Charging through the connector from the tow vehicle to the trailer is very slow. You would get perhaps a couple or few AH in a half an hour, which may not be enough to keep up with usage if you're running the furnace or water heater or some lights. You'd be far better off with some other system—a little generator and a good battery charger (or a good modern converter) or a solar setup. Granted, either of these does cost more money than the tow vehicle you already have...
You would get faster charging if you hooked up a good pair of jumper cables between the tow vehicle and the trailer battery. Still far from an ideal solution, but closer to workable than charging via the trailer connector.