estimation system 1 includes a measurement unit 4, a calculation unit 5, and a life estimation unit 6. The measurement unit 4 measures a first charging time and a second charging time for each cycle of the power storage device B1. The first charging time is the charging time of the power storage device B1 when it is charged by constant current constant voltage control. The second charging time is the charging time of the power storage device B1 when it is charged by constant voltage control. The calculation unit 5 calculates a ratio value γ obtained by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured by the measurement unit 4. The life estimation unit 6 calculates a difference Δc obtained by subtracting a first cycle number c1, which is the number of cycles when a minimum point P1 appears, from a second cycle number c2, which is the number of cycles when a maximum point P2 appears after the minimum point P1 appears, in a curve G4 along the upper end of a graph G2 showing the behavior of the ratio value γ with the transition of the cycle number of the power storage device B1. The life estimation unit 6 estimates the cycle life by adding the difference Δc to the second cycle number c2 to obtain a cycle number c3 (third cycle number).

[0077] According to this configuration, the cycle life of the power storage device B1 is estimated using the ratio value γ calculated for each cycle, so that the cycle life of the power storage device B1 can be estimated in the event that the power storage device B1 rapidly deteriorates toward the end of its life.

[0078] Furthermore, in estimation system 1, life estimation unit 6 calculates a rate of change in the deterioration state of power storage device B1 with respect to the transition in the number of cycles during a fixed period (second period T2) up to maximum point P2. Life estimation unit 6 calculates a cycle life when deterioration of power storage device B1 progresses at the calculated rate of change as a reference cycle life c4. When the number of cycles c3 (second number of cycles) is smaller than the reference cycle life c4, life estimation unit 6 determines the number of cycles c3 to be the cycle life, and when the number of cycles c3 is greater than the reference cycle life c4, determines the reference cycle life c4 to be the cycle life.

[0079] According to this configuration, it is possible to more accurately estimate the cycle life of power storage device B1 in the case where power storage device B1 rapidly deteriorates toward the end of its life.

[0080] Furthermore, in the estimation system 1, the degradation state of the power storage device B1 is calculated from the integrated value DS1 in each cycle based on information that defines the relationship between the integrated value DS1 in each cycle and the degradation state in each cycle. The integrated value DS1 is the product of the differential state of charge ΔSOC1 and the central state of charge SOCm1. The differential state of charge ΔSOC1 is the difference obtained by subtracting the minimum value (minimum state of charge SOC12) from the maximum value (maximum state of charge SOC11) of the state of charge of the power storage device B1 in each cycle. The central state of charge SOCm1 is the median value between the maximum value (maximum state of charge SOC11) and the minimum value (minimum state of charge SOC12).

[0081] According to this configuration, the degradation state of the power storage device B1 can be calculated using the integrated value DS1 as a parameter. By using the integrated value DS1 as a parameter, the degradation state of the power storage device B1 can be calculated taking into consideration that the charge state of the power storage device B1 can be not only 0% and 100% but also a state between 0% and 100% (e.g., 30% and 50%).

[0082] The estimation system 1 further includes a charge / discharge control unit 2. When the number of cycles c3 is smaller than a reference cycle life c4, the charge / discharge control unit 2 changes at least one set value (e.g., a rated value) of the charge voltage, the charge current, the discharge voltage, and the discharge current when charging / discharging the power storage device B1 to a smaller set value, and charges / discharges the power storage device B1.

[0083] This configuration reduces the load on the power storage device B1 during charging and discharging, thereby extending the cycle life of the power storage device B1.

[0084] (1-9) Forms of invention other than presumption systems Functions similar to those of the estimation system 1 according to the above embodiment may be embodied as an estimation method, a computer program (program), or a non-transitory recording medium on which a computer program is recorded.

[0085] An estimation method according to one embodiment estimates the cycle life of a power storage device B1 (e.g., a lithium ion battery). The power storage device B1 is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the power storage device B1 is charged by constant current control until the battery voltage of the power storage device B1 reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the power storage device B1 is charged by constant voltage control until the plate resistance of the power storage device B1 reaches a maximum. The estimation method includes a measurement step S3, a calculation step S4, and life estimation steps S5, S8, and S10. In the measurement step S3, a first charging time and a second charging time are measured for each cycle of the power storage device B1. The first charging time is the charging time of the power storage device B1 when it is charged by constant current constant voltage control. The second charging time is the charging time of the power storage device B1 when it is charged by constant voltage control. In the calculation step S4, a ratio value γ is calculated by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured in the measurement step S3. In the life estimation steps S5, S8, and S10, a difference Δc is calculated by subtracting a first cycle number c1, which is the number of cycles when a minimum point P1 appears, from a second cycle number c2, which is the number of cycles when a maximum point P2 appears after the minimum point P1 appears, in a curve G4 along the upper end of a graph G2 showing the behavior of the ratio value γ with the transition of the cycle number of the power storage device B1. In the life estimation steps S5, S8, and S10, a third cycle number c3, which is the second cycle number c2 plus the difference Δc, is set as an estimate of the cycle life.

[0086] A program according to one embodiment causes a computer to execute the estimation method.

[0087] A non-transitory recording medium according to one embodiment records a program for causing a computer to execute the estimation method.

[0088] (1-10) Variations A description will be given of modifications of the first embodiment. The following modifications can be implemented in combination.

