Powerex Precharged 8.4V Rechargeable Low Self Discharge NiMH Battery (MHR84VP);

The Powerex Precharged MHR84VP Rechargeable NiMH Battery (8.4V, 300mAh) is a nickel-metal hydride battery compatible with Powerex's MH-C1090F 10-Bank Charger or MH-C490F Stealth Charger. It is rated at a voltage of 8.4V and a capacity of 300mAh, with a minimum capacity of 270mAh. The battery is capable of being stored for an extended period of time and still retaining a full or nearly full charge. After a year, for instance, it will retain 85% of its capacity. The battery comes pre-charged. The purchase of an NiMH battery like this one saves you money, since you won't need to buy endless supplies of non-rechargeable alkaline batteries.