The most critical defect in electrochemical cells is connected with internal short circuit (ISCr) occurrence. It may cause a thermal runaway which can even lead to explosion of the cell. Although the causes are well know (manufacturing defect, overcharging, overdischarging), the timely detection of ISCr is very difficult. This work focuses on the detection of an internal short circuit while the cell is being charged using the time dependence of the capacity evaluation.