JP6156216B2 - Full charge capacity estimation device - Google Patents

Description

  The present invention relates to a full charge capacity estimation device that estimates the full charge capacity of a battery that decreases with charge and discharge.

  The battery deteriorates with repeated charging and discharging, and the full charge capacity, which is the capacity that can be charged before the fully discharged battery is fully charged, decreases. Therefore, in order to grasp the deterioration state of the battery, it is necessary to estimate the full charge capacity with high accuracy.

  In Patent Document 1, a first SOC (State of Charge) is determined from a first no-load voltage (OCV), and a second SOC is determined from a second OCV. Furthermore, the battery capacity change value is calculated from the integrated value of the charge / discharge current between the first no-load timing and the second no-load timing. In Patent Document 1, the full charge capacity is calculated by dividing the capacity change value by the difference between the first SOC and the second SOC.

JP 2008-261669 A

  Among batteries, there is a battery having a region where the amount of change in OCV with respect to SOC is small, such as an olivine battery. In such a battery, it is difficult to determine a plurality of SOCs from the correlation between OCV and SOC unless charging and discharging are performed to near full charge or complete discharge. It is difficult to calculate the full charge capacity.

  In view of the above circumstances, the present invention mainly aims to provide a full charge capacity estimation device capable of estimating the full charge capacity of a battery even in a battery having a region where the amount of change in OCV relative to the SOC is small. And

  In order to solve the above-mentioned problem, the invention according to claim 1 is a full-charge capacity estimation device for estimating a full-charge capacity of a lithium secondary battery, wherein the voltage of the battery is sequentially measured when the battery is charged. And a remaining capacity estimating means for estimating a remaining capacity of the battery at a predetermined time based on a time change rate of the voltage calculated from the above, and estimating a chargeable capacity of the battery at the predetermined time when the battery is charged. A full charge capacity estimation for estimating a full charge capacity at the predetermined time from a possible capacity estimation means, the remaining capacity estimated by the remaining capacity estimation means, and the chargeable capacity estimated by the possible capacity estimation means Means for estimating the chargeable capacity based on the voltage of the battery sequentially measured when the battery is charged.

  According to the present invention, when the battery is charged, the remaining capacity at a predetermined time is estimated based on the calculated time change rate of the battery voltage. Here, even when charging is performed in a region where the amount of change in OCV with respect to SOC is small, if a current flows through the lithium secondary battery during charging, the battery voltage varies with time during charging depending on the chargeable capacity at the start of charging. do. Therefore, the chargeable capacity can be estimated based on the battery voltage sequentially measured during charging. Then, the full charge capacity at a predetermined time is estimated from the estimated remaining capacity and chargeable capacity.

  Therefore, even for a battery having a region where the amount of change in OCV relative to the SOC is small, the remaining capacity and the chargeable capacity can be estimated during charging, and the full charge capacity of the battery can be estimated with high accuracy.

The figure which shows the structure of the full charge capacity estimation apparatus which concerns on this embodiment. The figure which shows the full charge capacity which changes with repetition of charge. The figure which shows the remaining capacity and chargeable capacity | capacitance of a predetermined time. The figure which shows the charge characteristic of the deteriorated battery voltage and remaining capacity. The figure which shows the time change rate of the battery voltage during charge. The figure which shows the lithium concentration contained in the positive electrode active material before charge and during charge. The figure which shows the time change of the battery voltage during charge. The figure which shows a battery reaction model. The flowchart which shows the process sequence which calculates chargeable capacity.

  Hereinafter, an embodiment in which a full charge capacity estimation device is embodied will be described with reference to the drawings. First, the configuration of the battery control device (full charge capacity estimation device) according to the present embodiment will be described with reference to FIG. In the present embodiment, the battery control device 100 estimates the full charge capacity of the assembled battery 400.

