Estimation device for state of charge of secondary battery, control device for secondary battery, and control device for power supply of electric vehicle

Abstract

The present invention addresses the problem of estimating the state of charge of a secondary battery with prescribed accuracy even within a prescribed range of state of charge in which changes in the state of charge in relation to changes in the voltage value of the secondary battery are relatively small. An estimation device 100 for the state of charge (SOC) of a secondary battery 21 estimates the SOC within a prescribed range (plateau region A). The fluctuations (ΔV) of the voltage value (OCV) of the secondary battery 21 in the plateau region A are smaller than the fluctuations (ΔV) of the OCV of the secondary battery 21 outside the prescribed SOC range (non-plateau region B). The estimation device 100 computes a first state of charge (SOCV) as the SOC of the secondary battery 21 and computes a second state of charge (SOCi) as the SOC of the secondary battery 21. The estimation device 100 reflects SOCi relatively greater than SOCv when estimating the SOC of the secondary battery 21 in the plateau region A than when estimating the SOC of the secondary battery 21 in the non-plateau region B.

Description

Device for estimating state of charge of secondary battery, control device for secondary battery, control device for power source of electric vehicle

[0001] The present invention relates to a device for estimating the state of charge of a secondary battery, a control device for the secondary battery, and a control device for the power source of an electric vehicle.

[0002] Conventionally, a technique for estimating the state of charge of a secondary battery has been known (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Application Publication No. 2023-121369

[0004] Regarding a secondary battery containing at least one of lithium iron phosphate and lithium manganese iron phosphate in a positive electrode active material, even within a predetermined state of charge range where the change in the state of charge with respect to the change in the voltage value of the secondary battery is relatively small, it is required to estimate the state of charge of the secondary battery with a predetermined accuracy.

[0005] The device for estimating the state of charge of the secondary battery of the present invention is a device for estimating the state of charge within a predetermined range of the secondary battery. By including a specific positive electrode active material and a negative electrode active material in the secondary battery, the fluctuation of the voltage value of the secondary battery within the predetermined state of charge range is relatively smaller than the fluctuation of the voltage value of the secondary battery outside the predetermined state of charge range. The positive electrode active material contains at least one of lithium iron phosphate and lithium manganese iron phosphate having a characteristic that the fluctuation of the voltage value of the secondary battery within the predetermined state of charge range is relatively smaller than the fluctuation of the voltage value of the secondary battery outside the predetermined state of charge range. The device for estimating the state of charge of the secondary battery calculates a first state of charge as the state of charge of the secondary battery based on at least the voltage value of the secondary battery. The estimating device calculates a second state of charge as the state of charge of the secondary battery based on at least the integrated amount of the current value of the secondary battery. When estimating the state of charge of the secondary battery within the predetermined state of charge range, the estimating device relatively reflects the second state of charge more greatly than the first state of charge as compared with the case of estimating the state of charge of the secondary battery outside the predetermined state of charge range.

[0006] The control device for a secondary battery of the present invention includes a device for estimating the charge level of the secondary battery. The estimation device controls at least one of the charging or discharging of the secondary battery by referring to the result of estimating the charge level of the secondary battery.

[0007] The power supply control device for electric vehicles of the present invention is used in an electric vehicle having electrical equipment, a power supply that supplies power to the electrical equipment, and the control device for the secondary battery described above. The power supply includes the secondary battery described above. The power supply control device for electric vehicles of the present invention controls the secondary battery by the control device for the secondary battery described above.

[0008] With respect to a secondary battery in which the positive electrode active material contains at least one of lithium iron phosphate and lithium manganese iron phosphate, the charge level of the secondary battery is estimated within a predetermined charge level range in which the change in charge level with respect to a change in the voltage value of the secondary battery is relatively small, by reflecting at least a first charge level based on the voltage value relatively small, while reflecting at least a second charge level based on the cumulative amount of current relatively large.Therefore, with this configuration, the charge level of the secondary battery can be estimated with a predetermined accuracy even within a predetermined charge level range in which the change in charge level with respect to a change in the voltage value of the secondary battery is relatively small.

[0009] A graph showing the relationship between the SOC and OCV of the secondary battery 21 used to estimate the SOC of the embodiment. A block diagram showing the configuration of the embodiment.

[0010] (Secondary battery 21 that estimates SOC in plateau region A) A secondary battery 21 that estimates the state of charge (SOC) in plateau region A will be explained with reference to Figure 1.

[0011] Figure 1 is a graph showing the relationship between the SOC and OCV of the secondary battery 21 used to estimate the SOC of the embodiment.

[0012] The secondary battery 21 used to estimate the State of Cost (SOC) in plateau region A is, for example, a lithium iron phosphate secondary battery. The secondary battery 21 may also be a manganese iron phosphate lithium secondary battery.

[0013] The plateau region is a region within a predetermined range of the State of Charge (SOC) of a secondary battery. By including specific positive electrode active materials and negative electrode active materials, the fluctuation of the voltage value V of the secondary battery 21 in plateau region A (ΔV) is relatively smaller than the fluctuation of the voltage value V of the secondary battery 21 in non-plateau region B. The fluctuation of the voltage value V of the secondary battery 21 (ΔV) corresponds to the range of fluctuation of the voltage value V of the secondary battery 21 due to fluctuations in the OCV of the secondary battery 21. The voltage value V of the secondary battery 21 is, for example, the OCV (open circuit voltage).

[0014] The plateau region is a region in which the voltage value V of the secondary battery 21 is flat during charging and discharging, or a region in which the fluctuation (ΔV) of the voltage value V is gradual. In other words, the plateau region is a region in which the charge-discharge curve of the secondary battery 21 is flat or gradual. The potential of the secondary battery 21 in the plateau region is called the plateau potential.

[0015] In plateau region A, the change in OCV of the secondary battery 21 is relatively very small compared to the change in SOC of the secondary battery 21. That is, in plateau region A, the increase or decrease in OCV of the secondary battery 21 does not correlate with the increase or decrease in SOC, and the increase or decrease in OCV plateaus. Plateau region A is defined based on the materials of the positive electrode active material and the negative electrode active material of the secondary battery 21. In other words, plateau region A is rate-limited by the materials of the positive electrode active material and the negative electrode active material of the secondary battery 21.

