So You Own An AGM Battery...

[MEXICOWANDERER]

AGM batteries can sulfate just like any other lead acid battery. Other than by Ouija Board how would YOU determine if a battery has become sulfated and how severe is the sulfation, and if desulfation (equalization) has been done properly.

I'll make this real interesting. Let's take a bank of eight AGM batteries and attempt to sort things out.

This is not a campground test BTW. An at-home test with time and resources at your disposal. How would you handle it?

I'm going to stay out of this and see the answers until and if I am asked to participate...

[MEXICOWANDERER]

Tom_M wrote:

MEXICOWANDERER wrote:
AGM batteries can sulfate just like any other lead acid battery. Other than by Ouija Board how would YOU determine if a battery has become sulfated and how severe is the sulfation, and if desulfation (equalization) has been done properly.

Desulfation and equalization are two different processes. You equalize wet cell batteries to distribute the acid equally within a cell. You can not equalize an AGM or gel battery. Here's an excerpt from a Deka battery document:

Acid stratification can occur in conventional wet cells. During charge, acid is released at the plate surfaces. During discharge, acid is consumed at the plate surfaces. Since the concentration is not uniform, diffusion (spontaneous mixing by random molecular motions) begins. If this mixing occurred rapidly, stratification would not occur, but it is relatively slow, allowing lighter parts of electrolyte to “float” toward the surface and heavier parts to “sink” toward the bottom.

The top portion of the plates do not perform as well in contact with lower concentration electrolyte. The bottom portion of the plates do not perform as well with the higher concentration, and will corrode prematurely. High voltage “equalization” charging is sometimes used in wet batteries to make gas bubbles that re-mix the electrolyte.

Because the immobilized gel will not “float” or “sink” within itself when a non-uniform concentration exists, it cannot stratify. Therefore, no high-voltage equalizing charge is necessary. Simply recharge at the standard 13.8 to 14.1 voltage setting. This means longer life and consistent performance in stationary and standby applications.

Electrolyte in an AGM battery is strongly held by the capillary forces between the glass mat fibers, but not completely immobilized. Stratification is possible in extremely tall cells, but cannot occur in batteries of the size covered in this document.

OKl here we go,

How would you explain and define the loss of capacity syndrome in absorbed glass mat accumulators? The process and the remedy?

[westend]

full_mosey wrote:
Is there proof that more than 14.xV are necessary to fully charge ANY AGM battery? We are talking about an otherwise healthy battery, not one that is damaged due to neglectful charging.

Even Lifeline says to fully charge at 14.3V and then observe a loss of capacity, before conditioning.

HTH;
John

John, it's not necessary but can be done. I have three Enersys AGM's and here is the specification sheet: Enersys AGM EP spec sheetOn page 10 is listed the recovery procedure for a fully discharged battery to retain capacity. It is remarked, "Charge the battery using a 0.05C10 constant current for
24 hours. The charger should be capable of providing
a driving voltage as high as 36V. Monitor the battery
temperature; discontinue charging if the battery
temperature rises by more than 20ºC."

When using a constant voltage charging regimen it is suggested,"In a float or standby application the CV charger should
be set at 13.5V to 13.8V at 25ºC (77ºF). For a cyclic
application, the charge voltage should be set between
14.4V and 15V at 25ºC (77ºF). In both cases, the linearized
temperature compensation factor is ±24mV per battery
per ºC variation from 25ºC (77ºF)."

[full_mosey]

Is there proof that more than 14.xV are necessary to fully charge ANY AGM battery? We are talking about an otherwise healthy battery, not one that is damaged due to neglectful charging.

Even Lifeline says to fully charge at 14.3V and then observe a loss of capacity, before conditioning.

HTH;
John

[Almot]

MEXICOWANDERER wrote:
Some tips: A 50 watt 12 volt trouble light bulb from a hardware or auto parts store is the cheapest reliable load I am aware of. 4 amperes more or less (connect it and see with your meter)

I would use time rather than voltage. A decent 100 amp battery should discharge to around 50% in 12 hours, right? So I set the alarm clock, then when it goes off I go and see where the voltage is.

Use your manufacturer's voltage charge percentage guide to calibrate the test.

Yes. This is how you measure the capacity (or loss of capacity).You know the answer, why are you asking? 🙂
Some clarification: for proper calibration you need to do this test soon after you've bought it. Fully charge, rest overnight and measure hours and minutes before it drops to 12V - doesn't matter what capacity is according to the charts. It's your individual battery and you need a reference point, for each battery. Then repeat the test after some years or if you suspect the loss of capacity.

AFAIK, Lifeline is the only brand that tells how to do the "conditioning" and when. I would think that any other AGM would benefit the same from this procedure, but other manufacturers don't tell at what voltage it has to be done. So if yours are not Lifeline and they lost capacity, you may "condition" it at your own risk. Please post the results if you do. Some "wouldn't care less", but batteries are costly and there are people who care about their own money.

