A battery module with a battery housing includes a first conducting layer, at least one battery cell, a second conducting layer, an insulating layer, and a detecting circuit. The first conducting layer is disposed inside the battery housing. The battery cell is disposed inside the battery housing and opposite to the first conducting layer. The second conducting layer is disposed on the battery cell. The insulating layer is disposed between the first conducting layer and the second conducting layer. The first conducting layer, the second conducting layer, and the insulating layer form an internal capacitor. The detecting circuit is electrically connected with the first conducting layer and the second conducting layer for detecting a capacitance value of the internal capacitor.