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Battery charging question

Old 12-05-2020, 10:02 AM
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I have a dual battery charger on my boat. When it is charging the batteries after use, it flashes yellow on both led light indicating batteries are charging. When both batteries are ready to be used again (I assume fully charged) the let lights blink green. When the system goes into maintain mode the lights turn solid green and should stay like that for months. I have one light that stays solid green and the other one stays blinking all the time. The one that stays solid is my trolling motor battery and the other one is the battery in the bilge that has everything else hooked to it. So the question is, does the flashing green light indicate that the battery is going bad because it can’t maintain a full charge and force the charger into maintain mode?

Sorry about rambling, but hard to explain.
Old 12-05-2020, 10:19 AM
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You should add the make and model of the charger if you want a better answer.

It could indicate that there is current continuing to be needed on that "house" battery and that could be because you have some other loads on it, which might be just fine for a normal "house" battery. Or it could mean that the battery itself is continuing to require a current which would indicate the battery is failing. How old is the battery?

I'm assuming that the "battery in the bilge" is the "house" battery but have no knowledge about your boat. Do you have separate "house" and "engine" batteries or just the "trolling" and "one in the bilge" (which does everything except run the trolling motor)?
Old 12-05-2020, 02:10 PM
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It is a Minkota 2 bank charger. I only have 2 batteries. The battery under the center console does just the trolling motor. The battery in the bilge handles the starter, bilge pump, live well pump, and fish finder. It is the battery in the bilge that never gets to a full charge and kicks in the maintainer. The bilge pump is an automatic style that kicks on every 2 1/2 minutes to look for water but wouldn’t think that would use enough juice to keep it from fully charging. Everything else is off. Boat is sitting in my garage for the winter. It is not a sealed battery so I should probably check the water level in the battery.
thanks for any answers.
Old 12-05-2020, 02:30 PM
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My man KM1125 provided the most likely answer. Parasitic draw on the start/house battery.

since you mentioned winter storage..... simply unhook batteries from boat, fully charge, disconnect charger from batteries, check water levels, and then let them hang out somewhere cool/cold.

a fully charged battery, stored in a cold place with nothing hooked up to them will self discharge at such a minuscule rate. No need whatsoever to have them hooked up to a charger for weeks or months on end.
Old 12-05-2020, 07:12 PM
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Thanks Onebadlarry. My boat is in a garage that is somewhat cool and never gets below 35 degrees. I could just disconnect everything from the batteries and leave them in the boat. I don’t see a need to remove them if they are kept cool in the boat. Amy I correct?
Old 12-05-2020, 08:28 PM
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Originally Posted by Fullthrottle52 View Post
Thanks Onebadlarry. My boat is in a garage that is somewhat cool and never gets below 35 degrees. I could just disconnect everything from the batteries and leave them in the boat. I don’t see a need to remove them if they are kept cool in the boat. Amy I correct?
Correct.


The colder it is, the less it will self discharge per month. A fully charged lead acid battery will freeze at -72F. So we have some wiggle room there haha.

The reputable Odyssey battery company even states their AGMS can be stored for 2+ years at 77F and 4+ years at 44F.

Old 12-06-2020, 06:52 AM
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You can leave the batteries in the boat. Pull the cables off the suspect battery and see if it will fully charge. If it does you have a vampire draw that you need to figure out. Probably that bilge pump. I always run the auto bilge pump supply from a three way, single pole double throw switch in the console. Up is auto, down is manual middle is off that way you are not running that bilge pump every 2.5 minutes. You never mentioned if you have a battery switch or not.
Old 12-06-2020, 09:05 AM
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If you have the MK2200, then the manual states shows:

So even though the Green Light is flashing, the battery is fully charged and it's in maintenance mode. If it was still flashing Yellow, then I'd be concerned because it never got fully charged.

Further down the manual, it shows:

This shows the difference between "regular" maintenance mode and "long term" maintenance mode, which is the difference between the flashing Green and the solid Green. The charger is looking for a 24 HOUR period where there's no drain. Your bilge pump, while it doesn't really drain much power, DOES take several amps of current while it is running even for the brief period of time and it's that surge that the charger likely sees. If it did not see that for a 24 hour period, it would likely go into long term maintenance.
Old 12-07-2020, 06:15 AM
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Thank you KM1125, I do have the manual but I misinterpreted it. Very good explanation. I will disconnect the accessories from the battery and see what happens.
That bilge pump doesn’t need to be checking for water for months anyway.
thanks for all for your answers.

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