JP2019113414A - Secondary battery degradation degree measuring device - Google Patents

Abstract

To provide a secondary battery degradation degree measuring device for estimating the degradation index of a secondary battery unit composed of a plurality of unit cells.SOLUTION: Provided is a secondary battery degradation degree measuring device for measuring the degradation degree of a secondary battery part (20) composed by connecting a plurality of unit cells (4n), comprising: a voltage sensor (7) for measuring the voltage of each of the plurality of unit cells; a discharge completion detection part (19) for detecting that there exists a unit cell, among the plurality of unit cells, that has reached a prescribed discharge completion voltage; a unit cell specification part (14) for specifying a specific unit cell (4c), among the plurality of unit cells, whose voltage is highest when the discharge completion voltage is reached; a degradation index estimation part (16) for estimating the degradation index of the specific unit cell specified by the unit cell specification part; a residual capacity calculation part (17) for computing a residual capacity at discharge completion time of the specific unit cell specified by the unit cell specification part; and a battery capacity calculation part (15) for calculating the degradation index of the secondary battery unit on the basis of the degradation index of the specific unit cell estimated by the degradation index estimation part and the residual capacity of the specific unit cell computed by the residual capacity calculation part.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an apparatus for measuring the degree of deterioration of a secondary battery, and more particularly to a technique for estimating a deterioration index of a secondary battery unit constituted by a plurality of single cells.

SOH (State Of Health), which is the ratio of the current full charge capacity to the full charge capacity at the time of a new product, is widely known as a deterioration index representing the degree of deterioration of the secondary battery.
This deterioration index SOH can be obtained, for example, by charging the secondary battery from the state of battery remaining capacity 0 to full charge, measuring the actual full charge capacity and dividing by the full charge capacity at the time of new product. However, in order to estimate the deterioration index, it is necessary to charge from the state of the remaining battery capacity 0 to the full charge, and there is a problem that the time required for the estimation becomes significantly long.

  Therefore, various methods have been proposed to estimate the deterioration indicator of the secondary battery by suppressing the time required for the estimation. For example, from the voltage value of the feature point appearing on the differential curve V-dQ / dV within the predetermined battery voltage V range, specifically, the voltage value of the maximum point which is the peak portion of the peak shape, The reduction rate is determined (Patent Document 1).

JP, 2013-19709, A

  However, in the technology disclosed in Patent Document 1 described above, the voltage of a secondary battery unit configured by including a plurality of secondary batteries (hereinafter referred to as single cells) is measured. Variations are not taken into account. That is, the full charge capacity after deterioration of the entire secondary battery unit having a plurality of single cells starts charging when any one of the plurality of single cells has a remaining battery capacity of 0, and among the plurality of single cells Since the charge amount when any one is charged to the full charge is obtained, it may be different from the full charge capacity defined by a specific cell. Therefore, it has been difficult to accurately estimate the SOH of the secondary battery unit.

  This invention is made in view of such a subject, The place made as the objective is the secondary battery which can estimate the degradation index of the secondary battery unit comprised with several cells accurately. It is providing a degradation degree measuring apparatus.

  In order to achieve the above object, the apparatus for measuring the degree of deterioration of a secondary battery according to the present invention is a apparatus for measuring the degree of deterioration of a secondary battery that measures the degree of deterioration of a secondary battery unit configured by connecting a plurality of single cells. And detecting, among the plurality of single cells measured by the voltage sensor, the presence of a single cell which has reached a predetermined discharge completion voltage, among the plurality of single cells measured by the voltage sensor. A discharge completion detection unit, a cell identification unit that identifies a specific cell with the highest voltage when the discharge completion voltage is reached among the plurality of cells by the discharge completion detection unit, and the cell identification unit A deterioration index estimation unit that estimates a deterioration index of the specified single battery, a remaining capacity calculation unit that calculates a remaining capacity at the time of discharge completion of the specified single battery specified by the cell specification unit, and the deterioration index estimation Depending on the department A battery capacity calculating unit that calculates a deterioration indicator of the secondary battery unit based on the estimated deterioration indicator of the specific battery and the remaining capacity of the specific battery calculated by the remaining capacity calculating unit; I assume.

