Dual Batteries

You must make sure that the +12 volt line is at least 10 gauge, even better would be 8 gauge.  Similarly the negative line must either be attached to the frame within 6-12 inches or must also be 10 or 8 gauge all the way back to the battery.  Unfortunately most hitch installers - and possibly factory-installed tow packages - use the same cheap 12 or 14 gauge wire that the rest of the Bargeman connections use (turn signals, running lights, etc).

The reason is by itself the battery, if fairly discharged, will draw so many amps you will get a large voltage drop and end up with not enough voltage potential to put any charge into the pod's battery.  Add on the fridge in 12 volt mode (around 10 amps) and the game is over when using the cheap stuff.  This is one area where you get what you pay for.