# dead battery?



## answer3 (Mar 4, 2015)

Hi guys
I have a 1 year old 122amp h marine deep cycle battery that I use for my trolling motor and a minn kota MK105P portable charger and have been using this setup for 1 year with no issue at all. But when I wanted to charge my battery about month ago the charger was charging for 5 seconds and stopped for 5 seconds and so on until I unplug it. I measured the voltage it is 12.4v so probably ~70% charged, but I cannot charge it further to 12.7v... I tested another 12v deep cycle marine battery which is charging perfectly fine up to 12.7v and the charger does not do this weird on-off cycles at all, so I assume that the charger is ok and the issue comes from the battery. I checked the electrolytes levels by opening the caps and they all seem ok. Does anyone know what is wrong with the battery? did this happen to anyone before?
Thanks
Damien


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## earl60446 (Mar 4, 2015)

So the charging led is going on and off every 5 seconds. Are any other led's coming on? Is the battery disconnected from the trolling motor and everything else? This may also be a desulfate mode operation on the battery. You might want to try a different charger on the battery or take it somewhere else for a quick charge. Some auto parts places do this for free and will load test it for you too.

Tim


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## answer3 (Mar 4, 2015)

there 3 leds on the charger: "charging", "charged" and "check connections". The "charging" led in on for 5sec then the "charged" led is on and so on... no other leds. I disconnected the battery from the trolling motor and even tried without the fuse and the circuit breaker, it is the same thing.


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## huntinfool (Mar 4, 2015)

My bet is, its charged. 

Try hooking up the battery and running something on it to discharge the battery. Once drained, try recharging it.


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## answer3 (Mar 5, 2015)

Thanks guys, I will try that this weekend


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## fish devil (Mar 6, 2015)

:twisted: More than likely you have a sulfated battery. Nothing you can do but replace it. Never let a Deep Cycle battery wear down. You must keep it charged.


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## slick (Mar 7, 2015)

Most batteries have a 1 year warranty. If you still have your receipt, you may get a free replacement.


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## answer3 (Mar 11, 2015)

huntinfool said:


> My bet is, its charged.
> 
> Try hooking up the battery and running something on it to discharge the battery. Once drained, try recharging it.




It worked! I run a trolling motor for 3 hours on the battery to discharge it and charged it back and the charging cycle went perfectly well. It is now fully charged. 
Thanks for the tip!


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## huntinfool (Mar 11, 2015)

Good to hear. You're welcome.


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## Riverdog (Mar 15, 2015)

The noco genius chargers claim to revive sulfated batteries.

[youtube]S2t3ZpJSNAY[/youtube]


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## river warrior (Sep 21, 2015)

Thx for the notes guys. I have the same problem.


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## nlester (Sep 22, 2015)

I find a cheap hydrometer from the auto parts store gives me a better reading on the battery than the volt meter.


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## bptjr (Nov 4, 2015)

try testing each cell of battery with a battery hydrometer. if you don't have one , they are cheep at any auto parts store. it floats a bunch of colored balls in its tube and this tells you % of charge on each cell. if one is a lot less than others it the problem. but befor replacing battery , turn something and draw the battery charge down some and then try to charge it again and re test. if still bad replace the battery. hope this helps.


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