  The assembled battery 400 is configured by connecting battery cells 40 in series. Each battery cell 40 is a lithium secondary battery. In the present embodiment, each battery cell 40 is an olivine-based lithium ion secondary battery in which the positive electrode active material includes at least one lithium metal phosphate having an olivine structure. Examples of the lithium metal phosphate include LiMnPO4, LiFePO4, LiCoPO4, and LiNiPO4. The active material of the negative electrode is not particularly limited, and examples thereof include carbon materials such as graphite and coke, lithium metal, and titanium oxide.

  The current sensor 41 sequentially measures the current flowing through each battery cell 40. Moreover, the voltage sensor 42 measures the voltage between terminals of each battery cell 40 sequentially. The current value and voltage value measured by the current sensor 41 and the voltage sensor 42 are transmitted to the battery control device 100.

  The battery control device 100 is a computer including a CPU, a ROM, a RAM, an I / O, and the like. The battery control apparatus 100 estimates the remaining capacity, the chargeable capacity, and the full charge capacity, which are absolute amounts of the capacity that can be discharged, using the measured current value and voltage value, and uses the estimated full charge capacity. Control charging / discharging of the battery pack 400. In the following, the absolute amount of capacity that can be discharged is referred to as the remaining capacity (Ah), and the ratio of the remaining capacity to the full charge capacity is referred to as SOC (%).

  In the battery control device 100, the remaining capacity estimation means 10, the chargeable capacity estimation means 20, and the full charge capacity estimation means 30 are realized by the CPU executing a program stored in a ROM or the like.

  FIG. 2 shows the characteristics of the capacity of the battery cell 40 with respect to the potentials of the positive electrode and the negative electrode of the battery cell 40. The capacity of the battery cell 40 corresponds to the average lithium concentration of each of the positive electrode active material and the negative electrode active material. The larger the capacity, the lower the average lithium concentration of the positive electrode active material and the higher the average lithium concentration of the negative electrode active material. The difference between the positive electrode potential and the negative electrode potential is the OCV of the battery cell 40. The hatched portion represents a capacity that cannot be used for charging / discharging the battery cell 40.

  In the battery cell 40, the full charge capacity Ca (Ah) is determined from the lithium concentrations of the positive electrode and the negative electrode at the time of manufacture before the first charge (see FIG. 2A). When the battery cell 40 is charged for the first time, lithium is consumed to form the inactive region (Solid Electrolyte Interface) at the negative electrode, and the capacity characteristic with respect to the positive electrode potential is in the inactive region with respect to the negative electrode characteristic. The capacity is shifted by X1 (Ah). As a result, the full charge capacity is reduced by the capacity X1 (Ah) of the inactive region and becomes Ca-X1 (Ah) (see FIG. 2B).

  Further, when charging is repeated, the capacity of the inactive region increases to X2 (Ah), the amount of deviation of the positive electrode characteristic from the negative electrode characteristic also increases, and the full charge capacity becomes Ca-X2 (Ah). That is, the battery cell 40 deteriorates while repeating charge and discharge, and the full charge capacity gradually decreases. Therefore, the full charge capacity of the battery cell 40 represents the deterioration state of the battery cell 40.

  The battery control device 100 needs to grasp the deterioration state of the battery cell 40 in order to restrict the use of the battery cell 40 according to the deterioration state of the battery cell 40. Therefore, the battery control apparatus 100 estimates the full charge capacity of the battery cell 40 using the remaining capacity estimation means 10, the chargeable capacity estimation means 20, and the full charge capacity estimation means 30.

  As shown in FIG. 3, the full charge capacity at the current position (predetermined time) includes the remaining capacity that can be discharged at the current position (capacity A1 in FIG. 3) and the chargeable capacity that can be charged at the current position (FIG. 3). 3 capacity A2). Here, even when the remaining capacity is the same, the chargeable capacity of the battery cell 40 after deterioration is smaller than the chargeable capacity of the battery cell 40 before deterioration. The chargeable capacity corresponds to the average lithium concentration in the positive electrode active material at the current position.

