Deep cycle marine battery questions

Not sure where to post this question regarding my Deep Cycle marine batteries which I used for the TM. Boat is 2015, onboard charger came with boat.

Recently I tried to plug in and charge the TM batteries (Lead acid FLOODED BATTERIES), I have 3 of them and a 3bank charger onboard. Once it's done charging, only 1 of the batteries were charged with a GREEN light on. The other two batteries had an indication of a blinking YELLOW light and doesn't show the Green charged light even if I left it over night or 2 days later (this never happened before). I just unhooked the batteries and check the water level and both batteries have no water at the plates, it is below it, well one battery had at least 2 cells with water at plate level. So I filled it up with distilled water and hooked it up to my portal battery charger and one was showing 12v but at 0% life. The other was at 10v and jumped to 11.5v- 11.9v, also at 0% life ( or discharge). I charged one for a good 30min or so I think, then it quit charging but says "charged and maintaining" on the charger. The other one was charged for 1hr or two and went to "charged/maintain" status as well. Charger was set at slow 6<>2amp. I tried to charge the first one again and still charging but it says 100% at 12v while the charger is on. when I stopped it, the voltage reads 13.9v and slowly dropped down to 13.5v..I noticed that the battery that still had some water in most of the cells was charged faster.

Now my question is, is it possible that my 2 batteries weren't holding charge when it was on the onboard charger was due to LOW WATER IN THE CELLS? or something else.? All 3 batteries were dated April/May 2020. TIA!!

You more than likely need to replace the 2 batteries. I assume the 2 bad ones are for the TM and the good one is your starting battery? If all 3 are for the TM, replace them all. Letting them get low on water is very hard on them. Check the water level more often on the new ones. But 5 years is pretty good life for flooded lead acid batteries.

IMHO you need to buy three new batteries. Five years is pretty much an extended lifespan for trolling batteries.

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Originally Posted by jejb

You more than likely need to replace the 2 batteries. I assume the 2 bad ones are for the TM and the good one is your starting battery? If all 3 are for the TM, replace them all. Letting them get low on water is very hard on them. Check the water level more often on the new ones. But 5 years is pretty good life for flooded lead acid batteries.

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All three are for TM. I did charge them with portable charger and stats on charger says 100% at 12v for both batteries now. Maybe Ill do a Load Test if they are still good? LOL

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Originally Posted by SoonerFan

IMHO you need to buy three new batteries. Five years is pretty much an extended lifespan for trolling batteries.

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I would agreed too!

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Originally Posted by 4motion

All three are for TM. I did charge them with portable charger and stats on charger says 100% at 12v for both batteries now. Maybe Ill do a Load Test if they are still good? LOL

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load testing never seems to be accurate on deep cycle batteries for me? have tried the cheap and the high end testers both, with mixed results.

But I also seen people trying or did bring used batteries to life?

I just used a multimeter and tests both batteries. The one with all no water in all the cells reads at 12.45v and the other one at 12.65v

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Originally Posted by 4motion

I just used a multimeter and tests both batteries. The one with all no water in all the cells reads at 12.45v and the other one at 12.65v

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That's about 65 and 80% respectively. Time for new batteries.

Time for 3 yes 3 new batteries, why?

In a series setup, all batteries see the same current load. If the batteries are not identical (e.g., different capacities or ages), one battery might experience a much larger or smaller current load than the others, potentially causing damage or premature failure.

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Originally Posted by Mr Phoenix55

Time for 3 yes 3 new batteries, why?

In a series setup, all batteries see the same current load. If the batteries are not identical (e.g., different capacities or ages), one battery might experience a much larger or smaller current load than the others, potentially causing damage or premature failure.

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all the 3 batteries are identical. Deka marine group 27, although two are parallel and one is separate but all are hooked up to same charger and TM. Only one of the two parallel shows weakness with low water in all the cells. And the separated one has 3 cells with low water.