My wife and I recently purchased an 2010 W&P 25UL.
I made a mistake and left a light on inside the other day and ran the battery down. I plugged into shore power for about a day to recharge the battery. Battery is now charged but for some reason I am not getting 12VDC from the battery to the trailer. Everything works fine when plugged into shore power or when my truck is plugged into the trailer. I checked all the fuses in the fuse panel/converter panel and they are fine. I found some type of auto resetting 30Amp circuit breaker on the side of the frame next to the battery and I am only getting 4VDC on the trailer side of the breaker (12VDC on the battery side). I believe this breaker must be bad, but am not sure if I am doing something wrong as this is the first RV we have had.
This is the breaker I am talking about
Amazon.com: Bussmann BP/CBC-30HB Type I 30 Amp Circuit Breaker Two 10-32 Threaded Studs: Automotive
I dont believe there is anything loading the circuit because all is fine when plugged into the truck or to shore power.