Abstract: A battery charger 10 includes a microprocessor device 12 coupled to a voltage to frequency converter 18 for determining a magnitude of a voltage potential appearing across a battery under charge. The microprocessor has an output for activating a source of battery charging power when the determined magnitude of the voltage is within a predetermined range of voltages. During a charge cycle the microprocessor maintains an elapsed time counter and determines if a battery reaches full charge within 30 minutes or does not reach a full charge after 16 hours. In either case the source is deactivated. The microprocessor also determines when a battery reaches a threshold voltage after which the rate of rise of the battery voltage is compared to a predetermined rate of rise. When the measured rate of rise is less than the predetermined rate of rise the microprocessor initiates a final charge cycle wherein the battery is charged for one additional hour.