Battery state estimation device and battery state estimation method

Abstract

To provide a battery state estimation device of a secondary batter and a battery state estimation method thereof that distinguish capacity reduction in the secondary battery, and a gain error of current acquisition means and offset error thereof to compute a correction value, and enable computing a more accurate estimation charge rate.SOLUTION: The present battery state estimation device and battery state estimation method are configured to compute a charge side correction value K(+) and discharge side correction value K(-) on the basis of a ratio of an amount of change in a charge rate based on open circuit voltages of at least three or more points of a reference point, a charge point and a discharge point, and an amount of change in the charge rate based on current integrated values ΔAh (+) and ΔAh (-) of at least two or more sections corresponding to these reference point, charge point and discharge point. Then, in cases where both correction values are less than 1, where both are greater than 1, and where only one of both correction values is less than 1, the correction is made by the method corresponding to respective cases. Therefor, corrections to reduction in a battery capacity of a secondary battery 10 and gain error of current acquisition means can be discriminated from a correction to offset error of the current acquisition means.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery state estimation device for estimating the state of a secondary battery and an estimation method thereof.

Background Art

[0002] In recent years, rechargeable lithium-ion batteries have been used in a wide range of fields from relatively small devices such as portable communication terminals and portable power tools to large devices such as home equipment applications. In particular, for lithium-ion batteries used in large connection devices, the SOC (State of Charge) as the state information of the secondary battery is indirectly calculated as the estimated state of charge SOC' from the current value of the secondary battery or the like. As a method for calculating this estimated state of charge SOC', the change amount ΔSOC of the state of charge is calculated based on the following formula (A) from the current integrated value ΔAh of the secondary battery and the battery capacity (BOL: Beginning of Life: reference total capacity Ah(0)) at the time of new secondary battery, and the estimated state of charge SOC' is calculated based on the following formula (A') from this change amount ΔSOC of the state of charge. Here, SOC(0) is the state of charge serving as a reference point, and is obtained based on the OCV-SOC characteristic with the voltage of the secondary battery at the start-up time of the system as the open circuit voltage OCV. ΔSOC = ΔAh / Ah(0) ···(A) SOC' = SOC(0) + ΔSOC ···(A')

[0003] However, since the battery capacity of the secondary battery decreases due to deterioration, when calculating ΔSOC using the reference total capacity Ah(0) that does not consider deterioration, ΔSOC becomes smaller than the true value. In this case, the estimated state of charge SOC' becomes a value with a smaller change range from SOC(0) than the true value. Performing charge and discharge control of the secondary battery based on such incorrect state information not only accelerates the deterioration of the secondary battery but also causes various problems.

[0004] Regarding this problem, [Patent Document 1] below discloses an invention for estimating the battery capacity of a secondary battery that has decreased due to degradation from the state of charge (SOC) corresponding to two open circuit voltages (OCV) and the integrated current value ΔAh between these two points. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-224901 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, factors that can cause changes in ΔSOC include not only a decrease in battery capacity, but also measurement errors (mainly gain error and offset error) in the current acquisition means (current sensor, etc.) that form the basis of the integrated current value ΔAh. However, in estimation methods based on the open-circuit voltage OCV between two points, as described in [Patent Document 1], it is not possible to distinguish between a decrease in battery capacity and the gain error and offset error of the current acquisition means, and all are calculated as a decrease in battery capacity. However, if the offset error is calculated as a decrease in battery capacity, the correction value will differ between charging and discharging of the secondary battery, which may cause problems with operational stability and continuity. In addition, there is the problem that an accurate estimated charge rate SOC' cannot be obtained.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a battery state estimation device and battery state estimation method for a secondary battery that can calculate a correction value by distinguishing between the capacity reduction of the secondary battery and the gain error and offset error of the current acquisition means, and calculate a more accurate estimated charge rate (SOC'). [Means for solving the problem]

