Apparatus and method for automatic recovery of sulfated lead acid batteries

• US 6,242,886 B1
• Filed: 10/25/1999
• Issued: 06/05/2001
• Est. Priority Date: 04/12/1999
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Alliedsignal Inc.
• Inventors: Palanisamy, Thirumalai G., Singh, Harmohan, Gollomp, Bernard P.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/426,372
• Time in Patent Office: 589 Days
• Field of Search: 320/100, 320/132, 320/161, 320/162, 320/134
• US Class Current: 320/100
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Apparatus and method for automatic recovery of sulfated lead acid batteries rely on monitoring battery voltage, current and internal resistance during battery charging. The lead acid battery is recovered for usage by measuring the internal resistance to see if it is so high such that the battery is unrecoverable, or so low such that the normal charging methods can be used. If the internal resistance is between the two limits, the battery receives a first constant charge current. As the lead acid battery is being charged slowly by a constant charge current, the battery voltage is measured. The decrease in the internal resistance (IR) of the battery causes the battery voltage to decrease during charging, while the charging causes the battery voltage to increase. According to the present invention, if it is detected that the battery voltage has reached the minimum voltage and begun to increase in a predetermined period of time, the charge current is substantially increased (e.g., doubled) because the capability of the lead acid battery to accept a higher charge current has increased. As the charge current is increased, the recovery and charging of the lead acid battery arc advantageously more expedient and efficient.

Claims

1. A method for selecting the discarding or recovery of a rechargeable battery that has an internal resistance of a normal limit value and a recoverable limit value, comprising the steps of:

measuring the battery internal resistance;

indicating that the battery is to be discarded if the measured internal resistance exceeds the recoverable limit value; and

charging the battery with current if the measured internal resistance is greater than said normal limit and less than said recoverable limit.

2. The method of claim 1, wherein the recoverable limit value is 5 ohms.

3. The method of claim 2, wherein the normal limit is 0.2 ohms.

4. The method of claim 1 wherein said charging step comprises applying successively higher levels of charging current to the battery.

5. The method of claim 4 further comprising monitoring the battery voltage as the battery is charged, and

said charging step comprises applying a higher level of charging current when the monitored battery voltage increases after reaching a minimum level.

6. The method of claim 4 wherein the charge current level is increased 100 percent.

7. The method of claim 5 further comprising the step of

determining if a higher level charge current applied has exceeded a predetermined current limit.

8. The method of claim 7 further comprising the step of

terminating recovery of a battery in which the higher level of charge current applied has exceeded a predetermined current limit and repeating the step of charging the battery and measuring its voltage.

9. The method of claim 1, further comprising the step of measuring the electrolyte level of a battery whose measured internal resistance is greater than said normal limit value and less than said recoverable limit value and signaling to correct electrolyte level of the battery if the electrolyte level is below an acceptable level, correcting the electrolyte level and then measuring the battery internal resistance.

10. The method of claim 1, further comprising the steps of:

measuring the charge current of the battery; and

charging the battery using normal charging if the charge current exceeds a charge current limit.

11. The method of claim 10 further comprising the steps of:

measuring the charge current of the battery; and

charging the battery at an increased amount of current if the measured charge current does not exceed a charge current limit.

12. The method of claim 11, further comprising the steps of:

monitoring the battery voltage for a first time period during charging with the increased charge current;

discontinuing the battery charging if the battery voltage continues to increase in the first time period; and

charging the battery after a second time period has lapsed.

13. The method of claim 12, wherein the first time period is one hour and the second time period is five minutes.

14. The method of claim 11 further comprising the steps of:

monitoring the battery voltage for a first time period during charging with the increased current;

determining if the battery voltage does not continue to increase during the charging with the increased current; and

determining if the battery voltage reached a minimum value and began to increase for a preset time interval.

15. The method of claim 14, further comprising the steps of:

discontinuing the battery charging if in the determining step the battery voltage has not reached minimum value and has begun to increase and the battery has been charged for more than a third time period; and

charging the battery after a second time period has lapsed.

16. The method of claim 15, wherein the second time period is five minutes, and the third time period is eight hours.

17. The method of claim 16, further comprising the step of charging the battery using normal charging if the charge voltage is not greater than a preset limit.

18. The method of claim 17, further comprising the step of continuing the battery charging if the charge voltage is greater than the preset limit.

19. The method of claim 11, wherein the steps of the method are implemented in software.

20. A method for recovering a lead acid battery that has an internal resistance of a normal limit value and a recoverable limit value, comprising the steps of:

measuring the battery internal resistance;

indicating that the battery is to be discarded if the measured internal resistance exceeds the recoverable limit value;

charging the battery if the measured internal resistance is greater than said normal limit value and less than said recoverable limit value;

charging the battery with a charge voltage;

measuring the battery current;

increasing the charge voltage if the battery current has not reached a first current limit.

21. The method of claim 20, further comprising the steps of decreasing the charge voltage if the battery current has reached a second current limit.

22. The method of claim 21, following the decreasing step, further comprising the step of continuing to decrease the charge voltage if the decreased charge voltage has not reached the first current limit.

23. An apparatus for recovering a lead acid storage battery comprising:

a variable current source for supplying current to the battery;

means for measuring battery voltage;

means for measuring battery current;

a programmable computer for receiving data of the measured battery voltage and measured battery current, and for controlling the output amount of said variable current source;

said computer computing the battery internal resistance and if the internal resistance is greater than a normal limit value and less than a recoverable limit value, operating said variable current source in sequence to the measured battery voltage and measured battery current to increase the charge current if the battery voltage has reached a minimum voltage and began to decrease.

24. The apparatus of claim 23, further comprising a control relay implementing normal charging of the battery.

25. The apparatus of claim 24, further comprising a relay module implementing commands from the computer to the control relay.

26. The apparatus of claim 23, further comprising a data acquisition device processing measured voltage and current data from the battery into a form useful by the computer.

27. The apparatus of claim 26, wherein the data acquisition device processes the data using one of the group consisting of analog-to-digital conversion, digital-to-analog conversion, amplification and noise reduction.

28. The apparatus of claim 23, further comprising a thermocouple connected to the battery, the thermocouple measuring a temperature of the battery.

29. The apparatus of claim 28, wherein the computer stops the variable current source from charging the battery if the battery temperature exceeds a tolerable limit.

30. The apparatus of claim 23, further comprising an electronic load connected in parallel with the variable current source for discharging the battery.

31. The apparatus of claim 23, further comprising a diode connected in series with the variable current source for protecting the variable current source from the battery discharging into the variable current source.

32. The apparatus of claim 23, wherein the computer measures the battery internal resistance and directs the variable current source to charge the battery using normal charging if the battery internal resistance is less than a normal limit.

33. The apparatus of claim 23, wherein the computer measures the battery internal resistance and sends a signal to discard the battery if the battery internal resistance is greater than a recoverable limit.

34. The apparatus of claim 23, wherein the computer directs the variable current source to charge the battery using normal charging if the charge is greater than a charge current limit.

35. The apparatus of claim 23, wherein the computer instructs the variable current source to stop charging the battery for a second time period if the battery voltage is still increasing after a first time period has lapsed.

36. The apparatus of claim 23, wherein the computer instructs the variable current source to stop charging the battery for a second time period if the battery has been charging for more than a third time period.