I tracked down the charge converter: you all had it right... my 2014 x213 has a multi stage converter (Progressive Dynamics PD4000 series), and it is in the bank of electronics just below the fridge. So, at least for now, I can cross that off the list of things I need! I do need to keep an eye on the battery though and see if it really did get too hot or if there was condensation or something from the case- not sure how the liquid on top of the battery got there... but when I popped open the battery case to add water they were full still...
so back to figuring out batteries... I am torn between getting 2 of the inexpensive Costco 6v golf cart batteries for ~$90 each or one 12v like I have that is around $120. Gonna do 3 nights in the trailer this weekend and think about it some more.
06 dbl cab tundra
P3 brake controller
14 Jayco x213