  Thereby, when there is a single battery that has reached the discharge completion voltage among the plurality of single batteries, the specific single battery with the highest voltage is identified, and the deterioration indicator of the specific single battery estimated by the deterioration indicator estimation unit By calculating the deterioration index of the secondary battery unit based on the remaining capacity at the time of discharge completion of the specific cell calculated by the remaining capacity calculation unit, there is a single cell at the discharge completion time of the secondary battery unit It is possible to estimate the substantial chargeable / dischargeable range from when the discharge completion detection unit detects that the specific cell is fully charged, that is, the deterioration index in consideration of the variations of the plurality of single cells It is assumed.

  In addition, preferably, a current sensor that measures an input / output current of each of the plurality of unit cells is provided, and the deterioration index estimation unit charges the secondary battery unit detected by the voltage sensor and the current sensor. The degradation index of the specific single battery is estimated based on the change of the voltage and the input / output current of the specific single battery, and the remaining capacity calculation unit determines the degradation index of the specific single battery estimated by the degradation index estimation unit. And any one of the cells reached the discharge completion voltage based on the open circuit voltage of the specific cell when any of the cells of the secondary battery unit reached the discharge completion voltage It is preferable to calculate the remaining capacity of the specific unit cell at that time.

Thus, the deterioration indicator of the specific battery and the discharge completion voltage of any battery of the secondary battery unit estimated based on the change in the voltage and the input / output current of the specific battery when charging the secondary battery unit The deterioration index of the secondary battery unit can be accurately estimated by calculating the remaining capacity of the specific single battery based on the open circuit voltage of the specific single battery at the time of reaching.
Preferably, the battery capacity calculation unit calculates the current full charge capacity of the specific cell based on the deterioration index of the specific cell estimated by the deterioration index estimation unit, and the battery capacity calculation unit calculates the current full charge capacity of the specific cell. It is preferable to estimate the deterioration index of the secondary battery unit based on the value obtained by subtracting the remaining capacity of the specific single battery calculated by the remaining capacity calculating unit.

  Thereby, from the current full charge capacity of the specific cell based on the deterioration index of the specific cell estimated by the deterioration index estimation unit, the specific unit when any cell of the secondary battery unit reaches the discharge completion voltage The deterioration index of the secondary battery unit can be accurately estimated by actually calculating the chargeable / dischargeable capacity of the secondary battery unit based on the value obtained by subtracting the remaining capacity of the battery.

In addition, preferably, the deterioration index estimation unit is a ratio dV of a voltage V of the specific cell and a variation dV of the voltage V of the specific cell to a variation dQ of the battery capacity Q of the specific cell. It is preferable to estimate the deterioration index of the specific single battery based on the voltage V of the feature point in the differential curve V-dV / dQ indicating the relationship with / dQ.
This makes it possible to estimate the deterioration index of the specific cell early based on the changes in voltage and input / output current.

Preferably, the deterioration index estimation unit is a ratio dQ of the voltage V of the specific cell and the change dQ of the battery capacity Q of the specific cell to the change dV of the voltage V of the specific cell. It is preferable to estimate the deterioration index of the specific cell based on the voltage V of the feature point in the differential curve V-dQ / dV indicating the relationship with / dV.
This makes it possible to estimate the deterioration index of the specific cell early based on the changes in voltage and input / output current.

  According to the apparatus for measuring the degree of deterioration of a secondary battery of the present invention, a specific unit cell with the highest voltage is identified among the plurality of unit cells when there is a unit cell that has reached the discharge completion voltage, and deterioration index estimation is performed. Since the deterioration index of the secondary battery unit was calculated based on the deterioration index of the specific single battery estimated by the storage unit and the remaining capacity at the time of discharge completion of the specific single battery calculated by the remaining capacity calculation unit, the secondary battery unit From the time when the discharge completion detection unit detects that there is a single battery at the discharge completion time until the specific single battery becomes fully charged, that is, the substantially chargeable / dischargeable range, that is, the deterioration indicator for a plurality of single batteries Can be estimated in consideration of the variation of

  This makes it possible to accurately estimate the deterioration index of the secondary battery unit configured of a plurality of single cells.

It is a schematic block diagram which shows the secondary battery system of this embodiment. It is a bar graph which shows the value of SOC of each single battery at the time of completion of discharge. It is a characteristic view which shows an example of differential curve V-dV / dQ. It is the flowchart in which degradation index presumption control procedure of the battery pack concerning the present invention which a main controller performs is shown. It is a bar graph which shows the value of SOC of each single battery at the time of completion of charge.

