How do you know when your trolling battery gives up its ghost?

[MRJ]

I have heard that it is an "old wives tale" that you need to put a battery on a board to keep it from discharged into the ground. As long as the plastic (non-conductive) case is clean, you won't have a problem. I have five deep cycle batteries for various things and three get stored through the winter directly on the concrete and two are on wood shelves. I just tested all five and there wasn't half a volt difference between any of them. At least from my experience, I tend to dismiss the notion of direct contact battery discharge into the ground. I would be interested if others had similar or different experiences.
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