Secondary cell residual capacity calculation method and battery pack

• US 20050024020A1
• Filed: 07/23/2004
• Published: 02/03/2005
• Est. Priority Date: 07/29/2003
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ohta, Yoshinori, Hogari, Masaki, Nakanouchi, Atsushi
• Granted Patent: US 7,492,126 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A secondary cell residual capacity calculation method and a battery pack capable of calculating the secondary cell residual capacity is provided. The calculation method includes detecting a temperature of a plurality of secondary cells; detecting a current and a terminal voltage of the plurality of secondary cells; digitizing temperature, current, and terminal voltage; calculating a cell polarization voltage from the digitized temperature, current and terminal voltage; calculating an original cell voltage from both of the calculated cell polarization voltage and the detected terminal voltage; and calculating a residual capacity rate based on the calculated original cell voltage with reference to a prearranged residual capacity reference data table.

Claims

1. A secondary cell residual capacity calculation method, comprising:

detecting a temperature of a plurality of secondary cells;

detecting a current and a terminal voltage of each of the secondary cells;

digitizing the temperature, the current, and the terminal voltage;

calculating a cell polarization voltage from the digitized temperature, current and terminal voltage;

calculating an original cell voltage from both of the calculated cell polarization voltage and the detected terminal voltage; and

calculating a residual capacity rate based on the calculated original cell voltage with reference to a prearranged residual capacity reference data table.

2. The method according to claim 1, wherein the calculating of the cell polarization voltage includes treating both of a charging current and a discharging current in a same manner as a load fluctuation.

3. The method according to claim 1, wherein the calculating of the cell polarization voltage includes calculating a final discharge prediction point;

obtaining a whole cell discharge capacity in a loaded condition thereof; and

calculating a relative residual capacity rate.

4. The method according to claim 1, further comprising:

calculating a cumulative discharge rate by integration of a Δ

residual capacity rate from the calculated residual capacity rate; and

incrementing a charge-discharge count value whenever the calculated cumulative discharge rate reaches a predetermined value.

5. The method according to claim 4, further comprising incrementing a deterioration coefficient and subtracting a reference capacity whenever the charge-discharge count value reaches a prefixed value.

6. A battery pack, comprising:

a plurality of secondary cells;

a cell temperature detector capable of detecting a temperature of the plurality of secondary cells;

a voltage current detector capable of detecting a current and a terminal voltage of each of the plurality of secondary cells; and

a controller capable of digitizing the temperature, the current and the terminal voltage, calculating a cell polarization voltage from the digitized temperature, current and terminal voltage, calculating an original cell voltage from both of the calculated cell polarization voltage and the detected terminal voltage, and calculating a residual capacity rate, based on the calculated original cell voltage with reference to a prearranged residual capacity reference data table.

7. The battery pack according to claim 6, wherein the controller treats both of a charging current and a discharging current in a same manner as a load fluctuation.

8. The battery pack according to claim 6, wherein the controller calculates a final discharge prediction point, obtains a whole cell discharge capacity in a loaded condition thereof, and calculates a relative residual capacity rate.

9. The battery pack according to claim 6, further comprising:

means for calculating a cumulative discharge rate by integration of a Δ

residual capacity rate from the calculated residual capacity rate and for incrementing a charge-discharge count value whenever the calculated cumulative discharge rate reaches a predetermined value.

10. The battery pack according to claim 9, further comprising:

means for incrementing a deterioration coefficient, and subtracting a reference capacity whenever the charge-discharge count value reaches a prefixed value.