[0089] (1-10-1) Variation 1 In the first embodiment, the ratio value γ is a value obtained by dividing the first charging time by the second charging time, but may be a value obtained by dividing the second charging time by the first charging time. In this case, the life estimation unit 6 calculates a difference Δc by subtracting the first cycle number c1, which is the cycle number when a maximum point appears, from the second cycle number c2, which is the cycle number when a minimum point appears after the maximum point appears, in a curve along the lower end of the graph showing the behavior of the ratio value γ with the transition of the cycle number, and sets the cycle number c3 (third cycle number) obtained by adding the difference Δc to the second cycle number c2 as an estimated value of the cycle life of the storage device B1. That is, the minimum point P1 of the behavior of the ratio value γ in the first embodiment appears as a maximum point in the first modification, and the maximum point P2 of the behavior of the ratio value γ in the first embodiment appears as a minimum point in the first modification. According to the first modification, as in the first embodiment, the cycle life of the storage device B1 can be estimated when the storage device B1 rapidly deteriorates at the end of its life.

[0090] (1-10-2) Variation 2 In the first embodiment, the ratio value γ is a value obtained by dividing a first charging time, which is a charging time of the power storage device B1 when it is charged by constant current / constant voltage control, by a second charging time, which is a charging time of the power storage device B1 when it is charged by constant voltage control. However, the ratio value γ may be a value obtained by dividing a first charging capacity, which is a charging capacity of the power storage device B1 when it is charged by constant current / constant voltage control, by a second charging capacity, which is a charging capacity of the power storage device B1 when it is charged by constant voltage control. In other words, the first charging capacity and the second charging capacity may be used instead of the first charging time and the second charging time. In this case, as in the above embodiment, life estimation unit 6 calculates difference Δc by subtracting number of cycles c1 (first number of cycles) when minimum point P1 appears from number of cycles c2 (second number of cycles) when maximum point P2 appears after minimum point P1 appears in a curve (graph G4) along the upper end of graph G2 showing the behavior of ratio value γ with change in cycle number, and calculates number of cycles c3 (third number of cycles) by adding difference Δc to number of cycles c2 as an estimate of cycle life of power storage device B1. As in the above embodiment, according to modification 2, it is possible to estimate the cycle life of power storage device B1 when power storage device B1 rapidly deteriorates at the end of its life.

[0091] (1-10-3) Variation 3 In the second modification, the ratio value γ is a value obtained by dividing the first charge capacity by the second charge capacity, but may be a value obtained by dividing the second charge capacity by the first charge capacity. In this case, the life estimation unit 6 calculates a difference Δc by subtracting the first cycle number c1, which is the cycle number when a maximum point appears, from the second cycle number c2, which is the cycle number when a minimum point appears after the maximum point appears, in the curve along the lower end of the graph showing the behavior of the ratio value γ with the transition of the cycle number, and sets the cycle number c3 (third cycle number) obtained by adding the difference Δc to the second cycle number c2 as the estimated value of the cycle life of the power storage device B1. That is, the minimum point P1 of the behavior of the ratio value γ in the second modification appears as a maximum point in the third modification, and the maximum point P2 of the behavior of the ratio value γ in the second modification appears as a minimum point in the third modification. As with the second modification, the third modification also makes it possible to estimate the cycle life of power storage device B1 in the case where power storage device B1 rapidly deteriorates toward the end of its life.

[0092] (1-10-4) Variation 4 In the first embodiment, the degradation state of power storage device B1 in each cycle is calculated from integrated value DS1 calculated based on first information (eg, Equation 2) that defines the relationship between integrated value DS1 in each cycle and the degradation state in each cycle.

[0093] However, the deterioration state of the storage device B1 in each cycle may be calculated from the calculated integrated value DS2 and the first change ΔQ1 or the second change ΔQ2, which is the change in the discharge capacity Q1 or the second change ΔQ2, based on second information that specifies the relationship between the integrated value DS2 in each cycle, the first change ΔQ1 which is the change in the discharge capacity Q1 or the second change ΔQ2 which is the change in the charge capacity Q2, and the deterioration state in each cycle.

[0094] The second information may be defined by a formula or a correspondence table, or may be defined based on actual measurements.

[0095] The integrated value DS2 is the product of a differential state of charge ΔSOC2, which is the difference obtained by subtracting the starting state of charge SOC21 at the start of charging of the storage device B1 in each cycle from the ending state of charge SOC22 at the end of charging, and a median state of charge SOCm2, which is the median value between the starting state of charge SOC21 and the ending state of charge SOC22.

[0096] The discharge capacity Q1 is the amount of current (amount of charge) discharged from the power storage device B1 from the rated discharge start voltage to the rated discharge end voltage. The first change amount ΔQ1 is the amount of change in the discharge capacity Q1 with the transition of the number of cycles.

[0097] The charge capacity Q2 is the amount of current (amount of charge) charged to the power storage device B1 from the rated charge start voltage to the rated charge end voltage. The second change amount ΔQ2 is the amount of change in the charge capacity Q2 with the transition of the number of cycles.

[0098] In the fourth modification, the measurement unit 4 measures the initial state of charge SOC21, the final state of charge SOC22, and the first amount of change ΔQ1 or the second amount of change ΔQ2 of the power storage device B1 for each cycle of the power storage device B1.

[0099] In the fourth modification, the calculation unit 5 calculates the differential state of charge ΔSOC2 and the median state of charge SOCm2 in each cycle based on the starting state of charge SOC21 and the ending state of charge SOC22 measured by the measurement unit 4. The calculation unit 5 then calculates an integrated value DS2 by integrating the differential state of charge ΔSOC2 and the median state of charge SOCm2 in each cycle. The calculation unit 5 then calculates the degradation state of the power storage device B1 in each cycle from the calculated integrated value DS2 and the first amount of change ΔQ1 or the second amount of change ΔQ2 measured by the measurement unit 4 based on the second information.

