Mechanical Foolproof Design of Battery Charger and Rechargeable Battery

A battery of a preselected type advantageously has a beveled edge formed between a front-end surface and a lateral surface of the battery. In a battery charger, a slot has a cap formed with an interior channel for receiving a front-end portion of the preselected-type battery. The cap has a stopping member for stopping the preselected-type battery so as to receive recharging. Advantageously, the stopping member may be shaped to complement the beveled edge for seamlessly receiving the beveled edge when the preselected-type battery is inserted into the slot. A mismatch between the stopping member and a line edge of an unaccepted-type battery causes the stopping member to block the unaccepted-type battery from reaching deeper into the channel than the preselected-type battery when the unaccepted-type battery is inserted, disconnecting a positive charging terminal from the unaccepted-type battery to avoid the charger from accidentally recharging the unaccepted-type battery.