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I purchased two AGM batteries 2 years ago. During the season I have no problems with them whatsoever. I charge them while at the dock but I have taken extended trips where I was on the hook or mooring for several days straight. Over he winter he batteries lost their charge over a 4-6 week period. I've looked for a battery drain but have found none. Any ideas or did I just buy defective batteries. BTW I swapped out he charger when I bought the new batteries. Any thoughts?
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MORGANNA
Greenport, N.Y.
Batteries should not self discharge very much at all in winter if they were fully charged when put away. If they work well during summer then I would suspect you have missed a load somewhere. You might want to fully charge them then totally disconnect them, take all the cables off both posts so you know for sure nothing can be drawing them down. If they discharge with nothing connected to the posts there's something wrong with them.
You didn't mention anything about the size/amps of the batteries, the charging system(s), how you use the boat, what you draw each day when off AC power and most importantly what voltage the batteries discharged down to. That information would be helpful in getting a better picture of what you've got and what might be happening.