[0100] According to the fourth modification, the degradation state of the power storage device B1 can be calculated using the integrated value DS2 as a parameter. By using the integrated value DS2 as a parameter, the degradation state of the power storage device B1 can be calculated taking into consideration that the charge state of the power storage device B1 can be not only 0% and 100% but also a state between 0% and 100% (e.g., 30% and 50%).

[0101] In addition, variant example 4 is a method of determining the deterioration state (deterioration rate) of power storage device B1 from the capacity of the nth (current) cycle and the capacity of the (n-1)th cycle of the SOC of power storage device B1 using a recurrence formula (sequence).

[0102] The capacity (charge capacity) during the charging period of the nth cycle of the power storage device B1 is the difference obtained by subtracting the minimum value from the maximum value of the SOC during the charging period of the nth cycle. The central SOC (central state of charge) at this time is half the charge capacity of the above-mentioned nth cycle. The capacity (discharge capacity) during the discharging period of the nth cycle of the power storage device B1 is the difference obtained by subtracting the minimum value from the maximum value of the SOC during the discharging period of the nth cycle. The central SOC (central state of charge) at this time is half the discharge capacity of the above-mentioned nth cycle. The charge / discharge capacity of the SOC of the power storage device B1 during the nth cycle is the average value of the charge capacity and discharge capacity of the nth cycle. The central SOC at this time is the average value of half the charge capacity of the nth cycle and half the discharge capacity of the nth cycle.

[0103] In addition, the charge / discharge capacity, charge capacity, discharge capacity, and their median SOC in the (n-1)th cycle of the storage device B1 can also be determined in the same manner as the charge / discharge capacity, charge capacity, discharge capacity, and their median SOC in the nth cycle described above.

[0104] In this manner, the charge / discharge capacity, charge capacity, discharge capacity and their median SOC in the nth cycle of power storage device B1, and the charge / discharge capacity, charge capacity, discharge capacity and their median SOC in the (n-1)th cycle are determined.

[0105] Then, the current deterioration state (deterioration rate) of the storage device B1 is calculated using the charge / discharge capacity, charge capacity, discharge capacity, and their median SOC in the nth cycle and the charge / discharge capacity, charge capacity, discharge capacity, and their median SOC in the (n-1)th cycle, using the following equation 3.

[0106]

number

[0107] Here, ZB on the right side of Equation 3 is a predetermined function that is determined when the charge / discharge capacity, charge capacity, discharge capacity, and center SOC thereof in the nth (current) cycle of the storage device B1, and the charge / discharge capacity, charge capacity, discharge capacity, and center SOC thereof in the (n-1)th cycle are given. The above ZB is a storage deterioration coefficient obtained from the Arrhenius law. Also, the above ZB is obtained by differentiating the root law.

[0108] (1-10-5) Variation 5 In the first embodiment, from the first cycle, the measurement unit 4 starts measuring the first charging time, the second charging time, the maximum state of charge SOC11, and the minimum state of charge SOC12, the calculation unit 5 starts calculating the ratio value γ and the degradation state of the power storage device B1, and the life estimation unit 6 calculates an estimate of the cycle life of the power storage device B1. However, from a cycle after a predetermined period has elapsed from the start of charging of the power storage device B1, the measurement unit 4 may start measuring the first charging time, the second charging time, the maximum state of charge SOC11, and the minimum state of charge SOC12, the calculation unit 5 starts calculating the ratio value γ and the degradation state of the power storage device B1, and the life estimation unit 6 may calculate an estimate of the cycle life of the power storage device B1.

[0109] According to the fifth modification, the cycle life can be efficiently estimated by reducing the processing load on the measurement unit 4, the calculation unit 5, and the life estimation unit 6. In other words, it is during the second period T2 (i.e., the period after a predetermined time has elapsed since the start of charging of the storage device B1) in which the degradation state of the storage device B1 stabilizes and deteriorates slowly that it becomes possible to estimate the occurrence of rapid deterioration of the storage device B1 that occurs at the end of the life of the storage device B1. Therefore, by limiting it as in the fifth modification, the processing load on the measurement unit 4, the calculation unit 5, and the life estimation unit 6 can be reduced, and the cycle life can be efficiently estimated.

[0110] (2) Embodiment 2 The estimation system 1 of the first embodiment is assumed to be a device in which the components of the estimation system 1 (the charge / discharge control unit 2, the storage unit 3, the measurement unit 4, the calculation unit 5, the life estimation unit 6, and the operation panel unit 7) are accommodated in one housing. In contrast, the estimation system 1B of the second embodiment is configured such that the components of the estimation system 1B (the calculation unit 30, the life estimation unit 31, and the operation panel unit 32) are distributed and connected via a communication network NT1.

[0111] More specifically, as shown in FIG. 7, the estimation system 1B of the second embodiment includes a calculation device 30, a lifespan estimation device 31, and an operation panel device 32.

[0112] The calculation device 30 includes a charge / discharge control unit 2, a storage unit 3, a measurement unit 4, a calculation unit 5, and a communication unit 8.

[0113] The charge / discharge control unit 2, memory unit 3, measurement unit 4 and calculation unit 5 of embodiment 1 have the same configuration as the charge / discharge control unit 2, memory unit 3, measurement unit 4 and calculation unit 5 of embodiment 1, so detailed descriptions thereof will be omitted.

