Type: Battery Specifications: Battery Rechargeable: Yes Battery Size: AA Battery Chemistry: Nickel-Metal Hydride (NiMH) Battery Capacity: 1000 mAh Number of Cells: 5 Output Voltage: 6 V DC Maximum Battery Recharge Time: 16 Hour Features: Telephone Back Up Battery Works as emergency power for the base unit during a power failure. Compatibility: Panasonic KX-TG4500 Cordless Phone.