You possibly cooked the batterys. In storage it really is not necessary to leave them on a maintainer/trickle charger. Look around out in the real world. Construction & farm equipment sits for months unused outside in storage. Boat owners leave boats for months out on moorings. No solar. Nothing to keep batterys topped up. Recently left my own boat 3 months untended. 2 year old wet cell battery. It spun the motor like it was last used yesterday.
Saw a boat owner lose 4 big 8D AGM batteries due to the battery maintainer going bad & cooking them. $600 each batterys only a year old. I have an AGM battery in my 5er. It sits disconnected & untended every winter Nov to April. Minimal power loss.
