This is simplified block diagram of your trailer 30AMP power system. As you can see both the Trailer Converter/Charger unit and the Battery feed the Power Distribution Panel which is the heart of your trailer power distribution. This panel allows your trailer's most critical components/appliances to be powered up by 120VAC shore Power or directly from the Battery when camping off the power grid.
If you have pulled the Battery cable protection fuse that is located next to the battery while the trailer is still connected to shore power 120VAC then the 12VDC items will still be powered up by the trailer on-board converter/charger unit...
Don't misplace this fuse as when you are connected to shore power the on-board converter/charger will not be able to keep your battery charged up with this fuse removed.