1.8 Watts at 12 volts = 0.15 amps.
Technically, yes this will charge a vehicle's battery..but it will take you at least a week of sunny days to get enough of a charge into the battery to make a real difference.
You could maybe use it to maintain a charged vehicle battery if you were not going to use the vehicle for a while - or use it to "top up" a 12 volt system if you were running a low current drain appliance off of it (portable radio, LED lighting, phone charger, etc.).