Abstract: A unique automatic battery charger (100) is described that recharges a battery (202) including a thermistor (206) for sensing the battery temperature. The charger (100) produces both a slow-charge current and a fast-charge current. Upon detecting the presence of the battery (202), the unique charger (100) turns on a fast-charge current produced by a switchable current source (110-113). The fast-charge current is subsequently turned off when the battery (202) is fully charged as indicated by the status of monitored temperature and voltage conditions. Comparators (180-184) are utilized to monitor these voltage and temperature conditions. According to a novel feature of the present invention, the monitored temperature thresholds are changed in response to the supply voltage. The automatic battery charging apparatus of the present invention may be advantageously utilized in a variety of applications for rapidly and safely charging batteries used in battery-operated electrical apparatus.