[0016] The positive electrode active material of the secondary battery 21 has the characteristic that the fluctuation of the OCV of the secondary battery 21 in the plateau region A of the secondary battery 21 is relatively smaller than the fluctuation of the OCV of the secondary battery 21 in the non-plateau region B of the secondary battery 21. The positive electrode active material of the secondary battery 21 includes, for example, lithium iron phosphate (LFP). The positive electrode active material of the secondary battery 21 may also be, for example, lithium manganese iron phosphate (LMFP).

[0017] The non-plateau region B corresponds to the area outside the predetermined SOC range of the secondary battery 21. In the non-plateau region B, the change in OCV of the secondary battery 21 is relatively large with respect to the change in SOC of the secondary battery 21. That is, in the non-plateau region B, the increase or decrease in OCV of the secondary battery 21 correlates with the increase or decrease in SOC, and the increase or decrease in OCV does not plateau. The non-plateau region B is defined based on the materials of the positive electrode active material and the negative electrode active material of the secondary battery 21. In other words, the non-plateau region B is rate-limited by the materials of the positive electrode active material and the negative electrode active material of the secondary battery 21.

[0018] The negative electrode active material of the secondary battery 21 has the characteristic that the fluctuation of the OCV of the secondary battery 21 in the plateau region A of the secondary battery 21 is equal to or relatively small compared to the fluctuation of the OCV of the secondary battery 21 in the non-plateau region B of the secondary battery 21. Compared to the positive electrode active material, the negative electrode active material of the secondary battery 21 has the characteristic that the fluctuation of the OCV of the secondary battery 21 in all or part of the non-plateau region B of the secondary battery 21 is relatively large. The negative electrode active material of the secondary battery 21 contains, for example, crystalline carbon. Crystalline means, for example, that it is different from amorphous. The negative electrode active material of the secondary battery 21 also contains, for example, graphite.

[0019] The OCV potential of the secondary battery 21 is the difference between the potential of the positive electrode active material and the potential of the negative electrode active material. When the positive electrode potential due to lithium iron phosphate in the positive electrode active material becomes a plateau potential, and the negative electrode potential due to graphite in the negative electrode active material also becomes a plateau potential, the potential difference of the secondary battery 21 becomes a plateau. In the plateau region of the secondary battery 21, a two-phase coexistence reaction occurs in the active material of the secondary battery 21. When the positive electrode active material of the secondary battery 21 is lithium iron phosphate, during charging and discharging of the secondary battery 21, LiFePO ４ and FePO ４ Both coexist.

[0020] When the positive electrode active material is lithium iron phosphate, the plateau region of the secondary battery 21 is relatively long. When the positive electrode active material is lithium manganese iron phosphate, the plateau region of the secondary battery 21 is relatively short compared to the case of lithium iron phosphate.

[0021] (Configuration of the battery pack 20 including the secondary battery 21) The configuration of the battery pack 20 including the secondary battery 21 will be explained with reference to Figure 2.

[0022] Figure 2 is a block diagram showing the configuration of the embodiment.

[0023] The battery pack 20 includes a plurality of secondary batteries 21. The plurality of secondary batteries 21 are connected in series. In adjacent secondary batteries 21, the positive terminal of one secondary battery 21 is connected to the negative terminal of the other secondary battery. The plurality of secondary batteries 21 may be connected in series and in parallel. The plurality of secondary batteries 21 may be connected in parallel.

[0024] The battery pack 20 can be used, for example, as a power source for a hybrid electric vehicle (HEV). The battery pack 20 may also be used as a power source for a plug-in hybrid electric vehicle (PHEV) and a battery electric vehicle (BEV). The battery pack 20 may also be used as a power source for an energy storage system (ESS).

[0025] (Configuration of the measurement unit 30 for measuring the electrical characteristics of the battery pack 20) ​​The configuration of the measurement unit 30 for measuring the electrical characteristics of the battery pack 20 will be explained with reference to Figure 2.

[0026] The measurement unit 30 includes a voltage measurement unit 31, a current measurement unit 32, and a temperature measurement unit 33. The voltage measurement unit 31 measures the voltage of each secondary battery 21. The voltage measurement unit 31 calculates the total voltage of multiple secondary batteries 21 connected in series. The voltage measurement unit 31 is provided in the battery control unit 200 of the control device 10 for the secondary batteries 21. The voltage measurement unit 31 is connected in parallel with each secondary battery 21. The current measurement unit 32 measures the total current of multiple secondary batteries 21 connected in series. The current measurement unit 32 is connected in series with the multiple secondary batteries 21 connected in series. That is, the current measurement unit 32 is connected in series with the battery pack 20. The temperature measurement unit 33 measures the temperature of one or more secondary batteries 21. The temperature measurement unit 33 is attached to one or more of the multiple secondary batteries 21.

[0027] (Configuration of the Embodiment) The control device 1 for the electric vehicle's power supply (secondary battery 21) includes a control device 10 for the secondary battery 21. The control device 10 for the secondary battery 21 includes a device 100 for estimating the charge level of the secondary battery 21. The following will be described in the order of the device 100 for estimating the charge level of the secondary battery 21, the control device 10 for the secondary battery 21, and the control device 1 for the electric vehicle's power supply (secondary battery 21).

[0028] (Configuration of the SOC estimation device 100 for the secondary battery 21 in the embodiment) The configuration of the SOC estimation device 100 for the secondary battery 21 in the embodiment will be described with reference to Figure 2.

[0029] The embodiment will be described as a device 100 for estimating the charge level of a battery pack 20 including multiple secondary batteries 21. The embodiment can also be used as a device 100 for estimating the charge level of a single secondary battery 21.

[0030] The estimation device 100 is a device that estimates the state of charge (SOC) of the secondary battery 21 in plateau region A. The estimation device 100 also estimates the SOC of the secondary battery 21 in non-plateau region B.

[0031] The estimation device 100 includes an SOCv calculation unit 110 (first calculation unit), an SOCi calculation unit 120 (second calculation unit), an SOC estimation unit 130 (estimation unit), an SOC correction unit 140 (correction unit), and a storage unit 150. The estimation device 100 is included in the control device 10. The configuration of the SOCv calculation unit 110 (first calculation unit), SOCi calculation unit 120 (second calculation unit), SOC estimation unit 130 (estimation unit), SOC correction unit 140 (correction unit), and storage unit 150 of the estimation device 100 will be described below.

[0032] (Configuration of SOCv calculation unit 110) The SOCv calculation unit 110 corresponds to the first calculation unit of the estimation device 100. The SOCv calculation unit 110 calculates SOCv as the SOC of the secondary battery 21 based on at least the OCV of the secondary battery 21. SOCv corresponds to the first charge level. The SOCv calculation unit 110 refers to the table 151 and calculates SOCv as the SOC of the secondary battery 21 that correlates with the OCV of the secondary battery 21.