Hereinafter, an embodiment of a secondary battery system embodying the present invention will be described.
FIG. 1 is a schematic configuration view showing a secondary battery system of the present embodiment.
The secondary battery system 1 of the present embodiment is mounted on an electric vehicle, and supplies power to a traveling motor which is a traveling power source. As a whole, the secondary battery system 1 is composed of a main controller 2 that integrally controls the whole and a battery pack 20 (secondary battery unit). The battery pack 20 is composed of a plurality of secondary battery modules 3 connected in parallel to the main controller 2.

The secondary battery module 3 is configured of a battery pack 4 (secondary battery unit), a sub controller 5 and a charge / discharge control unit 6.
The battery assembly 4 is configured by combining a plurality of unit cells 4 n in parallel and in series in order to achieve a desired battery capacity and output voltage. The battery pack 4 of the present embodiment includes, in its positive electrode plate, LiMn 2 O 4 and LiMO 2 (M is a transition metal element containing at least one of Co, Ni, Al, Mn, and Fe).

A voltage sensor 7, a current sensor 8 and a temperature sensor 9 are connected to the battery assembly 4. The voltage sensor 7 detects the battery voltage V of each of the unit cells 4n constituting the battery pack 4, the current sensor 8 detects the input / output current I of each unit cell 4n, and the temperature sensor 9 detects the temperature T of each unit cell 4n. Are detected, and their detection information is input to the sub controller 5.
The sub controller 5 includes an input / output device (not shown), a storage device (ROM, RAM, etc.) provided for storing control programs, control maps, etc., a central processing unit (CPU), a timer counter, etc. The sub controller 5 functions to drive the charge and discharge control unit 6 to control charge and discharge of the assembled battery 4, and in charge and discharge control, the maximum allowable current and the maximum allowable voltage according to the deterioration index of the assembled battery 4. Adjust the In the present embodiment, SOH (State Of Health), which is the ratio of the current full charge capacity to the full charge capacity at the time of a new product, is used as the deterioration index of the battery pack 4.

  The charge / discharge command unit 11 outputs a charge / discharge control command to the sub-controller 5 of each secondary battery module 3 via the input / output unit 12 based on SOH or the like estimated by the SOH estimation unit 16 described later. For example, to the secondary battery module 3 for which the SOH less than the predetermined value is estimated, a command for limiting the maximum allowable current and the maximum allowable voltage at the time of charge and discharge is output. The charge and discharge control by the sub controller 5 based on the command protects the battery pack 4 in which the deterioration has progressed.

In addition, when SOH below the life limit is estimated for any of the unit cells 4n of the unit cells 4n in the assembled battery 4, the charge / discharge command unit 11 displays the vehicle in the display unit 18 provided in the driver's seat. Display a message prompting an inspection. As a result, vehicle inspection is carried out at a sales company or the like, and the battery assembly 4 is replaced as necessary.
On the other hand, like the sub controller 5, the main controller 2 is an input / output device (not shown), a storage device (ROM, RAM etc.) provided for storage of control programs, control maps etc., central processing unit (CPU), timer counter etc. It consists of

The main controller 2 includes an input / output unit 12, a data storage unit 13, a battery capacity calculation unit 15, an SOH estimation unit 16 (deterioration index estimation unit), and an SOC calculation unit (remaining capacity calculation unit) 17.
The data storage unit 13 stores measured data input from the sub-controller 5 of each secondary battery module 3 via the input / output unit 12. In addition, data (hereinafter referred to as reference data) indicating the correlation between a specific feature point on the differential curve V-dV / dQ and the SOH of the assembled battery 4 is stored in the data storage unit 13 in advance for each temperature range. ing.

The process of creating reference data is as follows.
First, the deterioration test of the unit cell 4n of the same standard as the unit cell 4n of the present embodiment is performed, and charge and discharge of the unit cell 4n not in use are repeated to deteriorate stepwise to the life limit. In each SOH in the degradation process, the unit cell 4n is charged and discharged under a plurality of different temperature ranges.
Then, the battery capacity Q of the single battery 4n is sequentially calculated at predetermined time intervals when charging or discharging the single battery 4n, and the battery voltage V is acquired in synchronization with this. Thus, the differential value dV / dQ is calculated based on the battery voltage V and the battery capacity Q obtained by charge and discharge, and the differential curve V-dV / dQ indicating the relationship between the battery voltage V and the differential value dV / dQ is obtained. After calculation, the position (V, dV / dQ) of the specific feature point appearing on the differential curve V-dV / dQ is determined. The feature point may be, for example, a middle point of two peaks appearing in the differential curve V-dV / dQ in a predetermined range of the battery voltage V. As a result, the correlation between a specific feature point and the SOH of the assembled battery 4 is determined for each temperature range, and is stored in the data storage unit 13 in advance as common reference data of each secondary battery module 3.

