The device cannot be used to charge the car battery directly in order to avoid a discharged state. It is primarily designed as a jump-start booster to briefly start an already discharged 12V battery, but not as a charger for the vehicle battery itself.

The device itself is charged via USB or a 12V input, but it does not actively charge the car battery, but only provides a strong starting impulse if the battery is already discharged. A separate battery charger is required for permanent charging of the car battery.

To summarise: The device is used to jump-start a discharged battery, but does not replace a charger that continuously charges the battery to prevent discharge.