[0114] The communication unit 8 communicates with a communication unit 10 (to be described later) of the lifespan estimation device 31 and a communication unit 12 (to be described later) of the operation panel device 32 via the communication network NT1. The communication network NT1 is a WAN (Wide Area Network) such as an Internet network or a mobile phone communication network, but may also be a LAN (Local Area Network) such as wi-fi (registered trademark).

[0115] Communication unit 8 transmits the calculation results of calculation unit 5 (ratio value γ in each cycle and the deterioration state of power storage device B1) to a communication unit 10 (described later) of lifetime estimation device 31 via communication network NT1.

[0116] The lifespan estimation device 31 includes a lifespan estimation unit 6, a storage unit 9, and a communication unit 10.

[0117] The life estimation unit 6 of the second embodiment has the same configuration as the life estimation unit 6 of the first embodiment, and therefore a detailed description thereof will be omitted.

[0118] The storage unit 9 is a non-volatile storage device, and is configured, for example, with an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The storage unit 9 stores various information used in each process of the life estimation device 31. The various information includes the estimation results of the life estimation unit 6. The various information also includes various programs for operating the life estimation device 31.

[0119] Communication unit 10 communicates with communication unit 8 of calculation device 30 and communication unit 12 (described later) of operation panel device 32 via communication network NT1. When communication unit 10 receives a display request signal from communication unit 12 (described later) of operation panel device 32, communication unit 10 transmits the estimation result of life estimation unit 6 (estimated value of cycle life of power storage device B1) to communication unit 12 (described later) of operation panel device 32. The display request signal is a signal notifying that an operation (display operation) requesting display of the estimated value of cycle life of power storage device B1 has been input to operation input unit 71 (described later) of operation panel device 32.

[0120] The operation panel device 32 includes an operation panel unit 7 , a storage unit 11 , and a communication unit 12 .

[0121] The operation panel unit 7 of the second embodiment has the same configuration as the operation panel unit 7 of the first embodiment, and therefore a detailed description thereof will be omitted.

[0122] The storage unit 11 is a non-volatile storage device, and is configured, for example, by an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The storage unit 11 stores various information used in each process of the operation panel device 32. The various information includes various programs for operating the operation panel device 32.

[0123] When the display operation is input to the operation input unit 71 of the operation panel unit 7, the communication unit 12 transmits the display request signal to the communication unit 10 of the life estimation device 31 via the communication network NT1.

[0124] According to the estimation system 1B of the second embodiment, like the estimation system 1 of the first embodiment, it is possible to estimate the cycle life of the power storage device B1 when the power storage device B1 rapidly deteriorates at the end of its life. Moreover, the estimation system 1B can be configured by distributing it to a calculation device 30, a life estimation device 31, and an operation panel device 32. Moreover, among the charge / discharge control unit 2, the storage unit 3, the measurement unit 4, the calculation unit 5, and the life estimation unit 6 of the estimation system 1B, the charge / discharge control unit 2, the storage unit 3, the measurement unit 4, and the calculation unit 5 (particularly the calculation unit 5) can be separated from the life estimation unit 6 and treated as a single device (calculation device 30).

[0125] In the second embodiment, lifetime estimation device 31 may be mounted on a predetermined server connected to a communication network. Calculation device 30 may be set in a converter that controls power storage device B1.

[0126] (3) Description As is apparent from the above-described embodiment and modified examples, the present specification discloses the following aspects.

[0127] The estimation system (1, 1B) of the first aspect is an estimation system that estimates the cycle life of a lithium ion battery (B1). The lithium ion battery (B1) is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery (B1) is charged by constant current control until the battery voltage of the lithium ion battery (B1) reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the lithium ion battery (B1) is charged by constant voltage control until the plate resistance of the lithium ion battery (B1) reaches a maximum. The estimation system (1, 1B) includes a measurement unit (4), a calculation unit (5), and a life estimation unit (6). The measurement unit (4) measures a first charging time and a second charging time for each cycle of the lithium ion battery (B1). The first charging time is the charging time of the lithium ion battery (B1) when it is charged by constant current constant voltage control. The second charging time is the charging time of the lithium ion battery (B1) when it is charged by constant voltage control. The calculation unit (5) calculates a ratio value (γ) by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured by the measurement unit (4). The life estimation unit (6) calculates a difference (Δc) by subtracting a first cycle number (c1), which is the cycle number when a minimum point (P1) appears, from a second cycle number (c2), which is the cycle number when a maximum point (P2) appears after the minimum point (P1) appears, in a curve (G4) along the upper end of a graph (G2) showing the behavior of the ratio value (γ) with the transition of the cycle number of the lithium ion battery (B1). The life estimation unit (6) estimates the cycle life by adding the difference (Δc) to the second cycle number (c2) to obtain a third cycle number (c3).

[0128] According to this configuration, the cycle life of the lithium ion battery (B1) is estimated using the ratio value (γ) calculated for each cycle, so that the cycle life of the lithium ion battery (B1) can be estimated when the lithium ion battery (B1) rapidly deteriorates toward the end of its life.

