Ok, I live in sunny So.Cal. (sorry nor-easters, don't hate the playa') and when our lovely sun isn't blocked by the smoke and soot from raging wildfires I could see the benfits of having a solar unit on the roof. My question is, are these things practical? Are the one's that supposedly "trickle charge" the batteries by plugging them into the cig lighter useful? Is that even possible? Don't need an engineering answer but I didn't think that plugging something into the 12v socket could charge the coach or engine batteries.