Author Topic: Water added to AGM  (Read 21646 times)

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Lowhead

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Water added to AGM
« on: April 02, 2011, 02:43:04 PM »
I cobbled together a small PV system out of old parts for a mobile trailer my wife uses.  It has 3 old Hoxan 50 watt panels racked on some 80/20 extrusion, a C60 charge controller and I bought a brand new deep cycle AGM battery at the local Batteries + store.  It worked great and was stored in a barn for the winter but she didn't take the battery out.  I took the battery out a couple weeks ago and put it on the charger and everything was fine.  I wasn't there when her father towed the trailer out of the barn and hooked up the battery.  He didn't know it was an AGM. He pried off the caps and decided it was low on water and added nearly 1/2 gallon of distilled water to it.  Now I don't know what to do.  Could it truly have been low on water?  What happens if you add water to to an AGM?  The Batteries + people didn't seem concerned but I doubt they know any more than the average retail clerk about batteries.  Is this a problem? 

JW

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Re: Water added to AGM
« Reply #1 on: April 02, 2011, 03:11:32 PM »
Quote from: Lowhead
He didn't know it was an AGM. He pried off the caps and decided it was low on water and added nearly 1/2 gallon of distilled water to it.  Now I don't know what to do.  Could it truly have been low on water?

Yes, it could have been low on water, that type of "sealed batterys" are not really sealed (agm). usually they a "VRLA" what this means is, as the batterys are overcharged on a charger, the battery will emit hydrogen gas, and lower the electrolite level...

Quote from: Lowhead
What happens if you add water to to an AGM?

Its the same as adding water to a standard maintance battery, as long as the water was distilled, theres no problem with this.

You should pick up some "pre-mixed lead-acid battery electrolite" from your local autoparts store. here's a helpful link-  http://www.engineersedge.com/battery/specific_gravity_battery.htm

The specific gravity of the electrolite should be 1.260sg to 1.300sg at a full charge.

JW


SparWeb

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Re: Water added to AGM
« Reply #2 on: April 02, 2011, 03:43:33 PM »
But it could have been a true AGM (don't know what kind of model you have), so spelling it out to be painfully obvious: Absorbed Glass Mat.
I think much of the electrolyte is soaked into a series of fiberglass pads between the plates.  In some designs there might not be much water visible at all.  The empty space would be for gas/vapour/steam to collect during normal charging until it can later cool and re-combine.
With water added the SG may go down (diluted) and attempting to charge it again may cause it to vent acid.  I'm not sure about this though.
I've only taken the briefest of peeks inside one cell of my AGM set.  There are other guys who use the forum who have done some extensive restoration projects so let's hope they can find this thread and confirm.
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

JW

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Re: Water added to AGM
« Reply #3 on: April 02, 2011, 04:27:14 PM »
Here are some pictures of a battery thats "AGM"

This one is doing quite well.


I had to refill this AGM battery a coupla weeks ago, instead of using distilled water, I used electrolite with a specific gravity of 1.265


Here you can see the "VRLA" caps (valve regulated lead acid) I have found that the electrolite level inj each cell is about 1/4in above the plates. So a hydrometer can be used on this type of battery, if the caps have been damaged you need to be concerned if the battery tips over...


JW

Madscientist267

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Re: Water added to AGM
« Reply #4 on: April 02, 2011, 08:11:58 PM »
Dunno about AGM, but SLA will take water to a point.

Problem is, the SG might now be off, as mentioned.

I have had mixed results with the SLA variety being watered, but then again, most were being resurrected.  ???

The most notable difference that I've seen as far as behavior is that an SLA acts more like FLA after the watering.

Typical SLA hangs out around 13.0V or so when fully charged and sitting. After watering, it tends to hang lower, as FLA does, around 12.7-ish.

On one reasonably healthy battery that I watered just for giggles to get a comparison, there hasn't been much (if any) noticeable difference in capacity or 'CA' capabilities, so you might be just fine.

FWIW

Steve
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How much magic smoke it contains does !

dnix71

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Re: Water added to AGM
« Reply #5 on: April 03, 2011, 12:37:35 PM »
The battery in the pic is for marine use. It's nice to have a battery that won't spill acid if things get rough.

The S.G. does seem to have an effect on resting voltage. All my batteries are marine hybrid start/deep cycle flooded and after letting the water level drop a bit they would rest at 13.0 instead of 12.7/8 and hold more charge. I have the feeling battery makers don't add as much sulfate as they could to minimize sulfation and allow for extended warranties.

I added distilled water last week and miss the higher resting voltage. Buying a bag of acid might raise eyebrows some places. I just tell the clerk we overfilled a forklift battery at work and need to add some electrolyte to balance the cells and that usually makes them happy.

Lowhead

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Re: Water added to AGM
« Reply #6 on: April 04, 2011, 01:18:14 PM »
It was distilled water that was added.  It sounds like it was a bit of a false alarm.  What was supposed to be an AGM ended up being a plain old "sealed" marine battery that you could pry the caps off.  We never checked the water last year thinking it was an AGM.  She will have to check the water levels which isn't easy.  It's in a battery case under a cabinet in the corner.

