Update:
After reading this
article on RV battery charging and buying a hydrometer, I discharged by batteries yesterday and then charged them via the converter overnight, much like I did before the start of our trip. I went out this morning with the hydrometer and the batteries are only showing a charged state just above dead!!!
After reading the handy bob article, I started thinking about my stock converter placement. It's towards the rear while the batteries are near the front. So my thoughts are the converter is seeing the voltage come up high enough to drop into float mode, but due to the long wire run and voltage loss the batteries never get the charge the converter thinks they have. I'm guessing we left for our trip with nearly dead batteries and whatever charge we did get was from the truck on the drive down.
My next project will be relocation of the converter within a couple feet of the battery box...
