BATTERY PACK THERMISTOR TEST METHOD

• US 20140369376A1
• Filed: 06/18/2013
• Published: 12/18/2014
• Est. Priority Date: 06/18/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Keeton, Robert C.
• Granted Patent: US 9,488,535 B2
• Time in Patent Office: Days
• US Class Current: 374/1
• CPC Class Codes: G01K 15/007 Testing
• CPC Class Codes: G01K 2205/00 Application of thermometers in motors, e.g. of a vehicle

Abstract

A battery pack thermistor test method includes charging a battery pack, monitoring a rise in average temperature reported by at least one thermistor on the battery pack over a predetermined time period, preparing at least one thermistor slope by calculating a least square fit of time vs. temperature for the at least one thermistor and comparing the at least one thermistor slope to process-defined thermistor slope limits.

Claims

1. A battery pack thermistor test method, comprising:

charging a battery pack;

monitoring a rise in average temperature reported by at least one thermistor on the battery pack over a predetermined time period;

preparing at least one thermistor slope by calculating a least square fit of time vs. temperature for the at least one thermistor; and

comparing the at least one thermistor slope to process-defined thermistor slope limits.

2. The method of claim 1 wherein charging a battery pack comprises applying a controlled charge profile to a battery pack cell in the battery pack.

3. The method of claim 2 wherein applying a controlled charge profile comprises applying a stepped current over a predetermined time period.

4. The method of claim 3 wherein applying a stepped current comprises applying a stepped current of constant durations over a predetermined time period.

5. The method of claim 4 wherein applying a stepped current of constant durations over a predetermined time period comprises applying a stepped current of constant durations of about 5.0 seconds each.

6. The method of claim 3 wherein applying a stepped current over a predetermined time period comprises applying a stepped current having a final step corresponding to a peak current the battery pack and the battery pack cell can withstand.

7. The method of claim 6 wherein applying a stepped current having a final step corresponding to a peak current the battery pack and the battery pack cell can withstand comprises applying a stepped current of about 10.0 seconds.

8. The method of claim 1 further comprising rejecting the battery pack if the thermistor slope falls outside the thermistor slope limits.

9. A battery pack thermistor test method, comprising:

stabilizing a battery pack to room temperature with state of charge not exceeding about 10%;

monitoring a rise in average temperature as reported by at least one thermistor in the battery pack;

charging the battery pack;

monitoring a rise in average temperature reported by at least one thermistor on the battery pack over a predetermined time period;

preparing at least one thermistor slope by calculating a least square fit of time vs. temperature for the at least one thermistor; and

comparing the at least one thermistor slope to process-defined thermistor slope limits.

10. The method of claim 9 wherein charging a battery pack comprises applying a controlled charge profile to a battery pack cell in the battery pack.

11. The method of claim 10 wherein applying a controlled charge profile comprises applying a stepped current over a predetermined time period.

12. The method of claim 11 wherein applying a stepped current comprises applying a stepped current of constant durations over a predetermined time period.

13. The method of claim 12 wherein applying a stepped current of constant durations over a predetermined time period comprises applying a stepped current of constant durations of about 5.0 seconds each.

14. The method of claim 11 wherein applying a stepped current over a predetermined time period comprises applying a stepped current having a final step corresponding to a peak current the battery pack and the battery pack cell can withstand.

15. The method of claim 14 wherein applying a stepped current having a final step corresponding to a peak current the battery pack and the battery pack cell can withstand comprises applying a stepped current of about 10.0 seconds.

16. The method of claim 9 further comprising rejecting the battery pack if the thermistor slope falls outside the thermistor slope limits.

17. A battery pack thermistor test method, comprising:

stabilizing a battery pack to room temperature with state of charge not exceeding about 10%;

monitoring a rise in average temperature as reported by at least one thermistor in the battery pack;

cycling through a charge profile of stepped current applied to the battery pack;

waiting for a rise in temperature as reported by the at least one thermistor;

waiting for a duration of a final step in the charge profile;

determining whether a temperature rise is reported by the at least one thermistor within a predetermined time period;

waiting for a time period corresponding to the duration of the final step in the charge profile;

preparing at least one thermistor slope by calculating a least square fit of time vs. temperature for the at least one thermistor; and

comparing the at least one thermistor slope to process-defined thermistor slope limits.

18. The method of claim 17 further comprising rejecting the battery pack if the temperature rise is not reported by the at least one thermistor within the predetermined time period.

19. The method of claim 17 further comprising rejecting the battery pack if the thermistor slope falls outside the thermistor slope limits.

20. The method of claims 17 wherein cycling through a charge profile of stepped current comprises cycling through a charge profile of stepped current having constant durations of about 5.0 seconds each.