Thanks guys.
Andy

PeterDe

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Re: Water added to AGM
« Reply #7 on: May 06, 2011, 01:48:32 PM »
Guys;

As we all know AGM stands for Absorbed Glass Mat and it is one of the two VRLA designs (Valve-Regulated Lead-Acid).  The other is where the electrolyte is in a gelled form.  In an AGM battery all of the electrolyte is designed to be in the pores of the plates and in the space between the plates between those very fine glass fiberes.  If you open up any sizes AGM cell and tip it upside down NOTHING is supposed to come out.  What has occurred, now that water has been added is the Sg of the electrolyte that was in there is most likley lower, but just operate it like a normal flloded battery.  If the battery says AGM it is a VRLA and is not the type that the manufacturer wants water added to.  However if the battery had been excessively charged you can in some cases added water to re-establish proper saturation to the mats.  We do this all the time on large 2 volt VRLA cells.

A marine type battery that is designed for water to be added will not be a AGM design, nor will it say AGM on it anywhere.  They do make AGM marine batteries, but they are not designed to add water.

Also if you add electrolyte to a battery that is a flooded design you do change the acid desity severely.  Remember that the only thing that comes out of a flooded (vented) lead acid on charge is Hydrogen and Oxygen (H2O), that is why with flooded cells we add water.  We are jsut replacing that which has off gassed.  However if the electrolyte was low due to a battery being tipped over, then yes you would need to add electrolyte.

Sparweb summed it up pretty good.

kegman

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Re: Water added to AGM
« Reply #8 on: October 26, 2016, 10:14:48 AM »
Hey folks,

I'm new here..  Came across the forum on refilling / equalizing AGMs.  I've on my 2nd pair of BPS XPS 175 Ah AGM batteries similar to the ones in the pictures with the VLRA valves.  They are about 5 years old.  One of the batteries was on the charger (NoCo Genius 2 bank 4A "smart" charger) and I noticed that it wouldn't reach a full charge after a couple of days of charging.  Put some water on top of the valves to see that during charging there were bubbles coming out of the valves.  Some of the cells were gassing.  The first pair of BPS AGMs did the same thing after about 5 years of use. 

Is it worth it to try to equalize the water in the cells?
How do the valves come off?  Do I just unscrew it with a wrench after cutting the epoxy?


Thanks for your help!

clockmanFRA

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Re: Water added to AGM
« Reply #9 on: October 27, 2016, 01:38:10 AM »
Hi kegman, and welcome to this Forum. There are some decent knowledgeable folk on here.

I have a collection of REAL 12v AGM's, 48v 1300ah, But now getting ready to change to VRLA. AGM's are very fussy with what they want.

I lost one a few years back, and opened it to see why. Yes, the cells contain no fluid but absorbent matts between the plates that act like sponges. Each of the 6 cells has a pressure release valve only, and has an secondary expansion area. So no physical way of getting electrolyte into the cell.

Reason for failure, over time the cell plates expand. They only need to expand 5mm upwards and the plate bars short out on the main buz bars of the battery, then the cell is effectively dead and the 12v battery will only charge to and hold at 10.6v to 11v.

Please be careful, eyes, skin etc, when messing with batteries even Glass matts types have the Acid present.

 
Everything is possible, just give me time.

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kegman

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Re: Water added to AGM
« Reply #10 on: October 28, 2016, 08:24:11 AM »
Hey clockman,


Thanks for the quick reply.  So really the BPS batteries in the pictures above aren't REAL AGMs are they...   They appear similar to the Deka deep cycle batteries.  Are they just regular flooded with sealed valves?  If that's the case then marking them as "AGM" is a little (or very) misleading.....  I'll try unscrewing the valves with a wrench next time and see what's inside....... From the earlier post it seems like there are plates submerged in electrolyte.  But maybe there's a mat in the middle....


Kegman.

danniard

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Re: Water added to AGM
« Reply #11 on: November 02, 2016, 08:07:14 AM »
A bit of a digression here, but I seemed to have thought I knew something about batteries....

Is there a type of VRLA battery that has liquid electrolyte (no gel or glass mat)

Also what is the difference between sealed and Valve Regulated?

Source of my current definitions: http://www.batterytender.com/Intro-to-Lead-Acid-Batteries/

joestue

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Re: Water added to AGM
« Reply #12 on: November 02, 2016, 02:12:36 PM »
All of them are valve regulated,  it's not possible to seal them completely. Once the internal pressure exceeds 5psi or whatever the hydrogen and oxygen escapes out the rubber cap. The extra pressure accelerates recombination.

Agm batteries are only filled to 90% with electrolyte, the airspace lets the gas generated recombine. If you fill them saturated with water the battery will act like a flooded cell and the gas won't recombine, but rather float to the top and escape.

"Is there a type of VRLA battery that has liquid electrolyte (no gel or glass mat)"

yes, i suspect so. they are still position sensitive, must be right side up or when the valve opens under pressure you would get liquid spraying out..
« Last Edit: November 02, 2016, 06:55:04 PM by joestue »