Here is a typical wiring configuration for the 30AMP Electrical system in the trailers.
You should have 120VAC circuit breaker (usually the second one down the breaker side) that will turn off the converter/charger unit. This will only kill your 12VDC power source but the power distribution panel will then use the battery if it is charged up.
You can bring along your portable battery charger and keep your battery charged up doing this...
Again be sure to check out your battery before leaving for your trip - I'm really suspecting it is toast now...
This brings up another issue as well. DOT requires you to have a working battery on-board your trailer in the event your trailer becomes disconnected while being towed. This on-broad battery then immediately applies 12VDC to your run-away trailer electric brakes when this happens. It might go against any Insurance claims if you have a bad battery or travel without one. It could also be enforced by a DOT safety check along the way as well- i.e. could be a fine but I have never heard of this happening. Be safe sharing the DOT roadways with others...
Roy Ken