OPEN CIRCUIT VOLTAGE ESTIMATION DEVICE, CONDITION ESTIMATION DEVICE, AND METHOD OF ESTIMATING OPEN CIRCUIT VOLTAGE

• US 20130311118A1
• Filed: 05/17/2013
• Published: 11/21/2013
• Est. Priority Date: 05/17/2012
• Status: Active Grant

• Current Assignee: GS Yuasa International Ltd. (GS Yuasa Corporation)
• Original Assignee: GS Yuasa International Ltd. (GS Yuasa Corporation)
• Inventors: Sejima, Kenichi
• Granted Patent: US 10,901,039 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An open circuit voltage estimation device for estimating an open circuit voltage of an electric storage device includes a voltage measurement portion and a controller. The voltage measurement portion measures terminal voltages of the electric storage device. The controller is configured to: control the voltage measurement portion to measure the terminal voltages; store the terminal voltages in association with elapsed time since charge or discharge completion time; calculate a variation in terminal voltage per unit time at predetermined elapsed time since the charge or the discharge of the electric storage device is complete based on the terminal voltages measured by the voltage measurement portion; and estimate the open circuit voltage based on the predetermined elapsed time, the voltage at the predetermined elapsed time, and the variation.

Claims

1. An open circuit voltage estimation device for estimating an open circuit voltage of an electric storage device, the open circuit voltage estimation device comprising:

a voltage measurement portion configured to measure terminal voltages of the electric storage device; and

a controller configured to;

control the voltage measurement portion to measure the terminal voltages of the electric storage device after charge or discharge of the electric storage device is complete;

store the terminal voltages in association with elapsed time since charge or discharge completion time at which charge or discharge of the electric storage device is complete;

calculate a variation in terminal voltage per unit time at predetermined elapsed time since the charge or the discharge of the electric storage device is complete based on the terminal voltages measured by the voltage measurement portion; and

estimate the open circuit voltage based on the predetermined elapsed time, the voltage at the predetermined elapsed time, and the variation.

2. The open circuit voltage estimation device according to claim 1, wherein the controller is further configured to:

calculate the variation in terminal voltage per unit time by calculating an approximate equation of an approximate line of the terminal voltages, the approximate line being at the predetermined elapsed time; and

estimate the open circuit voltage;

by calculating calculation time based on the predetermined elapsed time and a coefficient defined according to an active material of the electric storage device and the predetermined elapsed time; and

by defining a value calculated substituting the calculation time in the approximate equation as an estimated open circuit voltage.

3. The open circuit voltage estimation device according to claim 2, wherein the controller is further configured to use a common logarithm of the predetermined elapsed time for calculating the approximate equation.

4. The open circuit voltage estimation device according to claim 2, wherein the controller is further configured to:

detect a peak at which a gradient of the terminal voltages is the largest; and

use elapsed time from when the charge or the discharge of the electric storage device is complete to when the terminal voltage reaches the peak as the predetermined elapsed time.

5. The open circuit voltage estimation device according to claim 2, further comprising a temperature measurement portion configured to measure a temperature of the electric storage device, wherein

the coefficient is defined based on a temperature of the electric storage device, and

the controller is further configured to determine the coefficient based on the temperature of the electric storage device at the predetermined elapsed time for calculating the calculation time.

6. The open circuit voltage estimation device according to claim 2, wherein the controller is further configured to control the voltage measurement portion to terminate the measurement of terminal voltages when the elapsed time has passed a predefined reference time.

7. The open circuit voltage estimation device according to claim 2, further comprising a current detection portion configured to detect at least one of charge and discharge currents of the electric storage device, wherein the controller is further configured to detect the charge or discharge completion time according to a detection result of the current detection portion for controlling the voltage measurement portion.

8. A condition estimation device comprising:

the open circuit voltage estimation device according to claim 1; and

a memory configured to store information on correlation between open circuit voltage and internal condition of the electric storage device, wherein

the controller is further configured to estimate an internal condition of the electric storage device based on the estimated open circuit voltage and the information on the correlation stored in the memory.

9. A method of estimating an internal condition of an electric storage device comprising:

measuring terminal voltages of the electric storage device after charge or discharge of the electric storage device is complete;

storing the terminal voltages in association with elapsed time since charge or discharge completion time at which charge or discharge of the electric storage device is complete;

calculating a variation in terminal voltages per unit time at predetermined elapsed time since the charge or the discharge of the electric storage device is complete based on the terminal voltages measured by the voltage measurement portion; and

estimating the open circuit voltage based on the predetermined elapsed time, the voltage at the predetermined elapsed time, and the variation.

10. The method according to claim 9, wherein

the calculating a variation in terminal voltages per unit time includes calculating an approximate equation of an approximate line of the terminal voltages, the approximate line being at the predetermined elapsed time;

and

the estimating the open circuit voltage includes;

calculating calculation time based on the predetermined elapsed time and coefficient defined according to an active material of the electric storage device and the predetermined elapsed time; and

defining a value calculated substituting the calculation time in the approximate equation as an estimated open circuit voltage.

11. The method according to claim 9, wherein the calculating an approximate equation includes using a common logarithm of the elapsed time for calculating the approximate equation.

12. The method according to claim 10, further comprising detecting a peak at which a gradient of the terminal voltages is the largest, wherein the calculating an approximate equation includes using elapsed time from when the charge or the discharge of the electric storage device is complete to when the terminal voltage reaches the peak as the predetermined elapsed time.

13. The method according to claim 10, wherein

the coefficient is defined based on a temperature of the electric storage device, and

the calculating calculation time includes determining the coefficient based on the temperature of the electric storage device at the predetermined elapsed time for calculating the calculation time.

14. The method according to claim 10, wherein the measuring terminal voltages includes terminating the measurement of terminal voltages when the elapsed time has passed a predefined reference time.

15. The method according to claim 10, wherein the measuring terminal voltages includes detecting the charge or discharge completion time according to a detection result of detection for detecting charge or discharge current of the electric storage device.