Fission Battery (Fallout 3)

A fission battery is a miscellaneous item in Fallout 3 and Fallout: New Vegas.

Background
Produced amongst others by Wattz Electronics, the fission battery has taken on the role of an on-hand generator. Throughout the Mojave Wasteland, fission batteries can be found in New Vegas streets, remote shacks in the wastes, and reoccupied suburban homes. They are used for powering a wide range of devices, like street lamps, electronic signs, light-bulbs, and other household appliances and are easily scavenged from the common robot or appliance store, making it invaluable to the common wastelander in the absence of a reliable power grid.

Fallout 3

 * Reilly's Rangers: A fission battery is required for fixing an access elevator during the quest, at the top of the Statesman Hotel. One can be found inside the hotel, but it is much easier to keep one extra in your inventory and bring it along for the quest.
 * A fission battery is used in the construction of the railway rifle.
 * A Spoonful of Whiskey: 6 fission batteries are required for the Point Lookout repeatable quest.

Fallout: New Vegas

 * Cass' moonshine: A fission battery is required to make Cass' moonshine.
 * Not Worth a Hill of Corn and Beans: Four fission batteries, along with many other supplies, are needed to repair a food processor.
 * My Kind of Town: Three fission batteries and 4 conductors can be used to reprogram Primm Slim to be the sheriff of Primm.
 * A fission battery, along with two pieces of scrap metal, are used to make Sierra Madre chips (listed as 'Sierra Madre Slugs' in-game) with the Coin Operator perk in the first add-on for Fallout: New Vegas, Dead Money.
 * Can be converted to energy cells in Honest Hearts, which can be in turn converted to other energy ammunition types.