Systems, methods and circuits for determining micro-short

• US 8,049,465 B2
• Filed: 10/10/2007
• Issued: 11/01/2011
• Est. Priority Date: 10/10/2007
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Elder, Garry, Qian, Jinrong, Barsoukov, Yevgen P.
• Primary Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US11/869,793
• Publication Number:
  US 20090099799A1
• Time in Patent Office: 1,483 Days
• Field of Search: 320/132
• US Class Current: 320/132
• 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 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Various systems and methods for determining micro-shorts are disclosed. For example, some embodiments of the present invention provide battery systems including a determination of potential micro-shorts based on rate of change of state of charge. Such battery systems include: a battery, a processor, and a computer readable medium. The computer readable medium includes instructions executable by the processor to: determine a rate of change of the state of charge of the battery; compare the rate of change of the state of charge of the battery against a threshold; and indicate a potential failure where the result of the comparison is beyond the threshold.

Claims

1. A method for predicting battery failure, the method comprising:

providing a battery comprising at least one cell;

determining a time rate of change of a state of charge of the cell during a period of no activity of a connected external load;

comparing the time rate of change of the state of charge of the cell against a threshold; and

determining a potential failure condition based on a value of self-discharge providing an indication of micro-shorts within the battery as a result of the comparison of the time rate of change of the state of charge of the cell with the threshold.

2. The method of claim 1, wherein the battery is a single cell battery, and wherein the method further comprises:

adjusting the time rate of change of the state of charge of the battery to compensate for external load current.

3. The method of claim 1, wherein the battery is a multi-cell battery having at least a first cell and a second cell, wherein determining the time rate of change of the state of charge of the battery includes determining the time rate of change of the state of charge of the first cell and determining the time rate of change of the state of charge of the second cell, and wherein the method further comprises:

determining a difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell.

4. The method of claim 3, wherein comparing the time rate of change of the state of charge of the battery against a threshold includes comparing the difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell with the threshold.

5. The method of claim 1, wherein the method further comprises:

determining whether the battery is relaxed; and

determining the state of charge of the battery, wherein the state of charge of the battery is used to determine the time rate of change of the state of charge of the battery.

6. The method of claim 5, wherein the battery is a multi-cell battery, wherein the multi-cell battery includes at least a first cell and a second cell, wherein determining the state of charge of the battery includes determining the state of charge of the first cell and determining the state of charge of the second cell, and wherein the method further comprises:

calculating a normalized state of charge of the first cell to a known state; and

calculating a normalized state of charge of the second cell to the known state.

7. The method of claim 6, wherein determining the time rate of change of the state of charge of the battery includes determining the time rate of change of the state of charge of the first cell using the normalized state of charge of the first cell, and determining the time rate of change of the state of charge of the second cell using the normalized state of charge of the second cell, and wherein the method further comprises:

determining a difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell; and

wherein comparing the time rate of change of the state of charge of the battery against a threshold includes comparing the difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell with the threshold.

8. The method of claim 1, wherein determining the time rate of change of the state of charge of the battery is done by correlating measured voltage with state-of-charge using a pre-defined correlation function.

9. A battery system including predictive failure determination capability based on time rate of change of state of charge, wherein the battery system comprises:

a battery comprising at least one cell;

a processor; and

a computer readable medium, wherein the computer readable medium includes instructions executable by the processor to;

determine a time rate of change of the state of charge of the cell during a period of no activity of a connected external load;

compare the time rate of change of the state of charge of the cell against a threshold; and

indicate a potential failure based on a value of self-discharge providing an indication of micro-shorts within the battery where the result of the comparison is beyond the threshold.

10. The battery system of claim 9, wherein the battery is a single cell battery.

11. The battery system of claim 10, wherein the computer readable medium further includes instructions executable by the processor to adjust the time rate of change of the state of charge of the battery to compensate for external load current.

12. The battery system of claim 9, wherein the battery is a multi-cell battery, and wherein the multi-cell battery includes at least a first cell and a second cell.

13. The battery system of claim 12, wherein determining the time rate of change of the state of charge of the battery includes determining the time rate of change of the state of charge of the first cell and determining the time rate of change of the state of charge of the second cell, and wherein the computer readable medium further includes instructions executable by the processor to:

determine a difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell.

14. The battery system of claim 13, wherein comparing the time rate of change of the state of charge of the battery against a threshold includes comparing the difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell with the threshold.

15. The battery system of claim 9, wherein the computer readable medium further includes instructions executable by the processor to:

determine whether the battery is relaxed; and

determine the state of charge of the cell , wherein the state of charge of the cell is used to determine the time rate of change of the state of charge of the cell.

16. The battery system of claim 15, wherein the battery is a multi-cell battery, wherein the multi-cell battery includes at least a first cell and a second cell, and wherein determining the state of charge of the battery includes determining the state of charge of the first cell and determining the state of charge of the second cell.

17. The battery system of claim 16, wherein the computer readable medium further includes instructions executable by the processor to:

calculating a normalized state of charge of the first cell to a known state; and

calculating a normalized state of charge of the second cell to the known state.

18. The battery system of claim 17, wherein determining the time rate of change of the state of charge of the battery includes determining the time rate of change of the state of charge of the first cell using the normalized state of charge of the first cell, and determining the time rate of change of the state of charge of the second cell using the normalized state of charge of the second cell.

19. The battery system of claim 18, wherein the computer readable medium further includes instructions executable by the processor to:

determine a difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell.

20. The battery system of claim 19, wherein comparing the time rate of change of the state of charge of the battery against a threshold includes comparing the difference between the time rate of change of the state of charge of the first cell and the time rate of change of the state of charge of the second cell with the threshold.

21. An electronic system, wherein the electronic system comprises:

a battery powered electronic circuit, wherein the battery powered electronic circuit includes a device processor; and

a battery system, wherein the battery system powers the electronic circuitry, and wherein the battery system includes;

a battery comprising at least one cell;

a processor; and

a computer readable medium, wherein the computer readable medium includes instructions executable by the processor to;

determine a time rate of change of the state of charge of the cell during a period of no activity of a connected external load;

compare the time rate of change of the state of charge of the cell against a threshold; and

indicate a potential failure based on a value of self-discharge providing an indication of micro-shorts within the battery where the result of the comparison is beyond the threshold.