Energizer Smart Charger for 2 or 4 "AA" or "AAA" NiMH rechargeable batteries. Charges batteries at a safe, steady rate to improve the long-term life of batteries. Countdown time shows time remaining until batteries are fully charged. Battery fuel gauge shows charge status. Bad battery alert, shuts down charging when a non-NiMN battery is inserted into charger. 4 AA included.