[full_mosey]

Snowman9000 wrote:
Do AGMs show as much surface charge after charging as a FLA battery does? Does it last as long with an AGM? It would be useful to know this when using voltage to monitor your daily AGM cycle.

The Deka manual wrote:
*The “true” O.C.V.(Open Circuit Voltage) of a battery can only be determined after the battery has been removed from the load (charge / discharge) for 24 hours.

HTH;
John

[Snowman9000]

Do AGMs show as much surface charge after charging as a FLA battery does? Does it last as long with an AGM? It would be useful to know this when using voltage to monitor your daily AGM cycle.

[full_mosey]

dons2346 wrote:
" You can not equalize an AGM or gel battery."

Then why does the manual for my LifeLines say to do so if needed?

There is a newer version of the manual. They have dropped the term equalizing.

For AGMs, equalizing means to fully charge all cells. That is, all sulphate is back in solution. If one or more cells are not fully charged, it may show as a loss of capacity.

Without expensive measuring tools with high precision, charging AGMs can be an art without individual cell SG readings.

A big problem is that too many cheaper tools give a full charge reading based on FLA tables. IOW, the full light may come on at 12.6V which would only be 75% SOC for an AGM.

My Deka Manual says wrote:

Capacity tests should not be run unless the battery’s
operation is questionable.

This should impress on you that it is better to focus on learning to recharge AGMs with the right tools.

I did capacity test two years ago and skipped the test this year due to no observed loss of capacity as advised by Deka's manual.

All;

I posted my charging 'art' above in this thread. I would appreciate any critique to improve that procedure.

HTH;
John

[Tom_M1]

dons2346 wrote:
" You can not equalize an AGM or gel battery."

Then why does the manual for my LifeLines say to do so if needed?

It's a matter of terms. Lifeline says to condition a battery as needed. They can become sulfated and thus need conditioning. The charging process for conditioning and equalizing is the same. You maintain a constant current for an extended period of time.

AGM and gel batteries can not be equalized.

Here's an excerpt from the Lifeline manual:
Conditioning should only be done when the battery is showing symptoms of capacity loss due to extended time in a partial or low state of charge condition. This could be caused, for example, by low charging voltage for an extended number of charge cycles, or by repeatedly charging to only 90% state of charge.

NOTE: Some chargers use the term Equalizing Charge instead of Conditioning Charge. An Equalizing Charge is generally applied to flooded lead acid batteries that are susceptible to acid stratification. However, an Equalizing Charge may be used to provide a Conditioning Charge for Lifeline® batteries ...

[MrWizard]

Agm and gel are different things

Agm can be 'conditioned' following mfg specs

Gel can Not be equalized

[dons2346]

TechWriter wrote:

dons2346 wrote:
" You can not equalize an AGM or gel battery."

Then why does the manual for my LifeLines say to do so if needed?

So the choice is between trusting the manufacturer or this forum. Tough choice, eh? 😉

Not to me!

[TechWriter]

dons2346 wrote:
" You can not equalize an AGM or gel battery."

Then why does the manual for my LifeLines say to do so if needed?

So the choice is between trusting the manufacturer or this forum. Tough choice, eh? 😉

[dons2346]

" You can not equalize an AGM or gel battery."

Then why does the manual for my LifeLines say to do so if needed?

[MEXICOWANDERER]

Some tips: A 50 watt 12 volt trouble light bulb from a hardware or auto parts store is the cheapest reliable load I am aware of. 4 amperes more or less (connect it and see with your meter)

I would use time rather than voltage. A decent 100 amp battery should discharge to around 50% in 12 hours, right? So I set the alarm clock, then when it goes off I go and see where the voltage is.

Use your manufacturer's voltage charge percentage guide to calibrate the test.

Want to test two or three batteries at the same time?

Buy two or three lights and bases. Connect them in series. Series connect two or three batteries accordingly. Same test done by hours. Carefully note the word SERIES. You are making a 24 or 36 volt circuit. Connect the light bulbs IN SERIES just like you do with golf car 6 volt batteries.

BUT when using multiple batteries, check the voltage of EACH 12 volt battery independently WHILE the batteries are under test near the end, say at 10 hours.

Have one with a half volt sag in it? Cull that battery. Or maybe 2 or all three batteries are not up to snuff.

All for the price of two or three light bulbs, wire big enough to run 4 amperes through, some handy boxes and ingenuity. Most any Digital multimeter will do fine.

You DO need to measure amperage to get a baseline. And you DO need the manufacturer's percentage state of charge voltage chart.

All this without using an amp hour meter. Perfectionist insist on a kWh meter but when the "magic light bulb" goes off over a person's head, the results can be impressive.

[2oldman]

MNtundraRet wrote:
You have to remember that That most people could "care less" until Murphy's Law happens. Then they come :h and ask for help.

Most people 'could', but it's really 'couldn't'.