A detecting module is for detecting a battery equalizer of a power supply device. The detecting module includes a current detecting unit, a drive circuit, and a control circuit. The current detecting unit is to be coupled to the battery equalizer and a battery set of the power supply device, and generates an output based on detected current flow through the battery equalizer. The drive circuit is to be coupled to the battery equalizer for driving operation of the battery equalizer. The control circuit is coupled to the drive circuit and the current detecting unit, controls the drive circuit to drive operation of the battery equalizer and determines, according to the output of the current detecting circuit, whether the battery equalizer is in a normal operating state.