It sounds to me you have no connection between the converter/charger and the batteries. You may have sparked something and blown some fuses between the batteries and the converter.
To prove you are not connected just turn off the converter/charger unit and see if you turn on your ceiling lights in the trailer.
When things are normal your batteries should be putting out 12.6-7VDC if fully charged and the converter/charger unit off. When you turn on the converter/charger your battery voltage to jump up to 13.6VDC showing you are connected properly.
Just to double check... Find the outside NEG CABLE connection on your two 6VDC BATTERIES and make sure this is the cable going to the trailer frame ground. It is very easy to get cables reversed...
When the cable get reversed even just for a second they will blow the REVERSE POLARITY fuses and the INLINE fuse close to the battery.
Don't know what 12VDC Power Distribution chassis you are running but most of them have two high value fuses off to them self maybe labeled REVERSE POLARITY.
Both the CONVERTER/CHARGER unit and the BATTERIES must feed the 12VDC Power Distribution Panel at the same point. This way your 12VDC FUSES located in the fuse panel will get DC power when you are on shore power or just running off the batteries.
This is a diagram on how the two 6VDC Batteries must be connected...
Roy Ken
