CELL BALANCING BATTERY PACK AND METHOD OF BALANCING THE CELLS OF A BATTERY

• US 20080180061A1
• Filed: 01/26/2007
• Published: 07/31/2008
• Est. Priority Date: 01/26/2007
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Lindquist, Paul Daniel, Koski, Roy Donald
• Granted Patent: US 7,598,706 B2
• Time in Patent Office: Days
• US Class Current: 320/117
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0024 Parallel/serial switching of connection of batteries to charge or load circuit
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery with a battery balancing assembly that regulates the discharge of battery cell charge and a method of evenly discharging battery cells, the battery comprising a plurality of cells. The balancing assembly includes switches disposed between the cells such that the switches may configure the cells in a normal configuration and a balance configuration, wherein in the normal configuration the plurality of cells may be connected to an electronic device and wherein in the balance configuration the plurality of cells are connected to a balancing circuit. The balancing circuit serving to balance the charge in the plurality of cells prior to the recharging of the cell.

Claims

1. A rechargeable battery for storing a charge and providing a charge to a load, comprising:

a plurality of cells disposed to be connected to the load;

a plurality of switches between the plurality of cells and the load, each of the switches being positionable in a closed state whereby electrical current is allowed to pass and an open state whereby no electrical current is allowed to pass, the plurality of switches having a normal configuration wherein the plurality of switches connect the cells in series and a balance configuration wherein the plurality of switches connect the cells in parallel; and

a balancing circuitry connected in parallel with the plurality of cells when the plurality of switches are in the balance configuration.

2. The battery of claim 1, wherein the balancing circuitry comprises a constant-current, constant-voltage discharge load.

3. The battery of claim 2, further comprising a controller that controls the movement of the switches between the open and closed states, wherein the controller operates the plurality of switches to the balance configuration and selectively connects the balancing circuitry to the plurality of cells.

4. The battery of claim 3, wherein the controller is manually operated to switch the configuration of the switches.

5. The battery of claim 3, wherein the controller uses software to switch the configuration of the switches.

6. The battery of claim 2 wherein the plurality of cells are a plurality of lithium ion cells.

7. The battery of claim 6, wherein the normal configuration and the balance configuration comprise at least one switch in the open state and at least one switch in the closed state.

8. A battery balancing assembly for regulating the discharge of a plurality of battery cells to a load, the balancing circuit comprising:

a plurality of switches between the plurality of battery cells and the load, each of the switches being positionable in a closed state whereby electrical current is allowed to pass and a open state whereby no electrical current is allowed to pass, the plurality of switches having a normal configuration wherein the plurality of switches connect the cells in series and a balance configuration wherein the plurality of switches connect the cells in parallel; and

a balancing circuitry, selectively connected to the plurality of battery cells, the balancing circuitry comprising a programmable discharge load;

wherein when the plurality of switches are in a balance configuration, a the plurality of battery cells are discharged by the balancing circuitry.

9. The balancing assembly of claim 8, further comprising a controller for controlling the position of the switches being in the normal configuration, wherein the plurality of battery cells are connected to a load, and the balance configuration, wherein the plurality of battery cells are connected to the balancing circuitry.

10. The balancing assembly of claim 9, wherein the normal configuration comprises the plurality of switches in a state to connect the plurality of battery cells in series and the balance configuration comprises the plurality of switches in a state to connect the plurality of battery cells in parallel with the balancing circuitry.

11. The balancing assembly of claim 8, wherein the balancing circuitry is attached to the plurality of battery cells in a battery for use in a medical device.

12. A method of evenly discharging a plurality of electrical cells configured to provide electrical power as a battery, the method comprising:

attaching the plurality of electrical cells to a balancing circuit, the balancing circuit comprising a programmable load, the programmable load drawing a current;

operating the programmable load until the voltage of each cell reaches a minimum discharge voltage;

increasing the resistance of the programmable load with respect to a change in the current to maintain the minimum recommended discharge voltage for each cell; and

discharging the cells until the current drawn from each cell is tapered below a predetermined threshold current.

13. The method of claim 12 wherein discharging the cells forces a balance in the voltage, state of charge, and remaining capacity at the point of chemical discharge.

14. The method of claim 13 wherein the remaining cell capacity for each cell is maintained constant throughout the charge and discharge cycle.

15. The method of claim 12, further comprising:

sensing the level of charge in each of the plurality of cells; and

upon sensing that the charge of one of the plurality of cells is below a predetermined threshold, discharging the plurality of cells.

16. The method of claim 15, further comprising:

producing an indication of the remaining charge in the plurality of cells based on the sensed level of charge; and

producing a signal indicative of the remaining charge in the plurality of cells.

17. The method of claim 12, further comprising recharging the battery pack to a full de-rated capacity.

18. The method of claim 17, wherein the cells are recharged until a cell is charged to a predetermined maximum cell voltage threshold.

19. The method of claim 18, wherein the method is performed before the cells are assembled into the battery.

20. The method of claim 18, wherein the method is performed after the cells are assembled into the battery.