The use of self-protecting charging resistors in the J10X series is recommended in order to handle typical malfunctions such as short-circuits or failure of the relay switch. In fault-free charging, these components act like a fixed ohmic resistor and limit the peak value of the charging current. In case of a malfunction, the temperature and inherent resistance of the PTC ceramic increases in line with the increased ohmic losses and limits the current to a safe operating level.