Like I just performed the same thing on my TT yesterday and come to find out my batteries afre fine but the wiring is corroded and warm for the first 6-9" inches from the battery. This tell me I got a internal resistance built up in the wire and need to replace this small length.
Like my TT is hook to shore power 24/7 and I figure OK just check the panel and see it full right. Now open the cabinet and unplug the battery charger. Now check again battery shows full. Now flip on 2 lights... Check again batteries are EMPTY.
But now shut off the light and the display shows full again.
So this basically shows the main wire off the batteries is corroded enough to choke the current flow to the point of appearing dead when it really isn't... Hence with this much choke the wire starts to heat up...
So helping you just help me...