Patent ID: 8581554

Claim:
A method of charging a battery in an uninterruptible power supply system, the method comprising acts of: making a determination as to whether the battery is being discharged for a first discharge cycle; setting a low battery shutdown voltage at a high non-zero level if the battery is being discharged for the first discharge cycle; setting the low battery shutdown voltage at a non-zero level lower than the high non-zero level if the battery is not being discharged for the first discharge cycle; monitoring an amount of charge supplied by the battery during a discharge cycle; suspending discharge of the battery if a voltage across terminals of the battery drops to the low battery shutdown voltage; 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.