A rechargeable battery system for a portable electronic device is provided. The system includes a battery pack having a first battery and a second battery. The battery pack is preferably configured to electrically connect one of the first and second batteries to the electronic device in a first position, but requires at least partial detachment from the electronic device and reattachment of the battery pack to the electronic device in a second position, different from the first position, to electrically connect the other of the first and second batteries to the electronic device. The system further includes at least one set of charging terminals on the battery pack for charging the first and second batteries.