A method which supplies power to an electronic device from a power supply device. The method includes setting a minimum power level of a power supply battery of a power supply device, detecting a current power level of the power supply battery and determining a current supply of the power supply battery, determining if the current supply exceeds a preset minimum power level, setting a required power level for extracting power from the power supply battery, extracting the power from the power supply battery according to a preset required power level, and transferring the power to a power charging battery of the electronic device. A related system is also provided.