BATTERY CHARGING METHOD AND APPARATUS

• US 20110006737A1
• Filed: 07/10/2009
• Published: 01/13/2011
• Est. Priority Date: 07/10/2009
• Status: Active Grant

• Current Assignee: Schneider Electric IT Corporation (Schneider Electric SE)
• Original Assignee: Schneider Electric IT Corporation (Schneider Electric SE)
• Inventors: Nair, Sreejakumar Sreekantan, Saligram, Narayana Prakash, Dighrasker, Milind, Krishnan, Ramakrishnan Madenoor
• Granted Patent: US 8,581,554 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00716 in response to integrated charge or discharge current
• CPC Class Codes: H02J 7/00719 in response to degree of gas development in the battery
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage

Abstract

Disclosed are methods for charging batteries utilizing a charge balance approach, and charger systems using those methods. In one example, a method for charging a battery includes monitoring an amount of charge released by the battery while in a discharge state, recording the amount of charge released while in the discharge state, applying a voltage which results in current in reverse direction to the battery at a first voltage level for a time sufficient to introduce an amount of charge substantially equal to the recorded amount of charge released by the battery while in the discharge state, and maintaining the battery in a stand-by mode by applying a voltage which results in current in reverse direction to the battery at a second voltage level, the second voltage level being in a range sufficient to prevent self-discharge of the battery and insufficient to induce evaporation of electrolyte in the battery.

Claims

1. A method of charging a battery in an uninterruptible power supply system, the method comprising acts of:

monitoring an amount of charge supplied by the battery during a discharge cycle;

re-charging the battery during a subsequent charge cycle;

monitoring charge supplied to the battery during the charge cycle; and

ending the charge cycle and placing the battery in a standby mode responsive to the charge supplied to the battery during the charge cycle exceeding the amount of charge supplied by the battery during the discharge cycle.

2. The method as claimed in claim 1, wherein re-charging the battery comprises applying a substantially constant voltage of a first value across terminals of the battery.

3. The method as claimed in claim 2, wherein re-charging the battery further comprises:

applying a substantially constant current to the battery in an opposite direction of current flow during the discharge cycle of the battery; and

suspending application of the substantially constant current when a voltage across terminals of the battery reaches the first value.

4. The method as claimed in claim 1, wherein placing the battery in the standby mode includes applying a substantially constant voltage of a second value across the terminals of the battery, the second value being less than the first value.

5. The method as claimed in claim 4, wherein applying the substantially constant voltage of the second value across the terminals of the battery includes applying a voltage with the second value being in a range sufficient to prevent self-discharge of the battery and insufficient to induce evaporation of electrolyte in the battery.

6. The method as claimed in claim 4, wherein the second value is between approximately 12 volts and approximately 13.4 volts.

7. The method as claimed in claim 1, further comprising:

recording a supplied charge value corresponding to the amount of charge supplied by the battery during the discharge cycle.

8. The method as claimed in claim 7, recording the supplied charge value is performed responsive to termination of the discharge cycle.

9. The method as claimed in claim 1, wherein monitoring the amount of charge supplied by the battery during the discharge cycle comprises monitoring watt-hours output by the battery;

and

wherein the method further comprises determining a total watt-hours output by the battery during the discharge cycle.

10. The method as claimed in claim 9, further comprising calculating amp-hours output by the battery from the determined total watt-hours output by the battery during the discharge cycle.

11. The method as claimed in claim 10, further comprising recording the total watt-hours output by the battery during the discharge cycle;

and

wherein calculating the amp-hours output by the battery includes calculating the amp-hours based on the recorded total watt-hours output by the battery during the discharge cycle.

12. The method as claimed in claim 1, further comprising repeating for multiple successive charge and discharge cycles the acts of:

monitoring the amount of charge supplied by the battery during the discharge cycle;

re-charging the battery during the subsequent charge cycle; and

monitoring the charge supplied to the battery during the charge cycle.

13. A method of charging a battery in an uninterruptible power supply system, the method comprising:

supplying power from the battery to a load connected to the uninterruptible power supply during a discharge cycle of the battery;

monitoring an amount of charge drawn from the battery during the discharge cycle;

at the end of the discharge cycle, re-charging the battery with a substantially constant voltage at a first level during a charge cycle of the battery;

monitoring an amount of charge supplied to the battery during the charge cycle; and

responsive to the amount of charge supplied to the battery exceeding the amount of charge drawn from the battery during the discharge cycle, reducing the substantially constant voltage to a second level lower than the first level to place the battery in a standby mode.

14. The method as claimed in claim 13, further comprising:

recording a first value corresponding to the amount of charge drawn from the battery during the discharge cycle; and

wherein reducing the substantially constant voltage to a second level lower than the first level to place the battery in a standby mode is performed responsive to the amount of charge supplied to the battery exceeding the first value.

15. An uninterruptible power supply system comprising:

a battery;

a battery charger coupled to the battery and configured to supply power to charge the battery; and

a controller coupled to the battery and to the battery charger, the controller configured to monitor and determine a first amount of charge released by the battery while discharging, to monitor a second amount of charge supplied to the battery by the battery charger during subsequent charging of the battery by the battery charger, and to control the battery charger to place the battery in a stand-by mode when the second amount of charge exceeds the first amount of charge.

16. The uninterruptible power supply system as claimed in claim 15, wherein the battery charger is configured to deliver a substantially constant current and a substantially constant voltage to the battery.

17. The uninterruptible power supply system as claimed in claim 16, wherein the battery charger is configured to deliver a substantially constant voltage of a first level to the battery during charging of the battery and a substantially constant voltage of a second level, lower than the first level, when the battery is in the stand-by mode.

18. The uninterruptible power supply system as claimed in claim 17, wherein the second level is in a range of approximately 12 volts to 13.4 volts.