A module having a housing, a battery, control circuitry and electrical conductors. The battery and control circuitry are contained in the housing. The housing is adapted to be removably connected to the frame of a firearm. The electrical conductors are located on the housing and allow the battery and control circuit to be electrically connected to other components of the firearm. The housing can be connected at a hand grip section of the firearm and forms a substantial portion of at least one exterior side of the firearm at the hand grip section.