AGM battery only 12.25 Volts

[bluestream]

I have an AGM power-sports battery that will only put out 12.25 Volts after charging. Does this mean its in its final days? My other AGM's are putting out 12.45V and one is from 2004.

I also have a lead acid power sports battery that is putting out 12.5V. Which would you use in your equipment, the Lead-Acid at 12.5 or the AGM at 12.25?

 

[Errtt]

Isn't a AGM a lead acid, just the acid is absorbed in glass mat?
Are you using the same charger/maintainer

 

[bluestream]

Yes, same charger.

 

[JHZR2]

Originally Posted By: Errtt
Isn't a AGM a lead acid, just the acid is absorbed in glass mat?
Are you using the same charger/maintainer


Yes, though sometimes the charging voltage ranges and whatnot differ slightly. The wrong charger may not be taking the battery actully to 100% SOC.

 

[bluestream]

Originally Posted By: JHZR2
Originally Posted By: Errtt
Isn't a AGM a lead acid, just the acid is absorbed in glass mat?
Are you using the same charger/maintainer


Yes, though sometimes the charging voltage ranges and whatnot differ slightly. The wrong charger may not be taking the battery actully to 100% SOC.


I have been using a Schumacher automatic trickle charger. I will try another...

 

[dparm]

Does the charger support "floating"?

 

[morris]

i have some "Schumacher" chargers, but they are manual, i have to keep a watch on them. the quality if that brand is very good.

 

[bluestream]

Originally Posted By: dparm
Does the charger support "floating"?


Yes, it does. Its the 1.5 amp automatic charger/maintainer. Made in China. It does bring my other AGM's up to full volts...

 

[wrcsixeight]

What dimensions and age is the battery you are charging?

How old is it?

How much of it's life was spent at or nearly fully charged?

How often was it left alone to slowly discharge, or discharged and left discharged for any amount of time?

Worst thing you can do to a lead acid battery is let it sit discharged.

No 'trickle/ float charger or maintainer is going to restore it to it's pre abuse capacity.

Higher amps causing a little temperature rise, not to exceed 120 f would stand a better chance of dissolving sulfates back to the electrolyte, then, a trickle charger might be of benefit.

In my opinion, 'trickle' charging a depleted or old abused battery(>35 lbs) is futile, or nearly so.

 

[GMBoy]

You need to get some more power into that battery to get it to full state of charge. A trickle charger is not meant to charge batteries - only to maintain. True, over a few days they can charge a battery but it is never as "full" of a charge as a larger battery charger.

 

[bluestream]

I know nothing about the history of the battery as it came in a used purchase I made. All I know is that it will only put out 12.25V

 

[bluestream]

I put it on my 6 amp charger for a few hours and now it is holding 12.43V. I never would have guessed this would help, but I am glad I asked the question; Thanks to GMBoy and wrcsixeight....

 

[bluestream]

Update....Battery voltage fell down to 12.3 after one day. All 3 of my chargers are automatic units that shut down when they think the battery is charged. I took this to my buddies battery shop and they put in on their charger for 3-4 hours, and The battery was good and warm when I came to get it. This is a Deka EXTL16 (East Penn) battery, and they told me it is one of the best made. It put out 12.8 volts after charging, and although rated at 325cca, they tested it at 590cca. I was told that the Deka batteries are way under rated, and for a small battery to crank out 590cca was amazing. 4 days later it is holding 12.75 volts, and I would recommend the DEKA battery to anyone even over the Yuasa, which is not as heavy a battery as the Deka.

 

[Volvohead]

Not knowing a battery's history, it's always hard to know whether it was abused or neglected. AGMs are usually sealed, which makes a visual of the plates that much harder.

Some AGM batts require a significantly higher charging voltage than a flooded type. A one-program charger sometimes won't work with them. The better chargers provide a special program for them the right voltage. You may need one of those for maintenance charging.

East Penn makes some of the very best, so to get a clunker would be an exception.

 

[bluestream]

Volvo, I expect the previous owner left the battery sit and the plates became sulfated.

