AGM Battery Getting HOT when charging

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AGM Battery Getting HOT when charging

Postby Evan Dunville » Wed Jul 26, 2017 3:00 pm

Hey Everyone,
I bought a second hand Nautlous Group 24 AGM deep cycle battery (76 amp hour) sold by Canadian tire, i had it load tested at a Canadian tire store and it passed just fine. I have put a charger to it a few times and it would charge but due to a few odd occurrences the charge never reached 100% at one point my dad disconnected the charger because the battery was getting hot and from moving the trailer around i was unable to leave a charger on it for long periods of time. I bought a matching Nautlus smart charger charger 2/10/15 amp and left it plugged in for 12 hours. when i cheek it in the morning the charger was running at 13.7 volts and had a reading of 60% on the battery charge level (previously only stated LOW). the battery was really hot and there was actually some vapor coming out of the pressure releaf of the battery. I was concerned so i shut off the charger and my next plan is to put it on the low setting and leave it overnight again. I didn't want to get the battery really hot for a long time. my Googling of the issue has not turned up a whole lot of info and i called a few battery stores and asked the employees but they didn't seem confident on any of the info they were saying. (one person told me AGM batterys are dry and have no liquid inside)

TL;DR
Bought a Used battery AGM had it checked and passed, upon charging (8 hrs@15amp smart charger) it got really hot. How should i proceed?


http://www.canadiantire.ca/en/pdp/motomaster-nautilus-battery-charger-15-10-2a-0111525p.0111525.html
http://www.canadiantire.ca/en/pdp/motomaster-nautilus-group-24-high-performance-agm-deep-cycle-battery-0102496p.html#srp
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Re: AGM Battery Getting HOT when charging

Postby MtnDon » Wed Jul 26, 2017 4:40 pm

AGM might seem to be dry inside to those who do not understand them, as nothing is supposed to run out if the case is cracked. The electrolyte is Absorbed in a Glass Mat.

How hot is hot? Do you have an IR thermometer? An AGM should not get hotter than 50C (~120F) when being charged.. It should definitely not "steam".

Second hand batteries may have been previously abused and not worth the trouble.
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Re: AGM Battery Getting HOT when charging

Postby H.A. » Wed Jul 26, 2017 6:23 pm

:cry:
Last edited by H.A. on Mon Aug 28, 2017 4:38 pm, edited 1 time in total.
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Re: AGM Battery Getting HOT when charging

Postby featherliteCT1 » Wed Jul 26, 2017 6:36 pm

Assuming the charger is working properly (for example never having been dropped on the floor) I suspect that the battery has one or more bad cells which could cause excessively high resistance, low acceptance of amps, and thus heat. To compensate for the low acceptance of amps, I would think that the volts would correspondingly be excessively high per ohms law.

FYI, not long ago I had a bad battery that would not hold a charge and exhibited the above symptoms. However, my hand held battery load tester said that the battery was good.

If it were me, I would bite the bullet and buy a new battery.
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Re: AGM Battery Getting HOT when charging

Postby Evan Dunville » Thu Jul 27, 2017 8:52 am

Thanks for the replies, I agree something is not right with the battery. I took a chance on the used one as it was regular priced at $400 and i bought it for $100. I was charging it again today and i watched the charger closely. I think the issue is something in the battery is not allowing it to reach the full voltage (it stopped at 13.7 volts but dropped to 13.1 when disconnected from the charger) and since the charger didn't see it "full" it did not go into the float mode and just kept putting power in which turned into heat and my issues. Canadian tire has a good return policy and they track battery warranties in store now so i might be able to return it for a new one. I suppose it still works as a battery with a diminished capacity i will just need to keep an eye on the charge level and not let the charger run at high power.
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Re: AGM Battery Getting HOT when charging

Postby Camp4Life » Mon Jul 31, 2017 1:49 pm

I have that same charger. You can select the charge rate manually. I assume when it was hot that it was running at near 15A? Mine took most of a day to recharge my deep cycle flooded battery as well. You can try running it manually at 10A, or even 2A, but this will take much longer. The charger should also detect if the battery is worn and switch to a reconditioning cycle automatically if needed. These are great chargers, so if you're still having issues, I would be looking at the battery.
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Re: AGM Battery Getting HOT when charging

Postby beezerboy » Wed Aug 16, 2017 12:10 am

what does the battery read 3-4 hours after the charge... thats when you want to check. 13.7 on the charger or right after tells you very little. (sometimes called the "float" charge

I also suspect a bad cell... lowering resistance and causing more current to flow at the assigned charge rate. the extra current is being turned into heat. when chargers vary the charge rate, they do so by changing voltage. if the resistance is fixed, the only way to get high current is to drive up the voltage
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