[0033] As shown in Figure 2, the SOCv calculation unit 110 includes an OCV estimation unit 111 and an SOCv calculation unit 112.

[0034] The OCV estimation unit 111 receives the voltage value V of the secondary battery 21 from the voltage measurement unit 31. The OCV estimation unit 111 receives the current value I of the secondary battery 21 from the current measurement unit 32. The OCV estimation unit 111 receives the DC resistance (DCR) of the secondary battery 21 from the battery control unit 200 of the control device 10 for the secondary battery 21. Based on the voltage value V, current value I, DC resistance, etc., the OCV estimation unit 111 estimates the open-circuit voltage (OCV) of the secondary battery 21. The OCV estimation unit 111 estimates the OCV of the battery pack 20, which includes multiple secondary batteries 21.

[0035] The SOCv calculation unit 112 refers to the table 151 stored in the storage unit 150 and calculates the SOCv as the SOC of the secondary battery 21 that correlates with the OCV of the secondary battery 21. The SOCv calculation unit 112 calculates the SOCv as the SOC of the battery pack 20.

[0036] (Configuration of the SOCi calculation unit 120) The SOCi calculation unit 120 corresponds to the second calculation unit of the estimation device 100. The SOCi calculation unit 120 calculates SOCi as the SOC of the secondary battery 21 based on the cumulative amount ΔI of at least the current value I of the secondary battery 21. SOCi corresponds to the second charge level. The SOCi calculation unit 120 uses the voltage value V of the secondary battery 21 at the time the SOC of the secondary battery 21 was estimated last time as the OCV. The SOCi calculation unit 120 obtains the SOC of the secondary battery 21 that correlates with the OCV of the secondary battery 21 by referring to the table 151. The SOCi calculation unit 120 calculates SOCi by reflecting the SOC corresponding to the cumulative amount ΔI of the current value I associated with the discharge or charge of the secondary battery 21 since the last time the SOC of the secondary battery 21 was estimated, based on the obtained SOC of the secondary battery 21. The SOCi calculation unit 120 calculates SOCi by subtracting the SOC corresponding to the accumulated amount ΔI associated with the discharge of the secondary battery 21 from the SOC of the acquired secondary battery 21. The SOCi calculation unit 120 also calculates SOCi by adding the SOC corresponding to the accumulated amount ΔI associated with the charging of the secondary battery 21 to the SOC of the acquired secondary battery 21. Since the SOCi calculation unit 120 can calculate the SOCi of the secondary battery 21 in various ways, the above method of calculating the SOCi of the secondary battery 21 is just one example.

[0037] As shown in Figure 2, the SoCi calculation unit 120 includes a current integration unit 121 and an SoCi calculation unit 122.

[0038] The current integration unit 121 receives the current value I of the secondary battery 21 from the current measurement unit 32. The current integration unit 121 calculates the integrated amount ΔI by accumulating the current value I of the secondary battery 21 since the most recent (previous) calculation of SOCi. The current integration unit 121 outputs the integrated amount ΔI to the SOCi calculation unit 122.

[0039] The SOCi calculation unit 122 receives the integrated current ΔI of the secondary battery 21 from the current integration unit 121. The SOCi calculation unit 122 receives the most recent (previous) calculated SOC value of the secondary battery 21 from the SOC calculation unit 132 of the SOC estimation unit 130. The full charge capacity Qmax of the secondary battery 21 is received from the storage unit 150. The full charge capacity Qmax of the secondary battery 21 corresponds to the charge capacity Q of the secondary battery 21 when it is new. The SOCi calculation unit 122 calculates SOCi by reflecting the SOC corresponding to the integrated current value I ΔI of the secondary battery 21 associated with discharge or charge since the previous time when the SOC of the secondary battery 21 was estimated, based on the acquired SOC of the secondary battery 21. The SOCi calculation unit 122 calculates SOCi as the SOC of the battery pack 20. The SOCi calculation unit 122 calculates the SOCi of the secondary battery 21 by referring to the integrated current ΔI of the secondary battery 21 obtained from the current integration unit 121, the SOC of the secondary battery 21 obtained from the SOC calculation unit 132, and the full charge capacity Qmax of the secondary battery 21 when new, obtained from the storage unit 150.

[0040] (Configuration of SOC Estimation Unit 130) The SOC estimation unit 130 corresponds to the estimation unit of the estimation device 100. The SOC estimation unit 130 estimates the SOC of the secondary battery 21 by reflecting SOCv and SOCi at different ratios. When estimating the SOC of the secondary battery 21 in plateau region A, the SOC estimation unit 130 reflects SOCi relatively more than SOCv compared to when estimating the SOC of the secondary battery 21 in non-plateau region B. When the SOC estimation unit 130 estimates the SOC of the secondary battery 21 in plateau region A if a certain period of time has elapsed since the previous estimation of the SOC of the secondary battery 21, it also reflects the SOCv of the secondary battery 21 in non-plateau region B. A certain period of time since the previous estimation of the SOC of the secondary battery 21 is, for example, a long period of time such as six months.

[0041] As shown in Figure 2, the SOC estimation unit 130 includes a weighting calculation unit 131 and an SOC calculation unit 132.

[0042] In the embodiment, the weighting calculation unit 131 is particularly applied to the estimation of the SOC in the non-plateau region B of the secondary battery 21. The weighting calculation unit 131 determines whether the SOC input from the SOC calculation unit 132 is within the range of the non-plateau region B of the secondary battery 21 stored in the storage unit 150, and identifies whether the SOC of the secondary battery 21 is in the non-plateau region B.

[0043] The voltage value V of the secondary battery 21 is input to the weighting calculation unit 131 from the voltage measurement unit 31. The current value I of the secondary battery 21 is input to the weighting calculation unit 131 from the current measurement unit 32. The DCR of the secondary battery 21 is input to the weighting calculation unit 131 from the battery control unit 200 of the control device 10 of the secondary battery 21. The temperature T of the secondary battery 21 is input to the weighting calculation unit 131 from the temperature measurement unit 33. The time C is input to the weighting calculation unit 131 from the battery control unit 200 of the control device 10 of the secondary battery 21. The weighting calculation unit 131 calculates the weighting value W of SOCv and SOCi.

[0044] Equation (1) represents a mathematical formula used by the weighting calculation unit 131 to calculate the weighting value W of SOCv and SOCi of the secondary battery 21 with respect to the non-plateau region B of the secondary battery 21.

