I think there is a load tester you can get at any
auto parts store. that can tell you pretty much the condition of the battery. I do know this weather has a big effect on them. What may test bad in this weather can test good in warm weather. Also there is a chemical system that rejuvenates LAbs if they are in decent condition.
My limited understanding is there are 2 basic things that kill a battery. 1. build up inside the battery that shorts out a cell. 2. a broken post. Im not an expert on batteries.
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