METHOD FOR PERFORMING CELL BALANCING OF A BATTERY SYSTEM BASED ON CELL CAPACITY VALUES

• US 20140114594A1
• Filed: 10/22/2012
• Published: 04/24/2014
• Est. Priority Date: 10/22/2012
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Schaefer, Sascha
• Granted Patent: US 9,379,416 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/21 having the same nominal voltage
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: H01M 10/4207 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 2010/4271 Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• 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

A method for calculating the charge to balance for cells in a multi-cell battery. The method determines a depletion-goal state of charge (SOC) for the battery cells. The method determines a corresponding set of depletion-goal charges and usable charges for the set of cells, where the depletion-goal charge is calculated using the corresponding charge capacity and depletion-goal SOC and the usable charge is calculated using the corresponding actual charge and depletion-goal charge. The method determines a charge-bias using the set of usable charges. The method determines for the set of cells a corresponding set of charges to balance from the set of usable charges and the charge-bias.

Claims

1. A method for calculating a charge to balance for cells in a multi-cell battery comprising:

determining a depletion-goal state of charge for the cells in the battery;

receiving a corresponding set of charge capacities and a corresponding set of actual charges for a set of cells in the battery;

determining a corresponding set of depletion-goal charges and a corresponding set of usable charges for the set of cells, where the depletion-goal charge is determined using the corresponding charge capacity, and the usable charge is determined using the corresponding actual charge and the corresponding depletion-goal charge;

determining a charge-bias using the set of usable charges; and

calculating a corresponding set of charges to balance from the set of usable charges and the charge-bias for the set of cells.

2. The method of claim 1 wherein determining the corresponding set of actual charges includes using a measurement of the corresponding cells.

3. The method of claim 2 where the measurement is a measurement of voltage.

4. The method of claim 1 wherein determining the corresponding set of actual charges includes using a measurement of charges flowing in and out of the corresponding cells.

5. The method of claim 1 wherein determining the charge-bias using the set of usable charges uses the lowest usable charge from the set of usable charges.

6. The method of claim 1 wherein determining the actual charge includes using the equation:

Q_i,actual=C_i·

SOC_i,actual,

where Q_i,actual is the actual charge content that individual cell i is currently holding, C_i is the capacity of cell i to hold charge, and SOC_i,actual is the actual state of charge of cell i.

7. The method of claim 1 wherein determining the depletion goal charge includes using the equation:

Q_i,goal=C_i·

SOC_goal,

where Q_i,goal is the depletion-goal charge for an individual cell i, C_i is the capacity of cell i to hold charge, and SOC_goal is the state of charge depletion-goal for the cells in the battery.

8. The method of claim 1 wherein determining the amount of charge to balance includes using the equation:

Q_i,CB=Q_i,actual−

Q_i,goal−

Q_Bias,

where Q_i,CB is the charge to balance for cell i, Q_i,actual is the actual charge content that individual cell i is currently holding, Q_i,goal is the depletion-goal charge for an individual cell i, and Q_Bias is the amount of charge that can be used during operation before the cell with least usable charge reaches depletion-goal charge.

9. The method of claim 1 further comprising controlling a balancing circuits of the battery using the set of charges to balance so that the battery gets closer to an optimized charge state.

10. The method of claim 9 wherein determining the depletion goal charge includes using the equation:

Q_i,goal=C_i·

SOC_goal,

where Q_i,goal is the depletion-goal charge for individual cell i and SOC_goal is the state of charge depletion-goal for the cells in the battery; and

wherein calculating the amount of charge to balance includes using the equation;

Q_i,CB=Q_i,actual−

Q_i,goal−

Q_Bias,

where Q_i,CB is the charge to balance for cell i and Q_Bias is the amount of charge that is the usable charge from the cell with the lowest useable charge that can be used during operation before the cell with least usable-charge reaches the depletion-goal charge.

11. The method of claim 1 wherein the set of cells in the battery includes all of the cells in the battery.

12. A method for calculating the charge to balance for a cell in a multi-cell battery comprising:

determining a first charge capacity for a first cell in the battery;

determining a second charge capacity for a second cell in the battery;

determining a first state of charge (SOC) for the first cell;

determining a second SOC for the second cell;

calculating a first usable charge for the first cell using the first charge capacity and the first SOC;

calculating a second usable charge for the second cell using the second charge capacity and the second SOC;

determining a charge-bias for calculating a charge to balance; and

calculating a first charge to balance using the first charge capacity, the first SOC and the charge-bias for the first cell.

13. The method of claim 12 wherein determining the first usable charge and the second usable charge includes using a depletion-goal SOC.

14. The method of claim 12 wherein determining the charge-bias includes using the first usable charge and the second usable charge.

15. The method of claim 12 further comprising using the charge to balance for controlling a balancing circuit of the battery so that the battery gets closer to an optimized charged state.

16. A method for calculating a charge to balance cells in a multi-cell battery comprising:

determining a first usable charge for a first cell of the multi-cell battery;

determining a second usable charge for a second cell of the multi-cell battery;

determining a charge-bias using the first usable charge and the second usable charge; and

calculating a charge to balance for the first cell using the charge-bias and the first usable charge.

17. The method of claim 16 wherein determining the first or second usable charge includes measuring the capacity of the first or second cell to hold charge.

18. The method of claim 16 wherein determining the first usable charge and the second usable charge includes using a depletion-goal state of charge.

19. The method of claim 16 wherein determining the first or second usable charge includes determining the state of charge of the first or second cell.

20. The method of claim 16 further comprising using the charge to balance to control the balancing circuit of the battery so that the battery gets closer to an optimized charged state.