A battery charger including a converter unit, a terminal adaptor, a cable, a battery, and/or multiple power connectors. A terminal, such as an electronic device, can be connected to the converter unit using the cable or directly to the converter unit without the cable. The converter unit determines when to draw power from an external power and when to cease drawing power from the external power source by detecting a power enablement condition or a power disablement condition. The power disablement condition occurs when the terminal is fully charged, the terminal is disconnected from the converter unit, and/or a charge time of the terminal exceeds the predetermined charge time threshold. The power enablement condition occurs when the terminal is initially connected to the converter unit and/or the terminal needs to be charged. The battery supplies power to components of the converter unit and/or the terminal.