Battery charging method and battery management system therefor

1. A battery charging method, comprising:

obtaining a voltage capacity ratio for a reference charge C-rate and voltage capacity ratios for N (N is an integer of 1 or more) charge C-rates greater than the reference charge C-rate, each of the voltage capacity ratios for the reference charge C-rate and the N charge C-rates being defined as a ratio of a voltage variance to a capacity variance depending on a change in state of charge (SOC) of a battery when the battery is charged at a corresponding one of the C-rates;

comparing the voltage capacity ratio of the reference charge C-rate with each of the voltage capacity ratios of the N charge C-rates, and then setting a charge C-rate of the N charge C-rates so that a difference in voltage capacity ratio is minimized for each of SOC sections; and

charging the battery with the charge C-rates corresponding to the SOC sections.

2. The battery charging method of claim 1 , wherein the obtaining the voltage capacity ratios comprises:

charging the battery with the reference charge C-rate, and then obtaining the voltage capacity ratio for the reference charge C-rate; and

discharging the battery and then charging the battery with a first charge C-rate greater than the C-rate of a previous charging act by a preset value, thus obtaining a corresponding one of the voltage capacity ratios for the first charge C-rate,

wherein the discharging and then charging of the battery is repeated N times so as to obtain the voltage capacity ratios for the first charge C-rate to an Nth charge C-rate.

3. The battery charging method of claim 2 , wherein the discharging of battery is performed by constant current-constant voltage (CCCV) discharging.

4. The battery charging method of claim 2 , wherein the comparing the voltage capacity ratio comprises:

selecting an SOC section in which a difference in voltage capacity ratio between the reference charge C-rate and the Nth charge C-rate is within a preset range, for all SOC sections of the battery, and then setting a charge C-rate of the selected SOC section to the Nth charge C-rate; and

selecting an SOC section in which a difference in voltage capacity ratio between the reference charge C-rate and an (N−1)th charge C-rate is within a preset range, for SOC sections other than the selected SOC section, and then setting a charge C-rate of the selected SOC section to the (N−1)th charge C-rate,

wherein selecting the SOC section is repeatedly performed for an (N−2)th charge C-rate to the first charge C-rate in substantially a same manner.

5. The battery charging method of claim 4 , wherein a charge C-rate of a section of the SOC sections in which any one of the N charge C-rates is not set, is set to the reference charge C-rate.

6. The battery charging method of claim 1 , wherein, during the charging the battery, constant current (CC) charging or constant current-constant voltage (CCCV) charging is performed in each of the SOC sections using a corresponding one of the charge C-rates.

7. The battery charging method of claim 6 , wherein, when the battery charging is performed by the CC charging, a first SOC section of the SOC sections is supplied with a corresponding one of the charge C-rates and then is charged until a voltage of the battery reaches a charge cutoff voltage set for the first SOC section.

8. The battery charging method of claim 7 , wherein, when the battery is charged at the charge C-rate corresponding to the first SOC section, a charge cutoff voltage set for the first SOC section is a voltage at which the SOC of the battery becomes a final SOC of the first SOC section.

9. The battery charging method of claim 6 , wherein, when the battery charging is performed by the CCCV charging,

a first SOC section of the SOC sections undergoes the CC charging by supplying the corresponding one of the charge C-rates until the voltage of the battery becomes a charge cutoff voltage set for the first SOC section, and undergoes constant voltage (CV) charging by supplying a charge C-rate that is sequentially reduced until the SOC of the battery becomes a final SOC of the first SOC section.

10. The battery charging method of claim 9 , wherein the charge cutoff voltage set for the first SOC section is a voltage at which the SOC of the battery becomes the final SOC of the first SOC section, when the battery is charged at a C-rate set for a second SOC section that is a section subsequent to the first SOC section.

11. The battery charging method of claim 9 , wherein the charge C-rate that is sequentially reduced is reduced to the charge C-rate set for the SOC section that is subsequent to the first SOC section.

12. The battery charging method of claim 1 , wherein, when a number of battery charging and discharging operations reaches a preset number, the obtaining the voltage capacity ratios and comparing the voltage capacity ratio are performed again to reset the charge C-rates corresponding to the SOC sections.

13. A battery management system, comprising:

a voltage-capacity-ratio acquisition unit configured to obtain a voltage capacity ratio for a reference charge C-rate and voltage capacity ratios for N (N is an integer of 1 or more) charge C-rates greater than the reference charge C-rate, each of the voltage capacity ratios for the reference charge C-rate and the N charge C-rates being defined as a ratio of a voltage variance to a capacity variance depending on a change in SOC of a battery when the battery is charged at a corresponding one of the C-rates;

a charge-current setting unit configured to compare the voltage capacity ratio of the reference charge C-rate with each of the voltage capacity ratios of the N charge C-rates, and then setting a charge C-rate of the N charge C-rates so that a difference in voltage capacity ratio is minimized for each of SOC sections; and

a micro control unit (MCU) configured to control charging of the battery such that the battery is charged at the charge C-rates corresponding to the SOC sections.

14. The battery management system of claim 13 , further comprising:

a sensing unit configured to sense a voltage and a current of the battery,

wherein the voltage-capacity-ratio acquisition unit obtains a corresponding one of the voltage capacity ratios of any one of the charge C-rates using the voltage and the current that are sensed by the sensing unit, when the battery is charged using any one of the reference charge C-rate and the N charge C-rates.

15. The battery management system of claim 13 , wherein the MCU is configured to perform CC charging or CCCV charging for each of the SOC sections, using a corresponding one of the charge C-rates.

16. The battery management system of claim 15 , wherein, when the battery charging is performed by the CC charging, a first SOC section of the SOC sections undergoes the CC charging by supplying a corresponding one of the charge C-rates until a voltage of the battery becomes a charge cutoff voltage set for the first SOC section.

17. The battery management system of claim 16 , wherein, when the battery is charged at the charge C-rate corresponding to the first SOC section, the charge cutoff voltage set for the first SOC section is a voltage at which the SOC of the battery becomes a final SOC of the first SOC section.

18. The battery management system of claim 15 , wherein, when the battery charging is performed by the CCCV charging,

a first SOC section of the SOC sections undergoes the CC charging by supplying the corresponding one of the charge C-rates until the voltage of the battery becomes a charge cutoff voltage set for the first SOC section, and undergoes the CV charging by supplying the charge C-rate that is sequentially reduced until the SOC of the battery becomes a final SOC of the first SOC section.

19. The battery management system of claim 18 , wherein the charge cutoff voltage set for the first SOC section is a voltage at which the SOC of the battery becomes the final SOC of the first SOC section, when the battery is charged at a C-rate set for a second SOC section that is a section subsequent to the first SOC section.

20. The battery management system of claim 13 , wherein the charge C-rate that is reduced, is reduced to the charge C-rate set for the SOC section that is subsequent to a first SOC section of the SOC sections.