[0045]

[0046] The weighting calculation unit 131 multiplies the value of (1 + current value I × DCR × Gain2) by the value of Gain1 to obtain the value of (1 + current value I × DCR × Gain2) × Gain1. The weighting calculation unit 131 calculates the reciprocal of {(1 + current value I × DCR × Gain2) × Gain1} as the weighting value W. Gain1 and Gain2 are predetermined maps or coefficients. Gain1 and Gain2 are maps or coefficients for correcting the change in the SOC of the secondary battery 21 due to the temperature T of the secondary battery 21, the degradation rate (SOH: State of Health), etc. When Gain1 and Gain2 are constituted by coefficients, either both or either one of them may be set to 1. Gain1 and Gain2 are stored in the storage unit 150.

[0047] In this embodiment, the SOC calculation unit 132 is particularly applied to the estimation of the SOC in the plateau region A of the secondary battery 21. The SOC calculation unit 132 receives the SOCv of the secondary battery 21 from the SOCv calculation unit 110. The SOC calculation unit 132 receives the SOCi of the secondary battery 21 from the SOCi calculation unit 120. The SOC calculation unit 132 receives the weighted value W of SOCv and SOCi from the weighting calculation unit 131. The SOC calculation unit 132 calculates the SOC of the secondary battery 21 by reflecting the SOCv and SOCi of the secondary battery 21 at different ratios.

[0048] Equation (2) represents the formula used by the SOC calculation unit 132 to calculate the SOC of the secondary battery 21.

[0049]

[0050] The SOC calculation unit 132 multiplies the weighted value W by the value of SOCv. The SOC calculation unit 132 multiplies the value obtained by subtracting the weighted value W from 1 (1-W) by the value of SOCi. The SOC calculation unit 132 calculates the SOC of the secondary battery 21 by adding the value obtained by multiplying the weighted value W and the value of SOCv (W×SOCv) and the value obtained by multiplying the value obtained by subtracting the weighted value W from 1 and the value of SOCi {(1-W)×SOCi}. The SOC of the secondary battery 21 calculated by the SOC calculation unit 132 is output to the battery control unit 200 of the control device 10 of the secondary battery 21.

[0051] (Configuration of SOC Correction Unit 140) The SOC correction unit 140 corresponds to the correction unit of the estimation device 100. The SOC correction unit 140 corrects the plateau region A of the secondary battery 21 based on the usage history of the secondary battery 21. That is, the SOC correction unit 140 changes the range of the plateau region A of the secondary battery 21 based on the usage history of the secondary battery 21, for example, using the SOC as a reference. The SOC correction unit 140 outputs the corrected plateau region A of the secondary battery 21 to the storage unit 150. The usage history of the secondary battery 21 is, for example, the degradation history of the secondary battery 21. The plateau region A of the secondary battery 21 changes as the secondary battery 21 degrades. For example, the plateau region A of the secondary battery 21 shrinks as the secondary battery 21 degrades. In particular, the plateau region A of the secondary battery 21 shrinks in the region where the SOC is relatively high. The reason for this is, for example, the decrease in the upper limit of the SOC due to the decrease in the battery capacity of the secondary battery 21. For this reason, the SOC correction unit 140 corrects the plateau region A of the secondary battery 21 to shrink it, for example, based on the usage history of the secondary battery 21.

[0052] (Configuration of the storage unit 150) The storage unit 150 stores the voltage value V, current value I, and temperature T of the secondary battery 21 measured by the measurement unit 30. The storage unit 150 stores the usage history (degradation history) of the secondary battery 21 obtained from the battery control unit 200. The storage unit 150 stores a table 151 showing the correlation between the SOC and OCV of the secondary battery 21. The storage unit 150 stores the plateau region of the secondary battery 21. The storage unit 150 stores the SOC of the secondary battery 21 corresponding to the plateau region A of the secondary battery 21, and the SOC of the secondary battery 21 corresponding to the non-plateau region B of the secondary battery 21. The storage unit 150 stores data related to the SOC calculated or estimated by the estimation device 100. The storage unit 150 accumulates the stored values ​​in chronological order and updates the stored values ​​by overwriting them.

[0053] (Effects of the SOC estimation device 100 for the secondary battery 21 in the embodiment) The effects of the SOC estimation device 100 for the secondary battery 21 in the embodiment will be explained.

[0054] (1) In one embodiment, the SOC (state of charge) estimation device 100 of the secondary battery 21 is a device that estimates the SOC (state of charge) of the secondary battery 21 in a plateau region A (within a predetermined SOC range). Due to the inclusion of specific positive electrode active material and negative electrode active material in the secondary battery 21, the fluctuation (ΔV) of the voltage value V of the secondary battery 21 in plateau region A is relatively smaller than the fluctuation of the OCV of the secondary battery 21 in a non-plateau region B (outside the predetermined SOC range). The voltage value V of the secondary battery 21 is, for example, the OCV (open circuit voltage). In one embodiment, the estimation device 100 has an SOCv calculation unit 110 (first calculation unit), an SOCi calculation unit 120 (second calculation unit), and an SOC estimation unit 130 (estimation unit). The SOCv calculation unit 110 calculates SOCv (first charge level) as the SOC of the secondary battery 21 based on at least the OCV of the secondary battery 21. The SOCi calculation unit 120 calculates SOCi (second charge rate) as the state of charge (SOC) of the secondary battery 21 based on the cumulative amount ΔI of at least the current value I of the secondary battery 21. When the SOC estimation unit 130 estimates the SOC of the secondary battery 21 in plateau region A, it reflects SOCi relatively more than SOCv compared to when estimating the SOC of the secondary battery 21 in non-plateau region B.

[0055] The estimation device 100 is not limited to a configuration having an SOCv calculation unit 110 (first calculation unit), an SOCi calculation unit 120 (second calculation unit), and an SOC estimation unit 130 (estimation unit). In this case, the estimation device 100 calculates SOCv (first charge level) as the SOC of the secondary battery 21 based on at least the OCV of the secondary battery 21. The estimation device 100 calculates SOCi (second charge level) as the SOC of the secondary battery 21 based on at least the integrated amount ΔI of the current value I of the secondary battery 21. When estimating the SOC of the secondary battery 21 in plateau region A, the estimation device 100 reflects SOCi relatively more than SOCv compared to when estimating the SOC of the secondary battery 21 in non-plateau region B.

