Method for detecting battery thermal events via battery pack isolation resistance monitoring

• US 8,178,227 B1
• Filed: 01/13/2012
• Issued: 05/15/2012
• Est. Priority Date: 08/23/2011
• Status: Active Grant

• Current Assignee: Tesla Motors Incorporated (Tesla Inc.)
• Original Assignee: Tesla Motors Incorporated (Tesla Inc.)
• Inventors: Hermann, Weston Arthur
• Primary Examiner(s): Ridley, Basia
• Assistant Examiner(s): Cullen, Sean P
• Application Number:
  US13/349,669
• Time in Patent Office: 123 Days
• Field of Search: 429/50, 429 90- 93, 324/500, 324/525
• US Class Current: 429/92
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2250/10 by alarm
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: B60L 3/04 Cutting off the power supply under fault conditions protective devices and circuit arrangements in general H01H; H02H
• CPC Class Codes: B60L 50/64 Constructional details of batteries specially adapted for electric vehicles
• CPC Class Codes: B60L 58/21 having the same nominal voltage
• CPC Class Codes: B60L 58/25 by controlling the electric load
• CPC Class Codes: B60L 58/26 by cooling
• CPC Class Codes: G01R 31/1263 of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/486 for measuring temperature
• 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 detecting cell failure within a battery pack based on variations in the measured electrical isolation resistance of the battery pack is provided. The method includes the steps of monitoring the isolation resistance; determining when the isolation resistance falls below a first preset value; determining how long it takes for the electrical isolation resistance to recover to greater than a second preset value; determining when the isolation resistance falls below a third preset value; and performing a predetermined response after the electrical isolation resistance falls below the first preset resistance value and recovers to greater than the second resistance value and then falls below the third preset resistance value and if the time period is within a preset time range.

Claims

1. A method of detecting and responding to a cell failure of at least one cell of a plurality of cells comprising a battery pack, the method comprising the steps of:

periodically monitoring an electrical isolation resistance of said battery pack;

comparing said electrical isolation resistance to a first preset resistance value;

determining when said electrical isolation resistance falls below said first preset resistance value;

determining when said electrical isolation resistance recovers to greater than a second preset resistance value, wherein said step of determining when said electrical isolation resistance recovers to greater than said second preset resistance value is performed after said electrical isolation resistance is determined to have fallen below said first preset resistance value;

determining a time period from a first time when said electrical isolation resistance is determined to have fallen below said first preset resistance value to a second time when said electrical isolation resistance is determined to have recovered to greater than said second preset resistance value;

determining if said time period is within a preset time range;

determining when said electrical isolation resistance falls below a third preset resistance value, wherein said step of determining when said electrical isolation resistance falls below said third preset resistance value is performed after said electrical isolation resistance recovers to greater than said second preset resistance value; and

performing a predetermined cell failure response after said electrical isolation resistance falls below said first preset resistance value and recovers to greater than said second resistance value and then falls below said third preset resistance value and if said time period is within than said preset time range.

2. The method of claim 1, further comprising the step of setting said first preset resistance value to a percentage of an initial electrical isolation resistance of said battery pack.

3. The method of claim 2, wherein said percentage is selected from a range of 25% to 50%.

4. The method of claim 2, wherein said percentage is selected from a range of 10% to 25%.

5. The method of claim 1, further comprising the steps of:

setting said first preset resistance value to a first percentage of an initial electrical isolation resistance of said battery pack, wherein said first percentage is selected from a range of 10% to 50%;

setting said second preset resistance value to a second percentage of said initial electrical isolation resistance of said battery pack, wherein said second percentage is selected from a range of 50% to 95%;

setting said third preset resistance value to a third percentage of said initial electrical isolation resistance of said battery pack, wherein said third percentage is selected from a range of 10% to 50%; and

setting said preset time range to be between 10 seconds and 20 minutes.

6. The method of claim 1, further comprising the steps of:

setting said first preset resistance value to a first percentage of an initial electrical isolation resistance of said battery pack, wherein said first percentage is selected from a range of 10% to 25%;

setting said second preset resistance value to a second percentage of said initial electrical isolation resistance of said battery pack, wherein said second percentage is selected from a range of 75% to 90%;

setting said third preset resistance value to a third percentage of said initial electrical isolation resistance of said battery pack, wherein said third percentage is selected from a range of 10% to 25%; and

setting said preset time range to be between 10 seconds and 20 minutes.

7. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of activating a visual warning indicator.

8. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of activating an audible warning indicator.

9. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of reducing an electrical load on said plurality of cells of said battery pack.

10. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of minimizing an electrical load on said plurality of cells of said battery pack.

11. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of increasing cooling applied to said battery pack by a battery pack cooling system.

12. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of activating a fire containment system.

13. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of recording date and time information corresponding to said electrical isolation resistance falling below said first preset resistance value.

14. The method of claim 1, wherein said step of performing said predetermined cell failure response further comprises a step of transmitting a notification message via a communication and notification subsystem.