METHOD OF DEACTIVATING FAULTY BATTERY CELLS

• US 20090023053A1
• Filed: 07/18/2007
• Published: 01/22/2009
• Est. Priority Date: 07/18/2007
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Motors Incorporated (Tesla Inc.)
• Inventors: Kohn, Scott Ira, Berdichevsky, Eugene Michael, Kelty, Kurt Russell
• Granted Patent: US 7,683,575 B2
• Time in Patent Office: Days
• US Class Current: 429/61
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• 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 and apparatus for deactivating a bad battery cell from a battery pack for an energy storage system of an electric vehicle is disclosed. The apparatus and methodology includes a clamshell member arranged at an end of the cells and a printed circuit board arranged adjacent to the clamshell member. A collector plate is arranged adjacent to the printed circuit board and a switch is arranged on the printed circuit board. A wire bond is arranged between the switch and one of the cells and a second wire bond is arranged between the switch and the collector plate. The plurality of switches will allow for the identification of the one individual cell having a weak short circuit within the battery pack. Upon identification of the cell with the weak short circuit that cell will have its switch placed in an open position thus electrically isolating the faulty or bad cell from the battery pack.

Claims

1. A method of deactivating bad battery cells in an electric vehicle, said method including the steps of:

checking for a weak short circuit in the cells;

determining which individual cell has said weak short circuit; and

disconnecting said cell with said weak short circuit from the other cells.

2. The method of claim 1 wherein said step of determining includes tracking via a battery monitor board which cell or group of cells self discharge the most during a predetermined period when the vehicle is at rest or over an aggregate of rest and drive periods.

3. The method of claim 1 wherein said step of determining includes tracking the amount of time each group of cells requires resistive balancing by a battery monitor board to determine which group of the cells requires the least amount of balancing time.

4. The method of claim 1 wherein said steps of determining includes tracking which cells require more energy during voltage balancing than a bleeder cell is capable of giving during said balancing.

5. The method of claim 1 wherein said step of disconnecting includes physically breaking the electrical contact of said weak short circuit cell from the electric vehicle.

6. The method of claim 1 wherein said step of disconnecting includes opening a switch electrically connected to said weak short circuit cell.

7. The method of claim 1 wherein said step of disconnecting includes leaving a switch open which is normally closed for said weak short circuit cell to isolate or disconnect said bad cell from the electric vehicle.

8. The method of claim 1 wherein said step of determining includes detecting said weak short circuit cell by switching each of the cells off one by one and monitoring if said weak short circuit continues or persists.

9. The method of claim 1 further including the step of connecting electrically in series with every cell an electronically controlled switch.

10. The method of claim 1 wherein said step of disconnecting includes reducing the likelihood of said weak short circuit via thermal management of the cells.

11. The method of claim 1 wherein said step of disconnecting includes implementing charge management of the cells to ensure no overcharge of the cells occur to reduce likelihood of said weak short circuit.

12. The method of claim 1 wherein said step of determining includes implementing instructions in service manuals to check the cells in the electric vehicle for weak short circuits before placement in the electric vehicle, before customers delivery of vehicle or during routine service of the electric vehicle.

13. The method of claim 1 wherein said step of determining includes charging a low parallel group of cells and tracking which of said cells has to have most of said charge added.

14. An apparatus for deactiving a bad battery cell from a battery pack of cells of an energy storage system for an electric vehicle, said apparatus includes:

a clamshell member arranged at an end of the cells;

a printed circuit board adjacent to said clamshell member;

a collector plate arranged adjacent to said printed circuit board;

a switch arranged on said printed circuit board;

a wire bond arranged between said switch and one of the cells; and

a second wire bond arranged between said switch and said collector plate.

15. The apparatus of claim 14 further including an embedded processor in electrical communication with said switch.

16. The apparatus of claim 15 wherein said switch is connected to every cell of the energy storage system, said switches are connected in series and electronically controlled by said embedded processor.

17. The apparatus of claim 15 wherein said embedded processor is arranged on said printed circuit board.

18. The apparatus of claim 16 wherein said switches are closed during normal operation connecting all cells of the battery pack.

19. The apparatus of claim 18 wherein one of said switches is opened when a weak short circuit is detected to eliminate said weak short circuit from the battery pack.

20. The apparatus of claim 19 wherein said weak short circuit is detected by said embedded processor by switching each said cell off one by one and monitoring if said weak short circuit persists.

21. The apparatus of claim 16 wherein said switches are normally open so an off state requires no power.

22. The apparatus of claim 21 wherein one of said switches is left in said open state when a weak short circuit is detected in one of the cells.

23. The apparatus of claim 14 wherein said printed circuit board having a pair of traces for each cell, said traces connect to a multiplexer which multiplexes said traces to a voltage measurement circuit.

24. The apparatus of claim 23 further including a third and fourth wirebond, a voltage is measured across all parallel cells one by one to check for a weak short circuit by detecting a negative voltage drop.

25. The apparatus of claim 24 wherein said traces are switched to a different circuit that would apply a current through said wirebond connected to the cell with said weak short circuit greater than the fusing current of said wirebond.