[0056] The positive electrode active material of the secondary battery 21 includes at least one of lithium iron phosphate (LFP) and lithium manganese iron phosphate (LMFP), which have the characteristic that the fluctuation of the OCV of the secondary battery 21 in the plateau region A of the secondary battery 21 is relatively smaller than the fluctuation of the OCV of the secondary battery 21 in the non-plateau region B of the secondary battery 21. Therefore, the estimation device 100 can estimate the SOC of the secondary battery 21 with a predetermined accuracy not only when the potential in the plateau region of the positive electrode of the secondary battery 21 is sufficiently plateaued, but also when the potential in the plateau region of the positive electrode of the secondary battery 21 is a plateau with a relatively gentle slope. When the potential of the secondary battery 21 is a plateau with a relatively gentle slope, the weighting of SOCv is relatively increased and the weighting of SOCi is relatively decreased compared to when the potential in the plateau region of the secondary battery 21 is sufficiently plateaued, in order to estimate the SOC of the secondary battery 21. In a specific example, the estimation device 100 estimates the SOC of the secondary battery 21 by setting the weighting of SOCv to, for example, 5% to 10% and the weighting of SOCi to 95% to 90% in the plateau region A of the secondary battery 21.

[0057] The positive electrode active material of the secondary battery 21 contains lithium iron phosphate (LFP). In this case, due to lithium iron phosphate, the potential of the positive electrode of the secondary battery 21 has a plateau region A. Therefore, it is preferable to estimate the state of charge (SOC) of the secondary battery 21 with a predetermined accuracy using the estimation device 100. Lithium iron phosphate has a plateau region A regardless of the time the SOC remains in a relatively low region. Lithium iron phosphate has a plateau region A regardless of the usage history of the secondary battery 21. The usage history of the secondary battery 21 refers to whether the secondary battery 21 is in a new state (BOL: Beginning Of Life) or in a deteriorated state (EOL: End Of Life).

[0058] The positive electrode active material of the secondary battery 21 may include lithium manganese iron phosphate (LMFP). In this case, due to the lithium manganese iron phosphate, the potential of the positive electrode of the secondary battery 21 has a plateau region A. Therefore, it is preferable to estimate the state of charge (SOC) of the secondary battery 21 with a predetermined accuracy using the estimation device 100. Lithium manganese iron phosphate has a plateau region A regardless of the time the SOC remains in a relatively low region. Lithium manganese iron phosphate has a plateau region A regardless of the usage history of the secondary battery 21.

[0059] According to the estimation device 100 with this configuration, in the plateau region A of the secondary battery 21 where the change in SOC with respect to the change in the voltage value V of the secondary battery 21 is relatively small, the SOC of the secondary battery 21 is estimated by reflecting at least a relatively small amount of SOCv based on the voltage value V, while reflecting at least a relatively large amount of SOCi based on the integrated amount ΔI of the current value I. Therefore, according to the estimation device 100, the SOC of the secondary battery 21 can be estimated with a predetermined accuracy even in the plateau region A where the change in SOC with respect to the change in the voltage value V of the secondary battery 21 is relatively small. In other words, when estimating the SOC of the secondary battery 21 in the plateau region A, the estimation device 100 reflects SOCi relatively more than SOCv compared to when estimating the SOC of the secondary battery 21 in the non-plateau region B.

[0060] In one embodiment, the estimation device 100 estimates the SOC of the secondary battery 21 by relatively lowering the weighting of the calculated SOCv and relatively increasing the weighting of the calculated SOCi in the plateau region A of the secondary battery 21. For example, the estimation device 100 estimates the SOC of the secondary battery 21 by setting the weighting of SOCv to 1% and the weighting of SOCi to 99% in the plateau region A of the secondary battery 21. Alternatively, the estimation device 100 estimates the SOC of the secondary battery 21 by setting the weighting of SOCv to 0% and the weighting of SOCi to 100% in the plateau region A of the secondary battery 21. Therefore, the estimation device 100 can estimate the SOC of the secondary battery 21 with a predetermined accuracy even in the plateau region A where the change in SOC with respect to the change in OCV of the secondary battery 21 is relatively small.

[0061] (2) When the SOC estimation unit 130 estimates the SOC of the secondary battery 21 in plateau region A, it gives relatively greater weight to SOCi than to SOCv compared to when estimating the SOC of the secondary battery 21 in non-plateau region B. That is, the SOC estimation unit 130 reflects SOCi relatively more than SOCv by giving relatively greater weight to SOCi (second charge level) than to SOCv (first charge level).

[0062] With this configuration, the SOC estimation unit 130 can reflect SOCv more significantly than SOCi based on a highly versatile method such as weighting.

[0063] (3) The plateau region A of the secondary battery 21 is defined based on the material of the positive electrode active material and the material of the negative electrode active material of the secondary battery 21.

[0064] With this configuration, the positive electrode active material and the negative electrode active material can be defined based on the combination of materials of the positive electrode active material and the negative electrode active material of the secondary battery 21, which is known in advance to reach a plateau in potential. Furthermore, the estimation device 100 can estimate the SOC of the secondary battery 21 with a predetermined accuracy, even in plateau region A where the change in SOC with respect to the change in OCV of the secondary battery 21 is relatively small.

[0065] (4) The negative electrode active material of the secondary battery 21 is one in which the fluctuation of the OCV of the secondary battery 21 in the plateau region A of the secondary battery 21 is equal to or relatively small compared to the fluctuation of the OCV of the secondary battery 21 in the non-plateau region B of the secondary battery 21.

[0066] With this configuration, the potential of the negative electrode of the secondary battery 21 tends to have a plateau region. Therefore, it is preferable to estimate the SOC of the secondary battery 21 with a predetermined accuracy using the estimation device 100. Crystallinity refers to being different from amorphous, for example.

[0067] (5) The negative electrode active material of the secondary battery 21 is one that has the characteristic of causing a relatively large fluctuation in the OCV of the secondary battery 21 in all or part of the non-plateau region B of the secondary battery 21, compared to the positive electrode active material.

[0068] According to the estimation device 100 with this configuration, in all or part of the non-plateau region of the negative electrode of the secondary battery 21, the weighting of SOCv is relatively increased while the weighting of SOCi is relatively decreased to estimate the SOC of the secondary battery 21.

[0069] (6) The negative electrode active material of the secondary battery 21 contains crystalline carbon.