The SOC calculating unit 17 can calculate the state of charge (SOC) and the remaining capacity of each of the unit cells 4 n based on the voltage and current calculated by the voltage sensor 7 and the current sensor 8. Further, the SOC calculating unit 17 outputs the calculated SOC of each unit cell 4 n to the unit cell specifying unit 14.
The SOH estimation unit 16 is configured of a differential curve calculation unit 10, a cell identification unit 14, and a discharge completion detection unit 19.

The unit cell identification unit 14 identifies a specific unit cell 4c that estimates SOH from among all the unit cells 4n.
Referring to FIG. 2, there is shown a bar graph indicating the SOC value of each of the unit cells 4n at the time of completion of discharge. Here, in the figure, 4i, 4ii, 4m, 4c are a part of all the unit cells 4n, and are connected in series with each other. In particular, the unit cell 4m indicates a unit cell (hereinafter, referred to as a minimum unit cell 4m (unit cell)) which first reaches a predetermined discharge completion voltage when all the unit cells 4n discharge simultaneously. At this time, the discharge completion detection unit 19 detects that the minimum unit cell 4m is present. Further, the SOC of the minimum battery cell 4m at this time is taken as the charging rate Cb. When the cell identification unit 14 detects that the minimum cell 4m that has reached the discharge completion voltage is present by the discharge completion detection unit 19, the cell with the highest voltage among all the cells 4n (hereinafter referred to as Identify the specific cell 4c). Furthermore, the voltage of the specific unit cell 4c at this time is OCV (Open Circuit Voltage), and the SOC of the specific unit cell 4c calculated based on the OCV is a charging rate C1.

  The differential curve calculation unit 10 sequentially calculates the battery capacity Q of the specific single battery 4c at predetermined time intervals when charging or discharging the specific single battery 4c, and acquires the battery voltage V in synchronization with this, to obtain the specific single battery A differential value dV / dQ, which is a ratio of the change amount dV of the battery voltage V to the change amount dQ of the battery capacity Q of 4c, is calculated. Then, the differential curve V-dV / dQ is calculated as a curve indicating the relationship between the obtained differential value dV / dQ and the battery voltage V.

  FIG. 3 is a characteristic diagram showing an example of the differential curve V-dV / dQ. In FIG. 3, the derivative value dV / dQ is taken as a vertical axis, and the battery voltage V is taken as a horizontal axis. A differential curve V-dV / dQ is shown. The battery voltage V increases or decreases together with the charging rate (SOC) of the specific cell 4c with the charging or discharging of the specific cell 4c, and the differential value dV / dQ changes accordingly, for example, the differential curve V Inflection points P1 and P2 appear on -dV / dQ.

The differential curve calculation unit 10 outputs the calculated differential curve V-dV / dQ to the SOH estimation unit 16. At this time, the sub-controller 5 outputs the temperature T (hereinafter, these will be referred to as actual measurement data) detected by the temperature sensor 9 to the SOH estimation unit 16.
The SOH estimating unit 16 estimates the SOH of the specific single battery 4c using the differential curve V-dV / dQ output from the differential curve calculating unit 10, the reference data, and the actual measurement data. For example, in the reference data, data matching or approximating actual data, and inflection points P1 and P2 appearing on the differential curve V-dV / dQ output from the differential curve calculation unit 10 are compared with each other to match or approximate Estimate SOH from reference data. In addition, the estimation method of SOH may be another method. For example, in the differential curve calculation unit 10, a differential curve V− showing a relationship between dQ / dV, which is a ratio of the change amount dQ of the battery capacity Q of the specific cell 4c to the change amount dV of the battery voltage V of the specific cell 4c. The SOH of the specific unit cell 4c may be estimated by calculating dQ / dV and identifying feature points from the differential curve V-dQ / dV. In this case, for example, in a predetermined range of the battery voltage V, a point at which the slope of the differential curve V-dQ / dV is maximum is taken as a feature point, or a midpoint between two points crossing one peak at a predetermined dQ / dV. As a feature point.

