Charging the truck battery with solar- will a 1.5W panel do?

Yeah, camper is on the truck full-time and currently I'm leaving the 7-way plug unplugged (would like to leave it in eventually). Indeed the goal is to be able to jump the truck from the camper's battery bank! Months at a time- that's my objective.

I'll check the glove compartment, and anything else simple, the next time I'm climbing around it...