  The average lithium concentration in the positive electrode active material is the concentration of lithium that can move from the positive electrode to the negative electrode. Even if the remaining capacity is the same, the average lithium concentration α in the positive electrode active material in the battery cell 40 after deterioration is consumed in the formation of the inactive region. Lower than the average lithium concentration β. Therefore, even when the remaining capacity is the same, the chargeable capacity of the battery cell 40 after deterioration is smaller than the chargeable capacity of the battery cell 40 after deterioration.

  The remaining capacity estimating means 10 estimates the remaining capacity of the battery cell 40 at a predetermined time based on the time change rate of the battery voltage calculated from the battery voltage measured sequentially when the battery cell 40 is charged. Details of the remaining capacity estimation method will be described later. The chargeable capacity estimation means 20 includes a calculation means 21, an update means 22, and a conversion means 23, and estimates the chargeable capacity at a predetermined time based on the battery voltage measured sequentially when the battery cell 40 is charged. To do. Details of the method for estimating the chargeable capacity will be described later. The full charge capacity estimation means 30 calculates the full charge capacity at the predetermined time by adding the remaining capacity at the predetermined time and the chargeable capacity at the predetermined time.

<Residual capacity estimation>
Next, a method for estimating the remaining capacity by the remaining capacity estimating means 10 will be described. As shown in FIG. 4, when the battery cell 40 deteriorates, in the charging characteristics of the remaining capacity with respect to the battery voltage, a steep region where the battery voltage rapidly increases moves in parallel to the side where the remaining capacity decreases. In the region surrounded by the square in FIG. 4, that is, on the side where the remaining capacity is smaller than the steep region where the battery voltage rapidly increases, the charging characteristics of the remaining capacity with respect to the battery voltage do not change.

  As shown in FIG. 3, when the battery cell 40 is deteriorated, the capacity characteristic with respect to the positive electrode potential is smaller than the capacity before the deterioration with respect to the specification of the capacity with respect to the negative electrode potential. This is to shift to the side.

  When the battery cell 40 is charged in a flat region where the change amount of the battery voltage in the charge characteristic is smaller than a predetermined amount, the battery cell 40 has a characteristic that the time change rate ΔV of the battery voltage varies. In the flat region, there is at least one range in which the time change rate ΔV of the battery voltage exceeds the second threshold value. This range is a unique range of the battery cell 40 that does not vary even when the battery cell 40 is deteriorated. As shown in FIG. 5, the time until the time change rate ΔV of the battery voltage becomes larger than the second threshold differs depending on the remaining capacity at the start of charging. In the present embodiment, a predetermined remaining capacity is associated with the second threshold value in advance.

  The remaining capacity estimating means 10 estimates the remaining capacity of the battery cell 40 at a predetermined time based on the time change rate ΔV of the voltage calculated from the battery voltage measured sequentially when the battery cell 40 is charged. In addition, the voltage measured sequentially is a closed circuit voltage (CCV: Closed Circuit Voltage).

  Specifically, the remaining capacity estimation means 10 estimates the remaining capacity corresponding to the second threshold as the remaining capacity at a predetermined time when the time change rate ΔV of the measured CCV becomes larger than the second threshold. (See JP2012-173048).

<Estimated chargeable capacity>
Next, a method for estimating the chargeable capacity by the chargeable capacity estimation means 20 will be described. As shown in FIG. 6A, the lithium concentration of the positive electrode active material is uniformly distributed before charging when no current flows through the battery cell 40. Therefore, the average lithium concentration in the positive electrode active material is equal to the surface lithium concentration on the surface of the positive electrode active material.

  On the other hand, as shown in FIG. 6B, when a current is passed through the battery cell 40 during charging, lithium ions move from the positive electrode active material to the negative electrode active material. Since the battery reaction occurs from the surface of the positive electrode active material, the surface lithium concentration of the positive electrode active material rapidly decreases during charging. On the other hand, the average lithium concentration in the positive electrode active material immediately after charging changes gradually. That is, at the time of charging, even if the chargeable capacity is hardly reduced, the surface lithium concentration greatly changes.

