US Patent 7859224 Charge control circuit for a vehicle vacuum cleaner battery

Disclosed herein is a battery charger control circuit having a voltage detector to generate a signal indicative of a source voltage level to select one of a first charging mode and a second charging mode, and a charge controller coupled to the voltage detector to enable charging in accordance with one of the first charging mode and the second charging mode based on the signal from the voltage detector. The first and second charging modes establish charging at differing, non-zero rates. The source voltage level may be sampled at a sampling rate to minimize power consumed by monitoring the source voltage level.