[ijames]

My $11 Walmart heating pad does not turn itself off, but I've had it at least 10 years so new ones might be more nannyified. Even if it turns itself off, you only want it on while you are sitting on it so that's a good feature. Get cold, turn it back on. Have to get out and check something out, don't have to worry about the battery getting too run down. Get a pad, check the wattage, then get a cheap inverter rated double that or a bit more, put the battery in a marine battery box to contain the acid, and either put it in the floor of the back seat or the trunk. Would be best if you strapped it down if it's in the trunk so it can't turn over. Again, put the inverter under your legs, and use a blanket to cover your legs.