An energy management system includes a power supply module, a charging module, an interface module and an energy management module. The power supply module provides an input power. The charging module generates, based on the input power, a first charge power and a second charge power in response to a first charge control signal and a second charge control signal. The interface module detects electrical energy stored in an energy storage device to generate a detection result. In response to the detection result, the energy management module determines an operating state of the energy storage device, and generates one of the first and second charge control signals.