This product is designed to boost a depleted battery on a host vehicle from a donor vehicle. Note: This unit will not start a flat battery and the process takes approximately 20 minutes. Draws power from donor car through 12V cigarette lighter socket and plugs into the lighter socket of the car requiring a boost. Suitable for petrol engines up to 3500cc and diesel engines up to 3000cc. LED light indicates charging process and ready connection. Automatic charging process with no buttons or switches. Manufacturer's 2 year guarantee.