[0008] The present invention (1) A battery state estimation device for calculating the estimated charge rate (SOC') of a rechargeable secondary battery 10 that supplies power to a system, A current acquisition unit 30 acquires the current value of the secondary battery 10, a current integration value calculation unit 32 calculates the integrated current value ΔAh of the secondary battery 10 based on the current value acquired by the current acquisition unit 30, and a voltage acquisition unit 34 acquires the voltage value of the secondary battery 10. Based on the voltage values ​​acquired by the voltage acquisition unit 34, the OCV-SOC acquisition unit 42 acquires the open-circuit voltage of at least one reference point, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, and further acquires the charge level of at least one reference point, the charge level SOC(+) of the charging point, and the charge level SOC(-) of the discharge point, corresponding to the open-circuit voltage of at least one of the reference points, the open-circuit voltage OCV(+) of the charging point, and the open-circuit voltage OCV(-) of the discharge point. Based on the current integrated value ΔAh input from the current integrated value calculation unit 32, the current integrated value ΔAh(+) of the charging point is obtained with reference to the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point is obtained with reference to the current integrated value of at least one of the reference points. Based on the obtained current integrated value ΔAh(+) of the charging point, ΔSOC1(+) is calculated as the change in the charge rate of the first charging side. A ΔSOC calculation unit 52 calculates ΔSOC1(-) as the change in charge rate of the first discharge side based on the integrated current value ΔAh(-), and calculates ΔSOC2(+) as the change in charge rate of the second charge side based on the charge rate of at least one reference point, the charge rate SOC(+) of the charging point, and the charge rate SOC(-) of the discharging point obtained from the OCV-SOC acquisition unit 42, and calculates ΔSOC2(-) as the change in charge rate of the second discharge side. A correction coefficient calculation unit 54 calculates a charge-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) calculated by the ΔSOC calculation unit 52, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination unit 56 determines whether the charging-side correction value K(+) and the discharging-side correction value K(-) calculated by the correction coefficient calculation unit 54 are greater than or less than 1, and selects a method for calculating the estimated charge rate (SOC') according to the determination result. If the determination unit 56 determines that both the charging-side correction value K(+) and the discharging-side correction value K(-) are less than 1, or that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting unit 57 calculates a correction value K'(n) based on the charging-side correction value K(+) and the discharging-side correction value K(-), and sets a capacity correction value K(n) based on the correction value K'(n). A capacity correction unit 58 calculates the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery 10 based on the capacity correction value K(n) set by the correction coefficient setting unit 57, The above problem is solved by providing a battery state estimation device 80, which is characterized by having an estimated charge rate calculation unit 60 that calculates the estimated charge rate SOC' based on the total capacity Ah(n) calculated by the capacity correction unit 58. (2) The ΔSOC calculation unit 52 calculates ΔSOC1(+) as the change in the charge rate on the first charging side based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(+) at the charging point using the following equation (1), and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(-) at the discharging point using the following equation (1'), ΔSOC1(+)=ΔAh(+) / Ah(n-1)···(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)···(1') Furthermore, ΔSOC2(+) as the change in the charge rate of the second charging side is calculated using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or ΔSOC2(+) as the change in the charge rate of the second charging side is calculated using equation (2'') below, based on the charge rate SOC(0') of a different reference point than the aforementioned charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the charge level (SOC(0)) of at least one reference point and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2') below, or based on the charge level (SOC(0')) of a different reference point than the aforementioned charge level (SOC(0)) and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2''') below. ΔSOC2(+)=|SOC(+)-SOC(0)|···(2) ΔSOC2(-)=|SOC(-)-SOC(0)|···(2') ΔSOC2(+)=|SOC(+)-SOC(0')|···(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|···(2''') The above problem is solved by providing the battery state estimation device 80 described in (1) above, characterized in that the correction coefficient calculation unit 54 calculates a charge-side correction value K(+) based on ΔSOC1(+) and ΔSOC2(+) using the following equation (3), and calculates a discharge-side correction value K(-) based on ΔSOC1(-) and ΔSOC2(-) using the following equation (3'). K(+)=ΔSOC1(+) / ΔSOC2(+)···(3) K(-)=ΔSOC1(-) / ΔSOC2(-)···(3') (3) When multiple charging points or multiple discharging points are obtained, The OCV-SOC acquisition unit 42 acquires the charge level SOC(+) at each charging point and the charge level SOC(-) at the discharge point, The ΔSOC calculation unit 52 calculates ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) individually for each charging point or discharging point. The battery state estimation device 80 described in (2) above is characterized in that the correction coefficient calculation unit 54 individually calculates provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3') above, and then sets the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-). (4) A battery state estimation device for calculating the estimated charge rate (SOC') of a rechargeable secondary battery 10 that supplies power to a system, A current acquisition unit 30 acquires the current value of the secondary battery 10, a current integration value calculation unit 32 calculates the integrated current value ΔAh of the secondary battery 10 based on the current value acquired by the current acquisition unit 30, and a voltage acquisition unit 34 acquires the voltage value of the secondary battery 10. Based on the voltage values ​​acquired by the voltage acquisition unit 34, the OCV-SOC acquisition unit 42 acquires the open-circuit voltage of at least one reference point, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, and further acquires the charge level of at least one reference point, the charge level SOC(+) of the charging point, and the charge level SOC(-) of the discharge point, corresponding to the open-circuit voltage of at least one of the reference points, the open-circuit voltage OCV(+) of the charging point, and the open-circuit voltage OCV(-) of the discharge point. Based on the current integrated value ΔAh input from the current integrated value calculation unit 32, the current integrated value ΔAh(+) of the charging point is obtained with reference to the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point is obtained with reference to the current integrated value of at least one of the reference points. Based on the obtained current integrated value ΔAh(+) of the charging point, ΔSOC1(+) is calculated as the change in the charge rate of the first charging side. A ΔSOC calculation unit 52 calculates ΔSOC1(-) as the change in charge rate of the first discharge side based on the integrated current value ΔAh(-), and calculates ΔSOC2(+) as the change in charge rate of the second charge side based on the charge rate of at least one reference point, the charge rate SOC(+) of the charging point, and the charge rate SOC(-) of the discharging point obtained from the OCV-SOC acquisition unit 42, and calculates ΔSOC2(-) as the change in charge rate of the second discharge side. A correction coefficient calculation unit 54 calculates a charge-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) calculated by the ΔSOC calculation unit 52, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination unit 56 determines whether the charging-side correction value K(+) and the discharging-side correction value K(-) calculated by the correction coefficient calculation unit 54 are greater than or less than 1, and selects a method for calculating the estimated charge rate (SOC') according to the determination result. If the determination unit 56 determines that one of the charging-side correction value K(+) and the discharging-side correction value K(-) is less than 1 and the other is greater than 1, the correction coefficient setting unit 57 sets the past capacity correction value K(n-1) to the capacity correction value K(n), A capacity correction unit 58 calculates the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery based on the capacity correction value K(n) set by the correction coefficient setting unit 57, An SOC correction unit 59 sets an SOC correction value K(soc) based on the values ​​of ΔSOC1(+), SOC1(-), ΔSOC2(+), and ΔSOC2(-), The above problem is solved by providing a battery state estimation device 80, which is characterized by having an estimated charge rate calculation unit 60 that calculates the estimated charge rate SOC' based on the total capacity Ah(n) and the SOC correction value K(soc). (5) The ΔSOC calculation unit 52 calculates ΔSOC1(+) as the change in the charge rate on the first charging side using the following equation (1) based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(+) at the charging point, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side using the following equation (1') based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(-) at the discharging point. ΔSOC1(+)=ΔAh(+) / Ah(n-1)···(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)···(1') Furthermore, ΔSOC2(+) as the change in the charge rate of the second charging side is calculated using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or ΔSOC2(+) as the change in the charge rate of the second charging side is calculated using equation (2'') below, based on the charge rate SOC(0') of a different reference point than the aforementioned charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the charge level (SOC(0)) of at least one reference point and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2') below, or based on the charge level (SOC(0')) of a different reference point than the aforementioned charge level (SOC(0)) and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2''') below. ΔSOC2(+)=|SOC(+)-SOC(0)|···(2) ΔSOC2(-) = |SOC(-) - SOC(0)| ··· (2’) ΔSOC2(+) = |SOC(+) - SOC(0’)| ··· (2’’) ΔSOC2(-) = |SOC(-) - SOC(0’)| ··· (2’’’) The correction coefficient calculation unit 54 calculates a charging-side correction value K(+) according to the following formula (3) based on the ΔSOC1(+) and ΔSOC2(+), and calculates a discharging-side correction value K(-) according to the following formula (3’) based on the ΔSOC1(-) and ΔSOC2(-), which is characterized in that the above-mentioned (4) The battery state estimation device 80 described above is provided to solve the above problems. K(+) = ΔSOC1(+) / ΔSOC2(+) ··· (3) K(-) = ΔSOC1(-) / ΔSOC2(-) ··· (3’) (6) When multiple charging points or multiple discharging points are obtained, The OCV-SOC acquisition unit 42 acquires the charge level SOC(+) at each charging point and the charge level SOC(-) at the discharge point, The ΔSOC calculation unit 52 calculates ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) individually for each charging point or discharging point. The battery state estimation device 80 described in (5) above is characterized in that the correction coefficient calculation unit 54 individually calculates provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3') above, and then sets the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-). (7) The correction coefficient setting unit 57 has a correction lower limit value K(min) smaller than 1, and when the correction value K’(n) is smaller than the correction lower limit value K(min), the correction lower limit value K(min) is set as the capacity correction value K(n), which is characterized in that the above-mentioned (1) or any of the above (3) The battery state estimation device 80 described above is provided to solve the above problems. (8) The correction coefficient setting unit 57 has a reduction coefficient A, and calculates the capacity correction value K(n) based on the following formula (4’) from the reduction coefficient A and the previous capacity correction value K(n - 1), which is characterized in that the above-mentioned (1) or any of the above (3) The battery state estimation device 80 described above is provided to solve the above problems. K(n) = (1 - A × (1 - K’(n))) × K(n - 1) ··· (4’) (9) The SOC correction unit 59 sets the SOC correction value K(soc) based on the values of |ΔSOC2(+) - ΔSOC1(+)| and |ΔSOC2(-) - ΔSOC1(-)|, which is characterized in that the above-mentioned (4) to any of the above (6) The above problems are solved by providing the battery state estimation device 80 described above. (10) The above description is characterized in that the SOC correction unit 59 takes the average of the values ​​of |ΔSOC2(+)-ΔSOC1(+)| and |ΔSOC2(-)-ΔSOC1(-)| as the SOC correction value K(soc). (9) The above problems are solved by providing the battery state estimation device 80 described above. (11) The above (1) to the above is characterized in that at least one of the open-circuit voltage OCV(0) at the reference point, the open-circuit voltage OCV(+) at the charging point, and the open-circuit voltage OCV(-) at the discharge point is the open-circuit voltage of the secondary battery 10 at the time of system startup. (10) The above problem is solved by providing a battery state estimation device 80 as described in any of the above. (12) If the determination unit 56 determines that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting unit 57 sets the capacity correction value K(n) as the value obtained by multiplying the average value of the charging-side correction value K(+) and the discharging-side correction value K(-) by the previous capacity correction value K(n-1) based on the following formula (4''), characterized in that (1) to the above (11) The above problem is solved by providing a battery state estimation device 80 as described in any of the above. K(n)=((K(+)+K(-)) / 2)×K(n-1)···(4'') (13) The capacity correction unit 58 performs the following: (7) The above (1) to the above is characterized by correcting the total capacity Ah(n-1) based on the formula and calculating the total capacity Ah(n). (12) The above problem is solved by providing a battery state estimation device 80 as described in any of the above. Ah(n) = Ah(n-1) × K(n) ... (5) (14) The above (1) to the above (13)The above problem is solved by providing a battery state estimation device 80 as described in any of the above. (15) The above (1) to the above is characterized by further having a relaxation state determination unit 56 that permits the OCV-SOC acquisition unit 42 to acquire an open circuit voltage when the current value from the current acquisition unit 30 remains near zero for a predetermined predetermined time. (14) The above problem is solved by providing a battery state estimation device 80 as described in any of the above. (16) The above (1) to the above is characterized by applying the corrected total capacity Ah(n) and then calculating the capacity correction value K(n+1) again. (15) A battery state estimation device 80 as described in any of the following. (17) The above is characterized by setting an upper limit on the number of calculation operations for the capacity correction value K(n) during a single system operating period. (16) The above problems are solved by providing the battery state estimation device 80 described above. (18) The system further includes a recording unit 55 that records at least the capacity correction value K(n-1) that was applied at the time the system was turned off. When the system is started, the capacity correction value K(n-1) recorded in the recording unit 55 is read out, the capacity correction value K(n-1) is set as the capacity correction value K(n), and the initial total capacity Ah(n) is calculated based on the following formula (5') as described above (1) to the above (17) The above problem is solved by providing a battery state estimation device 80 as described in any of the above. Ah(n) = Ah(0) × K(n)···(5') (19) The system further includes a recording unit 55 that records at least the capacity correction value K(n-1) applied at the time of system off, the reference point charge level SOC(0)' at that time, and the total current value ΔAh(total) for the entire period from the previous system startup to the time of system off. When the system starts up, the charge level SOC(0) is obtained from the open-circuit voltage OCV(0) at startup, and the charge level SOC(0)' of the reference point recorded in the recording unit 55 and the integrated current value ΔAh(total) are read out. After determining whether the cumulative current value ΔAh(total) is located on the charging side or the discharging side relative to the reference point at the time the system is turned off, the Integrated current value Based on ΔAh(total), calculate ΔSOC1(+) or ΔSOC1(-). The above (1) to the above is characterized by calculating ΔSOC2(+) or ΔSOC2(-) based on the charge rate SOC(0)' and charge rate SOC(0), and calculating either a charging-side correction value K(+) or a discharging-side correction value K(-). (17) The above problem is solved by providing a battery state estimation device 80 as described in any of the above. (20) The secondary battery 10 further has a data mapping that records the relationship between its internal resistance and battery capacity. The above (1) to the above is characterized by calculating the estimated internal resistance of the secondary battery 10 from the voltage value acquired by the voltage acquisition unit 34 and the current value acquired by the current acquisition unit 30, obtaining the battery capacity corresponding to the estimated internal resistance from the data mapping, and calculating the total capacity Ah(n) when the battery capacity shows a capacity decrease and the determination unit 56 determines that both the charge-side correction value K(+) and the discharge-side correction value K(-) are less than 1. (19) The above problem is solved by providing a battery state estimation device 80 as described in any of the above. (21) A battery state estimation method for calculating the estimated charge rate (SOC') of a rechargeable secondary battery 10 that supplies power to a system, A current acquisition step to acquire the current value of the secondary battery 10, A current integration value calculation step calculates the current integration value ΔAh of the secondary battery 10 based on the current value obtained in the current acquisition step, A voltage acquisition step to acquire the voltage value of the secondary battery 10, An open-circuit voltage acquisition step, which acquires the open-circuit voltage of at least one reference point based on the voltage value acquired in the voltage acquisition step, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, A charge rate acquisition step which acquires the open-circuit voltage of at least one reference point acquired in the open-circuit voltage acquisition step, the charge rate of at least one reference point corresponding to the open-circuit voltage OCV(+) of the charging point and the open-circuit voltage OCV(-) of the discharge point, the charge rate SOC(+) of the charging point and the charge rate SOC(-) of the discharge point, A charge / discharge current integrated value acquisition step, which acquires, based on the current integrated value ΔAh obtained in the current integrated value calculation step, the current integrated value ΔAh(+) of the charging point with reference to the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point with reference to the current integrated value of at least one of the reference points, respectively. A first charge rate change calculation step calculates ΔSOC1(+) as the change in charge rate on the first charging side based on the integrated current value ΔAh(+) at the charging point obtained in the charge / discharge current acquisition step, and calculates ΔSOC1(-) as the change in charge rate on the first discharging side based on the integrated current value ΔAh(-) at the discharging point, A second charge rate change calculation step calculates ΔSOC2(+) as the change in the charge rate of the second charging side based on the charge rate of at least one reference point obtained in the charge rate acquisition step and the charge rate SOC(+) of the charging point, and calculates ΔSOC2(-) as the change in the charge rate of the second discharging side based on the charge rate SOC(0) of the reference point and the charge rate SOC(-) of the discharging point, A correction coefficient calculation step which calculates a charging-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) obtained in the first charge rate change calculation step and the second charge rate change calculation step, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination step is to determine whether the charging-side correction value K(+) and the discharging-side correction value K(-) calculated in the correction coefficient calculation step are greater than or less than 1, and to select a method for calculating the estimated charge rate (SOC') according to the determination result. If the determination step determines that both the charging-side correction value K(+) and the discharging-side correction value K(-) are less than 1, or that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting step involves calculating a correction value K'(n) based on the charging-side correction value K(+) and the discharging-side correction value K(-), and setting a capacity correction value K(n) based on the correction value K'(n). A capacity value correction step to calculate the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery based on the capacity correction value K(n) set in the correction coefficient setting step, The above problem is solved by providing a battery state estimation method characterized by comprising: an estimated charge rate calculation step, which calculates the estimated charge rate SOC' based on the total capacity Ah(n) calculated in the capacity value correction step. (22) The first charge rate change calculation step calculates ΔSOC1(+) as the change in the charge rate on the first charging side using equation (1) below, based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(+) at the charging point, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side using equation (1') below, based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(-) at the discharging point. ΔSOC1(+)=ΔAh(+) / Ah(n-1)···(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)···(1') The second charge rate change calculation step calculates ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or calculates ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2'') below, based on the charge rate SOC(0') of a different reference point than the charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the charge level (SOC(0)) of at least one reference point and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2') below, or based on the charge level (SOC(0')) of a different reference point than the aforementioned charge level (SOC(0)) and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2''') below. ΔSOC2(+)=|SOC(+)-SOC(0)|···(2) ΔSOC2(-)=|SOC(-)-SOC(0)|···(2') ΔSOC2(+)=|SOC(+)-SOC(0')|···(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|···(2''') The correction coefficient calculation step is characterized by calculating the charge-side correction value K(+) based on ΔSOC1(+) and ΔSOC2(+) using the following equation (3), and calculating the discharge-side correction value K(-) based on ΔSOC1(-) and ΔSOC2(-) using the following equation (3'). (21) The above problem is solved by providing the battery state estimation method described above. K(+)=ΔSOC1(+) / ΔSOC2(+)···(3) K(-)=ΔSOC1(-) / ΔSOC2(-)···(3') (23) If the open-circuit voltage acquisition step acquires multiple charging points or multiple discharging points, the charge rate acquisition step acquires the charge rate SOC(+) at each charging point and the charge rate SOC(-) at each discharging point. The charge rate change calculation step involves individually calculating ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) for each charging or discharging point. The above problem is solved by providing the battery state estimation method described in (22) above, characterized in that the correction coefficient calculation step individually calculates provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3') above, and then sets the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-). (24) A battery state estimation method for calculating the estimated charge rate (SOC') of a rechargeable secondary battery 10 that supplies power to a system, A current acquisition step to acquire the current value of the secondary battery 10, A current integration value calculation step calculates the current integration value ΔAh of the secondary battery 10 based on the current value obtained in the current acquisition step, A voltage acquisition step to acquire the voltage value of the secondary battery 10, An open-circuit voltage acquisition step, which acquires the open-circuit voltage of at least one reference point based on the voltage value acquired in the voltage acquisition step, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, A charge rate acquisition step which acquires the open-circuit voltage of at least one reference point acquired in the open-circuit voltage acquisition step, the charge rate of at least one reference point corresponding to the open-circuit voltage OCV(+) of the charging point and the open-circuit voltage OCV(-) of the discharge point, the charge rate SOC(+) of the charging point and the charge rate SOC(-) of the discharge point, A charge / discharge current integrated value acquisition step, which acquires, based on the current integrated value ΔAh obtained in the current integrated value calculation step, the current integrated value ΔAh(+) of the charging point with reference to the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point with reference to the current integrated value of at least one of the reference points, respectively. A first charge rate change calculation step calculates ΔSOC1(+) as the change in charge rate on the first charging side based on the integrated current value ΔAh(+) at the charging point obtained in the charge / discharge current acquisition step, and calculates ΔSOC1(-) as the change in charge rate on the first discharging side based on the integrated current value ΔAh(-) at the discharging point, A second charge rate change calculation step calculates ΔSOC2(+) as the change in the charge rate of the second charging side based on the charge rate of at least one reference point obtained in the charge rate acquisition step and the charge rate SOC(+) of the charging point, and calculates ΔSOC2(-) as the change in the charge rate of the second discharging side based on the charge rate SOC(0) of the reference point and the charge rate SOC(-) of the discharging point, A correction coefficient calculation step which calculates a charging-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) obtained in the first charge rate change calculation step and the second charge rate change calculation step, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination step is to determine whether the charging-side correction value K(+) and the discharging-side correction value K(-) calculated in the correction coefficient calculation step are greater than or less than 1, and to select a method for calculating the estimated charge rate (SOC') according to the determination result. If, in the above determination step, it is determined that one of the charging-side correction value K(+) and the discharging-side correction value K(-) is less than 1 and the other is greater than 1, A correction coefficient setting step in which a capacity correction value K(n) is set based on past capacity correction values ​​K(n-1), A capacity value correction step to calculate the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery 10 based on the capacity correction value K(n) set in the correction coefficient setting step, A step to set an SOC correction value K(soc) based on the values ​​of ΔSOC1(+), SOC1(-), ΔSOC2(+), and ΔSOC2(-), The above problem is solved by providing a battery state estimation method characterized by having an estimated charge rate calculation step that calculates the estimated charge rate SOC' based on the total capacity Ah(n) calculated in the capacity value correction step and the SOC correction value K(soc) set in the SOC correction value setting step. (25) The first charge rate change calculation step calculates ΔSOC1(+) as the change in the charge rate on the first charging side using equation (1) below, based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(+) at the charging point, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side using equation (1') below, based on the total capacity Ah(n-1) of the secondary battery 10 and the integrated current value ΔAh(-) at the discharging point. ΔSOC1(+)=ΔAh(+) / Ah(n-1)···(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)···(1') The second charge rate change calculation step calculates ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or calculates ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2'') below, based on the charge rate SOC(0') of a different reference point than the charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the charge level (SOC(0)) of at least one reference point and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2') below, or based on the charge level (SOC(0')) of a different reference point than the aforementioned charge level (SOC(0)) and the charge level (SOC(-)) of the discharge point, ΔSOC2(-) is calculated as the change in the charge level on the second discharge side using equation (2''') below. ΔSOC2(+)=|SOC(+)-SOC(0)|···(2) ΔSOC2(-)=|SOC(-)-SOC(0)|···(2') ΔSOC2(+)=|SOC(+)-SOC(0')|···(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|···(2''') The correction coefficient calculation step is characterized by calculating the charge-side correction value K(+) based on ΔSOC1(+) and ΔSOC2(+) using the following equation (3), and calculating the discharge-side correction value K(-) based on ΔSOC1(-) and ΔSOC2(-) using the following equation (3'). (24) The above problem is solved by providing the battery state estimation method described above. K(+)=ΔSOC1(+) / ΔSOC2(+)···(3) K(-)=ΔSOC1(-) / ΔSOC2(-)···(3') (26) If the open-circuit voltage acquisition step acquires multiple charging points or multiple discharging points, the charge rate acquisition step acquires the charge rate SOC(+) at each charging point and the charge rate SOC(-) at each discharging point. The charge rate change calculation step involves individually calculating ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) for each charging or discharging point. The above problem is solved by providing the battery state estimation method described in (25) above, characterized in that the correction coefficient calculation step individually calculates provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3') above, and then sets the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-). (27)The above method is characterized in that, if the correction coefficient setting step is less than the correction lower limit K(min) which is less than 1, the correction value K'(n) is set to the correction lower limit K(min) as the capacity correction value K(n). (21) to any of (23) above The above problem is solved by providing the battery state estimation method described above. (28) The above is characterized in that the correction coefficient setting step calculates a capacity correction value K(n) based on the following equation (4') from a reduction coefficient A that is less than 1 and the previous capacity correction value K(n-1). (21) to any of (23) above The above problem is solved by providing the battery state estimation method described above. K(n)=(1-A×(1-K'(n)))×K(n-1)...(4') (29) The above is characterized in that the SOC correction value setting step sets the SOC correction value K(soc) based on the values ​​of |ΔSOC2(+)-ΔSOC1(+)| and |ΔSOC2(-)-ΔSOC1(-)|. (24) to any of the above (26) The above problem is solved by providing the battery state estimation method described above. (30) The above SOC correction value setting step is characterized in that the average value of |ΔSOC2(+)-ΔSOC1(+)| and the value of |ΔSOC2(-)-ΔSOC1(-)| is set as the SOC correction value K(soc). (29) The above problem is solved by providing the battery state estimation method described above. (31) The open-circuit voltage acquisition step is characterized in that at least one of the open-circuit voltage OCV(0) at the reference point, the open-circuit voltage OCV(+) at the charging point, and the open-circuit voltage OCV(-) at the discharge point is the open-circuit voltage of the secondary battery 10 at system startup. (21) or the above (30) The above problem is solved by providing a battery state estimation method described in any of the above. (32)In the determination step, if it is determined that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting step is characterized in that the capacity correction value K(n) is set to the average value of the charging-side correction value K(+) and the discharging-side correction value K(-) multiplied by the previous capacity correction value K(n-1) based on the following formula (4''). (21) or the above (31) The above problem is solved by providing a battery state estimation method described in any of the above. K(n)=((K(+)+K(-)) / 2)×K(n-1)···(4'') (33) The above is characterized in that the capacity value correction step corrects the total capacity Ah(n-1) based on the following equation (5) and calculates the total capacity Ah(n). (21) or the above (32) The above problem is solved by providing a battery state estimation method described in any of the above. Ah(n) = Ah(n-1) × K(n) ... (5) (34) The open-circuit voltage acquisition step is characterized in that, when the acquired charging point or discharging point exceeds a predetermined threshold range set above or below the reference point, this point is set as the charging point or discharging point. (21) or the above (33) The above problem is solved by providing a battery state estimation method described in any of the above. (35) The above is characterized in that the open-circuit voltage acquisition step further includes a relaxation state standby step in which the open-circuit voltage is acquired when the current value from the current acquisition unit 30 remains in a predetermined state of zero near zero for a predetermined predetermined time. (21) or the above (34) The above problem is solved by providing a battery state estimation method described in any of the above. (36) The above method is characterized by applying the corrected total capacity Ah(n) and then recalculating the capacity correction value K(n+1). (21) or the above (35) The above problem is solved by providing a battery state estimation method described in any of the above. (37) The above is characterized by setting an upper limit on the number of calculation operations for the capacity correction value K(n) during a single system operating period. (36) The above problem is solved by providing the battery state estimation method described above. (38) A recording step that records at least the capacity correction value K(n-1) that is applied at the time the system is turned off, The system further includes an initial correction value calculation step that is performed when the system starts up, The initial correction value calculation step is characterized by reading the capacity correction value K(n-1) recorded in the recording step, setting the capacity correction value K(n-1) as the capacity correction value K(n), and calculating the initial total capacity Ah(n) based on the following formula (5'). (21) or the above (37) The above problem is solved by providing a battery state estimation method described in any of the above. Ah(n) = Ah(0) × K(n)···(5') (39) The system further includes a recording step that records at least the capacity correction value K(n-1) applied at the time of system off, the reference point charge level SOC(0)' at that time, and the total current value ΔAh(total) for the entire period from the previous system startup to the time of system off. When the system starts up, the state of charge (SOC) is obtained from the open-circuit voltage (OCV) (0) at startup, The recordings made in the aforementioned recording step Read out the charge level SOC(0)' at the reference point and the integrated current value ΔAh(total), After determining whether the cumulative current value ΔAh(total) is located on the charging side or the discharging side relative to the reference point at the time the system is turned off, the Integrated current value Based on ΔAh(total), calculate ΔSOC1(+) or ΔSOC1(-). The above method is characterized by calculating ΔSOC2(+) or ΔSOC2(-) based on the charge level SOC(0)' and the charge level SOC(0), and then calculating either a charging-side correction value K(+) or a discharging-side correction value K(-). (21) or the above (37)The above problem is solved by providing a battery state estimation method described in any of the above. (40) It includes a data mapping that records the relationship between the internal resistance and battery capacity of the secondary battery 10, An internal resistance calculation step calculates the estimated internal resistance of the secondary battery 10 from the voltage value obtained in the voltage acquisition step and the current value obtained in the current acquisition step. A battery capacity acquisition step is performed to obtain the battery capacity corresponding to the estimated internal resistance value calculated in the internal resistance calculation step from the data mapping, The battery capacity acquisition step further includes a capacity degradation determination step that determines whether the battery capacity acquired by the battery capacity acquisition step indicates a capacity degradation, The above method is characterized in that, in the capacity reduction determination step, the battery capacity obtained in the battery capacity acquisition step shows a capacity reduction, and in the determination step, it is determined that both the charge-side correction value K(+) and the discharge-side correction value K(-) are less than 1, and the total capacity Ah(n) is calculated. (21) or the above (39) The above problem is solved by providing a battery state estimation method described in any of the above. [Effects of the Invention]