  The relationship between the surface lithium concentration of the positive electrode active material of the battery cell 40 and the surface potential of the positive electrode is the same as the relationship between the average lithium concentration of the positive electrode active material and the potential of the positive electrode shown in FIG. Further, the relationship between the surface lithium concentration of the negative electrode active material of the battery cell 40 and the surface potential of the negative electrode is the same as the relationship between the average lithium concentration of the negative electrode active material and the potential of the negative electrode shown in FIG. The difference between the surface potential of the positive electrode and the surface potential of the negative electrode is the CCV of the battery cell 40 during charging.

  When the battery cell 40 is deteriorated, the capacity characteristic with respect to the positive electrode potential shifts to a smaller capacity than before the deterioration. Therefore, on the positive electrode side, during the charging, the battery cell 40 that has deteriorated shifts earlier to a steep region where the positive electrode potential rapidly increases than the battery cell 40 that has not deteriorated. On the other hand, on the negative electrode side, the battery cell 40 that has deteriorated and the battery cell 40 that has not deteriorated during charging are shifted to a region where the capacity characteristics with respect to the negative electrode potential are flat.

  Therefore, a change in the surface lithium concentration of the positive electrode active material during charging appears as a change in the CCV of the battery cell 40 during charging. Therefore, by supplying a current to the battery cell 40, the CCV of the battery cell 40 can be changed with almost no change in the state of charge. And CCV of the battery cell 40 at the time of charge changes with different time with the average lithium concentration of the positive electrode active material in the present position. Therefore, the average lithium concentration of the positive electrode active material at the current position can be estimated based on the time change of the CCV of the battery cell 40 during charging.

  In FIG. 7, the average lithium concentration of the positive electrode active material at the current position is α and β (α <β), and the time variation of the calculated value of CCV when charging is performed from the current position is shown by a broken line and a one-dot chain line, respectively. It shows with. Moreover, the time change of the measured value of CCV at the time of charging from the present position is shown by a solid line.

  For about 2 seconds after the start of charging, both CCVs having the average lithium concentrations α and β are present in a flat region of the characteristics of the positive electrode potential with respect to the surface lithium concentration, so there is almost no difference in CCV. After about 2 seconds from the start of charging, the CCV with an average lithium concentration α shifts to a region where the characteristics of the positive electrode potential with respect to the surface lithium concentration are steep, so the difference between the two CCVs widens. In this case, since the measured value of CCV coincides with the time change of the calculated value of CCV where the average lithium concentration is α, the average lithium concentration of the positive electrode active material at the current position can be estimated as α.

  In the present embodiment, the chargeable capacity estimation means 20 sets an initial value of the average lithium concentration at the current position, the CCV of the battery cell 40 measured at the time of charging, the current flowing through the battery cell 40, the battery reaction model, Is used to correct the initial value to the true average lithium concentration.

  Specifically, the calculation means 21 sets the average lithium concentration in the positive electrode active material as an initial value, and sequentially calculates the surface lithium concentration on the surface of the positive electrode active material from the average lithium concentration, the sequentially measured current, and the battery reaction model. To do. Furthermore, the calculation means 21 calculates CCV sequentially from the surface lithium concentration calculated sequentially.

  The updating unit 22 sequentially updates the average lithium concentration so that the difference between the CCV sequentially calculated by the calculating unit 21 and the CCV measured at that time becomes small, and the estimated CCV and the measured CCV Is made smaller than the first threshold.

  The conversion means 23 converts the average lithium concentration (mol / m 3) updated by the update means 22 into a chargeable capacity (Ah) when the CCV difference becomes smaller than the first threshold. During charging, the average lithium concentration does not change rapidly but changes somewhat. Therefore, the conversion means 23 corrects the average lithium concentration updated by the update means 22 to the average lithium concentration at the current position when the CCV difference becomes smaller than the first threshold value, and then converts the average lithium concentration to the chargeable capacity. It is good to convert.