[0129] The estimation system (1, 1B) of the second aspect is an estimation system that estimates the cycle life of a lithium ion battery (B1). The lithium ion battery (B1) is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery (B1) is charged by constant current control until the battery voltage of the lithium ion battery (B1) reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the lithium ion battery (B1) is charged by constant voltage control until the plate resistance of the lithium ion battery (B1) reaches a maximum. The estimation system (1, 1B) includes a measurement unit (4), a calculation unit (5), and a life estimation unit (6). The measurement unit (4) measures a first charging time and a second charging time for each cycle of the lithium ion battery (B1). The first charging time is the charging time of the lithium ion battery (B1) when it is charged by constant current constant voltage control. The second charging time is the charging time of the lithium ion battery (B1) when it is charged by constant voltage control. The calculation unit (5) calculates a ratio value (γ) by dividing the second charging time by the first charging time based on the first charging time and the second charging time measured by the measurement unit (4). The life estimation unit (6) calculates a difference (Δc) by subtracting a first cycle number (c1), which is the cycle number when a maximum point appears, from a second cycle number (c2), which is the cycle number when a minimum point appears after the maximum point appears, in a curve along the upper end of a graph showing the behavior of the ratio value (γ) with the transition of the cycle number of the lithium ion battery (B1). The life estimation unit (6) estimates the cycle life by adding the difference (Δc) to the second cycle number (c2) to obtain a third cycle number (c3).

[0130] According to this configuration, in the estimation system (1, 1B) of the first aspect, the estimated value is calculated using a ratio (γ) obtained by dividing the first charging time by the second charging time, whereas in the estimation system (1, 1B) of the second aspect, the estimated value is calculated using a ratio (γ) obtained by dividing the second charging time by the first charging time. With this configuration, like the estimation system (1, 1B) of the first aspect, it is possible to estimate the cycle life of the lithium ion battery (B1) when the lithium ion battery (B1) rapidly deteriorates at the end of its life.

[0131] The estimation system (1, 1B) of the third aspect is an estimation system that estimates the cycle life of a lithium ion battery (B1). The lithium ion battery (B1) is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery (B1) is charged by constant current control until the battery voltage of the lithium ion battery (B1) reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the lithium ion battery (B1) is charged by constant voltage control until the plate resistance of the lithium ion battery (B1) reaches a maximum. The estimation system (1, 1B) includes a measurement unit (4), a calculation unit (5), and a life estimation unit (6). The measurement unit (4) measures a first charge capacity and a second charge capacity for each cycle of the lithium ion battery (B1). The first charge capacity is the charge capacity of the lithium ion battery (B1) when it is charged by constant current constant voltage control. The second charge capacity is the charge capacity of the lithium ion battery (B1) when it is charged by constant voltage control. The calculation unit (5) calculates a ratio value (γ) obtained by dividing the first charge capacity by the second charge capacity based on the first charge capacity and the second charge capacity measured by the measurement unit (4). The life estimation unit (6) calculates a difference (Δc) obtained by subtracting the first cycle number (c1), which is the cycle number when the minimum point (P1) appears, from the second cycle number (c2), which is the cycle number when the maximum point (P2) appears after the minimum point (P1) appears, in the curve (G4) along the upper end of the graph (G2) showing the behavior of the ratio value (γ) with the transition of the cycle number of the lithium ion battery (B1). The life estimation unit (6) estimates the cycle life by adding the difference (Δc) to the second cycle number (c2) to obtain a third cycle number (c3).

[0132] According to this configuration, the estimation system (1, 1B) of the third aspect is the estimation system (1, 1B) of the first aspect, in which the first charging time and the second charging time are changed to the first charging capacity and the second charging capacity. With this configuration, like the estimation system (1, 1B) of the first aspect, it is possible to estimate the cycle life taking into account the rapid deterioration of the lithium ion battery (B1) that occurs at the end of its life.

[0133] The estimation system (1, 1B) of the fourth aspect is an estimation system that estimates the cycle life of a lithium ion battery (B1). The lithium ion battery (B1) is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery (B1) is charged by constant current control until the battery voltage of the lithium ion battery (B1) reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the lithium ion battery (B1) is charged by constant voltage control until the plate resistance of the lithium ion battery (B1) reaches a maximum. The estimation system (1, 1B) includes a measurement unit (4), a calculation unit (5), and a life estimation unit (6). The measurement unit (4) measures a first charge capacity and a second charge capacity for each cycle of the lithium ion battery (B1). The first charge capacity is the charge capacity of the lithium ion battery (B1) when it is charged by constant current constant voltage control. The second charge capacity is the charge capacity of the lithium ion battery (B1) when it is charged by constant voltage control. The calculation unit (5) calculates a ratio value (γ) by dividing the second charge capacity by the first charge capacity based on the first charge capacity and the second charge capacity measured by the measurement unit (4). The life estimation unit (6) calculates a difference (Δc) by subtracting a first cycle number (c1), which is the cycle number when a maximum point appears, from a second cycle number (c2), which is the cycle number when a minimum point appears after the maximum point appears, in a curve along the upper end of a graph showing the behavior of the ratio value (γ) with the transition of the cycle number of the lithium ion battery (B1). The life estimation unit (6) estimates the cycle life by adding the difference (Δc) to the second cycle number (c2) to obtain a third cycle number (c3).

[0134] According to this configuration, in the estimation system (1, 1B) of the third aspect, the estimated value is calculated using the ratio (γ) obtained by dividing the first charge capacity by the second charge capacity, whereas in the estimation system (1, 1B) of the fourth aspect, the estimated value is calculated using the ratio (γ) obtained by dividing the second charge capacity by the first charge capacity. With this configuration, like the estimation system (1, 1B) of the third aspect, it is possible to estimate the cycle life of the lithium ion battery (B1) when the lithium ion battery (B1) rapidly deteriorates at the end of its life.