[0009] The battery state estimation device and battery state estimation method according to the present invention calculate a charging-side correction value K(+) and a discharge-side correction value K(-) based on the ratio of the change in charge rate SOC(0), SOC(+), and SOC(-) based on open-circuit voltages at least three points (a reference point, a charging point, and a discharge point) and the change in charge rate based on current integrated values ​​ΔAh(+) and ΔAh(-) for at least two intervals corresponding to these reference point, charging point, and discharge point. Then, correction is performed in a manner corresponding to the cases where both the charging-side correction value K(+) and the discharge-side correction value K(-) are less than 1, where both are greater than 1, and where only one is less than 1. This makes it possible to distinguish between correction for the decrease in battery capacity of the secondary battery and the gain error of the current acquisition means, and correction for the offset error of the current acquisition means, and to appropriately perform corrections corresponding to both. As a result, a more accurate estimated charge rate SOC' can be calculated. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing the schematic configuration of the battery state estimation device according to the present invention. [Figure 2] This is a flowchart of the battery state estimation method according to the present invention. [Figure 3] This is a flowchart of the battery state estimation method according to the present invention. [Figure 4] This is a flowchart of the battery state estimation method according to the present invention. [Figure 5] This diagram illustrates the battery state estimation method according to the present invention when there are multiple reference points. [Figure 6] This diagram explains current values ​​and integrated current values. [Figure 7] This diagram illustrates the relationship between the offset error and ΔSOC1 and ΔSOC2. [Modes for carrying out the invention]

[0011] The battery state estimation device 80 and the battery state estimation method according to the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing the schematic configuration of the battery state estimation device 80 according to the present invention. First, the battery state estimation device 80 according to the present invention estimates the state of a secondary battery 10 used as a power source for a load 1, and includes a battery information acquisition unit 20 that acquires information such as the battery voltage V and current value I of the secondary battery 10, a charge rate acquisition unit 40 that acquires the charge rate SOC based on the information from the battery information acquisition unit 20, a correction value setting unit 50 that sets a capacity correction value K(n) or an SOC correction value K(soc) based on at least three charge rate SOCs (SOC(0), SOC(+), SOC(-)) acquired by the charge rate acquisition unit 40 and the integrated current value ΔAh (ΔAh(+), ΔAh(-)) acquired from the battery information acquisition unit 20, and calculates the total capacity Ah(n) based on this capacity correction value K(n), and an estimated charge rate calculation unit 60 that calculates the estimated charge rate SOC' based on the total capacity Ah(n) calculated by the correction value setting unit 50 and the SOC correction value K(soc). Furthermore, the battery state estimation device 80 according to the present invention may also have a well-known configuration for acquiring or calculating other battery state information such as SOP (State of Power) and SOH (State of Health) in addition to the above configuration.

[0012] Next, the detailed configuration and operation of each part of the battery state estimation device 80 according to the present invention and the battery state estimation method according to the present invention will be described. Here, Figures 2 to 4 are flowcharts of the battery state estimation method according to the present invention. Here, a solar power generation system equipped with a secondary battery 10 and a solar panel as an external power source 7, and an electromechanical device equipped with a secondary battery 10 that is activated only when in use will be used as examples, but the present invention is not limited to these and can be applied to all machinery, equipment, etc. that have a secondary battery 10.

[0013] First, the system equipped with the battery state estimation device 80 according to the present invention comprises the battery state estimation device 80, a rechargeable secondary battery 10, a system control unit 5 that controls the entire system, an external power source 7 such as a solar panel or commercial power, a load 1 as a connected device that operates using power supplied from the secondary battery 10 or the external power source 7, a power converter 3 that converts the charging of the secondary battery 10 and the power supply to the load 1 into power suitable for both, and an operation unit (not shown) that performs predetermined operations based on battery state information such as the estimated charge rate (SOC') output by the battery state estimation device 80.

[0014] Furthermore, the battery information acquisition unit 20 of the battery state estimation device 80 includes a well-known current acquisition means 30a such as a current sensor installed on the secondary battery 10, a current acquisition unit 30 that acquires the current value I of the secondary battery 10 during charging and discharging from the output of the current acquisition means 30a, a current integration value calculation unit 32 that calculates the integrated current value ΔAh of the secondary battery 10 based on the current value I acquired by the current acquisition unit 30, a well-known voltage acquisition means 34a such as a voltage sensor installed on the secondary battery 10, and a voltage acquisition unit 34 that acquires the battery voltage V of the secondary battery 10 from the output of the voltage acquisition means 34a. Note that the current acquisition means 30a can be a current sensor using a Hall element that can measure current values ​​without contact, or any other well-known current acquisition means. Furthermore, if the secondary battery 10 is a battery pack, the voltage acquisition unit 34 may either install the voltage acquisition means 34a on both ends of the battery pack to directly acquire the battery voltage V, or it may install the voltage acquisition means 34a on each cell constituting the battery pack to individually acquire the voltage value of each cell, and the voltage acquisition unit 34 may sum these to obtain the battery voltage V of the secondary battery 10. In addition, the battery information acquisition unit 20 may further have a temperature acquisition unit 12 that acquires the battery temperature T of the secondary battery 10 via a well-known temperature acquisition means 12a such as a thermistor. Note that this temperature acquisition unit 12 may also be used as a protective device that detects abnormal heat generation of the secondary battery 10. The battery information acquisition unit 20 basically operates continuously while the system is running, acquires the battery voltage V, integrated current value ΔAh (current value I), and battery temperature T of the secondary battery 10, and outputs them to the charge rate acquisition unit 40.

[0015] Furthermore, the charge level acquisition unit 40 includes an SOC storage unit 44 in which the charge level SOC corresponding to the open-circuit voltage OCV of the secondary battery 10 is recorded, for example, as table data, and an OCV-SOC acquisition unit 42 that obtains the open-circuit voltage OCV of the secondary battery 10 and obtains the charge level SOC corresponding to this open-circuit voltage OCV by referring to the SOC storage unit 44.

[0016] Furthermore, the correction value setting unit 50 includes a ΔSOC calculation unit 52 that calculates ΔSOC1(+), ΔSOC1(-) and ΔSOC2(+), ΔSOC2(-) from at least three charge rate SOCs (SOC(0), SOC(+), SOC(-)) input from the charge rate acquisition unit 40 and the current integrated values ​​ΔAh(+), ΔAh(-) over two intervals, and a calculation unit 52 that calculates the charge-side correction value K(+) and discharge-side correction value K(-) from these ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), ΔSOC2(-). The system includes a correction coefficient calculation unit 54, a determination unit 56 that selects a correction method based on the charging-side correction value K(+) and the discharging-side correction value K(-), a correction coefficient setting unit 57 that sets a capacity correction value K(n) according to the determination result of the determination unit 56, a capacity correction unit 58 that calculates the total capacity Ah(n) by correcting the total capacity Ah(n-1) based on the capacity correction value K(n) set by the correction coefficient setting unit 57, and an SOC correction unit 59 that sets an SOC correction value K(soc) according to the determination result of the determination unit 56. Furthermore, the estimated charge rate calculation unit 60 (when no offset error occurs) calculates the estimated charge rate SOC' based on the following (A'') equation, which combines the above (A) and (A') equations, using the total capacity Ah(n) calculated by the capacity correction unit 58, the current integrated value ΔAh output by the current integrated value calculation unit 32, and the charge rate SOC(0) at the reference point. SOC'=ΔAh / Ah(n)+SOC(0)...(A'')

[0017] Furthermore, it is preferable to provide a recording unit 55 in the correction value setting unit 50 for recording each value when the system is powered off. As this recording unit 55, a well-known recording means such as EEPROM (Electrically Erasable and Programmable Read Only Memory), in which the recorded contents are not erased even when the power is turned off, can be used. Here, we will explain using an example in which the correction value setting unit 50 has a recording unit 55 and performs the initial correction value calculation step S120 described later when the system is started up. We will also explain using an example in which no current flows to the secondary battery 10 immediately after the system is started up.

[0018] First, when the entire system starts up (step S001), the control unit (not shown) of the battery state estimation device 80 reads and acquires data necessary for calculating the initial capacity correction value K(n) from the recording unit 55 (step S012). The data read at this time includes the capacity correction value K(n-1) that was applied at the time the system was last turned off, the reference point charge level SOC(0)' at that time, and the integrated current value ΔAh' at the time the system was turned off.

[0019] Next, when no current is flowing through the secondary battery 10 immediately after startup, the voltage acquisition means 34a acquires the potentials of, for example, the positive and negative electrodes of the secondary battery 10 and outputs them to the voltage acquisition unit 34. The voltage acquisition unit 34 then calculates the battery voltage V of the secondary battery 10 from these potential values ​​and outputs it to the OCV-SOC acquisition unit 42 of the charge rate acquisition unit 40 (step S102: voltage acquisition step). At this time, the control unit of the battery state estimation device 80 sets the system startup time as the reference point (step S103). Here, when the system is off, no current is flowing through the secondary battery 10, and the secondary battery 10 is in a relaxed state where the polarization voltage has been eliminated. Therefore, in a configuration where no current flows through the secondary battery 10 immediately after system startup, the open-circuit voltage OCV can be obtained immediately from the battery voltage V of the secondary battery 10. Therefore, the OCV-SOC acquisition unit 42 uses the battery voltage V at this time as the open-circuit voltage OCV(0) at the reference point (step S112: open-circuit voltage acquisition step). Then, the OCV-SOC acquisition unit 42 refers to the SOC storage unit 44 and acquires the charge level SOC(0) at the reference point corresponding to this open-circuit voltage OCV(0) (step S114: charge level acquisition step). Then, it outputs to the ΔSOC calculation unit 52 of the correction value setting unit 50.

[0020] Furthermore, when the control unit of the battery state estimation device 80 sets a reference point, the current integration value calculation unit 32 outputs the current integration value ΔAh(0) at this reference point to the ΔSOC calculation unit 52 (step S116).

[0021] The battery state estimation device 80 then uses the charge level SOC(0) and integrated current value ΔAh(0) at the reference point (startup), along with the data read from the recording unit 55, as appropriate to calculate the initial corrected total capacity Ah(n) (initial correction value calculation step S120). This initial correction value calculation step S120 will be described in detail later. Based on the total capacity Ah(n) calculated in this initial correction value calculation step S120, the estimated charge level SOC' is derived and used for determining the state of the secondary battery 10 and controlling the power converter 3. If the correction value setting unit 50 does not have a recording unit 55, the capacity correction value K(n) and estimated charge level SOC' are calculated when data from the three points—the reference point, the charging point, and the discharging point—are available. The estimated charge level SOC' obtained in this way is updated as needed in accordance with the update of the integrated current value ΔAh, as the integrated current value ΔAh is updated moment by moment. Of course, the estimated charge level (SOC') is also updated when the total capacity Ah(n) and the SOC correction value K(soc) are updated, in addition to the current integration value ΔAh.

[0022] Furthermore, if current is flowing to the secondary battery 10 immediately after startup, the recording unit 55 may record the estimated charge level SOC' at the time the system was turned off. When the system starts up, this estimated charge level SOC' may be read out and set as the charge level SOC(0) at startup, and the initial correction value calculation step S120 may be performed. Note that in this system, startup cannot be used as the reference point, so it is preferable to use, for example, the point at which the OCV-SOC acquisition unit 42 first acquires the open-circuit voltage OCV as the reference point.

[0023] Next, when the system uses the power of the secondary battery 10 to operate the load 1, the system control unit 5 instructs the system to supply power using the secondary battery 10 as the power source. As a result, the secondary battery 10 discharges and begins supplying power. The power output by the secondary battery 10 is then converted to power suitable for the load 1 by the power converter 3 and supplied, allowing the load 1 to perform its intended operation. Furthermore, if, for example, the solar panel acting as an external power source 7 generates power and the power supply from the secondary battery 10 becomes unnecessary, the system control unit 5 controls the power converter 3 to stop the power supply from the secondary battery 10. As a result, the current value I of the secondary battery 10 becomes zero. Moreover, if the amount of power supplied from the external power source 7 exceeds the amount used by the load 1, the system control unit 5 instructs the system to charge the secondary battery 10 with the excess power. As a result, the power converter 3 converts the power from the external power source 7 to an appropriate voltage and outputs it to the secondary battery 10. As a result, a charging current flows to the secondary battery 10, and the secondary battery 10 is charged.