  For example, in FIG. 7, when the initial value of the average lithium concentration is β, the initial value β, the current measured at the first time, and the battery reaction at the first time after several seconds (2 seconds or more) have elapsed from the start of charging. From the model, the current surface lithium concentration and CCV are estimated. The estimated CCV is compared with the CCV measured at that time. When the initial value β is equal to the true average lithium concentration, the CCV estimated at the first time point is equal to the measured CCV. However, when the true average lithium concentration is α, the CCV estimated at the first time point is smaller than the measured CCV.

  In this case, the initial value β is updated to a value that decreases so that the estimated CCV approaches the measured CCV, that is, the estimated CCV increases. Then, from the updated average lithium concentration, the current measured at the second time after the first time, and the battery reaction model, the surface lithium concentration and CCV at the second time are estimated, and the estimated CCV and the measured CCV Compare again. This is repeated so that the difference between the estimated CCV and the measured CCV is smaller than the first threshold value. Furthermore, when the CCV difference becomes smaller than the first threshold, the updated average lithium concentration is corrected to the average lithium concentration at the current position, and then converted into a chargeable capacity. Thus, the chargeable capacity at the current position can be estimated based on the behavior of CCV during charging.

  Next, an example of a battery reaction model will be briefly described with reference to FIG. FIG. 8A shows an outline of the internal configuration of the battery cell 40. Battery cell 40 includes a positive electrode, a separator, and a negative electrode. The separator is configured by infiltrating an electrolytic solution into a resin provided between the positive electrode and the negative electrode. Each of the positive electrode and the negative electrode is composed of an aggregate of spherical active materials. On the interface of the positive electrode active material, a chemical reaction that absorbs lithium ions and electrons is performed during discharging, and a chemical reaction that releases lithium ions and electrons is performed during charging. On the other hand, on the interface of the negative electrode active material, a chemical reaction that releases lithium ions and electrons is performed during discharging, and a chemical reaction that absorbs lithium ions and electrons is performed during charging. Charging current or discharging current is generated by the exchange of lithium ions through the separator.

  FIG. 8B shows a battery reaction model used for actually calculating the behavior inside the battery cell 40. In this battery reaction model, the positive electrode and the negative electrode are each represented by a single spherical active material having characteristics obtained by averaging an aggregate of active materials in order to reduce the calculation load. FIG. 8C shows a governing equation between the liquid phase, the solid phase, the solid phase and the liquid phase, and a relational expression between the voltage and current of the battery cell 40. FIG. 8D shows a list of variables and constants used in each equation of FIG.

  Equation (1) is an equation that defines the current flowing through the liquid phase portion, and Equation (2) is an equation that defines the balance of lithium ions in the liquid phase portion. Equation (3) is an equation that defines the current flowing through the solid phase portion, and Equation (4) is a diffusion equation that defines the concentration distribution of lithium in the solid phase portion. Equation (5) is an equation that defines the Faraday current between the solid phase and the liquid phase, and Equation (6) is an equation that defines the current balance between the solid phase and the liquid phase. Expression (7) is a relational expression between the voltage of the battery cell 40 and the current flowing through the battery cell 40. The initial values at the start of discharge are given to the formulas (1) to (6), and the formulas (1) to (6) are collectively solved at predetermined time intervals to calculate the surface lithium concentration.

  Next, a processing procedure for calculating the chargeable capacity of the battery cell 40 will be described with reference to the flowchart of FIG. This processing procedure is executed by the chargeable capacity estimation unit 20 at predetermined intervals. The chargeable capacity estimation means 20 starts executing this processing procedure when the remaining capacity is estimated by the remaining capacity estimation means 10.

