If you are loosing voltage and amps from the battery to the inside of the trailer, check the self resetting thermal breaker bolted to the trailer frame close to the battery. Corrosion on the connections will cause this. Happened to me on my 2003 outback. When I went to clean it, it fell apart, it was so rusted. Replaced the breaker and no more voltage drop.
Jason & Wendy
2014 Ford F-350 Lariat 6.7L PSD
2015 Keystone Montana 3711FL
B&W Patriot 16K Fifth Wheel Hitch