Reviving yet another old thread. After having persistent issues with my trolling motor batteries (again), I finally figured out the issue was actually my charger. The charger itself is fine, but the ring terminal connections were shot! So corroded that when I gave one a quick tug it came right off. I replaced with better heat shrink terminals and all issues seem to be resolved. It's a ProMariner charger, the brand 'Worst Marine' sells. Appears to be an 'ok' charger, but the electrical connections were really poor. They were heat shrinked originally, so it's a bit odd. When I re-connected everything, I used some dialectic grease. I was having moisture issues in the bow hatch where these batteries reside, which also should be fixed by a new Tempress hatch. It turns out the 30 year old hatch wasn't keeping out much water.