We have a camper set-up that we built into our van. We'll be heading to Northern Arizona next week, and we're VERY concerned about cold nights. Any suggestions for heating the van overnight? We tried one of those propane catalytic things a few years ago...piece of junk-I could actually set my hand on the thing that was supposed to be putting out heat! Is there such thing as a 'battery' that takes a standard household plug that we can charge in the cigarette lighter as we drive, then use at night when parked (for something like a household space heater)? Or any other suggestions out there??