  First, the surface lithium concentration at this time is calculated from the initial value of the average lithium concentration, the current measured at this time, the temperature of the battery cell 40 measured at this time by a temperature sensor (not shown), and the battery reaction model. (S10). The initial value of the average lithium concentration may be the average lithium concentration determined by executing this process last time or may be set to an appropriate value. Further, the temperature of the battery cell 40 may be a predetermined value instead of the measured value measured sequentially.

  Subsequently, an estimated CCV at this time is calculated from the surface lithium concentration calculated in S10, the measured current, the measured temperature, and the battery reaction model (S11). Subsequently, a voltage error ΔVn (n is the number of loops in this flowchart) = measured CCV−estimated CCV is calculated from the CCV measured at this time and the estimated CCV estimated in S11 (S12).

  Subsequently, it is determined whether or not to correct the average lithium concentration (S13). Specifically, it is determined whether or not the absolute value of the voltage error ΔVn calculated in S12 is greater than or equal to a determination value (first threshold). When the absolute value of the voltage error ΔVn is larger than the determination value (S13: YES), the difference between the average lithium concentration used for calculating the estimated CCV and the true lithium concentration is large, so the average lithium concentration is corrected ( S14). Specifically, the average lithium concentration is increased or decreased by αn = 2% × n. When the voltage error ΔVn is positive, the average lithium concentration is higher than the true average lithium concentration, so that the average lithium concentration is corrected so as to decrease by αn. When the voltage error ΔVn is negative, the average lithium concentration is lower than the true average lithium concentration, so that the average lithium concentration is corrected to increase by αn. Subsequently, n is incremented by 1 (S15), and the processes of S10 to S13 are repeatedly executed.

  On the other hand, when the absolute value of the voltage error ΔVn is equal to or smaller than the determination value (S13: NO), the difference between the average lithium concentration used for calculating the estimated CCV and the true lithium concentration is small. The average lithium concentration is determined as the true lithium concentration (S16). This process is complete | finished above.

  Thereafter, the average lithium concentration determined in S16 is corrected to the average lithium concentration at the current position based on the current that flows from the start of charging until the average lithium concentration is determined in S16, and then the chargeable capacity is obtained. Convert.

  According to this embodiment described above, the following effects are obtained.

  According to the present invention, when the battery cell 40 is charged, the remaining capacity at the current position is estimated based on the calculated time change rate of the CCV. Here, even when charging is performed in a region where the change amount of the OCV with respect to the SOC is small, when a current flows through the battery cell 40, the CCV changes with time during charging depending on the chargeable capacity at the start of charging. Therefore, the chargeable capacity can be estimated based on the battery voltage sequentially measured during charging. Then, the full charge capacity at a predetermined time is estimated from the estimated remaining capacity and chargeable capacity. Therefore, even if the battery cell 40 has a region where the amount of change in the OCV with respect to the SOC is small, the remaining capacity and the chargeable capacity can be estimated during charging, and the full charge capacity of the battery cell 40 can be estimated with high accuracy. it can.

  The average lithium concentration in the positive electrode active material is set as an initial value, and the CCV during charging is sequentially calculated based on the average lithium concentration. Then, the average lithium concentration set as the initial value is a true average so that the voltage error between the calculated CCV during charging and the measured CCV during charging is smaller than the first threshold value. Updated to approach lithium concentration. Furthermore, since the average lithium concentration in the positive electrode active material corresponds to the chargeable capacity, the chargeable capacity can be estimated by converting the updated average lithium concentration.

  From the average lithium concentration at a certain point in time, the measured current, and the battery reaction model, the surface lithium concentration at a certain point in time and the CCV are calculated. Then, the average lithium concentration at the next time is updated so that the voltage error between the calculated CCV at the certain time and the measured CCV at the certain time becomes small. In this way, the average lithium concentration is updated sequentially. Then, when the voltage error between the calculated CCV and the measured CCV becomes smaller than the first threshold, the updated average lithium concentration is converted into the chargeable capacity. Thereby, the chargeable capacity can be estimated from the average lithium concentration approaching the true lithium concentration at the current position.

