Battery Pack Overcharge Protection System

• US 20120105015A1
• Filed: 10/29/2010
• Published: 05/03/2012
• Est. Priority Date: 10/29/2010
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Motors Incorporated (Tesla Inc.)
• Inventors: Hermann, Weston Arthur, Kohn, Scott Ira, Kalayjian, Nicholas Robert, Cole, Philip David
• Granted Patent: US 8,659,270 B2
• Time in Patent Office: Days
• US Class Current: 320/164
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

An overcharge protection device (OPD) is provided that may be used alone, or in combination with conventional charging protection systems, to protect a battery pack from the occurrence of a potentially damaging overcharging event. The OPD is designed to be coupled to, and interposed between, the terminals of the battery pack. During normal system operation, the OPD has no effect on the operation of the charging system or the battery pack. During an overcharging event, if overcharging is not prevented by another conventional system, the OPD of the invention creates a short across the terminals of the battery pack causing a battery pack fuse designed to provide battery pack short circuit protection to blow, thereby interrupting the current path from the charger to the battery pack and preventing the battery pack from being overcharged.

Claims

1. A method of protecting a battery pack from overcharging during a battery pack charging cycle, wherein during said battery pack charging cycle a source of charging power is coupled to the battery pack and provides charging power to the battery pack, said method comprising the steps of:

electrically connecting a first lead of an overcharge protection device (OPD) to a first output terminal of said battery pack;

electrically connecting a second lead of said OPD to a second output terminal of said battery pack, wherein said second output terminal represents an oppositely charged terminal of said battery pack; and

monitoring a voltage corresponding to said charging power during said battery pack charging cycle, wherein said monitoring step is performed by said OPD and wherein if said voltage exceeds a predetermined trigger voltage said OPD further performs the step of creating a short between said first and second output terminals of said battery pack, wherein said short causes a fuse corresponding to said battery pack to blow.

2. The method of claim 1, wherein said step of electrically connecting said first lead of said OPD to said first output terminal of said battery pack further comprises the step of locating an electrical connection between said first lead of said OPD and said first output terminal of said battery pack between said source of charging power and a first terminal contactor, wherein said first terminal contactor corresponds to said source of charging power.

3. The method of claim 2, wherein said step of electrically connecting said second lead of said OPD to said second output terminal of said battery pack further comprises the step of locating an electrical connection between said second lead of said OPD and said second output terminal of said battery pack between said source of charging power and a second terminal contactor, wherein said second terminal contactor corresponds to said source of charging power.

4. The method of claim 1, wherein said step of electrically connecting said first lead of said OPD to said first output terminal of said battery pack further comprises the step of locating an electrical connection between said first lead of said OPD and said first output terminal of said battery pack between a first terminal contactor and said first output terminal of said battery pack, wherein said first terminal contactor corresponds to said source of charging power.

5. The method of claim 4, wherein said step of electrically connecting said second lead of said OPD to said second output terminal of said battery pack further comprises the step of locating an electrical connection between said second lead of said OPD and said second output terminal of said battery pack between a second terminal contactor and said second output terminal of said battery pack, wherein said second terminal contactor corresponds to said source of charging power.

6. The method of claim 1, further comprising the steps of selecting an IGBT with a threshold voltage corresponding to said predetermined trigger voltage for said OPD, wherein said IGBT passes current and shorts said battery pack when said voltage exceeds said threshold voltage.

7. The method of claim 6, further comprising the step of thermally coupling said IGBT to a heat sink to increase the I²t value of the IGBT.

8. The method of claim 1, further comprising the step of selecting a crowbar circuit with a trip voltage corresponding to said predetermined trigger voltage for said OPD, wherein said crowbar circuit passes current and shorts said battery pack when said voltage exceeds said trip voltage.

9. The method of claim 1, further comprising the step of selecting a solenoid relay switch with a threshold voltage corresponding to said predetermined trigger voltage for said OPD, wherein said solenoid relay switch closes and passes current and shorts said battery pack when said voltage exceeds said threshold voltage.

10. A system that provides overcharge protection for a battery pack during a battery pack charging cycle, wherein during said battery pack charging cycle a source of charging power is coupled to the battery pack and provides charging power to the battery pack, the system comprising an overcharge protection device (OPD) electrically coupled to a first output terminal and a second output terminal of the battery pack, said battery pack comprised of at least one cell, wherein said OPD is interposed between said first and second output terminals, wherein said OPD creates a short between said first and second output terminals if a charging voltage corresponding to said charging power exceeds a predetermined OPD trigger voltage, and wherein said OPD has a sufficiently large I²t to cause a fuse corresponding to the battery pack to blow.

11. The system of claim 10, wherein said OPD is electrically coupled to said first output terminal at a location between said source of charging power and a first terminal contactor, wherein said first terminal contactor corresponds to said source of charging power.

12. The system of claim 11, wherein said OPD is electrically coupled to said second output terminal at a location between said source of charging power and a second terminal contactor, wherein said second terminal contactor corresponds to said source of charging power.

13. The system of claim 10, wherein said OPD is electrically coupled to said first output terminal at a location between a first terminal contactor and said first output terminal, wherein said first terminal contactor corresponds to said source of charging power.

14. The system of claim 13, wherein said OPD is electrically coupled to said second output terminal at a location between a second terminal contactor and said second output terminal, wherein said second terminal contactor corresponds to said source of charging power.

15. The system of claim 10, further comprised of an RC circuit electrically interposed between said OPD and said first output terminal.

16. The system of claim 10, wherein said OPD does not include a processor and does not include a secondary source of power separate from the battery pack.

17. The system of claim 10, wherein said OPD is comprised of an IGBT.

18. The system of claim 17, further comprising a heat sink in thermal contact with said IGBT.

19. The system of claim 10, wherein said OPD is comprised of a crowbar circuit.

20. The system of claim 19, wherein said crowbar circuit is comprised of at least a zener diode and a silicon controlled rectifier.

21. The system of claim 10, wherein said OPD is comprised of at least one solenoid relay switch.