[0024] The current value flowing through the secondary battery 10 at this time is acquired by the current acquisition means 30a and output to the current acquisition unit 30. The current acquisition unit 30 distinguishes between the current value I during discharge and charging, for example, by positive or negative sign, and outputs it to the current integration value calculation unit 32 (current acquisition step S200). The current integration value calculation unit 32 then integrates the current value I input from the current acquisition unit 30 into the current integration value ΔAh (current integration value calculation step S202). In this case, if the current value I during discharge is negative (-) and the current value I during charging is positive (+), the current integration value ΔAh during discharge decreases, and the current integration value ΔAh during charging increases.

[0025] Furthermore, the voltage acquisition unit 34 continues to output the battery voltage V of the secondary battery 10 to the OCV-SOC acquisition unit 42 (step S203: voltage acquisition step). However, since the open-circuit voltage OCV required here is the voltage of the secondary battery 10 when no current is flowing through it, the OCV-SOC acquisition unit 42 does not acquire the open-circuit voltage OCV while the secondary battery 10 is performing a charge / discharge operation and remains in standby mode. Moreover, immediately after the current value I of the secondary battery 10 becomes zero, a polarization voltage remains, making it impossible to acquire an accurate open-circuit voltage OCV. Therefore, it is preferable to provide a relaxation state determination unit 46 in the charge rate acquisition unit 40 of the present invention. Note that if there is an influence such as noise, the current value output by the current acquisition means 30a may not be exactly zero. Also, if a large current was flowing just before, the polarization voltage will be relaxed even if only a small current is flowing instead of a completely zero current. Therefore, the relaxation state determination unit 46 obtains the current value I of the secondary battery 10 from the current acquisition unit 30, for example, and determines that the state is a state where the current value I of the secondary battery 10 is zero or less than or equal to a predetermined value near zero, for example, less than or equal to ±0.1C of the C rate, i.e., the current value I is -0.1C equivalent current value ≤ I ≤ +0.1C equivalent current value. Then, the relaxation state determination unit 46 permits the OCV-SOC acquisition unit 42 to acquire the open-circuit voltage OCV when it has maintained the zero-current state for a sufficient polarization relaxation time for the polarization voltage to dissipate. As a result, the OCV-SOC acquisition unit 42 can acquire the accurate open-circuit voltage OCV after the polarization voltage has dissipated. The threshold for the zero-current state is appropriately designed and set by the system based on the current value it expects to use (the current value of the secondary battery 10 during discharge), etc. Furthermore, in systems where the secondary battery 10 is repeatedly charged and discharged without interruption, the system control unit 5 may, for example, stop the charging and discharging operation of the secondary battery 10 for a sufficient amount of time to eliminate the polarization voltage when switching between charging and discharging, allowing the OCV-SOC acquisition unit 42 to acquire the open-circuit voltage OCV.

[0026] Furthermore, the polarization relaxation time varies depending on factors such as the capacity and specifications of the secondary battery 10, the operation of the system, the operating state of the secondary battery 10 on the system side, as well as the battery temperature T of the secondary battery 10, the charge level at that time, the degradation state of the secondary battery 10, and the magnitude of the charge / discharge current and energizing time up to the previous test. However, if the amount of change in the polarization relaxation time in response to changes in conditions is relatively small, the polarization relaxation time may be set to a fixed value. Also, if the polarization relaxation time varies greatly depending on the conditions, experiments may be conducted in advance for one or more of the major conditions with large variations, and table data of these polarization relaxation times may be created so that the relaxation state determination unit 46 can appropriately select and set the polarization relaxation time according to the state of the secondary battery 10.

[0027] The current value I in this zero-current state is acquired by the current acquisition unit 30 and output to the relaxation state determination unit 46 and the current integration value calculation unit 32. At this time, the current integration value calculation unit 32 may stop integrating the current value I into the current integration value ΔAh if the current value I is in a zero-current state. In this configuration, by optimizing the threshold for the zero-current state, it is possible to prevent slight detection errors due to noise or offset errors of the current acquisition means 30a from being integrated into the current integration value ΔAh. This makes it possible to reduce the error in the current integration value ΔAh. Furthermore, if the relaxation state determination unit 46 detects a zero-current state (step S204: Yes), and this zero-current state continues for a predetermined polarization relaxation time, for example, 1 minute (step S206: Yes), the relaxation state determination unit 46 permits the OCV-SOC acquisition unit 42 to acquire the open-circuit voltage OCV (step S207).

[0028] When the OCV-SOC acquisition unit 42 is in a state where it can acquire the open-circuit voltage OCV, the control unit of the battery state estimation device 80 determines whether the current integrated value ΔAh of the current integrated value calculation unit 32 is located on the discharge side (negative) or the charge side (positive) with respect to the current integrated value ΔAh(0). If the current integrated value ΔAh is located on the discharge side, i.e., ΔAh < ΔAh(0) (step S208: Yes), this point is set as the discharge point (step S210A). Also, if the current integrated value ΔAh is located on the charge side of the current integrated value ΔAh(0), i.e., ΔAh > ΔAh(0) (step S208: No, step S209: Yes), this point is set as the charge point (step S210B). Furthermore, if the integrated current value ΔAh and the integrated current value ΔAh(0) are the same (step S208: No, step S209: No), the system returns to the current acquisition step S200 without setting either the charging point or the discharging point.

[0029] Although the flowcharts in Figures 2 to 4 illustrate an example with one reference point, there is no need to be only one reference point; as shown in the following example, there may be at least one reference point. For example, a reference point for the integrated current value ΔAh(0) is set, and based on the integrated current value ΔAh(0) at this reference point, either a charging point or a discharging point is set. Then, as shown in Figures 5(a) and (b), a new reference point for the integrated current value ΔAh(0') at a different point (value) than ΔAh(0) is set, and the remaining discharging or charging points are set based on this new reference point. The procedure for this configuration is as follows: for example, when the open-circuit voltage OCV is acquired in step S207, if a predetermined condition is met, this is set as a new reference point. Then, the open-circuit voltage OCV(0'), state of charge (SOC(0'), and integrated current value ΔAh(0') at this new reference point are acquired, and the process proceeds to step S200.

[0030] Furthermore, after setting either a charging point or a discharge point based on the reference point of the integrated current value ΔAh(0), this set charging point or discharge point may be used as a new reference point. For example, as shown in Figures 5(c) and (d), after setting the charge rate SOC(-) of the discharge point based on the reference point of the integrated current value ΔAh(0), the charge rate SOC(-) and integrated current value ΔAh of this discharge point are reset as the charge rate SOC(0') and integrated current value ΔAh(0') of the new reference point. Then, the remaining charging points are set based on this new reference point. Note that the charging points at this time may be located on the charging side (positive side) or on the discharge side (negative side) of the initial reference point's integrated current value ΔAh(0), as shown in Figure 5(c). Furthermore, the procedure for this configuration includes, for example, if a "No" determination is made in step S240 (described later) and predetermined conditions are met, the charging or discharging point set immediately before is used as the new reference point, and the process proceeds to step S200.

[0031] Furthermore, in a configuration using one or more reference points, for example, the reference point may be located near the fully charged or completely discharged state of the secondary battery 10, thereby eliminating the situation where the charging point and the discharging point do not coincide for an extended period of time.

[0032] Furthermore, if the charging and discharging points set in steps S210A and S210B are located near their respective reference points, the values ​​of ΔSOC2(+) and ΔSOC2(-) calculated by equations (2) and (2') or (2'') and (2''') described later will be small, and the charging-side correction value K(+) and discharging-side correction value K(-) in equations (3) and (3') may become significantly large. Therefore, it is preferable not to set charging and discharging points if they are located near their respective reference points. As a method for determining this proximity position, for example, the OCV-SOC acquisition unit 42 sets a predetermined threshold range α above and below the current integrated value ΔAh(0)(ΔAh(0')) of the reference point, and in steps S208 and S209, if the current integrated value ΔAh exceeds the threshold α of each reference point, ΔAh < (ΔAh(0)-α) or ΔAh < (ΔAh(0')-α), it is set as a discharge point, and if ΔAh > (ΔAh(0)+α) or ΔAh > (ΔAh(0')+α), it is set as a charging point, and if (ΔAh(0)-α)≦ΔAh≦(ΔAh(0)+α) or (ΔAh(0')-α)≦ΔAh≦(ΔAh(0')+α), it is not set as a charging point or a discharge point.

[0033] Then, when the discharge point is set by step S210A above, the OCV-SOC acquisition unit 42 takes the battery voltage V of the secondary battery 10 at this time as the open-circuit voltage OCV(-) at the discharge point (step S214A: open-circuit voltage acquisition step). The OCV-SOC acquisition unit 42 then refers to the SOC storage unit 44 and acquires the charge rate SOC(-) at the discharge point corresponding to the open-circuit voltage OCV(-) (step S216A: charge rate acquisition step), and outputs it to the ΔSOC calculation unit 52. At this time, the current integration value calculation unit 32 also outputs the current integration value ΔAh at the discharge point to the ΔSOC calculation unit 52 (step S218A).

[0034] Furthermore, when the charging point is set by step S210B described above, the OCV-SOC acquisition unit 42 takes the battery voltage V of the secondary battery 10 at this time as the open-circuit voltage OCV(+) at the charging point (step S214B: open-circuit voltage acquisition step). Then, the OCV-SOC acquisition unit 42 refers to the SOC storage unit 44 and acquires the charge rate SOC(+) of the charging point corresponding to the open-circuit voltage OCV(+) (step S216B: charge rate acquisition step), and outputs it to the ΔSOC calculation unit 52. At this time, the current integration value calculation unit 32 also outputs the current integration value ΔAh of this charging point to the ΔSOC calculation unit 52 (step S218B).

[0035] Furthermore, the State of Charge (SOC) of the reference point, discharge point, and charge point can be obtained as needed when acquiring the open-circuit voltage at each point, as described above, or it can be done when the open-circuit voltages of the reference point, discharge point, and discharge point are all available. Also, in the example above, the reference point is set first, followed by the discharge point and charge point. However, in configurations where current flows to the secondary battery 10 immediately after system startup and the open-circuit voltage OCV(0) of the reference point cannot be acquired, it is not always necessary to set the reference point first. For example, the integrated current value ΔAh at the points where the open-circuit voltage OCV is acquired can be compared, and the discharge point, reference point, and charge point can be assigned based on their relative magnitudes.

[0036] Furthermore, when the battery state estimation device 80 includes a temperature acquisition unit 12 and acquires charge rates SOC(0), (SOC(0')), SOC(+), and SOC(-) that take the battery temperature T into consideration, the SOC storage unit 44 has an OCV-SOC data table for each battery temperature T, and the OCV-SOC acquisition unit 42 acquires the charge rates SOC(0), (SOC(0')), SOC(+), and SOC(-) respectively from the OCV-SOC data table corresponding to the battery temperature T at the time of each open-circuit voltage acquisition. With this configuration, the OCV-SOC acquisition unit 42 can acquire a more accurate charge rate that also takes the battery temperature T into consideration.

[0037] Furthermore, when the ΔSOC calculation unit 52 receives the integrated current value ΔAh at the discharge point from the integrated current value calculation unit 32, it calculates the difference between this value and the integrated current value ΔAh(0) or integrated current value ΔAh(0') at the corresponding reference point, i.e., |ΔAh-ΔAh(0)| or |ΔAh-ΔAh(0')|, and sets this as the integrated current value ΔAh(-) at the discharge point (Step S220A: Charge / Discharge Current Integrated Value Acquisition Step). Also, when the integrated current value ΔAh at the charging point is input, it calculates the difference between this value and the integrated current value ΔAh(0) or integrated current value ΔAh(0') at the corresponding reference point, i.e., |ΔAh-ΔAh(0)| or |ΔAh-ΔAh(0')|, and sets this as the integrated current value ΔAh(+) at the charging point (Step S220B: Charge / Discharge Current Integrated Value Acquisition Step).

[0038] The ΔSOC calculation unit 52 then uses these values ​​as input to determine whether all the open-circuit voltages OCV(+) and OCV(-) at the charging point and discharging point, the open-circuit voltage OCV(0) and (OCV(0')) at the reference point, and the corresponding integrated current values ​​ΔAh(+) and ΔAh(-) are available. If these data are not yet available (step S240: No), the unit returns to the current acquisition step S200.

[0039] Furthermore, if all of this data is available (Step S240: Yes), ΔSOC1(+) is calculated as the change in the charge rate on the first charging side based on equation (1) below, using the integrated current value ΔAh(+) at the charging point and the total capacity Ah(n-1) of the secondary battery 10 described later. Also, ΔSOC1(-) is calculated as the change in the charge rate on the first discharging side based on equation (1') below, using the integrated current value ΔAh(-) at the discharging point and the total capacity Ah(n-1) of the secondary battery 10 (First charge rate change calculation step S300). Note that the total capacity Ah(n-1) here refers to the value obtained by multiplying the previous capacity correction value K(n-1) recorded by the recording unit 55 by the reference total capacity Ah(0), i.e., Ah(n-1) = Ah(0) × K(n-1), if a recording unit 55 is present. Furthermore, if the previous capacity correction value K(n-1) does not exist, the standard total capacity Ah(0) is used as is. Note that the standard total capacity Ah(0) is the battery capacity of the secondary battery 10 when it is new, as mentioned above, and this value is acquired in advance and recorded in the recording unit 55, etc. ΔSOC1(+)=ΔAh(+) / Ah(n-1)···(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)···(1')

[0040] Here, Figure 6 shows the relationship between the current value I output by the current acquisition unit 30 and the integrated current value ΔAh output by the integrated current value calculation unit 32. In Figure 6, the horizontal axis represents time, the upper row shows the current value I, and the lower row shows the integrated current value ΔAh. If we assume that point A in Figure 6 is the reference point, then the integrated current value ΔAh at point A becomes the integrated current value ΔAh(0) at the reference point. Next, the system operates, and the secondary battery 10 repeatedly charges and discharges. As a result, the current value I of the secondary battery 10 moves back and forth between the charging region and the discharging region, as shown in the upper row of Figure 6. At this time, the integrated current value ΔAh moves back and forth between the charging region and the discharging region while the current value I is integrated, as shown in the lower row of Figure 6. Then, if the current becomes zero at point B in Figure 6 and the open-circuit voltage OCV can be obtained, the control unit of the battery state estimation device 80 determines whether the integrated current value ΔAh at point B is on the charging side (positive) or the discharging side (negative). In Figure 6, the integrated current value ΔAh at point B is on the charging side (positive), so the control unit of the battery state estimation device 80 sets point B as the charging point. The difference between the integrated current value ΔAh, represented by the arrow in Figure 6, and the integrated current value ΔAh(0) at the reference point, ΔAh-ΔAh(0), becomes the integrated current value ΔAh(+) at the charging point. Note that this integrated current value ΔAh(+) at the charging point is proportional to ΔSOC1(+) as shown in equation (1) above.

