I started the car with a dead battery up to 8 volts, the battery capacity is 72 Ah. The retractor did not even click on the key. Engine Audi a6s5, V6-2.4 liters, gasoline. I connected it to the battery terminals, pressed the boost button on the wires and staroval. The starter turned confidently despite the fact that the onboard voltmeter showed 10 volts with the device connected, but at the time of starting the voltage did not drop below 10 volts. Good product. It also properly charges mobile devices and provides 19 volts to power a laptop.