Secondary battery capacity measuring system and secondary battery capacity measuring method

Patent metadata

Field	Value
Publication number	US-10353009-B2
Application number	US-201715404275-A
Country	US
Kind code	B2
Filing date	Jan 12, 2017
Priority date	Jan 21, 2016
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

A secondary battery capacity measuring system that estimates maximum capacities of other cells using characteristics of a deteriorated cell even when a charging process in the deteriorated cell having a smaller maximum capacity than the other cells in cells constituting a battery module ends and data for measuring the maximum capacities of the other cells cannot be acquired is provided.

First claim

What is claimed is:

1. A secondary battery capacity measuring system comprising:
a processor;
a memory;
a current sensor; and
a voltage sensor,
wherein the processor executes a program stored in the memory to perform operations comprising:
calculating a differential characteristic curve indicating differential characteristics with parameters of capacity and voltage value in predetermined voltage ranges from history data of measured values obtained by causing the voltage sensor and the current sensor to acquire the voltage value and a current value of the battery configured by a plurality of cells in time series for each cell;
comparing a reference differential curve, which indicates differential characteristics with parameters of capacity and voltage value of a cell, includes a plurality of separated-wave differential curves multiplied by first coefficients, and is multiplied by a second coefficient indicating a deterioration ratio from an initial maximum capacity that is initially measured, with a differential characteristic curve indicating differential characteristics with parameters of measured capacity and measured voltage value of one cell selected from the plurality of cells, and calculating first coefficients of the separated-wave differential curves;
fitting the reference differential curve using the first coefficients to a partial differential characteristic curve in a measured voltage range of a non-selected cell other than the selected cell among the plurality of cells, calculating the second coefficient, multiplying the initial maximum capacity by the second coefficient, and setting the multiplication result as an estimation result of the maximum capacity of the non-selected cell, and
controlling at least one of charging and discharging of the battery on the basis of the estimation result of the maximum capacity of the non-selected cell,
wherein the separated-wave differential curves include a differential characteristic curve based on material characteristics of a positive electrode and a differential characteristic curve based on material characteristics of a negative electrode.

2. The secondary battery capacity measuring system according to claim 1 , wherein the processor is further configured to map a correspondence between third coefficients of the separated-wave differential curves acquired from the fitting result and the second coefficient of the selected cell on a graph, and set slopes of regression lines formed by the third coefficients of the separated-wave differential curves and the second coefficient as corrected values of the first coefficients.

3. The secondary battery capacity measuring system according to claim 1 , wherein the differential characteristic curve, the partial differential characteristic curve, and the reference differential curve include:
a differential curve indicating a first correspondence between the voltage value in the battery and a numerical value acquired by differentiating the capacity using a voltage variation as a differential operator; and
a differential curve indicating a second correspondence between the capacity in the battery and a numerical value acquired by differentiating the voltage value using a capacity variation as a differential operator.

4. The secondary battery capacity measuring system according to claim 1 , wherein the differential characteristic curve is generated from measured values in a range including feature points derived from a separated-wave differential curve which is used to perform fitting for calculating the first coefficients of the separated-wave differential curves.

5. The secondary battery capacity measuring system according to claim 1 , wherein the processor is further configured to calculate the first coefficients to correspond to an ambient temperature of the secondary battery and writes and stores the first coefficients to and in a table indicating a correspondence between the temperature and the first coefficients, and
read the first coefficients corresponding to the ambient temperature of the secondary battery from the table and performs an operation of estimating the maximum capacity of the non-selected cell when estimating the maximum capacity of the non-selected cell.

6. The secondary battery capacity measuring system according to claim 1 , wherein a deteriorated cell having a smallest maximum capacity is selected and used as the selected cell from the plurality of cells of the secondary battery.

7. The secondary battery capacity measuring system according to claim 1 , wherein a plurality of cells including a deteriorated cell having a smallest maximum capacity are selected and used as the selected cell from the plurality of cells of the secondary battery.

8. The secondary battery capacity measuring system according to claim 7 , further comprising a balance circuit configured to shift a capacity position at which charging of the deteriorated cell is started so as to measure the capacity and the voltage value of the selected cell within a range including feature points similar to the deteriorated cell.

9. A secondary battery capacity measuring method of measuring a maximum capacity of a secondary battery including a plurality of cells, the secondary battery capacity measuring method being executed by a secondary battery capacity measuring system comprising a processor, a memory, a current sensor, and a voltage sensor, the secondary battery capacity measuring method causing the processor to execute a program stored in a memory to perform operations comprising:
calculating a differential characteristic curve indicating differential characteristics with parameters of capacity and voltage value of a battery in predetermined voltage ranges as parameters from history data of measured values obtained by causing the voltage sensor and the current sensor to acquire the voltage value and a current value of the battery in time series for each cell;
comparing a reference differential curve, which indicates differential characteristics with parameters of the capacity and the voltage value of a cell, includes a plurality of separated-wave differential curves multiplied by first coefficients, and is multiplied by a second coefficient indicating a deterioration ratio from an initial maximum capacity that is initially measured, with a differential characteristic curve indicating differential characteristics with parameters of the measured capacity and the measured voltage value of one cell selected from the plurality of cells, to calculating the first coefficients of the separated-wave differential curves;
fitting the reference differential curve using the first coefficients to a partial differential characteristic curve in a measured voltage range of a non-selected cell other than the selected cell among the plurality of cells, calculating the second coefficient, multiplying the initial maximum capacity by the second coefficient, and setting the multiplication result as an estimation result of the maximum capacity of the non-selected cell, and
controlling at least one of charging and discharging of the battery on the basis of the estimation result of the maximum capacity of the non-selected cell,
wherein the separated-wave differential curves include a differential characteristic curve based on material characteristics of a positive electrode and a differential characteristic curve based on material characteristics of a negative electrode.

10. The secondary battery capacity measuring method according to claim 9 , wherein the processor is further configured to map a correspondence between third coefficients of the separated-wave differential curves acquired from the fitting result and the second coefficient of the selected cell on a

Assignees

• Yokogawa Electric Corp

Inventors

• Torai Soichiro
• Yoshitake Satoshi
• Kazumi Masahiro
• Nakagomi Masaru

Classifications

• H01M10/482

  for several batteries or cells simultaneously or sequentially · CPC title

• G01R31/396

  Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery · CPC title

• G01R31/367 Primary

  Software therefor, e.g. for battery testing using modelling or look-up tables · CPC title

• G01R31/392

  Determining battery ageing or deterioration, e.g. state of health · CPC title

• H01M10/4285

  Testing apparatus · CPC title