Battery on trailer breakaway switch

You know what I’ve been studying this I’ve never paid attention to it. This is in a horse trailer with living quarters my truck has two plug outlets one is the smaller 6 pin in the truck bed and the other is factory on the bumper . If I use a adapter and go from the bumper plug I would have a accessory wire , I believe it would charge from the truck when driving. Just trying to figure the cheapest and best way thanks for the advice that’s why I posted here there’s a lot of knowledge.