The machine is designed to test the batteries for leakage of the second cover after the heat-sealing machine. This is done by pressurizing the vent holes with overpressure which is then compared with a leak tester at the specified pressure drop rate. The batteries arriving on the conveying system of the machine, enter the automatic testing device separately and are accurately positioned and fixed under the probe. The probe is pressed onto the hole of the battery cover and the battery is pressurized with overpressure. Over a pre-programmed period the constancy of the pressure is then measured within a pre-programmed tolerance zone. Should the tolerance zone be exceeded a visual or audible signal serves as a warning of the defective battery. The measured values of different types of batteries are pre-stored.