Abstract: A battery case for selectively housing batteries of different sizes has a housing dimensioned to receive the largest of the batteries and provided with an opening through which the batteries are insertable into the housing, and a battery holder is movable in the housing in the direction toward and away from the opening to effectively vary the space available in the housing for accommodating a battery between the holder and a lid which is engageable in the opening for closing the housing. Locking arms are pivotally mounted at the opposite sides of the housing and are selectively engageable with the holder for determining the positions of the latter relative to the housing, and battery size detectors are integral with the locking arms and project into the housing for engagement by a battery inserted therein so as to position the locking arms, and hence the holder, in dependence on the size of the inserted battery.