Your “test button” and voltage at the batteries should read the same. If your reading at the batteries is correct (13.5v) after the coach has been plugged in for a week, then the converter/charger is probably not going into maintenance mode (about 13.1v). Putting 13.5v continuously into you batteries will “boil out” the electrolyte and can ruin them even if you continually add water. It’s not good for your batteries. In the long run it is cheaper to replace the converter/charger with a better quality one that works correctly. One of my WFCO chargers did not start in “boost” mode when the batteries were below 50% charge as well as never going into maintenance mode. By replacing the Thor converter/charger I got faster battery charging time as well as saving my batteries.
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