BTW, one of my chargers has a switch "maintenance free, or conventional" setting. I never knew what that meant and always left it on maintenance free...

 

[meep]

the battery has some age and was sulfated. using the higher power chargers can initiate an overcharge which can, if done correctly, return some of the sulfate into solution, extending its life. In a gel cel and agm, this can also damage the battery permanently-- all depends. If the battery was warm, it was def forced into an overcharge.

AGM do require slightly higher V to take a same charge rate. But it's not big.... it's like a volt or less. They must be limited on current however (Amps) to prevent from damaging.

The initial voltage after coming off a charger is called surface charge. it's not the true voltage. battery needs to settle, or a small load placed on it to get it to settle before taking an accurate reading.

A float charger can charge a battery-- it can just take a few days. May also overwhelm the charger, overtemp, and cause it to turn off and on (internally), taking even longer. But it can be done, just slowly.

I suspect the battery has some age on it. now that it's got some boost in it I'd put it on the maintainer and keep it there. Monitor the battery temp. if it's staying warm or looks like it might be ever so slightly swelling, I'd put a replacement on the list. Be careful, they hold a cpl psi of pressure.

M

 

[JHZR2]

Originally Posted By: meep
AGM do require slightly higher V to take a same charge rate. But it's not big.... it's like a volt or less. They must be limited on current however (Amps) to prevent from damaging.


This does not make sense to me. That implies that the impedance of the AGM battery is higher than a flooded battery. I believe that the highest rate-capable Pb-A batteries are indeed AGM.

 

[Volvohead]

Originally Posted By: Bluestream
Volvo, I expect the previous owner left the battery sit and the plates became sulfated.

BTW, one of my chargers has a switch "maintenance free, or conventional" setting. I never knew what that meant and always left it on maintenance free...


Well . . . if a battery is sulfated, you'll want a charger with a special de-sulfating stage for best results. I know Ctek makes a good one.

Still, I believe AGM batts are much more resistant to sulfation by design. If one has reached that point, it's probably been through a lot. By what's involved, I would think it would be equally difficult to de-sulfate an AGM.

One volt is not insignificant in a 12v system.

Hope it works out for you.

 

[JHZR2]

Went out to my 91 BMW, which has a Deka grp 49, a big battery in it.

The car has sat for more or less 2 weeks, it was started and stopped to go in the driveway once or twice. Stuck my meter into the cigarette lighter socket, and saw this:

Now I've done tests before that have shown that there is a 0.1V difference between the cigarette socket and the terminals on the battery.

But this is been about normal ever since I put that AGM battery into the car. Charging voltage during temperatures such as we are seeing now is about 13.7 V maximum. So I think what happens is that the battery does not quite get fully up to charge and the internal resistance starts to cause self discharge which takes the voltage lower than we would expect.

I use one here because the battery is installed in the trunk and so the minimization of hydrogen gas is a beneficial thing. The thing is that modern alternators can really put very high current into an AGM battery, and recombination is not guaranteed when charging at high rates. So in my opinion they are more prone to drying out and of course are not serviceable.

They can last nearly forever on a real true climate controlled float charging, but that's not what we have and most automotive applications.

 

[[email protected]]

I just went through the same thing.

Purchased an Optima yellow top at AAP. Had them test it before I took delivery. 12.1v. Date code sticker on battery of 3/12. So it sat on a shelf for 6.5 months, great. According to Optima, thats 60% SOC or less. Yikes!

Bad news was it was the only one they had in stock and I needed the battery "now" as the one I was replacing was stone dead.

Brought it home, put it on the Schumacher 'smart' charger. Wouldnt charge, lights blinking. Look up manual, the battery charger states the battery was too sulfated. Alrighty then!

Got out the old basic 8amp "non-smart" charger. Let it charge overnight at 8amps. In the morning, the battery showed 13.2v! Score. Well, except when I checked it later in the day I was back down to 12.3v.

Went yday and exchanged it for another one, they had it shipped from another store. Date code 6/12. Resting volts 12.75v - I can live with that.