[0041] Furthermore, if the values ​​of ΔSOC1(+) and ΔSOC1(-) are significantly small, the charging-side correction value K(+) and discharging-side correction value K(-), described later, will become small, and there is a possibility that an abnormal capacity correction value K(n) will be calculated. Therefore, if ΔSOC1(+) and ΔSOC1(-) are smaller than predetermined values, for example, if ΔSOC1(+) and ΔSOC1(-) are less than 10% of the charge rate SOC(+) and SOC(-), the settings as charging and discharging points may be canceled, and the system may return to the current acquisition step S200.

[0042] Furthermore, the ΔSOC calculation unit 52 calculates ΔSOC2(+) as the change in the charge rate on the second charging side based on equation (2) or (2'') below, using the charge rate SOC(0) or SOC(0') of the corresponding reference point and the charge rate SOC(+) of the charging point. Also, it calculates ΔSOC2(-) as the change in the charge rate on the second discharging side based on equation (2') or (2''') below, using the charge rate SOC(0) or SOC(0') of the corresponding reference point and the charge rate SOC(-) of the discharging point (second charge rate change calculation step S302). ΔSOC2(+)=|SOC(+)-SOC(0)|···(2) ΔSOC2(-)=|SOC(-)-SOC(0)|···(2') ΔSOC2(+)=|SOC(+)-SOC(0')|···(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|···(2''')

[0043] Furthermore, in a configuration where no threshold α is set for the integrated current value ΔAh(0) when setting the charging point and discharge point, if the charging point and discharge point are located near the reference point, the values ​​of ΔSOC2(+) and ΔSOC2(-) calculated by equations (2) to (2''') will be small, and the charging-side correction value K(+) and discharge-side correction value K(-) in equations (3) and (3') below may become significantly large. Therefore, if the ΔSOC2(+) and ΔSOC2(-) calculated by the ΔSOC calculation unit 52 are smaller than a predetermined value, for example, less than 10% of the charge rate SOC(+) and SOC(-), the setting of the charging point and discharge point may be canceled and the system may return to the current acquisition step S200.

[0044] The ΔSOC calculation unit 52 then outputs these ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) to the correction coefficient calculation unit 54. The correction coefficient calculation unit 54 also calculates the charging side correction value K(+) based on the ratio of the input ΔSOC1(+) and ΔSOC2(+), i.e., equation (3) below. It also calculates the discharge side correction value K(-) based on the ratio of the input ΔSOC1(-) and ΔSOC2(-), i.e., equation (3') below (correction coefficient calculation step S304). Finally, it outputs these charging side correction value K(+) and discharge side correction value K(-) to the determination unit 56. K(+)=ΔSOC1(+) / ΔSOC2(+)···(3) K(-)=ΔSOC1(-) / ΔSOC2(-)···(3')

[0045] Furthermore, if there are multiple reference points, charging points, and discharging points, it is preferable to individually calculate a provisional charging-side correction value K(+)' or a provisional discharging-side correction value K(-)' for each of them based on the corresponding reference point, and output the average values ​​of these provisional charging-side correction values ​​K(+)' and provisional discharging-side correction values ​​K(-)' for the charging side and discharging side respectively to the determination unit 56 as the charging-side correction value K(+) and discharging-side correction value K(-).

[0046] Furthermore, the determination unit 56 determines whether the charging-side correction value K(+) and the discharging-side correction value K(-) are both greater than or less than 1. If both the charging-side correction value K(+) and the discharging-side correction value K(-) are less than 1, that is, if K(+) < 1 and K(-) < 1 (step S306: Yes: determination step), the determination unit 56 outputs the charging-side correction value K(+) and the discharging-side correction value K(-) to the correction coefficient setting unit 57 along with the determination result. Upon receiving this determination result, the correction coefficient setting unit 57 sets the average value of the charging-side correction value K(+) and the discharging-side correction value K(-) as the correction value K'(n).

[0047] Furthermore, if a previous capacity correction value K(n-1) already exists after the capacity correction value has been calculated, the total capacity Ah(n-1) corrected using this capacity correction value K(n-1), i.e., Ah(n-1) = Ah(0) × K(n-1), is applied to equations (1) and (1') to calculate ΔSOC1(+) and ΔSOC1(-). In addition, the correction value K'(n) is calculated based on these ΔSOC1(+) and ΔSOC1(-). In this case, it is preferable to calculate the capacity correction value K(n) based on equation (4) below, taking into account the previous capacity correction value K(n-1). K(n) = K'(n) × K(n-1) ... (4) Furthermore, if there is no previous capacity correction value K(n-1), and in equations (1) and (1') the reference total capacity Ah(0) is used instead of Ah(n-1) to calculate ΔSOC1(+) and ΔSOC1(-), then this correction value K'(n) may be set as the capacity correction value K(n).

[0048] Furthermore, if sudden measurement errors occur in the battery information acquisition unit 20's measurements due to noise or other factors, an abnormal correction value K'(n) may be calculated, potentially adversely affecting the overall operation of the system. Therefore, in the battery state estimation device 80 according to the present invention, in order to mitigate the effects of sudden and abnormal correction values ​​K'(n), for example, in a system where the correction value K'(n) can be calculated frequently, the average value or moving average value of the correction value K'(n) may be used as the capacity correction value K(n). Alternatively, the average value of the correction value K'(n) calculated a predetermined number of times (e.g., 10 times) may be used as the capacity correction value K(n). Alternatively, intervals may be set at arbitrary time intervals (e.g., 10 minutes), and the latest correction value K'(n) within that time interval, or the average value of the correction values ​​K'(n) obtained within that time interval, may be used as the capacity correction value K(n). These configurations make it possible to mitigate the effects of sudden abnormal values ​​of the correction value K'(n).

[0049] Furthermore, a correction lower limit K(min) less than 1 may be pre-set in the correction coefficient setting unit 57, and if the calculated capacity correction value K(n) is less than the correction lower limit K(min), the correction lower limit K(min) may be set as the capacity correction value K(n).

[0050] Alternatively, a reduction factor A of a value less than 1 may be set, and the capacity correction value K(n) may be set using equation (4') below. K(n)=(1-A×(1-K'(n)))×K(n-1)...(4') Even with configurations that set these correction lower limit values ​​K(min) and configurations that set the reduction coefficient A, the impact of calculating an abnormally small correction value K'(n) can be mitigated. The correction coefficient setting unit 57 then outputs this calculated or set capacity correction value K(n) to the capacity correction unit 58. The above corresponds to the correction coefficient setting step (step S310A) when both the charging side correction value K(+) and the discharging side correction value K(-) are less than 1.

[0051] Here, the main reasons for the difference between ΔSOC1(+) and (-) and ΔSOC2(+) and (-) are considered to be the following three: First, the decrease in battery capacity due to the degradation of the secondary battery 10 as mentioned above. Second, the influence of measurement errors in the battery information acquisition unit 20, namely the gain error and offset error of the current acquisition means 30a and the measurement error of the voltage acquisition means 34a. Third, the influence of the polarization voltage immediately after the charging and discharging operation of the secondary battery 10 stops on the open-circuit voltage OCV. Of these, the measurement error of the voltage acquisition means 34a can be eliminated by adjustments during installation, etc. Also, the polarization voltage immediately after the charging and discharging operation stops can be dealt with by installing the relaxation state determination unit 46 as mentioned above. However, the gain error and offset error of the current acquisition means 30a may change over time, making a permanent solution difficult. Therefore, the three factors that need to be addressed are the decrease in battery capacity and the gain error and offset error of the current acquisition means 30a.

[0052] As mentioned above, a decrease in battery capacity manifests as a decrease in ΔSOC1(+) and ΔSOC1(-). Additionally, a decrease in ΔSOC1(+) and ΔSOC1(-) occurs when the absolute value of the current value I is obtained to be smaller than the true value due to a gain error in the current acquisition means 30a. Therefore, when the battery capacity of the secondary battery 10 is decreasing, or when the absolute value of the current value I is obtained to be smaller than the true value due to a gain error in the current acquisition means 30a, both the charging-side correction value K(+) and the discharging-side correction value K(-) will be less than 1. In this case, the capacity correction value K(n), calculated based on the charging-side correction value K(+) and discharging-side correction value K(-) which are less than 1, will also basically be less than 1, and the corrected total capacity Ah(n), corrected by this capacity correction value K(n) which is less than 1, will be a value less than the reference total capacity Ah(0). This makes it possible to calculate an appropriate estimated charge rate SOC' even when the battery capacity of the secondary battery 10 is decreasing. Furthermore, in the correction process where the absolute value of the current I is obtained to be smaller than the true value due to the gain error, and the total capacity Ah(n) decreases from the reference total capacity Ah(0), no correction is made to the magnitude of the current I itself. However, when applying the integrated current value ΔAh obtained with the current I including the gain error to equation (6) described below, the total capacity Ah(n) in equation (6) decreases from the reference total capacity Ah(0). Therefore, the effect of the gain error causing the absolute value of the current I to be obtained to be smaller than the true value and the integrated current value ΔAh to decrease is eliminated, and an appropriate ΔSOC (=ΔAh / Ah(n)) can be calculated. This makes it possible to calculate an appropriate estimated charge rate SOC' using equation (6). Furthermore, it is not possible to distinguish between the decrease in ΔSOC1(+) and ΔSOC1(-) due to the gain error and the decrease in ΔSOC1(+) and ΔSOC1(-) due to the decrease in battery capacity, but since the correction method is the same, there is no need to distinguish between them, and they can be corrected together using the method described above.

[0053] Furthermore, if both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, that is, if K(+)>1 and K(-)>1 (step S306: No, step S308: Yes: judgment step), this indicates that the previously calculated capacity correction value K(n-1) is too small, and the correction by the previously calculated capacity correction value K(n-1) is too large. This means that either the previously calculated capacity correction value K(n-1) reduces the capacity excessively compared to the actual decrease in battery capacity, or the absolute value of the current value I is obtained at a value larger than the true value due to the gain error of the current acquisition means 30a. Therefore, when the correction coefficient setting unit 57 receives this judgment result, it calculates the capacity correction value K(n) based on the following (4'') equation obtained by multiplying the average value of the charging-side correction value K(+) and the discharging-side correction value K(-) by the previous capacity correction value K(n-1). K(n)=((K(+)+K(-)) / 2)×K(n-1)···(4'') However, if K(n) calculated by equation (4'') is greater than 1, the correction coefficient setting unit 57 may set K(n) to "1".

[0054] Furthermore, considering the case where the absolute value of the current I is obtained at a value greater than the true value due to the gain error of the current acquisition means 30a, if the capacity correction value K(n) calculated by equation (4'') above exceeds a preset upper limit K(lim) of 1 or more, the correction coefficient setting unit 57 may set the capacity correction value K(n) to the upper limit K(lim). The correction coefficient setting unit 57 then outputs this capacity correction value K(n) to the capacity correction unit 58. Note that even when both the charging side correction value K(+) and the discharging side correction value K(-) are greater than 1, it is not possible to distinguish whether this is because the absolute value of the current I is obtained at a value greater than the true value due to the gain error of the current acquisition means 30a, or because the battery capacity correction is excessive. However, since the correction method is the same, there is no need to make a particular distinction, and the correction can be performed collectively using the method described above. The above corresponds to the correction coefficient setting step (step S310B) when both the charging side correction value K(+) and the discharging side correction value K(-) are greater than 1.

[0055] Furthermore, if either the charging-side correction value K(+) or the discharging-side correction value K(-) is greater than 1 and the other is less than 1, that is, if K(+)<1 and K(-)>1, or if K(+)>1 and K(-)<1 (Step S306: No, Step S308: No, Step S309: Yes: Judgment Step), the judgment unit 56 outputs this judgment result to the correction coefficient setting unit 57, and the ΔSOC calculation unit 52 outputs ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) to the SOC correction unit 59. Also, if the correction coefficient setting unit 57 receives this judgment result, it does not calculate a new capacity correction value K(n), but uses the previous capacity correction value K(n-1) as the capacity correction value K(n) (Step S310C: Correction coefficient setting step). The correction coefficient setting unit 57 then outputs this capacity correction value K(n) to the capacity correction unit 58.

[0056] Here, the case where K(+)<1 and K(-)>1 means, as shown in Figure 7(a), |ΔSOC1(+)|<|ΔSOC2(+)| and |ΔSOC2(-)|<|ΔSOC1(-)|, which means that ΔSOC1(+) and ΔSOC1(-), calculated from the integrated current values ​​ΔAh(+) and ΔAh(-), are generally offset towards the discharge side (negative direction) relative to ΔSOC2(+) and ΔSOC2(-), which are obtained based on the open-circuit voltage OCV. This is thought to be because the current value I is generally shifted in the negative direction (discharge direction) due to the offset error of the current acquisition means 30a. Furthermore, the case where K(+)>1 and K(-)<1 means, as shown in Figure 7(b), that |ΔSOC1(+)|>|ΔSOC2(+)| and |ΔSOC2(-)|>|ΔSOC1(-)|, which means that ΔSOC1(+) and ΔSOC1(-), calculated from the integrated current values ​​ΔAh(+) and ΔAh(-), are generally offset towards the charging side (positive direction) relative to ΔSOC2(+) and ΔSOC2(-), which are obtained based on the open-circuit voltage OCV. This is thought to be because the current value I is generally shifted in the positive direction (charging direction) due to the offset error of the current acquisition means 30a.

[0057] Therefore, if the determination result is K(+)<1 and K(-)>1, the SOC correction unit 59 calculates, for example, the value of |ΔSOC2(+)|-|ΔSOC1(+)| and the value of |ΔSOC1(-)|-|ΔSOC2(-)|, compares the two, and sets the smaller value or the average of the two values ​​as the "positive" (charging direction) SOC correction value K(soc). Also, if the determination result is K(+)>1 and K(-)<1, the SOC correction unit 59 calculates, for example, the value of |ΔSOC1(+)|-|ΔSOC2(+)| and the value of |ΔSOC2(-)|-|ΔSOC1(-)|, compares the two, and sets the smaller value or the average of the two values ​​as the "negative" (discharging direction) SOC correction value K(soc).

[0058] Furthermore, if there is an offset error in the current value I acquired by the current acquisition unit 30, the error in the integrated current value ΔAh will accumulate over time. As a result, the calculated SOC correction value K(soc) may be excessively large compared to the appropriate value. Therefore, although the SOC correction unit 59 may output the calculated SOC correction value K(soc) as is to the estimated charge rate calculation unit 60, it is preferable to reduce the calculated SOC correction value K(soc) before outputting it to the estimated charge rate calculation unit 60. This reduction of the SOC correction value K(soc) may be performed, for example, by multiplying it by an arbitrary reduction coefficient A' (fixed value) less than 1 that has been set in advance. However, it is preferable to calculate the reduction coefficient A'(+) and reduction coefficient A'(-) using the following equations (B) and (B') based on the integrated current values ​​ΔAh(+) and ΔAh(-), compare both of these, and multiply the smaller value or the average of both values ​​by the above SOC correction value K(soc). A'(+) = Sum of integrated current ΔAh(+) / (Absolute value of integrated current in the interval(+)) ... (B) A'(-) = Sum of integrated current ΔAh(-) / (Absolute value of integrated current in the interval(-)) ... (B') Here, the absolute value of the integrated current in each section (+) is the sum of the absolute values ​​of the integrated currents in all charging and discharging sections from the start point to the end point of measurement when measuring the integrated current value ΔAh(+) at the charging point. Also, the absolute value of the integrated current in each section (-) is the sum of the absolute values ​​of the integrated currents in all charging and discharging sections from the start point to the end point of measurement when measuring the integrated current value ΔAh(-) at the discharge point.

