Fully-charged battery capacity detection method

• US 7,974,796 B2
• Filed: 04/08/2008
• Issued: 07/05/2011
• Est. Priority Date: 04/10/2007
• Status: Active Grant

• Current Assignee: Panasonic Energy (Shanghai) Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Tamai, Mikitaka
• Primary Examiner(s): KHUU, HIEN DIEU THI
• Application Number:
  US12/078,921
• Publication Number:
  US 20080255783A1
• Time in Patent Office: 1,183 Days
• Field of Search: 702/63
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3828 using current integration

Abstract

A fully-charged battery capacity detection method detects first and second no-load voltages (VOCV1, VOCV2) of a battery at first no-load timing and second no-load timing, respectively. Further, first and second remaining capacities (SOC1 [%], SOC2 [%]) of the battery are determined based on the first and second no-load voltages, respectively, when the first no-load voltage (VOCV1) falls within a predetermined voltage range. Moreover, a fully-charged capacity (Ahf) of the battery is calculated based on a remaining capacity variation rate (δS [%]) and a capacity variation value (δAh) of the battery. Also, the variation rate of the remaining capacity is calculated based on a difference between the first and second remaining capacities. The capacity variation value of the battery is calculated based on an integrated value of the charging current and discharge currents of the battery to be charged/discharged from the first no-load timing to the second no-load timing.

Claims

1. A fully-charged battery capacity detection method of detecting a capacity of a battery, the method comprising:

detecting, via a voltage detection circuit, first and second no-load voltages (VOCV1, VOCV2) of the battery at a first no-load timing and a second no-load timing during which the battery is brought to a no-load state, respectively;

determining whether the detected first no-load voltage (VOCV1) falls within a predetermined voltage range, and determining, when the first no-load voltage (VOCV1) falls within the predetermined voltage range, first and second remaining capacities (SOC1 [%], SOC2 [%]) of the battery based on the first and second no-load voltages (VOCV1, VOCV2), respectively;

calculating a remaining capacity variation rate (δ

S [%]) based on a difference between the determined first and second remaining capacities (SOC1 [%], SOC2 [%]);

calculating a capacity variation value (δ

Ah) of the battery based on an integrated value of charging and discharging currents of the battery to be charged/discharged from the first no-load timing to the second no-load timing; and

calculating a fully-charged capacity (Ahf) of the battery based on the remaining capacity variation rate (δ

S [%]) and the capacity variation value (δ

Ah) according to the following formula;

Ahf=δ

Ah/(δ

S/100).

2. The fully-charged battery capacity detection method according to claim 1, further comprising determining whether the calculated capacity variation value (δ

Ah) is larger than a predetermined value, and calculating, when the capacity variation value (δ

Ah) is larger than the predetermined value, the fully-charged capacity (Ahf) of the battery based on the remaining capacity variation rate (δ

S [%]) and the capacity variation value (δ

Ah).

3. The fully-charged battery capacity detection method according to claim 2, wherein the second no-load timing is based on a time when the battery is brought to the no-load state after the capacity variation value (δ

Ah) becomes larger than 10% of a rated capacity of the battery.

4. The fully-charged battery capacity detection method according to claim 1, wherein the second no-load timing is based on a time when a predetermined period elapses after the first no-load timing.

5. The fully-charged battery capacity detection method according to claim 4, wherein the second no-load timing is based on a time when a period of a few minutes to a few hours elapses after the first no-load timing.

6. The fully-charged battery capacity detection method according to claim 5, wherein the second no-load timing is based on a time when the battery is in the no-load state when a period of five minutes to one hour elapses after an end of a battery charging operation.

7. The fully-charged battery capacity detection method according to claim 1, wherein the first no-load timing is based on a time when the battery is in the no-load state before the battery is brought in a charging operation, and the second no-load timing is based on a time when the battery is in the no-load state after an end of the charging operation.

8. The fully-charged battery capacity detection method according to claim 1,

wherein the second no-load timing is a timing before the battery is fully charged, and

wherein the method further comprises determining whether the detected second no-load voltage (VOCV2) falls within a predetermined voltage range, and determining, when the second no-load voltage (VOCV2) falls within the predetermined voltage range, the second remaining capacity (SOC2 [%]) of the battery based on the second no-load voltage (VOCV2).

9. The fully-charged battery capacity detection method according to claim 1, wherein the battery is a lithium-ion rechargeable battery.

10. The fully-charged battery capacity detection method according to claim 9, wherein the battery includes a positive electrode that contains a three-compositional material.

11. The fully-charged battery capacity detection method according to claim 1, wherein the battery is a lithium-polymer battery.

12. The fully-charged battery capacity detection method according to claim 1, wherein the first remaining capacity (SOC1 [%]) of the battery is determined based on the first no-load voltage (VOCV1) using a stored function.

13. The fully-charged battery capacity detection method according to claim 12, further comprising:

correcting, using a remaining capacity correction circuit, a remaining capacity (SOC [%]) of the battery based on the calculated fully-charged capacity (Ahf) of the battery, and detecting an accurate remaining capacity of the battery.

14. The fully-charged battery capacity detection method according to claim 1, wherein the first remaining capacity (SOC1 [%]) of the battery is determined based on the first no-load voltage (VOCV1) by referring to a stored table.

15. The fully-charged battery capacity detection method according to claim 1, wherein the second remaining capacity (SOC2 [%]) of the battery is determined based on the second no-load voltage (VOCV2) using a stored function.

16. The fully-charged battery capacity detection method according to claim 1, wherein the second remaining capacity (SOC2 [%]) of the battery is determined based on the second no-load voltage (VOCV2) by referring to a stored table.

17. The fully-charged battery capacity detection method according to claim 1, wherein a deterioration degree of the battery is determined based on the calculated fully-charged capacity (Ahf).

18. The fully-charged battery capacity detection method according to claim 1, further comprising transmitting, via a communication processing portion, information to a mobile device, the information including the calculated fully-charged capacity (Ahf).