Battery string performance measurement

• US 20060017444A1
• Filed: 05/24/2005
• Published: 01/26/2006
• Est. Priority Date: 07/21/2004
• Status: Active Grant

• Current Assignee: C&C Power Incorporated
• Original Assignee: C&C Power Incorporated
• Inventors: Conrardy, N. William, Fechalos, William
• Granted Patent: US 7,772,852 B2
• Time in Patent Office: Days
• US Class Current: 324/433
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A DC power supply system in which the resistance of a battery is measured. The voltage of the DC power supply is reduced such that the battery supplies some current to the load, and the voltage and current are measured. The voltage of the DC power supply is further reduced such that the battery supplies increased power to the load, and the voltage and current are measured. A resistance value is computed, and may be compared with various pre-established criteria. The battery resistance may also be measured by comparing the charging time of a known resistive-capacitive circuit with the charging time established at a prior measurement epoch.

Claims

1. A resistance measuring apparatus comprising:

a first voltmeter;

an ammeter;

a first terminal of the ammeter connected to a first terminal of a first voltmeter;

a second terminal of the first voltmeter connected to ground;

a second terminal of the ammeter connected to a first external connection terminal;

a second external connection terminal connected to ground;

an output terminal connected to the first terminal of the ammeter; and

a DC power supply having a variable output voltage capability, the DC power supply connected to the first terminal of the ammeter.

2. The apparatus of claim 1, wherein a battery is connected between the first external connection terminal and the second external connection terminal.

3. The apparatus of claim 2, wherein the battery is a lead-acid battery.

4. The apparatus of claim 2, wherein the battery further comprises a plurality of batteries connected in series.

5. A method of measuring resistance, the method comprising:

providing a DC power supply connected a battery, the DC power supply having a variable output voltage;

measuring a first voltage value and first current value of the battery when the DC power supply output voltage is varied to a value such that the battery supplies a first current value to the load;

measuring a second voltage value and a second current value of the battery string when the DC power supply output voltage is varied to a value such that the battery supplies the second current to the load, wherein the second current value is greater than the first current value; and

calculating a battery resistance.

6. The method of claim 5, further comprising controlling the DC power supply output voltage such that the output voltage is gradually reduced to a first voltage, and then reduced to a second voltage.

7. The method of claim 6, wherein the output voltage is rapidly reduced to a second voltage.

8. The method of claim 5, wherein the first current value is approximately half of a maximum current value.

9. The method of claim 8, wherein the second current value is substantially the maximum current value.

10. A battery resistance measuring apparatus comprising:

an ammeter;

a switch, the switch having a first terminal selectably connectable one of a second terminal and a third terminal;

a second terminal of the switch connectable to a first electrical load;

a third terminal of the switch connected to a second electrical load, the second electrical load having a controllable resistance value;

a first terminal of the ammeter connected to the first terminal of the switch;

a second terminal of the ammeter connected to a first battery connection terminal;

a second battery connection terminal connected to a ground; and

a voltmeter connected between the first terminal of the ammeter and the ground.

11. The apparatus of claim 10, wherein the second electrical load is a resistor having a plurality of selectable values.

12. The apparatus of claim 10, wherein a stored-program computer controls the switch, controls the resistance value of the second electrical load, receives measurements of voltage and current, computes the resistance of the battery, and outputs the computed battery resistance.

13. The apparatus of claim 10, wherein a stored-program computer controls the switch, controls the resistance value of the second electrical load, measures the voltage and current voltmeter, computes the battery resistance, and outputs the computed battery resistance.

14. A method of measuring resistance, the method comprising:

connecting a battery to a load resistance;

varying the value of the load resistance to a first value such that a first current value is supplied to the load resistance and a first voltage value is imposed on the load resistance;

varying the value of the load resistance to a second value such that a second current value is supplied to the load resistance and a second voltage value is imposed on the load resistance;

calculating a battery resistance from the measured first and second current values and the measured first and second voltage values.

15. The method of claim 14, wherein the first voltage value has a magnitude greater than the second voltage value.

16. The method of claim 14, wherein the value of the first value of load resistance is rapidly varied to the second value of load resistance.

17. An apparatus for measuring resistance, comprising:

a first battery connection terminal;

a second battery connection terminal connected to ground;

a first resistive divider comprising a first and a second resistor having a first node between a first end of each of the first and second resistors, a second end of the first resistor connected to the first battery connection terminal and a second end of the second resistor connected to ground;

a network having a second node between a first end of a third resistor and a first end of a capacitor, the first end of the third resistor connected to the first battery connection terminal and a second end of the capacitor connected to ground;

a voltage comparator having a first input connected to the first node and a second input connected to the second node; and

a first switch connected between the first battery connection terminal and an output terminal.

18. The apparatus of claim 17, wherein a stored-program computer controls the first switch and the output of the voltage comparator, computes the battery resistance, and outputs the computed battery resistance.

19. The apparatus of claim 17, wherein a second switch is disposed between the first end of third resistor and the second node.

20. The apparatus of claim 17, wherein a second switch is disposed between a second end of the third resistor and the first battery connection terminal.

21. A method of measuring battery resistance, the method comprising:

connecting an input terminal to a resistive divider;

disconnecting the input terminal from an output terminal;

connecting the input terminal to an input of a resistive-capacitive circuit;

determining the time required for the voltage across the terminals of a capacitor of the resistive-capacitive network to become equal to the voltage at an output of the resistive divider; and

calculating a battery parameter.

22. The method of claim 21, wherein the battery parameter is a resistance.

23. A backup battery system, comprising:

a battery;

a DC power supply; and

means for measuring battery resistance.

24. The backup battery system of claim 23, further comprising a means for displaying the result of measuring battery resistance.

25. The battery backup system of claim 23, wherein the battery is a lead-acid battery.