[0059] Furthermore, the reduction coefficients A'(+) and A'(-) may be multiplied before calculating the SOC correction value K(soc). That is, the reduction coefficient A'(+) may be multiplied by the value of |ΔSOC2(+)|-|ΔSOC1(+)| or |ΔSOC1(+)|-|ΔSOC2(+)| before calculating the SOC correction value K(soc). Alternatively, the reduction coefficient A'(-) may be multiplied by the value of |ΔSOC1(-)|-|ΔSOC2(-)| or |ΔSOC2(-)|-|ΔSOC1(-)| before calculating the SOC correction value K(soc).

[0060] The SOC correction unit 59 then applies the reduction coefficient A'(+) and the reduction coefficient A'(-) to calculate the SOC correction value K(soc), which is then set as the final SOC correction value K(soc). The calculated SOC correction value K(soc) is then output to the estimated charge rate calculation unit 60. This completes the SOC correction value setting step S320.

[0061] Furthermore, if both the charging-side correction value K(+) and the discharging-side correction value K(-) are 1 (step S306: No, step S308: No, step S309: No: judgment step), it is determined that there is no capacity reduction in the secondary battery 10, or that the currently applied capacity correction value K(n-1) is appropriate, and a new capacity correction value K(n) is not calculated, and the process returns to the current acquisition step S200.

[0062] Furthermore, when the capacity correction unit 58 receives a new capacity correction value K(n) set in the above correction coefficient setting step, it uses this new capacity correction value K(n) to calculate the corrected total capacity Ah(n) based on the following equation (5) (capacity value correction step S312). Ah(n) = Ah(0) × K(n) ···(5) Then, this corrected total capacity Ah(n) is output to the estimated charge rate calculation unit 60.

[0063] Furthermore, the estimated charge rate calculation unit 60 calculates the estimated charge rate SOC' based on the following equation (6) using the corrected total capacity Ah(n) calculated by the capacity correction unit 58, the current integrated value ΔAh output by the current integrated value calculation unit 32, the charge rate SOC(0) at the reference point, and the SOC correction value K(soc) calculated by the SOC correction unit 59 (estimated charge rate calculation step S330). SOC'=ΔAh / Ah(n)+SOC(0)+K(soc)...(6) Furthermore, if no SOC correction value K(soc) exists, K(soc) = 0. Also, if no new SOC correction value K(soc) is calculated, the past value of SOC correction value K(soc) is maintained. Alternatively, the recording unit 55 may be used to record the SOC correction value K(soc), and this past SOC correction value K(soc) may be read out and used when the system is restarted. With this configuration, when current flows to the secondary battery 10 at startup and the open-circuit voltage OCV(0) cannot be obtained, and the estimated charge rate SOC' at the time the system is turned off is used as the reference charge rate SOC(0), the SOC correction value K(soc) can be read out and applied, so the estimated charge rate SOC' at startup can be calculated more accurately.

[0064] The estimated charge rate SOC' calculated by equation (6) above is output to various parts of the system and used for determining the state of the secondary battery 10 and controlling the power converter 3. It is preferable to perform annealing on the estimated charge rate SOC' output from the estimated charge rate calculation unit 60 using a low-pass filter or the like to prevent sudden changes in the estimated charge rate SOC' (annealing step S332).

[0065] Furthermore, even when a decrease in the capacity of the secondary battery 10 and an offset error of the current acquisition means 30a are present, or when a gain error of the current acquisition means 30a and an offset error of the current acquisition means 30a are present, or even when a decrease in the capacity of the secondary battery 10 and both the gain error and offset error of the current acquisition means 30a are present, performing the above correction process multiple times will correct each case accordingly, ultimately enabling the calculation of an appropriate estimated charge rate (SOC').

[0066] Then, once the estimated charge level (SOC') is calculated, the discharge point and charge point are reset, and the process returns to the current acquisition step S200. At this point, the reference point may also be reset, and the point after the polarization relaxation time may be set as the new reference point, or the last acquired discharge point or charge point may be set as the new reference point. Furthermore, the reference point at system startup may be maintained until system shutdown.

[0067] Furthermore, in systems where the correction value K'(n) can be calculated frequently, an upper limit may be set on the number of times the capacity correction value K(n) is calculated during a single system operating period (the period from system startup to power-off). Alternatively, an upper limit may be set on the number of times the capacity correction value K(n) is calculated within a predetermined time interval. These configurations can suppress the frequent execution of correction operations and reduce the processing load.

[0068] Next, when the system is instructed to turn off (step S400: Yes), if the battery state estimation device 80 has a recording unit 55, the recording unit 55 records the capacity correction value K(n-1) that was applied at the time the system was turned off, the charge level SOC(0)' of the reference point when the capacity correction value K(n-1) was calculated, the integrated current value ΔAh' at the time the system was turned off, and the SOC correction value K(soc) (recording step S402). Then, it communicates to the system control unit 5, etc., that the termination process of the battery state estimation device 80 is complete. Then, the system is turned off (step S404).

[0069] Next, a preferred example of the initial correction value calculation step S120 will be described. First, the system is restarted with the data at the time the system was turned off recorded in the recording unit 55, and if no current flows to the secondary battery 10 immediately after startup, step S012 is performed to read the previous capacity correction value K(n-1) that was applied at the time the system was turned off from the recording unit 55. In addition, the charge rate acquisition unit 40 performs the steps S102, reference point setting (step S103), open circuit voltage acquisition step (step S112), charge rate acquisition step (step S114), and acquisition of the integrated current value ΔAh(0) at the reference point (step S116) as described above, to obtain the charge rate SOC(0) and the integrated current value ΔAh(0) at the reference point. Then, the capacity correction value K(n-1) read from the recording unit 55 is converted to the capacity correction value K(n) by the correction coefficient setting unit 57, and the capacity correction unit 58 calculates the initial corrected total capacity Ah(n) based on this capacity correction value K(n) and the reference total capacity Ah(0) using the following formula (5'), and outputs it to the estimated charge rate calculation unit 60. Ah(n) = Ah(0) × K(n)···(5') Furthermore, the estimated charge rate calculation unit 60 calculates the estimated charge rate SOC' using equation (6) above, based on the corrected total capacity Ah(n), the charge rate SOC(0) at startup obtained in steps S114 and S116 above, and the integrated current value ΔAh(0) (=ΔAh) at that time. The above corresponds to the initial correction value calculation step S120.

[0070] Furthermore, the battery state estimation method according to the present invention may also include the following configuration in addition to the initial correction value calculation step S120. First, the recording unit 55 records the capacity correction value K(n-1) applied at the time the system was turned off, the charge level SOC(0)' at the reference point at that time, and the integrated current value ΔAh(total). The integrated current value ΔAh(total) is the integrated value of the current value I for the entire period from the most recent system startup time to the system shutdown time. Then, when the system is restarted, the OCV-SOC acquisition unit 42 uses the battery voltage V at startup as the open-circuit voltage OCV(0) at the reference point, and acquires the charge level SOC(0) at the reference point corresponding to this open-circuit voltage OCV(0). Furthermore, the capacity correction value K(n-1), charge level SOC(0)', and integrated current value ΔAh(total) recorded in the recording unit 55 are read out, and first, it is checked whether the integrated current value ΔAh(total) is on the charging side or the discharging side relative to the previous reference point. Note that the integrated current value ΔAh(total) is the integrated current value from the previous reference point at the time the system was turned off and corresponds to the charge level SOC(0) at startup. Therefore, the positional relationship between the charge level SOC(0)' read out from the recording unit 55 and the charge level SOC(0) is compared, and if the charge level SOC(0) is on the charging side than the charge level SOC(0)' at the reference point at the time the system was turned off, the integrated current value ΔAh(total) is also located on the charging side, and if it is on the discharging side, the integrated current value ΔAh(total) is also located on the discharging side. If the integrated current value ΔAh(total) is on the charging side, the SOC calculation unit 52 uses the integrated current value ΔAh(total) as the integrated current value ΔAh(+) at the charging point and calculates ΔSOC1(+) based on the capacity correction value K(n-1) read from the recording unit 55 and the above equation (1). If it is on the discharge side, the integrated current value ΔAh(total) is used as the integrated current value ΔAh(-) at the discharge point and calculates ΔSOC1(-) based on the capacity correction value K(n-1) and the above equation (1'). The result is then output to the correction coefficient calculation unit 54.

[0071] Furthermore, the unit checks whether the charge level SOC(0) is on the charging side or the discharging side relative to the charge level SOC(0)'. If it is on the charging side, the ΔSOC calculation unit 52 considers the charge level SOC(0) as the charge level SOC(+) at the charging point and calculates ΔSOC2(+) based on equation (2) above. If it is on the discharging side, the unit considers the charge level SOC(0) as the charge level SOC(-) at the discharging point and calculates ΔSOC2(-) based on equation (2') above.

[0072] Next, if ΔSOC1(+) and ΔSOC2(+) are obtained, the correction coefficient calculation unit 54 calculates the charging side correction value K(+) based on equation (3) above. Also, if ΔSOC1(-) and ΔSOC2(-) are obtained, the discharge side correction value K(-) is calculated based on equation (3') above.

[0073] Then, with one of the charging-side correction values ​​K(+) or discharging-side correction values ​​K(-) calculated, steps S200 to S240 are performed to obtain the other discharging-side correction value K(-) or charging-side correction value K(+). These charging-side correction values ​​K(+) and discharging-side correction values ​​K(-) are output to the correction coefficient setting unit 57 only on the first use. The correction coefficient setting unit 57 sets the capacity correction value K(n) based on the input charging-side correction value K(+) and discharging-side correction value K(-), for example by taking the average of both. The capacity correction unit 58 then calculates the initial corrected total capacity Ah(n) using equation (5') above with this capacity correction value K(n). The estimated charge rate calculation unit 60 then calculates the estimated charge rate SOC' using equation (6) above with this corrected total capacity Ah(n).

[0074] Alternatively, the initial correction value calculation step S120 may be performed as follows. First, step S012 is performed to read out the previous capacity correction value K(n-1) that was applied at the time of system off, the reference point charge rate SOC(0)' at that time, and the integrated current value ΔAh' at the time of system off from the recording unit 55. In addition, the charge rate acquisition unit 40 performs steps S102 to S116 to acquire the reference point charge rate SOC(0) and the integrated current value ΔAh(0).

[0075] Furthermore, the correction coefficient setting unit 57 calculates ΔSOC1' and ΔSOC2' only on the first use, based on equations (7) and (8) below, if the difference between the charge rate SOC(0)' and the charge rate SOC(0) is sufficiently large and the integrated current value ΔAh' is greater than a predetermined value. ΔSOC1'=ΔAh' / (Ah(0)×K(n-1))...(7) ΔSOC2'=|SOC(0)-SOC(0)'|···(8) Then, the capacity correction value K(n) is calculated based on equation (9) below. K(n) = ΔSOC1' / ΔSOC2'···(9) The correction coefficient setting unit 57 then outputs this capacity correction value K(n) to the capacity correction unit 58. The capacity correction unit 58 then calculates the initial corrected total capacity Ah(n) using equation (5') above based on this capacity correction value K(n) and outputs it to the estimated charge rate calculation unit 60. The estimated charge rate calculation unit 60 then uses this corrected total capacity Ah(n) to calculate the estimated charge rate SOC' using equation (6) above.

[0076] Furthermore, in configurations using equations (7), (8), and (9) above, if the difference between the charge rate SOC(0)' and the charge rate SOC(0) is small, or if the value of the integrated current value ΔAh' is smaller than a predetermined value, the capacity correction value K(n) calculated by equation (9) may be significantly large or small. In such cases, the correction coefficient setting unit 57 may not perform the calculation using equations (7), (8), and (9) above, but instead use the capacity correction value K(n-1) recorded in the recording unit 55 as the capacity correction value K(n), calculate the initial corrected total capacity Ah(n) using equation (5') above, and obtain the estimated charge rate SOC'.

[0077] In a configuration that includes these initial correction value calculation steps S120, the total capacity of the secondary battery 10 (reference total capacity Ah(0)) is corrected by inheriting the corrected total capacity Ah(n-1) value from the previous system-off point, so that an appropriate estimated charge rate SOC' can be calculated from startup.

[0078] Furthermore, the battery state estimation device 80 and battery state estimation method according to the present invention may also be used in combination with the detection method for battery capacity reduction based on the estimated internal resistance value shown below. First, in the battery state estimation device 80 with this configuration, the relationship between the increase in internal resistance due to the deterioration of the secondary battery 10 and the decrease in battery capacity is obtained in advance by measurement or the like, and recorded by data mapping. Then, in the operation of the correction value setting unit 50 described above, if both the charge-side correction value K(+) and the discharge-side correction value K(-) calculated by the correction coefficient calculation unit 54 are less than 1, the determination unit 56 temporarily suspends the output of this determination result.

[0079] Then, an internal resistance acquisition unit (not shown) calculates the estimated internal resistance R of the secondary battery 10 from the ratio of the change between the battery voltage V acquired by the voltage acquisition unit 34 and the current value I acquired by the current acquisition unit 30 (internal resistance calculation step). Next, the battery capacity corresponding to the calculated estimated internal resistance R is acquired by referring to the data map above (battery capacity acquisition step). Next, it is determined whether this battery capacity indicates a decrease in the capacity of the secondary battery 10 (capacity decrease determination step). If the determination result based on this internal resistance value indicates a decrease in the capacity of the secondary battery 10, the determination unit 56 outputs the pending determination result "both the charge-side correction value K(+) and the discharge-side correction value K(-) are less than 1" to the correction coefficient setting unit 57 and calculates the capacity correction value K(n) and the estimated charge rate SOC' according to the steps described above. If the determination result based on the estimated internal resistance R does not indicate a decrease in the capacity of the secondary battery 10, the determination unit 56 clears the pending determination result and returns to the current acquisition step S200. In this configuration, the determination of the capacity degradation of the secondary battery 10 is performed in two stages, including a determination based on the estimated internal resistance value R. Therefore, the occurrence of erroneous corrections due to measurement errors can be further prevented.

[0080] As described above, the battery state estimation device 80 and battery state estimation method according to the present invention calculate a charging-side correction value K(+) and a discharge-side correction value K(-) from at least three or more charge rates SOC(0), SOC(+), and SOC(-) at a reference point, a charging point, and a discharge point, and at least two or more current integrated values ​​ΔAh(+) and ΔAh(-) corresponding to these. Then, correction is performed in a manner corresponding to the cases where both the charging-side correction value K(+) and the discharge-side correction value K(-) are less than 1, where both are greater than 1, and where only one is less than 1. This allows for the correction of the offset error of the current acquisition means 30a and the correction of the decrease in battery capacity of the secondary battery 10, the gain error of the current acquisition means 30a, and the state in which both coexist. This makes it possible to appropriately perform corrections corresponding to both of these factors, and to calculate a more accurate estimated charge rate SOC'.