[0135] In the estimation system (1, 1B) of the fifth aspect, in any one of the first to fourth aspects, the life estimation unit (6) calculates a rate of change of the deterioration state of the lithium ion battery (B1) with respect to the transition of the cycle number in a certain period until the maximum point (P2). The life estimation unit (6) calculates a cycle life when the deterioration of the lithium ion battery (B1) progresses at the calculated rate of change as a reference cycle life (c4). When the third cycle number (c3) is smaller than the reference cycle life (c4), the life estimation unit (6) determines the third cycle number (c3) as the cycle life, and when the third cycle number (c3) is equal to or greater than the reference cycle life (c4), determines the reference cycle life (c4) as the cycle life.

[0136] According to this configuration, it is possible to more accurately estimate the cycle life of the lithium ion battery (B1) when the lithium ion battery (B1) rapidly deteriorates toward the end of its life.

[0137] In the estimation system (1, 1B) of the sixth aspect, in the fifth aspect, the deterioration state of the lithium ion battery (B1) is calculated from the integrated value (DS1) in each cycle based on information that specifies the relationship between the integrated value (DS1) in each cycle and the deterioration state in each cycle. The integrated value (DS1) is the product of the differential state of charge (ΔSOC1) and the central state of charge (SOCm1). The differential state of charge (ΔSOC1) is the difference obtained by subtracting the minimum value (SOC12) from the maximum value (SOC11) of the state of charge of the lithium ion battery (B1) in each cycle. The central state of charge (SOCm1) is the central value between the maximum value (SOC11) and the minimum value (SOC12).

[0138] According to this configuration, the deterioration state of the lithium ion battery (B1) can be calculated using the integrated value (DS1) as a parameter. By using the integrated value (DS1) as a parameter, the deterioration state of the lithium ion battery (B1) can be calculated taking into consideration that the charge state of the lithium ion battery (B1) can be not only 0% and 100% but also a state between 0% and 100% (e.g., 30% and 50%).

[0139] In the estimation system (1, 1B) of the seventh aspect, in the fifth aspect, the deterioration state of the lithium ion battery (B1) is calculated from the integrated value (DS2) calculated based on the information that defines the relationship between the integrated value (DS2) in each cycle, the first change (ΔQ1) which is the change in the discharge capacity (Q1) or the second change (ΔQ2) which is the change in the charge capacity (Q2), and the deterioration state in each cycle. The integrated value (DS2) is the product of the differential state of charge (ΔSOC2) and the central state of charge (SOCm2). The differential state of charge (ΔSOC2) is the difference obtained by subtracting the start state of charge (SOC21) at the start of charging the lithium ion battery (B1) from the end state of charge (SOC22) at the end of charging in each cycle. The central state of charge (SOCm2) is the central value between the start state of charge (SOC21) and the end state of charge (SOC22). The discharge capacity (Q1) is the amount of current discharged from the lithium ion battery (B1) from the rated discharge start voltage to the rated discharge end voltage. The first change (ΔQ1) is the amount of change in the discharge capacity (Q1) with the change in the number of cycles. The charge capacity (Q2) is the capacity charged into the lithium ion battery (B1) from the rated charge start voltage to the rated charge end voltage. The second change (ΔQ2) is the amount of change in the charge capacity (Q2) with the change in the number of cycles.

[0140] According to this configuration, the deterioration state of the lithium ion battery (B1) can be calculated using the integrated value (DS2) as a parameter. By using the integrated value (DS2) as a parameter, the deterioration state of the lithium ion battery (B1) can be calculated taking into consideration that the charge state of the lithium ion battery (B1) can be not only 0% and 100% but also a state between 0% and 100% (e.g., 30% and 50%).

[0141] The estimation system (1, 1B) of an eighth aspect is any one of the fifth to seventh aspects, and further includes a charge / discharge control unit (2). When the third cycle number (c3) is smaller than the reference cycle life (c4), the charge / discharge control unit (2) changes at least one set value of the charge voltage, charge current, discharge voltage, and discharge current when charging / discharging the lithium ion battery (B1) to a smaller set value, and charges / discharges the lithium ion battery (B1).

[0142] This configuration reduces the load on the lithium ion battery (B1) during charging and discharging, thereby extending the cycle life of the lithium ion battery (B1).

[0143] In the estimation system (1, 1B) of the ninth aspect, in the first or second aspect, after a predetermined period of time has elapsed from the start of charging of the lithium ion battery (B1), the measurement unit (4) starts measuring the first charging time and the second charging time, the calculation unit (5) starts calculating the ratio value (γ), and the life estimation unit (6) calculates the third cycle number (c3).

[0144] According to this configuration, the processing load on the measurement unit (4), the calculation unit (5), and the life estimation unit (6) can be reduced, and the cycle life of the lithium ion battery (B1) can be efficiently estimated. In other words, it is during a period in which the degradation state of the lithium ion battery (B1) stabilizes and gradually deteriorates (i.e., a period (T2) after a predetermined time has elapsed since the start of charging the lithium ion battery (B1)) that it becomes possible to estimate the occurrence of rapid deterioration of the lithium ion battery (B1) that occurs at the end of the life of the lithium ion battery (B1). Therefore, by limiting it to the ninth aspect, the processing load on the measurement unit (4), the calculation unit (5), and the life estimation unit (6) can be reduced, and the cycle life of the lithium ion battery (B1) can be efficiently estimated.

[0145] A calculation device (30) of a tenth aspect is used in the estimation system (1B) of any one of the first to ninth aspects. The calculation device (30) includes a measurement unit (4), a calculation unit (5), and a communication unit (8). The communication unit (8) transmits information related to the ratio value (γ) calculated by the calculation unit (5) to a predetermined device (31).

[0146] According to this configuration, of the measurement unit (4), the calculation unit (5), and the lifespan estimation unit (6) of the estimation system (1B), the measurement unit (4) and the calculation unit (5) can be separated from the lifespan estimation unit (6) and treated as a standalone device (calculation device (30)).

