Ponch, I replaced my original "Interstate" batteries with the Lifeline GPL-4C deep cycle 6 volt batteries. These are the AGM (absorbed glass mat) type batteries, and are 100% maintenance free.
These are expensive as compaired to standard type liquid acid batteries, but, these are the type of batteries being used in marine and aircraft applications (and some motor homes). I bought my Lifelines on the internet, from Solar Biz.
There are also other types of AGM batteries available. Sam's Club sells an AGM - I think Sam's yellow case is suited for our application. Not sure whether it fits in our provided space???
http://www.thesolar.biz/
http://www.thesolar.biz/LIFELINE%20B...20and%20RV.htm
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