Thanks again for the responses. The whole charging thing makes sense. The battery does fine for the first few days of my trip and then it begins to lose its charge. I usually do most of my driving at the beginning and then I'm driving shorter distances.
I took my rig into my local shop. We're going to toss the existing 12v battery and put in two 6v AGM batteries. No custom fabrication necessary. One will go in the existing compartment. The other will go inside the coach. I'm going to look into solar as well. Any suggestions on solar systems for a smaller RV?
