More AGM storage...

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I've been reading posts regarding AGM battery storage, am I'm still not sure what to do.

I have 4 AGM batteries.

1 Optima Red (starting)
1 Optima Yellow (deep cycle)
1 Orbital Red (dual purpose)
1 Orbital Blue (deep cycle)

I the past I always took the batteries into my basement for the winter, had hooked each of them to a Harbor Freight float charger.

Now,I read that float chargers should NOT be used on AGM batteries

My battery charger has 2amp, 10amp, and starting modes for both flooded and AGM batteries.

The Optima red is still in the car, parked in the garage. Mainly because I don't feel like having to go through all of my audio settings come spring and setting everything up again (I have a lot of audio equipment in that vehicle) and the others are in my basement with nothing attached.

Will my Red top be ok in the cold if I attached the 2amp AGM charger to it every couple of weeks? or am I better off bringing it inside?

Is it REALLY ok to leave my other 3 AGM batteries sitting in the basement with no charge, or should I do something else?

are the "Battery Tenders" safe to leave on AGMs? Or does someone make a battery product?

I just don't like the idea of replacing my $150 batteries come spring.

Thanks.
 
I've used my regular plain jane schumacher 2/10 auto charger on my red-top. The battery is 4 years old. it's literally been sitting on a shelf taking up space. I put the charger on every few months (if I remember) and it's been fine. a few weeks ago my neighbor called & whined to me about his optima giving out. So I gave him my old one because I was gonna toss it anyway.. this is a REAL optima, not the one made by johnson controls.
He's been happy since.
I do have a craftsman battery that has an AGM seting.. no clue what it does.. but I've used regular chargers on the optimas..
I had a guy break the sulfation on a yellow top by blasting 125amps at one for 15 minutes on and off.
Needless to say.. the battery came back to life and was fine again..but it was scary to watch the case expand and contract
 
smart chargers can be used on AGM, the charge profile/float voltage is varied a bit.

I would get one that has the setting though...
 
Originally Posted By: Johnny248
I've been reading posts regarding AGM battery storage, am I'm still not sure what to do.


Good questions, here is my advice:

I have an XS Power AGM battery, not an Optima but the same AGM technology. I also use a conventional / old school charger that has a 2A setting (it has 2A, 40A and 200A starting), I didn't go and buy a "smart" or AGM specific charger... however you need to pay close attention to your charging voltage if you are using a non-AGM charger. There is nothing wrong with using the old chargers if you are careful. If you want to "set and forget" then get a proper charger. My AGM, and probably yours too, is far more resiliant to long term storage. I shut my car down in October and the voltage only dropped to 12v by Xmas day... previous lead-acid batteries I was down to 12v in 3-4 weeks so in this way the AGM is living up to expectations (less leakage). My normal drain is in the milliamps range (diode leakage in the alt. and a clock is pretty much it), I can't remember it off hand but it is very low and normal. When my AGM gets to around 12v I put it on the 2A setting of my charger, this equals around 13.5 - 13.8 volts usually. You should ideally stay around this number for charging and never exceed 14.5v that is what kills AGM batteries. I charge until the battery is around 13.2v. I accidentally flipped the switch to 40A one time and the voltage jumped to 16v... clearly the 40A setting is too high for an AGM. I leave the battery in my car year round and I do not keep heat on in my garage, it was around 10F the day I went out to charge it. This is a big story I know, in summary this is the deal:

1) Don't sit the AGM on a charger all winter, no need, they drain slow and partial discharges do not harm them (unlike a Pb-acid).

2) Wait for around 12v (check it weekly until you get a feel for it, your discharge rate is going to be different than mine which is every 3 months) then do a 2A slow charge until it reaches ~13.2v (for me that takes 4-6 hours). I could go lower without damaging the battery but I have settled on 12v and it has been fine for me, the battery is solid.

3) Never exceed 14.5v charging.
 
Originally Posted By: marc1

1) Don't sit the AGM on a charger all winter, no need, they drain slow and partial discharges do not harm them (unlike a Pb-acid).

2) Wait for around 12v (check it weekly until you get a feel for it, your discharge rate is going to be different than mine which is every 3 months) then do a 2A slow charge until it reaches ~13.2v (for me that takes 4-6 hours). I could go lower without damaging the battery but I have settled on 12v and it has been fine for me, the battery is solid.

3) Never exceed 14.5v charging.


First, an AGM is a Pb-acid battery. There is no difference other than how the electrolyte and offgassing is handled.

Second, 12V is 0% SOC at normal temperatures. It is too low. After removing surface charge, 12.75 is roughly 100%. Id not want mine to sink much lower than 12.5V
 
Originally Posted By: JHZR2
First, an AGM is a Pb-acid battery. There is no difference other than how the electrolyte and offgassing is handled.

Second, 12V is 0% SOC at normal temperatures. It is too low. After removing surface charge, 12.75 is roughly 100%. Id not want mine to sink much lower than 12.5V


Pb-acid - Right, I am referring to a "traditional" flooded lead Pb-acid when I said that, sorry for the confusion.

12v - This has been fine for me... however I understand your calculation but the information on Optima's site indicates anything above 10.5v is safe but sure, I don't have any argument for setting 12.5v to the lower limit.
 
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