  ・ The average lithium concentration during charging does not change rapidly, but changes somewhat. Therefore, when the difference between the calculated CCV and the measured CCV becomes smaller than the first threshold value, the updated average lithium concentration is corrected to the average lithium concentration at the current position. Thereby, the full charge capacity can be estimated by estimating the average lithium concentration at the current position with higher accuracy.

  -Even if it is the battery cell 40 which has the area | region where the variation | change_quantity of OCV with respect to SOC is small, there exists a location where the time change rate of CCV becomes larger than a 2nd threshold value. Therefore, when the time change rate of CCV becomes larger than the second threshold, the remaining capacity can be estimated with high accuracy.

(Other embodiments)
-Prepare a map of CCV time change during charging according to the average lithium concentration at the current position and the current during charging, and compare the voltage measured sequentially during charging with the map to determine the current position. The average lithium concentration at may be estimated. Furthermore, you may use the map of the time change of CCV at the time of charge according to the average lithium density | concentration in the present position, the electric current at the time of charge, and the temperature of the battery cell 40. FIG.

  -Battery cell 40 should just be not only an olivine type | system | group but a lithium secondary battery. The battery control device 100 can be applied to any lithium secondary battery.

  DESCRIPTION OF SYMBOLS 10 ... Remaining capacity estimation means, 20 ... Chargeable capacity estimation means, 21 ... Calculation means, 22 ... Update means, 23 ... Conversion means, 30 ... Full charge capacity estimation means, 40 ... Battery cell, 100 ... Battery control apparatus.

Claims (4)

A full charge capacity estimation device (100) for estimating a full charge capacity of a lithium secondary battery (40), comprising:
A remaining capacity estimating means (10) for estimating a remaining capacity of the battery at a predetermined time based on a time change rate of the voltage calculated from the voltage of the battery measured sequentially when the battery is charged;
A possible capacity estimating means (20) for estimating a chargeable capacity of the battery at the predetermined time when charging the battery;
A full charge capacity estimation means (30) for estimating a full charge capacity at the predetermined time from the remaining capacity estimated by the remaining capacity estimation means and the chargeable capacity estimated by the possible capacity estimation means; With
The possible capacity estimating means estimates the chargeable capacity based on the battery voltage sequentially measured when the battery is charged ,
The possible capacity estimation means includes
Calculating means (21) for setting an average lithium concentration in the positive electrode active material of the battery as an initial value, and sequentially calculating the voltage at the time of charging the battery based on the average lithium concentration;
Updating means (22) for updating the average lithium concentration so that a difference between the voltage calculated by the calculating means and the measured voltage is smaller than a first threshold;
A full charge capacity estimation device comprising: conversion means (23) for converting the average lithium concentration updated by the update means into the chargeable capacity. The calculating means sequentially calculates the surface lithium concentration on the surface of the positive electrode active material of the battery from the average lithium concentration, the measured current flowing through the battery, and a battery reaction model, and calculates the voltage from the calculated surface lithium concentration. Calculate sequentially,
The updating means sequentially updates the average lithium concentration so that a difference between the voltage sequentially calculated by the calculating means and the voltage measured at that time becomes small,
The full charge capacity estimation device according to claim 1 , wherein the conversion means converts the average lithium concentration updated by the update means into the chargeable capacity when the difference becomes smaller than the first threshold value. . The conversion means corrects the average lithium concentration updated by the updating means to the average lithium concentration at the predetermined time when the difference becomes smaller than the first threshold, and then the chargeable capacity. The full charge capacity estimation device according to claim 1 or 2 , wherein The battery has a characteristic that a time change rate of the voltage fluctuates when charging in a region where a change amount of the battery voltage with respect to a remaining capacity is smaller than a predetermined amount,
The remaining capacity estimating means sets the remaining capacity corresponding to the second threshold as the remaining capacity at the predetermined time when the time change rate of the measured voltage becomes larger than a second threshold. full charge capacity estimating apparatus according to any one of claims 1-3.

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