Method and apparatus to determine the location and resistance of an electrical leak within a battery without measuring individual battery cells

• US 5,811,976 A
• Filed: 01/03/1997
• Issued: 09/22/1998
• Est. Priority Date: 01/03/1997
• Status: Expired due to Term

• Current Assignee: Joy Mm Delaware Incorporated (Mitsui & Company Limited)
• Original Assignee: Joy Mm Delaware Incorporated (Mitsui & Company Limited)
• Inventors: Fischer, George A.
• Primary Examiner(s): Do, Diep N.
• Application Number:
  US08/778,896
• Time in Patent Office: 627 Days
• Field of Search: 324/426, 324/427, 324/430, 324/433, 324/434, 324/435, 324/691, 324/713, 324/718, 324/522, 340/636, 340/650, 340/651, 320/48, 364/481, 364/482
• US Class Current: 324/434
• 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 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

An apparatus and method for determining a location and resistance of an electrical leak in a battery having a first and second terminals. The apparatus includes a resistor, a switch assembly for selectively connecting the resistor to the first terminal of the battery and for selectively connecting the resistor to the second terminal of the battery, and a controller. When the apparatus determine the location of the leak, the controller is responsive to a first signal indicative of a voltage across the resistor, responsive to a second signal indicative of a feature of the battery, and calculates a quotient formed from first and second values and indicative of the location of the leak, the first value including a product of the first signal when the resistor is connected to the first terminal of the battery and the second signal, and the second value including a sum of the first signal when the resistor is connected to the first terminal of the battery and the first signal when the resistor is connected to the second terminal of the battery.

Claims

1. An apparatus for determining a location of an electrical leak in a battery having first and second terminals, comprising:

a resistor;

a switch assembly for selectively connecting said resistor to the first terminal of the battery and for selectively connecting said resistor to the second terminal of the battery; and

a controller responsive to a first signal indicative of a voltage across said resistor, responsive to a second signal indicative of a feature of the battery, and for calculating a quotient formed from first and second values and indicative of the location of the leak, the first value including a product of the first signal when said resistor is connected to the first terminal of the battery and the second signal, and the second value including a sum of the first signal when said resistor is connected to the first terminal of the battery and the first signal when said resistor is connected to the second terminal of the battery.

2. The apparatus of claim 1, wherein said controller is responsive to the second signal, and the second signal is indicative of a voltage across the first and second terminals of the battery.

3. The apparatus of claim 1, wherein said controller is responsive to the second signal, and the second signal is indicative of a number of cells in the battery.

4. The apparatus of claim 2, additionally comprising:

a first voltage converter responsive to the voltage across said resistor for generating the first signal; and

a second voltage converter responsive to the voltage across the battery for generating the second signal.

5. The apparatus of claim 4, wherein:

said first voltage converter generates the first signal having an amplitude less than the voltage across said resistor; and

said second voltage converter generates the second signal having an amplitude less than the voltage across the first and second terminals of the battery.

6. The apparatus of claim 1, additionally comprising a memory for storing an offset value, wherein said controller is responsive to a sum formed from the offset value and the quotient of the first and second values, for determining the location of the leak.

7. The apparatus of claim 1, additionally comprising a memory for storing a spread value, wherein said controller is responsive to the quotient of the first and second values, and the first value includes the first signal multiplied by the sum of the second signal and a spread value.

8. The apparatus of claim 1, wherein:

said resistor has a first end and said resistor has a second end connected to ground;

said switch assembly includes a first switch for selectively connecting the first end of said resistor to the first terminal of the battery; and

said switch assembly includes a second switch for selectively connecting the first end of said resistor to the second terminal of the battery.

9. The apparatus of claim 1, wherein:

said resistor has a first end and said resistor has a second end connected to ground;

said switch assembly includes a first switch having a first terminal, said first switch for selectively connecting said first terminal of said first switch to one of the first and second terminals of the battery; and

said switch assembly includes a second switch for selectively connecting the first end of said resistor to said first terminal of said first switch.