[0081] Furthermore, the configuration, operation, mechanism, calculation formulas, etc. of each part of the battery state estimation device 80 and battery state estimation method shown in this example are merely examples and are not limited to this example. For example, the configuration of the system side to which the battery state estimation device 80 is applied, i.e., the load 1, power converter 3, system control unit 5, and external power source 7, is not limited to this. In addition, the external power source 7 can be a solar panel or a commercial power supply. Furthermore, if the load 1 is a motor, the power generated during deceleration is consumed by returning it to the commercial power supply, charging the secondary battery 10, or dissipating it as heat through a load resistor (not shown). Moreover, the present invention can be modified and implemented without departing from the gist of the invention. [Explanation of symbols]

[0082] 10 Secondary battery 30 Current acquisition section 32 Current Integration Value Calculation Unit 34 Voltage acquisition unit 42 OCV-SOC Acquisition Department 46 Relaxation state determination unit 52 ΔSOC Calculation Unit 54 Correction coefficient calculation unit 55 Records Section 56 Judgment section 57 Correction coefficient setting section 58 Capacitance Correction Section 59 SOC Correction Unit 60 Estimated charging rate calculation section 80 Battery State Estimation Device

Claims

1. A battery state estimation device for calculating the estimated state of charge (SOC') of a rechargeable secondary battery that supplies power to a system, A current acquisition unit that acquires the current value of the secondary battery, A current integration value calculation unit calculates the current integration value ΔAh of the secondary battery based on the current value acquired by the current acquisition unit, A voltage acquisition unit that acquires the voltage value of the secondary battery, An OCV-SOC acquisition unit acquires, based on the voltage values ​​acquired by the voltage acquisition unit, the open-circuit voltage of at least one reference point, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, and further acquires the charge level of at least one reference point, the charge level SOC(+) of the charging point, and the charge level SOC(-) of the discharge point, corresponding to the open-circuit voltage of at least one of the reference points, the open-circuit voltage OCV(+) of the charging point, and the open-circuit voltage OCV(-) of the discharge point. Based on the current integrated value ΔAh input from the current integrated value calculation unit, the ΔSOC calculation unit obtains the current integrated value ΔAh(+) of the charging point based on the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point based on the current integrated value of at least one of the reference points, and calculates ΔSOC1(+) as the change in the charge rate of the first charging side based on the obtained current integrated value ΔAh(+) of the charging point, and calculates ΔSOC1(-) as the change in the charge rate of the first discharge side based on the obtained current integrated value ΔAh(-) of the discharge point, and calculates ΔSOC2(+) as the change in the charge rate of the second charging side, and calculates ΔSOC2(-) as the change in the charge rate of the second discharge side, based on the charge rate of at least one reference point, the charge rate SOC(+) of the charging point, and the charge rate SOC(-) of the discharge point obtained from the OCV-SOC acquisition unit, A correction coefficient calculation unit calculates a charging-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) calculated by the ΔSOC calculation unit, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination unit determines whether the charging-side correction value K(+) and the discharging-side correction value K(-) calculated by the correction coefficient calculation unit are greater than or less than 1, and selects a method for calculating the estimated charge rate (SOC') according to the determination result. If the determination unit determines that both the charging-side correction value K(+) and the discharging-side correction value K(-) are less than 1, or that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting unit calculates a correction value K'(n) based on the charging-side correction value K(+) and the discharging-side correction value K(-), and sets a capacity correction value K(n) based on the correction value K'(n). A capacity correction unit calculates the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery based on the capacity correction value K(n) set by the correction coefficient setting unit, A battery state estimation device characterized by having an estimated charge rate calculation unit that calculates the estimated charge rate SOC' based on the total capacity Ah(n) calculated by the capacity correction unit.

2. The ΔSOC calculation unit calculates ΔSOC1(+) as the change in the charge rate on the first charging side using the following equation (1) based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(+) at the charging point, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side using the following equation (1') based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(-) at the discharging point. ΔSOC1(+)=ΔAh(+) / Ah(n-1)...(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)...(1') Furthermore, ΔSOC2(+) is calculated as the change in the charge rate of the second charging side using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or ΔSOC2(+) is calculated as the change in the charge rate of the second charging side using equation (2'') below, based on the charge rate SOC(0') of a different reference point than the charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the state of charge (SOC)(0) of at least one reference point and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2') below, or based on the state of charge (SOC)(0') of a different reference point than the aforementioned state of charge (SOC)(0) and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2''') below. ΔSOC2(+)=|SOC(+)−SOC(0)|...(2) ΔSOC2(-)=|SOC(-)-SOC(0)|...(2') ΔSOC2(+)=|SOC(+)−SOC(0')|...(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|...(2''') The battery state estimation device according to claim 1, characterized in that the correction coefficient calculation unit calculates a charge-side correction value K(+) based on ΔSOC1(+) and ΔSOC2(+) using the following formula (3), and calculates a discharge-side correction value K(-) based on ΔSOC1(-) and ΔSOC2(-) using the following formula (3'). K(+)=ΔSOC1(+) / ΔSOC2(+)...(3) K(-)=ΔSOC1(-) / ΔSOC2(-)...(3')

3. When multiple charging points or multiple discharging points are obtained, The OCV-SOC acquisition unit acquires the charge level SOC(+) at each charging point and the charge level SOC(-) at the discharge point, The ΔSOC calculation unit calculates ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) individually for each charging point or discharging point. The battery state estimation device according to claim 2, characterized in that the correction coefficient calculation unit individually calculates provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3'), and then sets the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-).

4. A battery state estimation device for calculating the estimated state of charge (SOC') of a rechargeable secondary battery that supplies power to a system, A current acquisition unit that acquires the current value of the secondary battery, A current integration value calculation unit calculates the current integration value ΔAh of the secondary battery based on the current value acquired by the current acquisition unit, A voltage acquisition unit that acquires the voltage value of the secondary battery, An OCV-SOC acquisition unit acquires, based on the voltage values ​​acquired by the voltage acquisition unit, the open-circuit voltage of at least one reference point, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, and further acquires the charge level of at least one reference point, the charge level SOC(+) of the charging point, and the charge level SOC(-) of the discharge point, corresponding to the open-circuit voltage of at least one of the reference points, the open-circuit voltage OCV(+) of the charging point, and the open-circuit voltage OCV(-) of the discharge point. Based on the current integrated value ΔAh input from the current integrated value calculation unit, the ΔSOC calculation unit obtains the current integrated value ΔAh(+) of the charging point based on the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point based on the current integrated value of at least one of the reference points, and calculates ΔSOC1(+) as the change in the charge rate of the first charging side based on the obtained current integrated value ΔAh(+) of the charging point, and calculates ΔSOC1(-) as the change in the charge rate of the first discharge side based on the obtained current integrated value ΔAh(-) of the discharge point, and calculates ΔSOC2(+) as the change in the charge rate of the second charging side, and calculates ΔSOC2(-) as the change in the charge rate of the second discharge side, based on the charge rate of at least one reference point, the charge rate SOC(+) of the charging point, and the charge rate SOC(-) of the discharge point obtained from the OCV-SOC acquisition unit, A correction coefficient calculation unit calculates a charging-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) calculated by the ΔSOC calculation unit, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination unit determines whether the charging-side correction value K(+) and the discharging-side correction value K(-) calculated by the correction coefficient calculation unit are greater than or less than 1, and selects a method for calculating the estimated charge rate (SOC') according to the determination result. If the determination unit determines that one of the charging-side correction value K(+) and the discharging-side correction value K(-) is less than 1 and the other is greater than 1, the correction coefficient setting unit sets the past capacity correction value K(n-1) to the capacity correction value K(n). A capacity correction unit calculates the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery based on the capacity correction value K(n) set by the correction coefficient setting unit, An SOC correction unit sets an SOC correction value K(soc) based on the values ​​of ΔSOC1(+), SOC1(-), ΔSOC2(+), and ΔSOC2(-), A battery state estimation device characterized by having an estimated charge rate calculation unit that calculates the estimated charge rate SOC' based on the total capacity Ah(n) and the SOC correction value K(soc).

5. The ΔSOC calculation unit calculates ΔSOC1(+) as the change in the charge rate on the first charging side using the following equation (1) based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(+) at the charging point, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side using the following equation (1') based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(-) at the discharging point. ΔSOC1(+)=ΔAh(+) / Ah(n-1)...(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)...(1') Furthermore, ΔSOC2(+) is calculated as the change in the charge rate of the second charging side using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or ΔSOC2(+) is calculated as the change in the charge rate of the second charging side using equation (2'') below, based on the charge rate SOC(0') of a different reference point than the charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the state of charge (SOC)(0) of at least one reference point and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2') below, or based on the state of charge (SOC)(0') of a different reference point than the aforementioned state of charge (SOC)(0) and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2''') below. ΔSOC2(+)=|SOC(+)−SOC(0)|...(2) ΔSOC2(-)=|SOC(-)-SOC(0)|...(2') ΔSOC2(+)=|SOC(+)−SOC(0')|...(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|...(2''') The battery state estimation device according to claim 4, characterized in that the correction coefficient calculation unit calculates a charge-side correction value K(+) based on ΔSOC1(+) and ΔSOC2(+) using the following formula (3), and calculates a discharge-side correction value K(-) based on ΔSOC1(-) and ΔSOC2(-) using the following formula (3'). K(+)=ΔSOC1(+) / ΔSOC2(+)...(3) K(-)=ΔSOC1(-) / ΔSOC2(-)...(3')

6. When multiple charging points or multiple discharging points are obtained, The OCV-SOC acquisition unit acquires the charge level SOC(+) at each charging point and the charge level SOC(-) at the discharge point, The ΔSOC calculation unit calculates ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) individually for each charging point or discharging point. The battery state estimation device according to claim 5, characterized in that the correction coefficient calculation unit individually calculates provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3'), and then sets the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-).

7. The battery state estimation device according to any one of claims 1 to 3, characterized in that the correction coefficient setting unit has a correction lower limit K(min) that is less than 1, and when the correction value K'(n) is less than the correction lower limit K(min), the correction lower limit K(min) is set as the capacity correction value K(n).

8. The battery state estimation device according to any one of claims 1 to 3, characterized in that the correction coefficient setting unit has a reduction coefficient A, and calculates a capacity correction value K(n) from the reduction coefficient A and the previous capacity correction value K(n-1) based on the following formula (4'). K(n)=(1-A×(1-K'(n)))×K(n-1)...(4')

9. The battery state estimation device according to any one of claims 4 to 6, characterized in that the SOC correction unit sets an SOC correction value K(soc) based on the values ​​of |ΔSOC2(+)-ΔSOC1(+)| and |ΔSOC2(-)-ΔSOC1(-)|.

10. The battery state estimation device according to claim 9, characterized in that the SOC correction unit takes the average value of the value of |ΔSOC2(+) - ΔSOC1(+)| and the value of |ΔSOC2(-) - ΔSOC1(-)| as the SOC correction value K(soc).

11. The battery state estimation device according to any one of claims 1 to 10, characterized in that at least one of the open-circuit voltage OCV(0) at the reference point, the open-circuit voltage OCV(+) at the charging point, and the open-circuit voltage OCV(-) at the discharge point is the open-circuit voltage of the secondary battery at system startup.

12. The battery state estimation device according to any one of claims 1 to 11, characterized in that, if the determination unit determines that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting unit sets the capacity correction value K(n) as the value obtained by multiplying the average value of the charging-side correction value K(+) and the discharging-side correction value K(-) by the previous capacity correction value K(n-1) based on the following formula (4''). K(n)=((K(+)+K(-)) / 2)×K(n-1)...(4'')

13. The battery state estimation device according to any one of claims 1 to 12, characterized in that the capacity correction unit corrects the total capacity Ah(n-1) based on the following formula (5) and calculates the total capacity Ah(n). Ah(n)=Ah(n-1)×K(n)...(5)

14. The battery state estimation device according to any one of claims 1 to 13, characterized in that when the charging point or discharging point acquired by the OCV-SOC acquisition unit exceeds a predetermined threshold range set above or below a reference point, this point is set as the charging point or discharging point.

15. The battery state estimation device according to any one of claims 1 to 14, further comprising a relaxation state determination unit that permits the OCV-SOC acquisition unit to acquire an open-circuit voltage when the current value from the current acquisition unit remains in a predetermined state of zero near zero for a predetermined predetermined time.

16. The battery state estimation device according to any one of claims 1 to 15, characterized in that after applying the corrected total capacity Ah(n), the capacity correction value K(n+1) is calculated again.

17. The battery state estimation device according to claim 16, characterized in that an upper limit is set on the number of calculation operations for the capacity correction value K(n) during a single system operating period.

18. The system further includes a recording unit that records at least the capacity correction value K(n-1) that was applied at the time the system was turned off. The battery state estimation device according to any one of claims 1 to 17, characterized in that when the system is started, the capacity correction value K(n-1) recorded in the recording unit is read out, the capacity correction value K(n-1) is set as the capacity correction value K(n), and the initial total capacity Ah(n) is calculated based on the following formula (5'). Ah(n)=Ah(0)×K(n)...(5')

19. The system further includes a recording unit that records at least the capacity correction value K(n-1) applied at the time of system off, the reference point charge state of charge (SOC(0)') at that time, and the total current value ΔAh (total) for the entire period from the previous system startup to the time of system off. When the system starts up, the state of charge (SOC) is obtained from the open-circuit voltage OCV(0) at startup, and the state of charge (SOC)' of the reference point recorded in the recording unit and the integrated current value ΔAh(total) are read out. After determining whether the integrated current value ΔAh(total) is located on the charging side or the discharging side relative to the reference point at the time the system is turned off, ΔSOC1(+) or ΔSOC1(-) is calculated based on the integrated current value ΔAh(total). The battery state estimation device according to any one of claims 1 to 17, characterized in that it calculates ΔSOC2(+) or ΔSOC2(-) based on the charge rate SOC(0)' and charge rate SOC(0), and calculates either a charge-side correction value K(+) or a discharge-side correction value K(-).

20. Furthermore, it includes a data mapping that records the relationship between the internal resistance and battery capacity of a secondary battery. A battery state estimation device according to any one of claims 1 to 19, characterized in that it calculates an estimated internal resistance value of a secondary battery from the voltage value acquired by the voltage acquisition unit and the current value acquired by the current acquisition unit, obtains the battery capacity corresponding to the estimated internal resistance value from the data mapping, and calculates the total capacity Ah(n) when the battery capacity indicates a capacity decrease and the determination unit determines that both the charge-side correction value K(+) and the discharge-side correction value K(-) are less than 1.