Referring to FIG. 4, a routine executed by the main controller 2 and indicating a control procedure for estimating the deterioration index of the battery pack 20 according to the present invention is shown in the form of a flowchart, which will be described below.
In step S10, the charge / discharge control unit 6 is in a discharged state by the charge / discharge command unit 11, and the discharge of all the unit cells 4n is started. Then, the process proceeds to step S12.

In step S12, the voltage sensor 7 detects the voltages of all the unit cells 4n whose discharge has been started in step S10. Then, the process proceeds to step S14.
In step S14, the discharge completion detection unit 19 determines whether or not there is a minimum single battery 4m that has reached the discharge completion voltage from the voltages of all the unit cells 4n detected in step S12. If it is determined that the minimum unit cell 4m that has reached the discharge completion voltage does not exist, the process returns to step S12, and the voltages of all the unit cells 4n are detected again. When it is determined that the minimum unit cell 4m that has reached the discharge completion voltage is present, the process proceeds to step S16, and the discharge ends.

That is, after the discharge is started in step S10, the discharge is continued until the minimum cell 4m reaching the discharge completion voltage by repeating steps S12 and S14, and the minimum cell 4m reaching the discharge completion voltage is If it exists, the discharge ends in step S16. Then, the process proceeds to step S18.
In step S18, when the discharge is ended in step S16, the unit cell 4n having the highest voltage, that is, the specific unit cell 4c is identified. At the same time, the open circuit voltage (OCV) of the specific cell 4 c is measured and stored in the data storage unit 13. Then, the process proceeds to step S20.

At step S20, the charge / discharge command unit 11 starts charging, and the process proceeds to step S22.
In step S22, the differential curve calculation unit and the SOH estimation unit 16 estimate the SOH of the specific cell 4c. Then, the process proceeds to step S24.
In step S24, the remaining capacity of the specific cell 4c at the end of the discharge is calculated. Specifically, at the time of discharge completion based on the full charge capacity of the current specific single battery 4c calculated from the SOH of the specific single battery 4c estimated in step S22 and the SOC calculated from the OCV stored in step S18. The remaining capacity of the specific unit cell 4c is calculated. Then, the process proceeds to step S26.

  In step S26, the SOH of the battery pack 20 is estimated based on the SOH of the specific cell 4c estimated in step S22 and the remaining capacity of the specific cell 4c at the end of the discharge calculated in step S24. Specifically, the full charge capacity of the current specific single battery 4c is calculated from the SOH of the specific single battery 4c estimated in step S22, and the remaining specific single battery 4c at the end of the discharge calculated in step S22 from the full charge capacity. The capacity is subtracted to calculate the range of usable capacity when the battery pack 20 is charged and discharged. Then, the SOH of the battery pack 20 defined by the usable capacity is calculated, and this routine ends.

  Referring to FIG. 5, there is shown a bar graph indicating the SOC value of each of the unit cells 4n when charging is completed. Hereinafter, the voltage characteristics of the unit cell 4n and the SOH of the specific unit cell 4c specified in step S18 are estimated in step S22, and the full charge capacity and the discharge end calculated from the SOH of the specific unit cell 4c in step S24 and step S26 The effect of calculating the SOH of the battery pack 20 on the basis of the remaining capacity of the specific battery 4c at the time will be described.

  When all the cells 4n are charged from the discharge completion state, the respective cells 4n are charged at substantially the same speed. Specifically, when charging is started from the charging rate C1, the specific cell 4c can be charged until the charging rate Cmax (SOC = 100%, full charge capacity) is reached. Here, the charging rate Cmax−charging rate C1 = charging rate C2, that is, the charging rate at which the specific single battery 4c is charged until the charging rate C1 reaches the charging rate Cmax is taken as a charging rate C2. At this time, all the cells 4n (4i, 4ii, 4m,...) Are equally charged by the charge amount corresponding to the charge rate C2. Further, when the specific cell 4c is charged to the charging rate Cmax, the charging of all the cells 4n is completed in order to prevent overcharging of the specific cell 4c.

