If you have a heavy duty alternator and you put in larger wires on the charging circuit it can work but as someone else suggested, you are drawing a lot of amps.
If you are only traveling a 2-3hrs, probably easier to just turn off the unit and turn it on when you arrive. As long as the door stays shut it should stay cold.
That said, I think you are worried about nothing. Sure there could be a strange set of circumstances that set it off but very unlikely. The bulk of RV's go down the road with the fridge set to propane and running.
