AGM Batteries Do Not "Dry Out" Unless Physically Damaged

MEXICOWANDERER wrote:
AGM batteries do not dry out unless violently mistreated
- The batteries are sealed
- Special battery caps recombine oxygen and hydrogen and precipitate it back onto the glass mat
- Special relief valves built into the cap maintain pressure within the battery until a threshold is reached
- The caps then pop open, release pressure then automatically reseal: In practice it takes upwards of high 16's into the 17's of voltage to build up enough pressure to cause venting
- Prolonged excessive charging causes positive plates to shed
- It is because electrolyte in an AGM is extra potent 1.300 that the battery is sensitive to excessively high voltage.

I suspect that the pressure that makes the valves pop is vapor pressure that comes from too much heat build-up inside the battery. Too much heat built-up probably comes from too much current flow inside the battery.

The question is - what applied voltage values, versus air temperatures around the battery ... does it take to drive those too-high currents?

Lifeline told me that even too high of a float voltage applied too long can build up this internal battery vapor pressure to the point where the valves periodically open and reduce internal moisture via escaping vapor. What Lifeline didn't tell me was ... at what ambient air temperatures around their battteries does it take, versus applied float voltages in excess of their specs does it take, versus state of charge does it take when the float voltages begin to be applied ... for vapor pressure to eventually become high enough to open Lifeline's over-pressure valves.

The above physics probably also apply to charging voltages being used, versus average ambient air temperatues around the battery during charging, versus how high the average charging currents are during the charging.

Most likely all the above also applies to all sealed lead acid batteries - AGM or otherwise.

Did the weak lifeline get weighed yet? Just curious

MW - You do have a method of phraseology that brings a smile:)!

Good call to day with Lifeline. I've been asked to provide two readings of voltage.
>Make sure batteries are fully charged. Or indicated as such.
>Disconnect the Negative feed.
>Take bank and individual battery multi meter readings at 2 hours.
>Take another reading at 24 hours.

Call back with results.

About an hour away from the first reading now...

Best to you, and all,
Smitty

Page 22 Lifeline manual

Deep discharge recovery.

400 amp hours. In series 2 batteries 12 volts.

3% of 400 amp hours is 12 amps. Must CONTINUE to charge batteries for 4 hours at a constant TWELVE AMPS beyond 15.4 volts for 4 hours maximum. Voltage can reach as high as 18.0 volts.

It takes a charger like a Meanwell-RSP-400-15 connected to a pair of 12 volt light bulbs to achieve this formula.

Lifeline, may ask you to take your batteries to an authorized Lifeline service center to get this done.

But electrochemical is fussy. You could hold a steady 15.4 on those batteries for 2 weeks and achieve nothing. Plate thickness wise you probably have 50% left but shrouded in sulfation

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Possible sulfation of positive plates

So I recently stated on two different threads here the term dried out, or used up the juice, in regards to the behavior of X's 4 L16's that are just over 5 years old. To the best of my knowledge, they've never been overcharged. If anything, they may have been undercharged. But the full bank has greatly diminished capacity. And after 4 series of Magnum 15.4V four our conditioning runs, capacity seems to have actually been reduced. (Will be calling Lifeline today to review, and ask for guidance of if they feel they're recoverable. And a re-review of my Magnum MS2812 settings, basically AGM1 Lifeline setting the last 4 or so years.).

If I can't get the tapering Amps to drop below 13-15 Amps after prolonged attempts, including ~48-52 hour run of 14.4V, I came to a high probability of using the terms I picked up on this and the forums 'dried out mats'.

It sounds like I should be saying 'Possible positive plates shedding.' - instead? (Just trying to understand the buzzwords, and get the correct vocabulary:)!)

Now that we're off the road from traveling, I'll separate each battery and get some 24 hours pure resting voltage readings.

And, will see what advice Lifeline has for me too...
Smitty

not in the same league with the batteries Mexi was referring too , aka what we are using
thats a far cry from the 135 AmpHr 100+ pound AGM telco/server batteries,
i and others have been getting 'replaced surplus' (cycled out of service) and using in our RV's

pianotuna wrote:
GordonThree,

Are those data center batteries a "surplus acid" design AGM?

Don,

I do not know. Most are the common 12v 7ah type, connected in various ways, series for bigger ups, parallel for smaller ones. A few very small ups have series 6v AGM inside.

When they vent due to old age DAMAGE yes gasses can escape. It takes a pound of overpressure to pop the vent. Any destroyed battery can build up pressure. Telecommunications batteries are unsupervised and like me, go to hell with old age. Five years is not old age. 99% of playing possum RV AGMs I see were mistreated. Remember, cheap junk cannot be compared to good quality stuff.

GordonThree,

Are those data center batteries a "surplus acid" design AGM?