Method and apparatus for automatic determination of lead-acid battery specific gravity

• US 20050270033A1
• Filed: 06/04/2004
• Published: 12/08/2005
• Est. Priority Date: 06/04/2004
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Palanisamy, Thirumalai G., Singh, Harmohan N., Hoenig, Steven, Atehortua, Hector M.
• Granted Patent: US 7,224,168 B2
• Time in Patent Office: Days
• US Class Current: 324/440
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: H01M 10/06 Lead-acid accumulators semi-lead accumulators H01M10/20
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/484 for measuring electrolyte level, electrolyte density or electrolyte conductivity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

In accordance with various embodiments, there is a method for determining the specific gravity of a battery. Various embodiments include the steps of applying an increasing current ramp to a battery and measuring a response voltage of the battery when the increasing current ramp is applied to the battery. When the current ramp reaches a predetermined current a decreasing current is supplied to the battery and the battery'"'"'s voltage response is measured. The specific gravity of the battery can be determined based on the voltage response of the battery to the applied current ramp.

Claims

1. A method of determining a specific gravity of a lead-acid battery the method comprising:

applying a current ramp to the battery while measuring a battery voltage and detecting gas points;

calculating a maximum voltage per cell by dividing a maximum measured battery voltage by a number of cells of the battery; and

determining the specific gravity of the battery when one or more gas points are detected by comparing the maximum voltage per cell to an SG_Lim,

wherein the SG_Lim is an upper limit of a maximum measured battery voltage for a low specific gravity battery divided by a number of cells of the low specific gravity battery, and

wherein the maximum voltage per cell being less than the SG_Lim indicates a lower specific gravity lead-acid battery.

2. The method of claim 1, wherein the maximum voltage per cell being greater than the SG_Lim indicates a higher specific gravity lead-acid battery.

3. The method of claim 1, further comprising determining the specific gravity of the battery when no gas points are detected by comparing a calculated state of charge of the battery to a state of charge threshold value.

4. The method of claim 3, wherein the state of charge threshold value is a 75% state of charge threshold.

5. The method of claim 1, wherein applying the current ramp comprises:

applying a linearly increasing current until the battery voltage reaches a predetermined limit; and

applying a linearly decreasing current after reaching the predetermined limit.

6. The method of claim 4, wherein a slope of the linearly increasing current is approximately equal to an absolute value of a slope of the linearly decreasing current.

7. The method of claim 1, wherein SG_Lim is about 2.53 volts.

8. The method of claim 4, wherein the state of charge threshold represents a maximum state of charge for which gas points should not be detectable.

9. The method of claim 3 further comprising, determining the battery to be a high specific gravity battery, where no gas points are detected and where the calculated state of charge exceeds the state of charge threshold value.

10. The method of claim 3, further comprising charging the battery when no gas points are detected.

11. The method of claim 10, further comprising repeating the method for determining the specific gravity beginning at a step of applying the current ramp.

12. An apparatus for determining a specific gravity of a battery comprising:

a power supply;

a controller that controls the power supply to apply a current ramp to the battery;

a control relay electrically connected to the power supply;

at least one sensor that detects a battery voltage response to the current ramp, the at least one sensor electrically connected to the control relay; and

a processor configured to compare a maximum battery voltage detected in the battery voltage response divided by a number of cells of the battery, to an SG_Lim, where the SG_Lim is an upper limit of a maximum measured battery voltage for a low specific gravity battery divided by the number of cells of the low specific gravity battery.

13. The apparatus of claim 12, wherein the processor is further configured to determine the number of gas points of the battery.

14. The apparatus of claim 12, wherein the processor is further configured to compare a state of charge of the battery to a 75% state of charge threshold.

15. The apparatus of claim 12, further comprising a display for indicating a specific gravity of the battery.

16. The apparatus of claim 12, wherein the current ramp comprises:

a linearly increasing current to a predetermined limit; and

a linearly decreasing current after reaching the predetermined limit.

17. A computer readable medium for determining a specific gravity of a battery, the computer readable medium comprising:

program code for applying a current ramp to a battery comprising a number of cells;

program code for measuring a battery voltage response and detecting gas points;

program code for calculating a state of charge of the battery and a maximum voltage per cell of the battery; and

program code for comparing a maximum battery voltage detected in the battery voltage response divided by the number of cells of the battery, to an SG_Lim, where the SG_Lim is an upper limit of a maximum measured battery voltage of a low specific gravity battery divided by the number of cells of the low specific gravity battery.

18. The computer readable medium of claim 17, further comprising program code for comparing the state of charge of the battery to a 75% state of charge threshold.

19. The computer readable medium of claim 17, wherein the program code for applying a current ramp to the battery comprises:

a linearly increasing current to a predetermined limit; and

a linearly decreasing current after reaching the predetermined limit.

20. The computer readable medium of claim 17, further comprising program code for indicating a specific gravity of the battery.

21. An automated battery charger comprising:

a power supply;

a controller to cause the power supply to apply a current ramp to a test battery and to control charging of the test battery;

a sensor to detect a test battery voltage and detect gas points in response to the current ramp; and

a computer to determine a specific gravity of the test battery based on a comparison of a maximum measured voltage per cell to an SG_Lim, wherein the SG_Lim represents a determination threshold between a higher specific gravity battery and a lower specific gravity battery,

wherein charging of the test battery is based on the computer'"'"'s determination of the specific gravity of the test battery.

22. The automated battery charger of claim 21, wherein the SG_Lim is determined by dividing an upper limit of a maximum measured battery voltage for a low specific gravity battery divided by a number of cells of the low specific gravity battery.