George, my Interstates are factory originals, i.e. 14 years old. But you beat me... the coach has been parked for 3 years and the house set mostly started leaving a couple years ago, and now pretty much are all gone but one of the four, which still has a little life. Like yours, the solar kept them pretty much charged while at home here. But as the deep cycles aged, and I often switched to 30 amp input during low-sun winters, they tended to demand more from the charger. That is a vicious cycle that hits the batteries harder and harder over time, until they easily boil dry. The inverter doesn't read anything anymore unless I reset it by unplugging its phone connector in back.
I'm not sure but what the chassis set are still viable; they still read okay voltage-wise, are maintenance-free, and may still have enough to start the engine. Since advice was to either fully road-warm up after starting or don't start at all, and getting the rig out on the street here is a major operation, I simply don't start it, despite strong temptation and urges to hear that great CAT diesel sound. Regardless, I will be changing all 6 batteries when I do it.
But the 6 volt ones are so bad off now that I have to add water often, and just the solar charging is enough to boil that off and cause a lot of corrosion on some posts and the tray, which I'll refurbish during the switch out job. The older the batteries get, however long their viability and usefulness, the more they demand charger effort and the more they gas and corrode surrounding copper or steel and melt plastic.
So for any one with wet cell deep cycles, I'd not advise retaining them as long as you and I have, even though it sounds like some sort of record or impressive accomplishment. Mine should have been replaced 3 years ago.
Joel
