Automatic Charge Equalization Method and Apparatus for Series Connected Battery String

• US 20100207578A1
• Filed: 10/16/2008
• Published: 08/19/2010
• Est. Priority Date: 10/16/2007
• Status: Active Grant

• Current Assignee: Korea Advanced Institute of Science and Technology, SK On Company Limited (SK Innovation Company Limited)
• Original Assignee: Korea Advanced Institute of Science and Technology, SK Energy Corporation (SK Innovation Company Limited)
• Inventors: Oh, Jeon Keun, Kim, Chong Eun, Jang, Soo Yeup, Lee, Joong Hui, Moon, Gun Woo, Park, Hong Sun, Kim, Chol Ho
• Granted Patent: US 8,310,204 B2
• Time in Patent Office: Days
• US Class Current: 320/118
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

The present invention relates to an automatic charge equalization apparatus and method having an automatic PWM generating means for a series-connected battery string. The automatic charge equalization method and apparatus for a series-connected battery string according to the present invention can improve charge equalization by accomplishing charge equalization operation after comparing the potential of the corresponding battery cell with the average potential of the plurality of battery cells including the corresponding battery cell upon charging or discharging the corresponding battery cell.

Claims

1. A charge equalization apparatus for a series-connected battery string, comprising:

a battery string consisted of a plurality of batteries connected in series;

nth battery cell composing the battery string;

a battery string of m which is one portion of the battery string and has m battery cells including the nth battery cell connected in series;

an automatic PWM generating means connected in parallel to each of the batteries composing the battery string; and

a charge equalizer connected in parallel to each of the batteries composing the battery string,

wherein the automatic PWM generating means comprises a comparator and a PWM generator automatically generating a PWM signal by an output of the comparator, and the comparator generates an output by comparing a potential of the nth battery cell with an average potential of the battery string of m, and the charge equalizer is automatically controlled to charge or discharge the nth battery cell according to the PWM signal automatically generated by the PWM generator.

(where, the nth battery cell refers to any single battery of the plurality of series-connected batteries composing the battery string, and the m is at least 3 and up to the number (k) of total batteries composing the battery string.)

2. The charge equalization apparatus according to claim 1, wherein two inputs of the comparator are a potential of nth battery cell and an average potential of the batteries composing the battery string of m.

3. The charge equalization apparatus according to claim 2, wherein the two inputs of the comparator are equipped with a resistor respectively, which compares the average potential of the battery string of m with the potential of the nth battery cell.

4. The charge equalization apparatus according to claim 1, wherein the charge equalizer comprises a DC/DC converter connected in parallel to each of batteries composing the battery string.

5. The charge equalization apparatus according to claim 4, wherein the DC/DC converter is a charge-type converter and has a total potential of the battery string of m as an input.

6. The charge equalization apparatus according to claim 5, wherein the automatic PWM generating means generates the PWM signal if the potential of the nth battery cell is lower than the average potential of the battery string of m.

7. The charge equalization apparatus according to claim 4, wherein the DC/DC converter is a discharge-type DC/DC converter.

8. The charge equalization apparatus according to claim 7, wherein the automatic PWM generating means generates the PWM signal if the potential of the nth battery cell is higher than the average potential of the battery string of m.

9. The charge equalization apparatus according to claim 4, wherein the DC/DC converter is operated under a control of the automatic PWM generating means.

10. The charge equalization apparatus according to claim 1, wherein the nth battery cell belongs to each of the battery string of m in a range of at least 1 to up to m.

11. The charge equalization apparatus according to claim 10, wherein two inputs of a comparator provided in a battery cell located in an end portion of the battery string are a potential of the battery cell and an average potential of the batteries composing the battery string.

12. A charge equalization method for a charge equalization apparatus for a series-connected battery string comprising a battery string consisted of a plurality of batteries connected in series;

an automatic PWM generating means including a comparator connected in parallel to each of the batteries composing the battery string; and

a charge equalizer including a DC/DC converter connected in parallel to each of the batteries composing the battery string, comprising steps of;

(a) automatically generating a PWM signal by comparing a potential of nth battery cell composing the battery string with an average potential of the battery string of m which is one portion of the battery string and has m battery cells connected in series including the nth battery cell; and

(b) controlling the charge equalizer to charge or discharge the nth battery cell according to the PWM signal.

(where, the nth battery cell refers to any single battery of the plurality of series-connected batteries composing the battery string, and the m is at least 3 and up to the number (k) of total batteries composing the battery string.)

13. The charge equalization method according to claim 12, wherein the operation of the DC/DC converter is controlled to be started and stopped according to the PWM signal in the step (b).

14. The charge equalization method according to claim 13, wherein the nth battery cell is charged or discharged by operating a charge-type DC/DC converter or a discharge-type DC/DC converter.

15. The charge equalization method according to claim 14, wherein an input or an output of the DC/DC converter is connected to the battery string of m, so that charging current of the nth battery cell is caused by total potential of the battery string of m and discharging current of the nth battery cell serves as total potential of the battery string of m.

16. The charge equalization method according to claim 12, wherein the PWM signal generated by the automatic PWM generating means is controlled according to an output of the comparator in the step (a).

17. The charge equalization method according to claim 12, wherein two inputs of the comparator are a potential of the nth battery cell and an average potential of the batteries composing the battery string of m respectively, and the average potential of the battery string of m and the potential of the nth battery cell are compared using resistors connected to the two inputs respectively.

18. The charge equalization method according to claim 17, wherein the automatic PWM generating means generates the PWM signal if a potential of the nth battery cell is higher than an average potential of the battery string of m, in the step (a).

19. The charge equalization method according to claim 17, wherein the automatic PWM generating means generates the PWM signal if a potential of the nth battery cell is lower than an average potential of the battery string of m, in the step (a).