Method and apparatus for detecting a bad cell in a storage battery

• US 5,757,192 A
• Filed: 05/20/1996
• Issued: 05/26/1998
• Est. Priority Date: 05/20/1996
• Status: Expired due to Term

• Current Assignee: Midtronics Incorporated
• Original Assignee: Midtronics Incorporated
• Inventors: Bertness, Kevin I., McShane, Stephen J.
• Primary Examiner(s): Oda, Christine K.
• Application Number:
  US08/650,431
• Time in Patent Office: 736 Days
• Field of Search: 320/48, 340/636, 364/483, 324/433, 324/434, 324/426, 324/427
• US Class Current: 324/427
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

A method and apparatus for detecting a bad cell in a storage battery having a plurality of cells as provided. Input circuitry electrically couples to first and second terminals of the storage battery. Voltage measuring circuitry coupled to the input circuitry provides a voltage output related to a voltage potential between the first and second terminals of the storage battery. Conductance measuring circuitry coupled to the input circuitry provides a conductance output related to conductance of the storage battery. Voltage and conductance comparison circuitry compares the measured voltage and conductance to references and provide outputs. Output circuitry provides a bad cell output based upon the results of the comparisons.

Claims

1. An apparatus for detecting a bad cell in a storage battery having a plurality of cells, comprising:

input circuitry for electrically coupling to first and second terminals of the storage battery;

voltage measuring circuitry coupled to the input circuitry providing voltage output related to a voltage potential between the first and second terminals of the storage battery;

conductance measuring circuitry coupled to the input circuitry providing a conductance output related to conductance of the storage battery measured between the first and second terminals

voltage comparison circuitry comparing the voltage output to a voltage reference and providing a discharged output if the voltage output is less than the voltage reference;

conductance comparison circuitry comparing the conductance output to a conductance reference and providing a high conductance output if the conductance output is greater than the conductance reference; and

output circuitry providing a bad cell output in response to detection of a discharged output and a high conductance output, the bad cell output indicative of a bad cell among the plurality of cells in the storage battery.

2. The apparatus of claim 1 including a memory containing the voltage reference and the conductance reference.

3. The apparatus of claim 2 including an input device for receiving an input from an operator used to select the voltage reference and conductance reference from a plurality of references stored in the memory.

4. The apparatus of claim 1 wherein the conductance measurement circuitry determines conductance by measuring resistance.

5. The apparatus of claim 1 wherein the voltage measuring circuitry, conductance measuring circuitry, voltage comparison circuitry, conductance comparison circuitry and the output circuitry are implemented using a microprocessor.

6. The apparatus of claim 1 including a known current source for injecting a known current into the storage battery and the conductance measuring circuitry measure conductance based upon the known current and a resultant change in voltage of the storage battery.

7. The apparatus of claim 1 wherein the conductance measuring circuitry uses a Kelvin connection to connect to the storage battery.

8. A method of detecting a bad cell in a storage battery having a plurality of cells, comprising the steps of:

measuring a voltage (V_BAT) across terminals of the storage battery;

measuring a conductance (G_BAT) of the storage battery;

comparing the voltage (V_BAT) to a reference voltage (V_REF);

comparing the conductance (G_BAT) to a reference conductance (G_REF); and

indicating a bad cell exists in the battery based upon the comparisons.

9. The method of claim 8 including:

detecting a discharged condition if the voltage V_BAT is less than the reference voltage (V_REF);

detecting a high conductance condition if the conductance (G_BAT) is greater than the reference conductance (G_REF); and

indicating the bad cells exists in response to the discharged condition and the high conductance condition.

10. The method of claim 8 wherein determining the conductance comprises injecting a current and measuring change in voltage.

11. The method of claim 8 including retrieving the reference voltage V_REF and the reference conductance G_REF from a memory.

12. The method of claim 8 wherein the reference voltage V_REF and the reference conductance G_REF are selected based upon the type of the storage battery.