Abstract: A charging device includes a charging circuit having a power inlet and a power outlet which is preferably connected to the charging circuit by means of a cable. An adaptor which is adapted to electrically connect to a given external power source, such as a wall outlet or a cigarette lighter holder provided on the control panel of an automobile, has a connection portion for releasable connection with the power inlet of the charging circuit for supplying electricity from the power source to the charging circuit. The adaptor may be provided with a voltage transformer to allow the charging circuit to be used with external power source of different voltage outputs. A battery holder has a connection portion for releasable connection with the power outlet of the charging circuit to supply the output of the charging device to the battery holder.