Apparatus and method for testing rechargeable energy storage batteries

• US 6,441,585 B1
• Filed: 06/15/2000
• Issued: 08/27/2002
• Est. Priority Date: 06/16/1999
• Status: Expired due to Term

• Current Assignee: Midtronics Incorporated
• Original Assignee: Midtronics Incorporated
• Inventors: Bertness, Kevin I.
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/595,102
• Time in Patent Office: 803 Days
• Field of Search: 320/132, 320/149, 320/DIG.21, 324/426, 324/427, 324/430, 324/433, 324/446
• US Class Current: 320/132
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

An improved battery testing system and method is disclosed. The system measures an open circuit voltage and a dynamic parameter of a test battery, and uses those measurements, along with correlation data stored in memory, to determine a physical condition and/or charge state of the battery. The measured dynamic parameter may be scaled based on the rating of the test battery. Also, a high current load pulse may be applied to the test battery and a wait period implemented before the open circuit voltage is measured. In addition, the charge state may be determined from a state of charge value, and categorized into one of several charge state ranges. In one embodiment, the state of charge value is determined from the relative distance along a curve, represented by the correlation data stored in memory, that the measured open circuit voltage is not greater than or equal to such correlation data.

Claims

1. A method of testing a rechargeable energy storage battery comprising:

measuring an open circuit voltage of a test battery having an unknown physical condition;

measuring a dynamic parameter of the test battery;

scaling the dynamic parameter measured based on the dynamic parameter of a standard battery corresponding to the test battery; and

determining the physical condition of the test battery using the measured open circuit voltage, the scaled dynamic parameter, and correlation data based on the dynamic parameter of at least one battery at at least one charge state.

2. The method of claim 1 wherein the scaling comprises multiplying the measured dynamic parameter by the ratio of the rating of the test battery to the rating of the standard battery.

3. The method of claim 2 wherein the dynamic parameter is the internal alternating current resistance.

4. The method of claim 1 further comprising displaying an indication of the physical condition of the test battery.

5. The method of claim 1 further comprising:

applying a high current load pulse to the test battery; and

after the applying, waiting a predetermined rest period before measuring the open circuit voltage of the test battery.

6. The method of claim 1 wherein the at least one charge state comprises a single charge state, and further comprising indicating a failure condition if the physical condition determined falls below the correlation data of the at least one battery.

7. The method of claim 1 further comprising determining a charge state of the test battery.

8. The method of claim 7 wherein determining the charge state of the test battery comprises calculating a state of charge value and categorizing the state of charge value into one of a plurality of value ranges, each of the plurality of value ranges representing a different charge state.

9. The method claim 7 wherein determining the charge state of the test battery is based on calculating a state of charge of the test battery.

10. The method of claim 9 wherein at least a portion of the correlation data is representative of at least one open circuit voltage versus amp hour removed curve, and wherein calculating a state of charge value comprises:

determining the relative distance along the curve that the measured open circuit voltage becomes greater than or equal to the correlated open circuit voltage; and

subtracting the relative distance determined from one.

11. The method of claim 10 wherein determining the relative distance along the curve comprises dividing the number of points along the curve at which the measured open circuit voltage is not greater than or equal to the correlated open circuit voltage by the total number of points along the curve.

12. A method of testing a rechargeable energy storage battery comprising:

measuring an open circuit voltage of a test battery;

measuring a dynamic parameter of the test battery;

scaling the dynamic parameter measured based on the dynamic parameter of a standard battery corresponding to the test battery; and

determining a charge state of the test battery using the measured open circuit voltage, the scaled dynamic parameter, and correlation data based on the dynamic parameter of at least one battery at at least one charge state.

13. The method of claim 12 wherein the scaling comprises multiplying the measured dynamic parameter by the ratio of the rating of the test battery to the rating of the standard battery.

14. The method of claim 13 wherein the dynamic parameter is the internal alternating current resistance.

15. The method of claim 12 further comprising:

applying a high current load pulse to the test battery; and

after the applying, waiting a predetermined rest period before measuring the open circuit voltage of the test battery.