[0070] With this configuration, the potential of the negative electrode of the secondary battery 21 will have a plateau region due to the crystalline carbon. Therefore, it is preferable to estimate the SOC of the secondary battery 21 with a predetermined accuracy using the estimation device 100. Crystallinity refers to being different from amorphous, for example.

[0071] (7) The negative electrode active material of the secondary battery 21 contains graphite.

[0072] With this configuration, the potential of the negative electrode of the secondary battery 21 will have a plateau region due to the presence of graphite. Therefore, it is preferable to estimate the state of charge (SOC) of the secondary battery 21 with a predetermined accuracy using the estimation device 100.

[0073] (8) The estimation device 100 has an SOC correction unit 140 (correction unit). The SOC correction unit 140 corrects the plateau region A of the secondary battery 21 based on the usage history of the secondary battery 21.

[0074] According to the estimation device 100 with this configuration, the State of Cost (SOC) of the secondary battery 21 can be estimated with a predetermined accuracy even when the plateau region A of the secondary battery 21 changes due to the use of the secondary battery 21. The usage history of the secondary battery 21 is, for example, the degradation history of the secondary battery 21.

[0075] (9) When the SOC estimation unit 130 estimates the SOC of the secondary battery 21 in the plateau region A of the secondary battery 21 if a certain period of time has elapsed since the previous estimation of the SOC of the secondary battery 21, it also reflects the SOCv of the secondary battery 21 in the non-plateau region B of the secondary battery 21.

[0076] With an estimation device 100 configured in this way, even if the SOC in plateau region A of the secondary battery 21 has fluctuated over a certain period since the previous estimation, the SOC of the secondary battery 21 in plateau region A can be estimated with a predetermined accuracy by correcting the SOC of the secondary battery 21 by also reflecting the SOCv in non-plateau region B of the secondary battery 21. The reason for this is that, as shown in Figure 1, plateau region A is continuous with non-plateau region B at both ends. For example, the estimation device 100 estimates the SOC of the secondary battery 21 in plateau region A by also reflecting the SOCv of the secondary battery 21 in non-plateau region B adjacent to plateau region A. The certain period since the previous estimation of the SOC of the secondary battery 21 is, for example, a relatively long period of time such as six months.

[0077] (10) The estimation device 100 has a table 151. The voltage value V of the secondary battery 21 is the OCV (open circuit voltage) of the secondary battery 21. The table 151 shows the correlation between the SOC and OCV of the secondary battery 21. The SOCv calculation unit 110 refers to the table 151 and calculates SOCv as the SOC of the secondary battery 21 that correlates with the OCV of the secondary battery 21.

[0078] With the estimation device 100 configured in this way, when estimating the SOC of the secondary battery 21 by reflecting SOCv and SOCi in different ratios, SOCv can be calculated using the above-mentioned highly versatile and general configuration.

[0079] (11) The SOCi calculation unit 120 refers to the table 151 and obtains the SOC of the secondary battery 21 that correlates with the OCV of the secondary battery 21 when the SOC of the secondary battery 21 was estimated last time. The SOCi calculation unit 120 calculates the SOC from the obtained SOC of the secondary battery 21, reflecting the SOC corresponding to the cumulative amount ΔI of the current value I associated with the discharge or charge of the secondary battery 21 since the last time the SOC of the secondary battery 21 was estimated.

[0080] With the estimation device 100 configured in this way, when estimating the SOC of the secondary battery 21 by reflecting SOCv and SOCi in different ratios, SOCi can be calculated using the above-mentioned highly versatile and general configuration.

[0081] (Configuration of the control device 10 for the secondary battery 21 in the embodiment) The configuration of the control device 10 for the secondary battery 21 in the embodiment will be described with reference to Figure 2.

[0082] The embodiment will be described as a control device 10 for a battery pack 20 including multiple secondary batteries 21. The embodiment can also be used as a control device 10 for a single secondary battery 21.

[0083] The control device 10 is a device that estimates the state of charge (SOC) of the secondary battery 21 in plateau region A and controls at least one of the charging or discharging of the secondary battery 21. The control device 10 also estimates the SOC of the secondary battery 21 in non-plateau region B and controls at least one of the charging or discharging of the secondary battery 21.

[0084] The control device 10 includes a device 100 for estimating the state of charge (SOC) of the secondary battery 21 and a battery control unit 200. In other words, the control device 10 includes the estimation device 100. The configuration of the battery control unit 200 included in the control device 10 will be described below.

[0085] (Configuration of the battery control unit 200) The battery control unit 200 controls the charging and discharging of the secondary battery 21 by referring to the result of the SOC estimation of the secondary battery 21 by the SOC estimation unit 130. That is, in the plateau region A of the secondary battery 21, the battery control unit 200 controls the charging and discharging of the secondary battery 21 based on the estimated SOC of the secondary battery 21, which is obtained by relatively lowering the weighting of the calculated SOCv and relatively increasing the weighting of the calculated SOCi. The battery control unit 200 is configured by, for example, a cell control integrated circuit (CCIC), or includes a CCIC.

[0086] (Effects of the control device 10 for the secondary battery 21 in the embodiment) The effects of the control device 10 for the secondary battery 21 in the embodiment will be explained.

[0087] (12) The control device 10 for the secondary battery 21 has the SOC (state of charge) estimation device 100 for the secondary battery 21 described in (1). The control device 10 for the secondary battery 21 controls at least one of the charging or discharging of the secondary battery 21 by referring to the result of the estimation of the SOC of the secondary battery 21.

[0088] (12) In other words, the control device 10 for the secondary battery 21 is, in an embodiment, a device that estimates the SOC (state of charge) in the plateau region A (within a predetermined SOC range) of the secondary battery 21 and controls the charging or discharging of the secondary battery 21. The control device 10 for the secondary battery 21 may be configured as a device that controls at least one of the charging or discharging of the secondary battery 21. In an embodiment, the control device 10 has an estimation device 100 and a battery control unit 200. The control device 10 is not limited to a configuration having an estimation device 100 and a battery control unit 200. The battery control unit 200 controls at least one of the charging or discharging of the secondary battery 21 by referring to the result of the SOC estimation of the secondary battery 21 by the SOC estimation unit 130.