21. A battery state estimation method for calculating the estimated state of charge (SOC') of a rechargeable secondary battery that supplies power to a system, A current acquisition step to acquire the current value of the secondary battery, A current integration value calculation step calculates the current integration value ΔAh of the secondary battery based on the current value obtained in the current acquisition step, A voltage acquisition step to acquire the voltage value of the secondary battery, An open-circuit voltage acquisition step, which acquires the open-circuit voltage of at least one reference point based on the voltage value acquired in the voltage acquisition step, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, A charge rate acquisition step which acquires the open-circuit voltage of at least one reference point acquired in the open-circuit voltage acquisition step, the charge rate of at least one reference point corresponding to the open-circuit voltage OCV(+) of the charging point and the open-circuit voltage OCV(-) of the discharge point, the charge rate SOC(+) of the charging point and the charge rate SOC(-) of the discharge point, A charge / discharge current integrated value acquisition step, which acquires, based on the current integrated value ΔAh obtained in the current integrated value calculation step, the current integrated value ΔAh(+) of the charging point with reference to the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point with reference to the current integrated value of at least one of the reference points, respectively. A first charge rate change calculation step calculates ΔSOC1(+) as the change in the charge rate on the first charging side based on the integrated current value ΔAh(+) at the charging point obtained in the charge / discharge current acquisition step, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side based on the integrated current value ΔAh(-) at the discharging point, A second charge rate change calculation step calculates ΔSOC2(+) as the change in the charge rate of the second charging side based on the charge rate of at least one reference point obtained in the charge rate acquisition step and the charge rate SOC(+) of the charging point, and calculates ΔSOC2(-) as the change in the charge rate of the second discharging side based on the charge rate SOC(0) of the reference point and the charge rate SOC(-) of the discharging point, A correction coefficient calculation step which calculates a charging-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) obtained in the first charge rate change calculation step and the second charge rate change calculation step, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination step in which the charging-side correction value K(+) and the discharging-side correction value K(-) calculated in the correction coefficient calculation step are determined to be greater than or less than 1, and a method for calculating the estimated charge rate (SOC') is selected according to the determination result, If the determination step determines that both the charging-side correction value K(+) and the discharging-side correction value K(-) are less than 1, or that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting step involves calculating a correction value K'(n) based on the charging-side correction value K(+) and the discharging-side correction value K(-), and setting a capacity correction value K(n) based on the correction value K'(n). A capacity value correction step to calculate the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery based on the capacity correction value K(n) set in the correction coefficient setting step, A battery state estimation method characterized by comprising: an estimated charge rate calculation step of calculating the estimated charge rate SOC' based on the total capacity Ah(n) calculated in the capacity value correction step.

22. The first charge rate change calculation step calculates ΔSOC1(+) as the change in the charge rate on the first charging side using the following equation (1) based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(+) at the charging point, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side using the following equation (1') based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(-) at the discharging point. ΔSOC1(+)=ΔAh(+) / Ah(n-1)...(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)...(1') The second step of calculating the change in charge rate involves calculating ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or calculating ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2'') below, based on the charge rate SOC(0') of another reference point different from the charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the state of charge (SOC)(0) of at least one reference point and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2') below, or based on the state of charge (SOC)(0') of a different reference point than the aforementioned state of charge (SOC)(0) and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2''') below. ΔSOC2(+)=|SOC(+)−SOC(0)|...(2) ΔSOC2(-)=|SOC(-)-SOC(0)|...(2') ΔSOC2(+)=|SOC(+)−SOC(0')|...(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|...(2''') The battery state estimation method according to claim 21, characterized in that the correction coefficient calculation step calculates a charge-side correction value K(+) based on ΔSOC1(+) and ΔSOC2(+) using the following formula (3), and calculates a discharge-side correction value K(-) based on ΔSOC1(-) and ΔSOC2(-) using the following formula (3'). K(+)=ΔSOC1(+) / ΔSOC2(+)...(3) K(-)=ΔSOC1(-) / ΔSOC2(-)...(3')

23. When the open-circuit voltage acquisition step acquires multiple charging points or multiple discharging points, The charge rate acquisition step acquires the charge rate SOC(+) at each charging point and the charge rate SOC(-) at the discharge point. The charge rate change calculation step involves individually calculating ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) for each charging or discharging point. The battery state estimation method according to 22, characterized in that the correction coefficient calculation step involves individually calculating provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3'), and then taking the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-).

24. A battery state estimation method for calculating the estimated state of charge (SOC') of a rechargeable secondary battery that supplies power to a system, A current acquisition step to acquire the current value of the secondary battery, A current integration value calculation step calculates the current integration value ΔAh of the secondary battery based on the current value obtained in the current acquisition step, A voltage acquisition step to acquire the voltage value of the secondary battery, An open-circuit voltage acquisition step, which acquires the open-circuit voltage of at least one reference point based on the voltage value acquired in the voltage acquisition step, the open-circuit voltage OCV(+) of a charging point located in the charging direction from at least one of the reference points, and the open-circuit voltage OCV(-) of a discharge point located in the discharge direction from at least one of the reference points, A charge rate acquisition step which acquires the open-circuit voltage of at least one reference point acquired in the open-circuit voltage acquisition step, the charge rate of at least one reference point corresponding to the open-circuit voltage OCV(+) of the charging point and the open-circuit voltage OCV(-) of the discharge point, the charge rate SOC(+) of the charging point and the charge rate SOC(-) of the discharge point, A charge / discharge current integrated value acquisition step, which acquires, based on the current integrated value ΔAh obtained in the current integrated value calculation step, the current integrated value ΔAh(+) of the charging point with reference to the current integrated value of at least one of the reference points, and the current integrated value ΔAh(-) of the discharge point with reference to the current integrated value of at least one of the reference points, respectively. A first charge rate change calculation step calculates ΔSOC1(+) as the change in the charge rate on the first charging side based on the integrated current value ΔAh(+) at the charging point obtained in the charge / discharge current acquisition step, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side based on the integrated current value ΔAh(-) at the discharging point, A second charge rate change calculation step calculates ΔSOC2(+) as the change in the charge rate of the second charging side based on the charge rate of at least one reference point obtained in the charge rate acquisition step and the charge rate SOC(+) of the charging point, and calculates ΔSOC2(-) as the change in the charge rate of the second discharging side based on the charge rate SOC(0) of the reference point and the charge rate SOC(-) of the discharging point, A correction coefficient calculation step which calculates a charging-side correction value K(+) based on the ratio of ΔSOC1(+) and ΔSOC2(+) obtained in the first charge rate change calculation step and the second charge rate change calculation step, and calculates a discharge-side correction value K(-) based on the ratio of ΔSOC1(-) and ΔSOC2(-), A determination step in which the charging-side correction value K(+) and the discharging-side correction value K(-) calculated in the correction coefficient calculation step are determined to be greater than or less than 1, and a method for calculating the estimated charge rate (SOC') is selected according to the determination result, If, in the determination step, it is determined that one of the charging-side correction value K(+) and the discharging-side correction value K(-) is less than 1 and the other is greater than 1, A correction coefficient setting step in which a capacity correction value K(n) is set based on past capacity correction values ​​K(n-1), A capacity value correction step to calculate the total capacity Ah(n) by correcting the total capacity Ah(n-1) of the secondary battery based on the capacity correction value K(n) set in the correction coefficient setting step, An SOC correction value setting step in which an SOC correction value K(soc) is set based on the values ​​of ΔSOC1(+), SOC1(-), ΔSOC2(+), and ΔSOC2(-), A battery state estimation method characterized by comprising: an estimated charge rate calculation step which calculates the estimated charge rate SOC' based on the total capacity Ah(n) calculated in the capacity value correction step and the SOC correction value K(soc) set in the SOC correction value setting step.

25. The first charge rate change calculation step calculates ΔSOC1(+) as the change in the charge rate on the first charging side using the following equation (1) based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(+) at the charging point, and calculates ΔSOC1(-) as the change in the charge rate on the first discharging side using the following equation (1') based on the total capacity Ah(n-1) of the secondary battery and the integrated current value ΔAh(-) at the discharging point. ΔSOC1(+)=ΔAh(+) / Ah(n-1)...(1) ΔSOC1(-)=ΔAh(-) / Ah(n-1)...(1') The second step of calculating the change in charge rate involves calculating ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2) below, based on the charge rate SOC(0) of at least one reference point and the charge rate SOC(+) of the charging point, or calculating ΔSOC2(+) as the change in the charge rate of the second charging side using equation (2'') below, based on the charge rate SOC(0') of another reference point different from the charge rate SOC(0) and the charge rate SOC(+) of the charging point. Based on the state of charge (SOC)(0) of at least one reference point and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2') below, or based on the state of charge (SOC)(0') of a different reference point than the aforementioned state of charge (SOC)(0) and the state of charge (SOC)(-) of the discharge point, ΔSOC2(-) is calculated as the change in the second discharge side's charge rate using equation (2''') below. ΔSOC2(+)=|SOC(+)−SOC(0)|...(2) ΔSOC2(-)=|SOC(-)-SOC(0)|...(2') ΔSOC2(+)=|SOC(+)−SOC(0')|...(2'') ΔSOC2(-)=|SOC(-)-SOC(0')|...(2''') The battery state estimation method according to claim 24, characterized in that the correction coefficient calculation step calculates a charge-side correction value K(+) based on ΔSOC1(+) and ΔSOC2(+) using the following formula (3), and calculates a discharge-side correction value K(-) based on ΔSOC1(-) and ΔSOC2(-) using the following formula (3'). K(+)=ΔSOC1(+) / ΔSOC2(+)...(3) K(-)=ΔSOC1(-) / ΔSOC2(-)...(3')

26. When the open-circuit voltage acquisition step acquires multiple charging points or multiple discharging points, The charge rate acquisition step acquires the charge rate SOC(+) at each charging point and the charge rate SOC(-) at the discharge point. The charge rate change calculation step involves individually calculating ΔSOC1(+), ΔSOC1(-), ΔSOC2(+), and ΔSOC2(-) for each charging or discharging point. The battery state estimation method according to claim 25, characterized in that the correction coefficient calculation step involves individually calculating provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point based on equations (3) and (3'), and then taking the average value of these provisional charge-side correction values ​​and provisional discharge-side correction values ​​for each charge point or discharge point as the charge-side correction value K(+) and the discharge-side correction value K(-).

27. The battery state estimation method according to any one of claims 21 to 23, characterized in that, in the correction coefficient setting step, if the correction value K'(n) is smaller than the correction lower limit K(min) which is less than 1, the correction lower limit K(min) is set as the capacity correction value K(n).

28. The battery state estimation method according to any one of claims 21 to 23, characterized in that the correction coefficient setting step calculates a capacity correction value K(n) based on the following equation (4') from a reduction coefficient A that is less than 1 and the previous capacity correction value K(n-1). K(n)=(1-A×(1-K'(n)))×K(n-1)...(4')

29. The battery state estimation method according to any one of claims 24 to 26, characterized in that the SOC correction value setting step sets an SOC correction value K(soc) based on the values ​​of |ΔSOC2(+)-ΔSOC1(+)| and |ΔSOC2(-)-ΔSOC1(-)|.

30. The battery state estimation method according to claim 29, characterized in that the SOC correction value setting step is to set the average value of the value of |ΔSOC2(+) - ΔSOC1(+)| and the value of |ΔSOC2(-) - ΔSOC1(-)| as the SOC correction value K(soc).

31. The battery state estimation method according to any one of claims 21 to 30, characterized in that the open-circuit voltage acquisition step uses the open-circuit voltage of the secondary battery at system startup for at least one of the open-circuit voltage OCV(0) at the reference point, the open-circuit voltage OCV(+) at the charging point, and the open-circuit voltage OCV(-) at the discharge point.

32. The battery state estimation method according to any one of claims 21 to 31, characterized in that, in the determination step, if it is determined that both the charging-side correction value K(+) and the discharging-side correction value K(-) are greater than 1, the correction coefficient setting step sets the capacity correction value K(n) as the value obtained by multiplying the average value of the charging-side correction value K(+) and the discharging-side correction value K(-) by the previous capacity correction value K(n-1) based on the following formula (4''). K(n)=((K(+)+K(-)) / 2)×K(n-1)...(4'')

33. The battery state estimation method according to any one of claims 21 to 32, characterized in that the capacity value correction step corrects the total capacity Ah(n-1) based on the following formula (5) and calculates the total capacity Ah(n). Ah(n)=Ah(n-1)×K(n)...(5)

34. The battery state estimation method according to any one of claims 21 to 33, characterized in that the open-circuit voltage acquisition step sets the acquired charging point or discharging point as the charging point or discharging point when the acquired charging point or discharging point exceeds a predetermined threshold range set above or below the reference point.

35. The battery state estimation method according to any one of claims 21 to 34, characterized in that the open-circuit voltage acquisition step further comprises a relaxation state waiting step in which an open-circuit voltage is acquired when the current value from the current acquisition unit remains in a predetermined state of zero near zero for a predetermined predetermined time.

36. A battery state estimation method according to any one of claims 21 to 35, characterized in that after applying the corrected total capacity Ah(n), the capacity correction value K(n+1) is calculated again.

37. The battery state estimation method according to claim 36, characterized in that an upper limit is set on the number of calculation operations for the capacity correction value K(n) during a single system operating period.

38. A recording step that records at least the capacity correction value K(n-1) that is applied at the time the system is turned off, The system further includes an initial correction value calculation step that is performed when the system starts up, The battery state estimation method according to any one of claims 21 to 37, characterized in that the initial correction value calculation step reads out the capacity correction value K(n-1) recorded in the recording step, sets the capacity correction value K(n-1) as the capacity correction value K(n), and calculates the initial total capacity Ah(n) based on the following formula (5'). Ah(n)=Ah(0)×K(n)...(5')

39. The system further includes a recording step that records at least the capacity correction value K(n-1) applied at the time of system off, the reference point charge state of charge (SOC(0)') at that time, and the total current value ΔAh(total) for the entire period from the previous system startup to the time of system off. When the system starts up, the state of charge (SOC) is obtained from the open-circuit voltage OCV(0) at startup, and the state of charge (SOC)' of the reference point recorded in the recording step and the integrated current value ΔAh(total) are read out. After determining whether the integrated current value ΔAh(total) is located on the charging side or the discharging side relative to the reference point at the time the system is turned off, ΔSOC1(+) or ΔSOC1(-) is calculated based on the integrated current value ΔAh(total). A battery state estimation method according to any one of claims 21 to 37, characterized in that ΔSOC2(+) or ΔSOC2(-) is calculated based on the charge rate SOC(0)' and charge rate SOC(0), and either a charge-side correction value K(+) or a discharge-side correction value K(-) is calculated.

40. It includes a data mapping system that records the relationship between the internal resistance and capacity of a secondary battery, An internal resistance calculation step calculates the estimated internal resistance of the secondary battery from the voltage value obtained in the voltage acquisition step and the current value obtained in the current acquisition step. A battery capacity acquisition step is performed to obtain the battery capacity corresponding to the estimated internal resistance value calculated in the internal resistance calculation step from the data mapping, The battery capacity acquisition step further includes a capacity reduction determination step that determines whether the battery capacity acquired by the battery capacity acquisition step indicates a capacity reduction, A battery state estimation method according to any one of claims 21 to 39, characterized in that in the capacity reduction determination step, the battery capacity obtained in the battery capacity acquisition step indicates a capacity reduction, and in the determination step, the total capacity Ah(n) is calculated when both the charge-side correction value K(+) and the discharge-side correction value K(-) are determined to be less than 1.

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