[0147] The estimation method of the eleventh aspect is a method for estimating the cycle life of a lithium ion battery (B1). The lithium ion battery (B1) is charged by constant current constant voltage control for each cycle. In the constant current constant voltage control, the lithium ion battery (B1) is charged by constant current control until the battery voltage of the lithium ion battery (B1) reaches a predetermined voltage. When the battery voltage reaches the predetermined voltage, the lithium ion battery (B1) is charged by constant voltage control until the plate resistance of the lithium ion battery (B1) reaches a maximum. The estimation method includes a measurement step (S3), a calculation step (S4), and a life estimation step (S5, S8, S10). In the measurement step (S3), a first charging time and a second charging time are measured for each cycle of the lithium ion battery (B1). The first charging time is the charging time of the lithium ion battery (B1) when it is charged by constant current constant voltage control. The second charging time is the charging time of the lithium ion battery (B1) when it is charged by constant voltage control. In the calculation step (S4), a ratio value (γ) is calculated by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured in the measurement step (S3). In the life estimation step (S5, S8, S10), a difference (Δc) is calculated by subtracting the first cycle number (c1), which is the cycle number when the minimum point (P1) appears, from the second cycle number (c2), which is the cycle number when the maximum point (P2) appears after the minimum point (P1) appears, in the curve (G4) along the upper end of the graph (G2) showing the behavior of the ratio value (γ) with the transition of the cycle number of the lithium ion battery (B1). In the life estimation step (S5, S8, S10), a third cycle number (c3) obtained by adding the difference (Δc) to the second cycle number (c2) is set as the estimated value of the cycle life.

[0148] According to this configuration, the cycle life is estimated using the ratio value (γ) calculated for each cycle, so that the cycle life of the lithium ion battery (B1) can be estimated when the lithium ion battery (B1) rapidly deteriorates toward the end of its life.

[0149] A program according to a twelfth aspect causes a computer to execute the estimation method according to the eleventh aspect.

[0150] According to this configuration, it is possible to provide a program for executing the above estimation method. [Explanation of symbols]

[0151] 1,1B Estimation System B1 Energy storage device (lithium ion battery) 4. Measurement section 5 Calculation section 6 Life estimation part c1 Cycle number (first cycle number) c2 Cycle number (second cycle number) c3 Cycle number (3rd cycle number) c4 Reference cycle life Δc difference DS1, DS2 integrated value G2 Graph G4 Graph (Curve) P1 Minimum point P2 local maximum point Q1 Discharge capacity Q2 Charging capacity ΔQ1 First change amount ΔQ2 Second change amount ΔSOC1, ΔSOC2 Differential state of charge SOCm1, SOCm2 central state of charge SOC11 Maximum state of charge SOC12 Minimum State of Charge SOC21 Starting State of Charge SOC22 End of Charge State S3 Step (measurement process) S4 Step (Calculation process) S5, S8, S10 steps (life estimation process) Gamma ratio value

Claims

1. An estimation system for estimating a cycle life of a lithium ion battery, comprising: The lithium ion battery is charged in a cycle-by-cycle manner under constant current and constant voltage control; In the constant current / constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum; a measurement unit that measures, for each cycle of the lithium ion battery, a first charging time that is a charging time of the lithium ion battery when the lithium ion battery is charged under the constant current / constant voltage control, and a second charging time that is a charging time of the lithium ion battery when the lithium ion battery is charged under the constant voltage control; a calculation unit that calculates a ratio obtained by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured by the measurement unit; a life estimation unit that calculates a difference by subtracting a first cycle number, which is the number of cycles when a minimum point appears, from a second cycle number, which is the number of cycles when a maximum point appears after the minimum point appears, in a curve along an upper end of a graph showing the behavior of the value of the ratio with the transition of the number of cycles of the lithium ion battery, and adds the difference to the second cycle number to obtain a third cycle number as an estimated value of the cycle life. Estimation system.

2. An estimation system for estimating a cycle life of a lithium ion battery, comprising: The lithium ion battery is charged in a cycle-by-cycle manner under constant current and constant voltage control; In the constant current / constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum; a measurement unit that measures, for each cycle of the lithium ion battery, a first charging time that is a charging time of the lithium ion battery when the lithium ion battery is charged under the constant current / constant voltage control, and a second charging time that is a charging time of the lithium ion battery when the lithium ion battery is charged under the constant voltage control; a calculation unit that calculates a ratio obtained by dividing the second charging time by the first charging time based on the first charging time and the second charging time measured by the measurement unit; a life estimation unit that calculates a difference by subtracting a first cycle number, which is the cycle number when a maximum point appears, from a second cycle number, which is the cycle number when a minimum point appears after the maximum point appears, in a curve along a lower end of a graph showing the behavior of the value of the ratio with the transition of the number of cycles of the lithium ion battery, and adds the difference to the second cycle number to obtain a third cycle number as an estimated value of the cycle life. Estimation system.

3. An estimation system for estimating a cycle life of a lithium ion battery, comprising: The lithium ion battery is charged in a cycle-by-cycle manner under constant current and constant voltage control; In the constant current / constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum; a measurement unit that measures, for each cycle of the lithium ion battery, a first charge capacity that is a charge capacity of the lithium ion battery when the lithium ion battery is charged under the constant current / constant voltage control, and a second charge capacity that is a charge capacity of the lithium ion battery when the lithium ion battery is charged under the constant voltage control; a calculation unit that calculates a ratio of the first charge capacity to the second charge capacity based on the first charge capacity and the second charge capacity measured by the measurement unit; a life estimation unit that calculates a difference by subtracting a first cycle number, which is the number of cycles when a minimum point appears, from a second cycle number, which is the number of cycles when a maximum point appears after the minimum point appears, in a curve along an upper end of a graph showing the behavior of the value of the ratio with the transition of the number of cycles of the lithium ion battery, and adds the difference to the second cycle number to obtain a third cycle number as an estimated value of the cycle life. Estimation system.