10. The apparatus of claim 1, wherein:

said controller includes a first analog-to-digital converter responsive to the first signal for generating a first digital signal indicative of the first signal; and

said controller includes a second analog-to-digital converter responsive to the second signal for generating a second digital signal indicative of the second signal.

11. The apparatus of claim 10, wherein said controller includes a microprocessor responsive to the first and second digital signals for determining the location of the leak.

12. The apparatus of claim 1, wherein said controller includes an output driver for producing first and second output signals for controlling said switch assembly.

13. An apparatus for determining electrical resistance of an electrical leak in a battery having first and second terminals, comprising:

a resistor having a first resistance;

a switch assembly for selectively connecting said resistor to the first terminal of the battery and for selectively connecting said resistor to the second terminal of the battery; and

a controller responsive to a first signal indicative of a voltage across said resistor and responsive to a second signal indicative of a voltage across the first and second terminals of the battery, for calculating a product formed from the first resistance and a quotient of first and second values for determining the resistance of the leak, the first value including the second signal minus the first signal when said resistor is connected to the first terminal of the battery, minus the first signal when said resistor is connected to the second terminal of the battery, and the second value including a sum of the first signal when said resistor is connected to the first terminal of the battery and the first signal when said resistor is connected to the second terminal of the battery.

14. The apparatus of claim 13 for use with an electric motor, additionally comprising a fault switch responsive to said controller and in series with one of the terminals of the battery and in series with the electric motor, for selectively disconnecting the electric motor from one of the terminals of the battery when a fault having a resistance less than a predetermined value is detected.

15. The apparatus of claim 14, wherein the predetermined value is adjustable.

16. The apparatus of claim 15, wherein the predetermined value is between approximately five hundred ohms and approximately one thousand ohms.

17. The apparatus of claim 14, wherein said controller includes an output driver for producing first and second output signals for controlling said switch assembly and for producing a third output signal for controlling said fault switch.

18. The apparatus of claim 13, additionally comprising an operator interface for providing instructions from an operator to said controller.

19. A method of determining a location of an electrical leak within a battery having first and second terminals, comprising the steps of:

connecting a resistor to the first terminal of the battery;

producing a first signal indicative of a voltage across the resistor;

connecting the resistor to the second terminal of the battery;

producing a second signal indicative of the voltage across the resistor;

producing a third signal indicative of a feature of the battery;

determining a first value including a product of the first signal and the third signal;

determining a second value including a sum of the first and second signals; and

determining the location of the leak from a quotient formed from the first and second values.

20. The method of claim 19, wherein the step of producing the third signal includes producing the third signal indicative of the voltage across the first and second terminals of the battery.

21. The method of claim 19, wherein the step of producing the third signal includes the step of producing the third signal indicative of a number of cells in the battery.

22. The method of claim 19, wherein the step of determining the location of the leak includes determining a sum formed from an offset value and the quotient of the first and second values.

23. The method of claim 19, wherein the step of determining the location of the leak includes the step of determining the quotient of the first and second values when the first value includes the first signal multiplied by the sum of the third signal and a spread value.

24. A method for determining the resistance an electrical leak within a battery having first and second terminals, comprising the steps of:

connecting a resistor having a first resistance to the first terminal of the battery;

producing a first signal indicative of a voltage across the resistor;

connecting the resistor to the second terminal of the battery;

producing a second signal indicative of the voltage across the resistor;

producing a third signal indicative of the voltage across the first and second terminals of the battery;

determining a first value including the third signal minus the first signal, minus the second signal;

determining a second value including the sum of the first and second signals; and

determining the resistance of the leak from a product formed from the first resistance and a quotient of the first and second values.

25. The method of claim 24 for use with an electric motor, additionally comprising the step of disconnecting power from the electric motor when the resistance of a leak is below a predetermined value.

26. The method of claim 25, wherein said predetermined value is adjustable.

27. The method of claim 26, wherein said predetermined value is between approximately five hundred ohms and approximately one thousand ohms.