That is, since all the cells 4n are charged and discharged within the same range of charge capacity as the charge capacity calculated from the charge rate C2 of the specific cell 4c, the full charge capacity calculated from SOH of the specific cell 4c It is possible to calculate the SOH of the battery pack 20 by using a value obtained by subtracting the charging capacity corresponding to the charging rate C1 from the above.
Thus, the specific cell 4c is specified (step S18), the SOH of the specific cell 4c is estimated (step S22), and the remaining capacity of the specific cell 4c at the time of discharge completion is calculated (step S24). By subtracting the full charge capacity of the battery 4c (step S26), the SOH of the battery pack 20 can be estimated.

  As described above, the apparatus for measuring the degree of deterioration of the secondary battery according to the present invention is a deterioration of the secondary battery for measuring the degree of deterioration of the battery pack 20 configured by connecting a plurality of single cells 4n in parallel and in series. It is a degree measurement device, and a minimum of 4m of single cells that have reached a predetermined discharge completion voltage among voltage cells 7 measuring voltage of each of all cells 4n and all cells 4n measured by voltage sensor 7 Of all the cells 4n by the discharge completion detection unit 19 that detects the presence of a single battery, and a battery specification that identifies the specific single battery 4c with the highest voltage when the discharge completion voltage is reached among all the cells 4n The remaining capacity at the time of discharge completion of the specified single battery 4c specified by the unit 14 and the SOH estimating unit 16 that estimates the SOH of the specified single battery 4c specified by the single battery specification unit 14 is calculated. Battery capacity for calculating the SOH of the battery pack 20 based on the SOC calculation unit 17 and the SOH of the specific battery 4c estimated by the SOH estimation unit 16 and the remaining capacity of the specific battery 4c calculated by the SOC calculation unit 17 And a calculation unit 15.

  Therefore, among all the unit cells 4n, when the minimum unit cell 4m which has reached the discharge completion voltage is present, the unit cell identification unit 14 identifies the specific unit cell 4c having the highest voltage, and the SOH estimation unit 16 estimates it. Since the SOH of the battery pack 20 is calculated based on the specific cell 4c to be stored and the remaining capacity at the completion of the discharge of the specific cell 4c calculated by the SOC calculation unit 17, the discharge completion time of the battery pack 20 From the time the discharge completion detection unit 19 detects that the minimum unit cell 4m is present to a full chargeable / dischargeable range until the specific unit cell 4c is fully charged, that is, SOH Can be estimated in consideration of the variation of

  In particular, the SOH estimating unit 16 includes the current sensor 8 that measures the input / output current of each of the plurality of unit cells 4 n, and the specific unit cell when charging the battery pack 20 detected by the voltage sensor 7 and the current sensor 8 The SOC calculating unit 17 estimates the SOH of the specific cell 4c based on the change of the voltage of 4c and the input / output current, and the SOC calculating unit 17 calculates the SOH of the specific cell 4c estimated by the SOH estimating unit 16 or any one of the battery packs 20. Based on the OCV (open circuit voltage) of the specific battery 4c when the battery 4n reaches the discharge completion voltage, the SOC of the specific battery 4c when any battery 4n reaches the discharge completion voltage Calculate

Therefore, based on the SOH of the specific cell 4c and the OCV of the specific cell 4c estimated based on the change of the voltage and the input / output current of the specific cell 4c when the battery pack 20 is charged, the specific cell 4c By calculating the remaining capacity, the SOH of the battery pack 20 can be accurately estimated.
Then, the battery capacity calculation unit 15 calculates the current full charge capacity of the specific single battery 4 c based on the SOH of the specific single battery 4 c estimated by the SOH estimation unit 16, and calculates it by the SOC calculation unit 17 from the full charge capacity. The remaining capacity calculated from the charging rate C1 of the specific battery 4c is subtracted to estimate the SOH of the battery pack 20.

  Therefore, from the current full charge capacity of the specific single battery 4c based on the SOH of the specific single battery 4c estimated by the SOH estimating unit 16, a specific single battery when any single battery 4n of the battery pack 20 reaches the discharge completion voltage. By subtracting the remaining capacity of battery 4c, the SOH of battery pack 20 can be accurately estimated by actually calculating the chargeable / dischargeable capacity of battery pack 20 based on the subtracted value. .

