Method for Balancing of High Voltage Battery Pack

• US 20100277123A1
• Filed: 12/03/2008
• Published: 11/04/2010
• Est. Priority Date: 12/31/2007
• Status: Active Grant

• Current Assignee: SK On Company Limited (SK Innovation Company Limited)
• Original Assignee: SK Energy Corporation (SK Innovation Company Limited)
• Inventors: Han, Se Kyung, Lim, Jae Hwan
• Granted Patent: US 8,648,570 B2
• Time in Patent Office: Days
• US Class Current: 320/116
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The present invention relates to a cell balancing method for a high-voltage battery pack, and the method comprises steps of a) measuring an electromotive force of each cell composing the battery pack; b) selecting the cell to be balanced based on the electromotive force of the each cell; c) computing a total amount of charges used for balancing of the cell to be balanced; d) obtaining an accumulative amount of charges by accumulating an amount of current consumed for the balancing while performing the balancing of the cell to be balanced; and e) completing the balancing of the cell to be balanced when the accumulative amount of charges equals the total amount of charges.

Claims

1. A cell balancing method for a high-voltage battery pack, comprising steps of:

a) measuring an electromotive force of each cell composing the battery pack;

b) selecting the cell to be balanced based on the electromotive force of the each cell;

c) computing a total amount of charges used for balancing of the cell to be balanced;

d) obtaining an accumulative amount of charges by accumulating an amount of current consumed for the balancing while performing the balancing of the cell to be balanced; and

e) completing the balancing of the cell to be balanced when the accumulative amount of charges equals the total amount of charges.

2. The cell balancing method according to claim 1, wherein the step a) further comprises steps of:

a1) discriminating whether or not a zero current state exists in which the current is not supplied from the battery pack to a load connected to the battery pack;

a2) measuring the terminal voltage of each cell composing the battery pack to use the measured terminal voltage of each cell as the electromotive force of each cell when a duration time of the zero current state is greater than a first threshold time t1, if the zero current state exists;

a3) measuring the terminal voltage of each cell composing the battery pack to use the measured terminal voltage of each cell as the electromotive force of each cell when the current of the battery pack of less than a threshold amount of current i1 flows for greater than a second threshold time t2, if the zero current state does not exist.

3. The cell balancing method according to claim 2, wherein the first threshold time t1 and the second threshold time t2 are 30 seconds to 60 seconds independently from each other, respectively.

4. The cell balancing method according to claim 2, wherein the threshold amount of current it is up to 3A.

5. The cell balancing method according to claim 1, wherein the step b) comprises selecting the cell having a deviation greater than an allowable deviation from a lowest electromotive force as the cell to be balanced, based on the lowest electromotive force of cell.

6. The cell balancing method according to claim 5, wherein the allowable deviation is in a range of 2% to 5%.

7. The cell balancing method according to claim 1, wherein the total amount of charges in the step c) is computed from the state of charge (SOC) of each cell corresponding to the electromotive force of each cell using a lookup table of the electromotive force and the state of charge (SOC).

8. The cell balancing method according to claim 1, wherein the accumulative amount of charges in the step d) is obtained by measuring the terminal voltage of the cell to be balanced at a regular time interval, finding a balancing amount of charges consumed for a regular time interval using the lookup table of the terminal voltage and the state of charge (SOC), and accumulating the balancing amount of charges.

9. The cell balancing method according to claim 7, wherein the lookup table is a two-dimensional lookup table of the electromotive force, the temperature and the state of charge (SOC).

10. The cell balancing method according to claim 8, wherein the lookup table is a two-dimensional lookup table of the terminal voltage, the temperature and the state of charge (SOC).