[0089] With a control device 10 configured in this way, when estimating the SOC of the secondary battery 21 in plateau region A, the control device 10 reflects SOCi relatively more than SOCv compared to when estimating the SOC of the secondary battery 21 in non-plateau region B, thereby controlling at least one of the charging or discharging of the secondary battery 21. That is, in plateau region A of the secondary battery 21, the control device 10 relatively lowers the weighting of the calculated SOCv and relatively increases the weighting of the calculated SOCi to estimate the SOC of the secondary battery 21 and controls at least one of the charging or discharging of the secondary battery 21. Therefore, even in plateau region A where the change in SOC with respect to the change in OCV of the secondary battery 21 is relatively small, the control device 10 can estimate the SOC of the secondary battery 21 with a predetermined accuracy and control at least one of the charging or discharging of the secondary battery 21. In other words, the control device 10 can effectively control at least one of the charging or discharging of the secondary battery 21.

[0090] (Configuration of the control device 1 for the secondary battery 21 (power source) of the electric vehicle in the embodiment) The configuration of the control device 1 for the secondary battery 21 (power source) of the electric vehicle in the embodiment will be described with reference to Figure 2.

[0091] The electric vehicle is equipped with a control device 1, a battery pack 20, a measuring unit 30, a switch 40, a power generation unit 50, an inverter 60, an on-board motor 70 (electrical equipment), and a vehicle control unit 80. The battery pack 20 includes a secondary battery 21 which serves as the power source. The vehicle control unit 80 includes a control device 10 for the secondary battery 21.

[0092] The control device 1 includes a control device 10 for the secondary battery 21 and a vehicle control unit 80. That is, the control device 1 includes the control device 10 for the secondary battery 21. In the control device 1, the secondary battery 21 corresponds to a power source that supplies power to electrical equipment. The electrical equipment is, for example, an on-board motor 70 that rotates the tires of an electric vehicle. The electrical equipment may also be, for example, an air conditioner for an electric vehicle.

[0093] The vehicle control unit 80 controls the battery control unit 200, the switch 40, the power generation unit 50, the inverter 60, and the on-board motor 70. The vehicle control unit 80 receives data from the measurement unit 30 regarding the voltage V, current I, and temperature T of the secondary battery 21. The vehicle control unit 80 is composed of, for example, an electronic control unit (ECU) or includes an ECU. The vehicle control unit 80 controls the battery control unit 200, the switch 40, the power generation unit 50, the inverter 60, and the on-board motor 70. The vehicle control unit 80 receives data from the measurement unit 30 regarding the voltage V, current I, and temperature T of the secondary battery 21. The vehicle control unit 80 is composed of, for example, an electronic control unit (ECU) or includes an ECU.

[0094] (Configuration for charging the battery pack 20 in an electric vehicle) When the vehicle control unit 80 connects the first changeover switch 41 of the switch 40 to one connection terminal a1 on the power generation unit 50 side, and the second changeover switch 42 to the other connection terminal a2 on the power generation unit 50 side, the battery pack 20 and the power generation unit 50 are electrically connected. The switch 40 is, for example, a relay. The power generation unit 50 includes a generator. The power generated by the power generation unit 50 is converted to DC and the voltage is adjusted, and then the multiple secondary batteries 21 provided in the battery pack 20 are charged.

[0095] (Configuration concerning the discharge of the battery pack 20 in an electric vehicle) When the vehicle control unit 80 connects the first changeover switch 41 of the switch 40 to one connection terminal b1 on the inverter 60 side, and the second changeover switch 42 to the other connection terminal b2 on the inverter 60 side, the battery pack 20 and the inverter 60 are electrically connected. The DC power discharged from the battery pack 20 is converted to AC by the inverter 60, and after the voltage is adjusted, it is supplied to the on-board motor 70.

[0096] (Effects of the control device 1 for the secondary battery 21 of the electric vehicle in the embodiment) The effects of the control device 1 for the secondary battery 21 of the electric vehicle in the embodiment will be explained with reference.

[0097] (13) The control device 1 for the secondary battery 21 (power source) of an electric vehicle is used in an electric vehicle having an on-board motor 70 (electrical equipment), a secondary battery 21 that supplies power to the on-board motor 70, and a control device 10 for the secondary battery 21. The control device 1 controls at least one of the charging or discharging of the secondary battery 21 of the electric vehicle by the control device 10.

[0098] With the control device 1 configured in this way, in the embodiment, when estimating the SOC of the secondary battery 21 in plateau region A, the control device 1 reflects SOCi relatively more than SOCv compared to when estimating the SOC of the secondary battery 21 in non-plateau region B, thereby controlling at least one of the charging or discharging of the secondary battery 21. That is, in plateau region A of the secondary battery 21, the control device 1 relatively lowers the weighting of the calculated SOCv and relatively increases the weighting of the calculated SOCi to estimate the SOC of the secondary battery 21 and controls at least one of the charging or discharging of the secondary battery 21. Therefore, in controlling the secondary battery 21 of an electric vehicle, the control device 1 can estimate the SOC of the secondary battery 21 with a predetermined accuracy even in plateau region A where the change in SOC with respect to the change in OCV of the secondary battery 21 is relatively small, and control at least one of the charging or discharging of the secondary battery 21. In other words, the control device 1 can effectively control at least one of the charging or discharging of the secondary battery 21, which is the power source of the electric vehicle.

[0099] (Definitions of secondary battery charge rate estimation device, secondary battery control device, and electric vehicle power supply control device) The definitions of secondary battery charge rate estimation device, secondary battery control device, and electric vehicle power supply control device will be explained.

[0100] The secondary battery charge rate estimation device, the secondary battery control device, and the electric vehicle power supply control device may be configured as a single processing device or distributed across two or more processing devices. The secondary battery charge rate estimation device may consist of a first calculation unit, a second calculation unit, and an estimation unit corresponding to the embodiment, which may be configured as a single processing device or distributed across two or more processing devices.

[0101] A processing unit is, for example, a computer, controller, and processor. A computer is equivalent to an electronic computer. A processing unit is composed of, for example, a microprocessing unit (MPU), a central processing unit (CPU), a cell controller integrated circuit (CCIC), a large-scale integrated circuit (LSI), or an integrated circuit (IC).

[0102] The processing unit may be configured by any combination of microprocessing units, central processing units, cell control integrated circuits, large-scale integrated circuits, and integrated circuits. Specifically, the processing unit may be configured by combining a microprocessing unit and a central processing unit. The processing unit may be configured using multiple units of one or more types of microprocessing units, central processing units, cell control integrated circuits, large-scale integrated circuits, and integrated circuits. Specifically, the processing unit may be configured using two microprocessing units. Similarly, the processing unit may be configured using two microprocessing units and one central processing unit.

[0103] (Other Embodiments) The device for estimating the charge level of a secondary battery, the control device for a secondary battery, and the control device for a power supply of an electric vehicle of the present invention are not limited to the configurations described in the embodiments, but can be appropriately configured based on the contents described in the claims.