  Then, the SOH estimating unit 16 calculates the voltage V of the specific cell 4c and dV / dQ, which is the ratio of the change amount dV of the voltage V of the specific cell 4c to the change amount dQ of the battery capacity Q of the specific cell 4c. The amount of change in the battery capacity Q of the specific battery 4c with respect to the voltage V of the feature point in the differential curve V-dV / dQ indicating the relationship or the voltage V of the specific battery 4c and the amount of change dV of the voltage V of the specific battery 4c Based on the voltage V of the feature point in the differential curve V-dQ / dV which shows the relationship with dQ / dV which is a ratio of dQ, SOH of the specific cell 4c is estimated.

Therefore, the SOH of the specific cell 4c can be estimated early based on the change of the voltage and the input / output current.
The description of the deterioration degree measuring device for a secondary battery according to the present invention is finished above, but the present invention is not limited to the above embodiment, and can be changed without departing from the scope of the invention.
For example, in the present embodiment, the SOH of the battery pack 20 is estimated, but the SOH of each of the assembled battery 4 may be estimated.

  Further, in the present embodiment, the main controller 2 is mounted on a vehicle, but the main controller 2 may be separate from the vehicle and may be connected only when the SOH is estimated.

4 Battery pack (secondary battery unit)
4c Specified single battery 4m minimum single battery (single battery)
4n single battery 7 voltage sensor 8 current sensor 14 single battery specification unit 15 battery capacity calculation unit 16 SOH estimation unit (deterioration index estimation unit)
17 SOC calculation unit (remaining capacity calculation unit)
19 discharge completion detection unit 20 battery pack (secondary battery unit)

Claims (5)

A secondary battery deterioration degree measuring device for measuring the deterioration degree of a secondary battery unit configured by connecting a plurality of single cells,
A voltage sensor that measures a voltage of each of the plurality of unit cells;
A discharge completion detection unit configured to detect the presence of a single battery having reached a predetermined discharge completion voltage among the plurality of single batteries measured by the voltage sensor;
A single battery identification unit that identifies a specific single battery having the highest voltage when the discharge completion voltage is reached among the plurality of single batteries by the discharge completion detection unit;
A deterioration index estimation unit configured to estimate a deterioration index of the specific single battery specified by the single battery specification unit;
A remaining capacity calculation unit that calculates a remaining capacity at the completion of discharging of the specific battery specified by the unit cell specification unit;
A battery capacity calculation unit that calculates a deterioration indicator of a secondary battery unit based on the deterioration indicator of the specific cell estimated by the deterioration indicator estimation unit and the remaining capacity of the specific cell calculated by the remaining capacity calculation unit; And a secondary battery deterioration degree measuring device. It has a current sensor which measures the input and output current of each of the plurality of unit cells,
The deterioration index estimation unit is a deterioration index of the specific single battery based on changes in the voltage and the input / output current of the specific single battery at the time of charging the secondary battery unit detected by the voltage sensor and the current sensor. Estimate
The remaining capacity calculation unit includes the deterioration index of the specific cell estimated by the deterioration index estimation unit, and the specific cell when any cell of the secondary battery unit reaches the discharge completion voltage. The deterioration of the secondary battery according to claim 1, wherein the remaining capacity of the specific cell when any one of the cells reaches the discharge completion voltage is calculated based on the open circuit voltage. Degree measuring device.   The battery capacity calculation unit calculates the current full charge capacity of the specific single battery based on the deterioration indicator of the specific single battery estimated by the deterioration index estimation unit, and the remaining capacity calculation unit calculates the full charge capacity of the specific single battery. The deterioration degree measuring device for a secondary battery according to claim 2, wherein the deterioration index of the secondary battery unit is estimated based on a value obtained by subtracting the calculated remaining capacity of the specific single battery.   The deterioration index estimation unit relates the voltage V of the specific cell, and dV / dQ, which is a ratio of the change amount dV of the voltage V of the specific cell to the change amount dQ of the battery capacity Q of the specific cell. The deterioration degree measuring device of a secondary battery according to claim 2 or 3, wherein the deterioration index of the specific cell is estimated based on a voltage V of a characteristic point in a differential curve V-dV / dQ indicating .   The deterioration index estimation unit is a relationship between the voltage V of the specific cell and dQ / dV which is a ratio of the change amount dQ of the battery capacity Q of the specific cell to the change amount dV of the voltage V of the specific cell. The deterioration degree measuring device of a secondary battery according to claim 2 or 3, wherein the deterioration index of the specific cell is estimated based on a voltage V of a feature point in a differential curve V-dQ / dV indicating. .

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