4. An estimation system for estimating a cycle life of a lithium ion battery, comprising: The lithium ion battery is charged in a cycle-by-cycle manner under constant current and constant voltage control; In the constant current / constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum; a measurement unit that measures, for each cycle of the lithium ion battery, a first charge capacity that is a charge capacity of the lithium ion battery when the lithium ion battery is charged under the constant current / constant voltage control, and a second charge capacity that is a charge capacity of the lithium ion battery when the lithium ion battery is charged under the constant voltage control; a calculation unit that calculates a ratio obtained by dividing the second charge capacity by the first charge capacity based on the first charge capacity and the second charge capacity measured by the measurement unit; a life estimation unit that calculates a difference by subtracting a first cycle number, which is the cycle number when a maximum point appears, from a second cycle number, which is the cycle number when a minimum point appears after the maximum point appears, in a curve along an upper end of a graph showing the behavior of the value of the ratio with the transition of the number of cycles of the lithium ion battery, and adds the difference to the second cycle number to obtain a third cycle number as an estimated value of the cycle life. Estimation system.

5. the life estimation unit calculates a rate of change in a deterioration state of the lithium ion battery with respect to a transition in the number of cycles during a certain period up to the maximum point, calculates the cycle life when deterioration of the lithium ion battery has progressed at the calculated rate of change as a reference cycle life, and determines the third cycle number to be the cycle life if the third cycle number is smaller than the reference cycle life, and determines the reference cycle life to be the cycle life if the third cycle number is equal to or greater than the reference cycle life. The estimation system according to any one of claims 1 to 4.

6. a deterioration state of the lithium ion battery is calculated from the integrated value in each cycle based on information defining a relationship between the integrated value in each cycle and the deterioration state in each cycle; The integrated value is a product of a differential state of charge, which is a difference between a maximum value and a minimum value of the state of charge in each cycle of the lithium ion battery, and a median state of charge, which is a median value between the maximum value and the minimum value. The estimation system according to claim 5 .

7. the deterioration state of the lithium ion battery is calculated from the integrated value and the change amount calculated based on information defining a relationship between the integrated value in each cycle, a first change amount which is a change amount of a discharge capacity or a second change amount which is a change amount of a charge capacity, and the deterioration state in each cycle; the integrated value is a product of a differential state of charge, which is a difference obtained by subtracting a starting state of charge at the start of charging of the lithium ion battery from a finishing state of charge at the end of charging, and a median state of charge, which is a median value between the starting state of charge and the finishing state of charge, the discharge capacity is an amount of current discharged from the lithium ion battery from a rated discharge start voltage to a rated discharge end voltage, and the first change amount is an amount of change in the discharge capacity with a change in the number of cycles; The charge capacity is a capacity charged into the lithium ion battery from a rated charge start voltage to a rated charge end voltage, and the second change amount is an amount of change in the charge capacity with a change in the number of cycles. The estimation system according to claim 5 .

8. A charge / discharge control unit is further provided, When the third cycle number is smaller than the reference cycle life, the charge / discharge control unit changes at least one set value of a charging voltage, a charging current, a discharging voltage, and a discharging current when charging / discharging the lithium ion battery to a smaller set value, and charges / discharges the lithium ion battery. The estimation system according to claim 5 .

9. After a predetermined period of time has elapsed since the start of charging the lithium ion battery, the measurement unit starts measuring the first charging time and the second charging time, the calculation unit starts calculating the value of the ratio, and the life estimation unit calculates the third cycle number. The estimation system according to claim 1 or 2.

10. A calculation device for use in the estimation system according to any one of claims 1 to 4, The measurement unit; The calculation unit, A communication unit that transmits information about the value of the ratio calculated by the calculation unit to a predetermined device. Calculation device.

11. 1. A method for estimating a cycle life of a lithium ion battery, comprising: The lithium ion battery is charged in a cycle-by-cycle manner under constant current and constant voltage control; In the constant current / constant voltage control, the lithium ion battery is charged by constant current control until the battery voltage of the lithium ion battery reaches a predetermined voltage, and when the battery voltage reaches the predetermined voltage, the lithium ion battery is charged by constant voltage control until the plate resistance of the lithium ion battery reaches a maximum point; a measuring step of measuring, for each cycle of the lithium ion battery, a first charging time which is the charging time of the lithium ion battery when the lithium ion battery is charged under the constant current / constant voltage control, and a second charging time which is the charging time of the lithium ion battery when the lithium ion battery is charged under the constant voltage control; a calculation step of calculating a ratio obtained by dividing the first charging time by the second charging time based on the first charging time and the second charging time measured in the measurement step; a life estimation step of calculating a difference by subtracting a first cycle number, which is the cycle number when a minimum point appears, from a second cycle number, which is the cycle number when a maximum point appears after the minimum point appears, in a curve along an upper end of a graph showing the behavior of the value of the ratio with the transition of the number of cycles of the lithium ion battery, and adding the difference to the second cycle number to obtain a third cycle number as an estimated value of the cycle life. Estimation method.

12. A method for estimating a parameter according to claim 11, program.

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