[0104] The embodiments are described in detail or in a simplified manner to make the present invention easier to understand, and it is not necessary to have all the configurations described, or to have configurations that are not shown. Furthermore, some of the configurations of the embodiments may be deleted, replaced with configurations from other embodiments, or combined with configurations from other embodiments.

[0105] The secondary battery charge rate estimation device and secondary battery control device of the present invention are not limited to configurations applicable to control devices for power sources (secondary batteries) of electric vehicles. The secondary battery charge rate estimation device and secondary battery control device of the present invention may also be configured to be applied to, for example, a control device for a power source (secondary battery) of a stationary facility. A power source (secondary battery) of a stationary facility is, for example, a secondary battery installed in a commercial or industrial facility, or a secondary battery that temporarily stores electricity generated by wind power generation, solar power generation, etc.

[0106] The number of secondary batteries 21 included in the battery pack 20 is not limited. The secondary battery charge rate estimation device and secondary battery control device of the present invention may be a single secondary battery charge rate estimation device and a single secondary battery control device. The power supply control device for an electric vehicle of the present invention may use a single secondary battery as the power source.

[0107] 1 Control device (control device for the power supply (secondary battery 21) of the electric vehicle) 10 Control device (control device for the secondary battery 21) 20 Battery pack 21 Secondary battery (power supply) 30 Measurement unit 31 Voltage measurement unit 32 Current measurement unit 33 Temperature measurement unit 40 Switch 41 First changeover switch 42 Second changeover switch 50 Power generation unit 60 Inverter 70 Onboard motor (electrical equipment) 80 Vehicle control unit 100 Estimation device (device for estimating the charge level of the secondary battery 21) 110 SOCv calculation unit (first calculation unit) 111 OCV estimation unit 112 SOCv calculation unit 120 SOCi calculation unit (second calculation unit) 121 Current integration unit 122 SOCi calculation unit 130 SOC estimation unit (estimation unit) 131 Weighting calculation unit 132 SOC calculation unit 140 SOC Correction Unit (Correction Unit) 150 Storage Unit 151 Table 200 Battery Control Unit A Plateau Region (within a predetermined range of the charge rate of the secondary battery 21) B Non-Plateau Region (outside a predetermined range of the charge rate of the secondary battery 21) V Voltage Value ΔV Voltage Value Fluctuation I Current Value ΔI Cumulative Amount Q Charge Capacity Qmax Full Charge Capacity T Temperature W Weighted Value (of SOCi and SOCv)

Claims

1. A device for estimating the charge level of a secondary battery within a predetermined range, wherein the secondary battery contains a specific positive electrode active material and a negative electrode active material such that the fluctuation of the voltage value of the secondary battery within the predetermined charge level range is relatively smaller than the fluctuation of the voltage value of the secondary battery outside the predetermined charge level range, the positive electrode active material contains at least one of lithium iron phosphate and lithium manganese iron phosphate having the characteristic that the fluctuation of the voltage value of the secondary battery within the predetermined charge level range is relatively smaller than the fluctuation of the voltage value of the secondary battery outside the predetermined charge level range, a first charge level is calculated as the charge level of the secondary battery based on at least the voltage value of the secondary battery, a second charge level is calculated as the charge level of the secondary battery based on at least the cumulative amount of the current value of the secondary battery, and when estimating the charge level of the secondary battery within the predetermined charge level range, the second charge level is reflected relatively more than the first charge level compared to when estimating the charge level of the secondary battery outside the predetermined charge level range.

2. The device for estimating the charge level of a secondary battery according to claim 1, wherein the second charge level is given relatively greater weight than the first charge level, thereby reflecting the second charge level more strongly than the first charge level.

3. The charging rate estimation device for a secondary battery according to claim 1, wherein the predetermined range of charging rates is defined based on the material of the positive electrode active material and the material of the negative electrode active material.

4. The device for estimating the charge level of a secondary battery according to claim 1, wherein the negative electrode active material used has the characteristic that the fluctuation of the voltage value of the secondary battery within the predetermined charge level range is equal to or relatively smaller than the fluctuation of the voltage value of the secondary battery outside the predetermined charge level range.

5. The device for estimating the charge level of a secondary battery according to claim 1, wherein the negative electrode active material has the characteristic of causing a relatively larger fluctuation in the voltage value of the secondary battery in all or part of the range outside the predetermined charge level, compared to the positive electrode active material.

6. The device for estimating the charge level of a secondary battery according to claim 1, wherein the negative electrode active material contains crystalline carbon.

7. The device for estimating the charge level of a secondary battery according to claim 1, wherein the negative electrode active material contains graphite.

8. A device for estimating the charge level of a secondary battery according to claim 1, which corrects the predetermined charge level range based on the usage history of the secondary battery.

9. When estimating the charge level of a secondary battery within a predetermined charge level range, if a certain period of time has elapsed since the previous estimation of the charge level of the secondary battery, the device for estimating the charge level of the secondary battery further reflects the first charge level of the secondary battery outside the predetermined charge level range, as described in claim 1.

10. The device for estimating the charge level of a secondary battery according to claim 1, further comprising a table showing the correlation between the charge level of the secondary battery and the open-circuit voltage, wherein the voltage value of the secondary battery is the open-circuit voltage of the secondary battery, and the first charge level is calculated as the charge level of the secondary battery that correlates with the open-circuit voltage of the secondary battery by referring to the table.

11. The secondary battery charge level estimation device according to claim 1, further comprising a table showing the correlation between the charge level of the secondary battery and the open-circuit voltage, wherein the device obtains the charge level of the secondary battery that correlates with the open-circuit voltage of the secondary battery when the charge level of the secondary battery was previously estimated by referring to the table, and calculates the second charge level from the obtained charge level of the secondary battery, reflecting the charge level corresponding to the cumulative amount of current values ​​associated with the discharge or charge of the secondary battery since the previous time when the charge level of the secondary battery was estimated.

12. A control device for a secondary battery, comprising a device for estimating the charge level of a secondary battery as described in claim 1, and controlling at least one of charging or discharging the secondary battery by referring to the result of estimating the charge level of the secondary battery.

13. A power supply control device for an electric vehicle, which includes an electrical device, a power supply that supplies power to the electrical device, and a secondary battery control device as described in claim 12, wherein the power supply includes the secondary battery, and the secondary battery is controlled by the control device of the secondary battery.

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