A battery charging unit is disclosed for use in connection with a rechargeable, battery-powered device, such as a flashlight, of the type having a contact-foot that includes at least two contacts connected to the battery terminals and an asymmetrical end-profile. The battery charging unit has a receptacle that includes an asymmetrical aperture that corresponds to the end-profile of the contact-foot to ensure that proper electrical polarity is maintained between the charging unit and the contact-foot. The receptacle also includes a retractable barrier and retaining walls that are formed to ensure that the contact-foot is retained in the receptacle regardless of the orientation of the charging unit.