The USAlert WatchDog LT Battery Charger is both a smart charger and a rapid charger. Using a 12VDC 1.0A power adapter, it will charge both the WatchDog LT pager and a spare set of three NiMH (Nickel Metal Hydride) batteries simultaneously or individually. The rapid charge period is approximately 3-4 hours from a completely discharged state. A typical recharge period for moderately discharged batteries is approximately 2 hours. Recharging batteries with the pager powered on will take a slightly longer time complete as the charger must compensate for the amount of current being drawn by the pager. The WatchDog Charger is compatible with both the USAlert WatchDog LT and WatchDog Pagers.