Mechanical Foolproof Design of Battery Charger and Rechargeable Battery

A battery charger comprising one or more slots, an individual slot being used for recharging a preselected-type battery after the preselected-type battery is accommodated into the individual slot, the preselected-type battery having a lateral surface and a front-end surface, an edge formed between the lateral and front-end surfaces being a beveled edge, an unaccepted-type battery being defined as the preselected-type battery with the lateral and front-end surfaces extended such that the beveled edge is replaced by a line edge, the individual slot comprising:

• a cap formed with an interior channel used for receiving a front-end portion of the preselected-type battery, the cap comprising a stopping member, wherein the stopping member gradually narrows the channel along a battery-insertion direction for stopping the preselected-type battery and the unaccepted-type battery from further advancement into the channel while the beveled edge enables the preselected-type battery to go deeper into the channel than the unaccepted-type battery does to thereby enable the battery charger to distinguish the preselected-type battery from the unaccepted-type battery;
• and
• a positive charging terminal for providing an external voltage to a positive electrode of the preselected-type battery to recharge the preselected-type battery, wherein the positive charging terminal is positioned in the channel to barely touch the positive electrode when the preselected-type battery is stopped by the stopping member such that while the preselected-type battery is allowed to be recharged, the positive charging terminal is disconnected from the unaccepted-type battery when the unaccepted-type battery is inserted into the channel, thereby avoiding the battery charger from accidentally recharging the unaccepted-type battery.