Series-type charging device and charging method thereof

The series-type charging device comprises an input-terminal, an output-terminal, a control unit and a detector unit. The input-terminal receives an input power. The output-terminal connects the input-terminal and another series-type charging device, and provides a next-level power. The control unit connects the input-terminal and the output-terminal, and stores an upper limit value of the input power, and obtains an output power by shunt of the input power. The control unit generates a charging power according to the output power, and charges a battery. The detector unit is connected between the input-terminal and the output-terminal to measure a supply power of the input power. Wherein, charging the battery of another series-type charging device first when another series-type charging device is connected with the output-terminal and the remaining power is arranged for the other series-type charging device.