Could you post the model of your converter/charger unit. Your 2004 model trailer probably only is using a single mode voltage converter/charger unless you have added a smart mode converter/charger.
I have used different small wattage size INVERTERs here in my off-road setup an finally have settled down to a 600WATT AIMS PURE SINE WAVE type inverter for all my electronics including 120VAC speaker amps for the computer here... The only thing I ever put on a MSW TYPE INVERTER is outside lights. My PSW INVERTERS were always hard wired installed as close to the battery switch as I can get. Never had much luck plugging them in 12VDC cigarette lighter type connectors inside my trailer. Internal trailer 12VDC wiring is too small to handle the inverters. Even a small 300WATT INVERTER will draw around 24 AMPS DC Current at 12.3VDC input (FULL LOAD).
I have a nice cool spot in a cabinet within five feet from my battery switches where I mount my PSW INVERTER. This area has good spot for INVERTER chassis frame ground and has a positive air flow for cooling.
Like everyone else here just poking around with comments... Maybe a light will come on and help out...
Roy Ken