16. The method of claim 12 wherein determining the charge state of the test battery comprises calculating a state of charge value, and categorizing the state of charge value into one of a plurality of value ranges, each of the plurality of value ranges representing a different charge state.

17. The method of claim 12 wherein determining the charge state is based on calculating a state of charge of the test battery.

18. The method of claim 17 wherein at least a portion of the correlation data is representative of at least one open circuit voltage versus amp hour removed curve, and wherein calculating a state of charge value comprises:

determining the relative distance along the curve that the measured open circuit voltage becomes greater than or equal to the correlated open circuit voltage; and

subtracting the relative distance determined from one.

19. The method of claim 18 wherein determining the relative distance along the curve comprises dividing the number of points along the curve at which the measured open circuit voltage is not greater than or equal to the correlated open circuit voltage by the total number of points along the curve.

20. The method of claim 12 further comprising displaying an indication of the charge state of the test battery.

21. A method of testing a rechargeable energy storage battery comprising:

applying a high current load pulse to a test battery;

after the applying, waiting a predetermined rest period;

after the waiting, measuring an open circuit voltage of the test battery;

after the waiting, measuring a dynamic parameter of the test battery; and

determining at least one of a physical condition and a charge state of the test battery using the measured open circuit voltage, the measured dynamic parameter, and correlation data based on the dynamic parameter of at least one battery at at least one charge state.

22. The method of claim 21 wherein the at least one charge state comprises a single charge state, and further comprising indicating a failure condition if a determined physical condition of the test battery falls below the correlation data of the at least one battery.

23. The method of claim 21 wherein determining the charge state of the test battery comprises calculating a state of charge value and categorizing the state of charge value into one of a plurality of value ranges, each of the plurality of value ranges representing a different charge state.

24. The method of claim 21 wherein determining the charge state of the test battery is based on calculating a state of charge of the test battery.

25. The method of claim 24 wherein at least a portion of the correlation data is representative of at least one open circuit voltage versus amp hour removed curve, and wherein calculating a state of charge value comprises:

determining the relative distance along the curve that the measured open circuit voltage becomes greater than or equal to the correlated open circuit voltage; and

subtracting the relative distance determined from one.

26. The method of claim 25 wherein determining the relative distance along the curve comprises dividing the number of points along the curve at which the measured open circuit voltage is not greater than or equal to the correlated open circuit voltage by the total number of points along the curve.

27. A method of testing a rechargeable energy storage battery comprising:

measuring an open circuit voltage of a test battery;

measuring a dynamic parameter of the test battery;

calculating a state of charge value using the measured open circuit voltage, the measured dynamic parameter, and correlation data based on the dynamic parameter of at least one battery at at least one charge state; and

categorizing the state of charge value into one of a plurality of value ranges, each of the plurality of value ranges representing a different charge state.

28. The method of claim 27 further comprising displaying an indication of the charge state.

29. The method of claim 27 wherein at least a portion of the correlation data is representative of at least one open circuit voltage versus amp hour removed curve, and wherein calculating a state of charge value comprises:

determining the relative distance along the curve that the measured open circuit voltage becomes greater than or equal to the correlated open circuit voltage; and

subtracting the relative distance determined from one.

30. The method of claim 29 wherein determining the relative distance along the curve comprises dividing the number of points along the curve at which the measured open circuit voltage is not greater than or equal to the correlated open circuit voltage by the total number of points along the curve.

31. A method of testing a rechargeable energy storage battery, the method utilizing stored correlation data representative of at least one open circuit voltage versus amp hour removed curve for at least one battery, the method comprising:

measuring an open circuit voltage for a test battery;

determining the relative distance along the curve that the measured open circuit voltage becomes greater than or equal to the stored correlation data;

calculating the state of charge of the test battery by subtracting the relative distance determined from one.

32. The method of claim 31 wherein determining the relative distance along the curve comprises dividing the number of points along the curve at which the measured open circuit voltage is not greater than or equal to the correlated open circuit voltage by the total number of points along the curve.

33. The method of claim 31 further comprising determining the charge state of the test battery based on the calculated state of charge.

34. The method of claim 33 further comprising displaying an indication of the charge state of the test battery.