VRLA Battery Recovery

MarkC

First, my apologies for starting what is likely a fully vetted subject. However, after searching/reading the forum (and after many hours of trial and mostly error experimentation), I still have lingering questions:

The questions are specific to the (cheap - construction at the least) VRLA batteries found in many uninterruptible power supplies. Most of these are relatively low AH ratings, (5-9 AH) and usually many are arranged in series to supply high voltages (48 to 192) for the DC/AC inverter sections. They don't have much use for off-grid except for "hot starts" and configurations of the UPSs. Dealing with these types of UPSs, often you get several hundred $$'s (original value) of these batteries that have set on a shelf, never been put on an external load, but never charged for several years. Some have some level of charge remaining, others none. None of these types show any physical signs of damage (swelling, etc).

So questions;
1. Does the fact that many of these have never been put under any load (only self discharge) alter the likelihood of any meaningful recovery? Is the processes of sulfation and/or plate degeneration the same? Is "drying" of the electrolyte the main culprit - would that occur before/after plate sulfation (just hypothesizing here!).
2. I've dissected these batteries and are very simple - each cell is a rubber valve cap over what appears to be a (essentially dry) white fiber mat between grey plates. If there is a catalyst for gas recombination, I don't see it. Does this mean that once you have opened the caps, any chance of recovery is done?
3. Due to the required use just about any "recovery" at or above 70-80% of original makes them very useful (they must pass a "boot-up" test by the UPS) - does anyone have suggestions on a controlled process that would restore them that takes into account the cells are likely "dry". My experience has been that re-wetting with pure water and/or fresh electrolyte (various ratios/amounts) shows some immediate results, but not long term success. De-sulfation (pulse type) doesn't seem to affect any real change either.

Expecting a resounding "no - forget it, not worth the trouble", and actually support that from my experience. Just looking for any "out of box" thoughts - especially on those batteries that come out of a 4 year old, never been opened UPS - what a waste!!!

inetdog

Some people have reported success in "restoring" VRLA (AGM) batteries that have been overcharged and vented. They opened the vents, replaced a measured quantity of either distilled water or electrolyte (depending on the details of the venting event) and resealed the battery (in a way which would not interfere with the vents opening again if needed.
But I have not seen any info on the long term viability of the batteries treated this way.

Others have just opened the vent to get access to enough electrolyte to make an SG measurement using a refractometer. (There would not be any way to get enough electrolyte out to use a float hydrometer.)

VRLA GEL type batteries, on the other hand, do not seem to be candidates for any such process.

BB.

With batteries, you are talking about many forms of failure. And of battery types. This seems to be correct (from my limited knowledge):

https://en.wikipedia.org/wiki/VRLA_battery

A VRLA battery (valve-regulated lead-acid battery), more commonly known as a sealed battery or maintenance free battery, is a type of lead-acid rechargeable battery. Due to their construction, they can be mounted in any orientation, and do not require constant maintenance.^[1] The term "maintenance free" is a misnomer as VRLA batteries still require cleaning and regular functional testing. They are widely used in large portable electrical devices, off-grid power systems and similar roles, where large amounts of storage are needed at a lower cost than other low-maintenance technologies like lithium-ion.
There are two primary types of VRLA batteries, gel cells and AGM. Gel cells add silica dust to the electrolyte, forming a thick putty-like gel. These are sometimes referred to as "silicone batteries". AGM (absorbed glass mat) batteries feature fiberglass mesh between the battery plates which serves to contain the electrolyte. Both designs offer advantages and disadvantages compared to conventional batteries, as well as each other.

And regarding catalyst:

If these gases are allowed to escape, as in a conventional flooded cell, the battery may need to be topped up with water from time to time. In contrast, in VRLA batteries the gases are retained within the battery as long as the pressure remains within safe levels. Under normal operating conditions the gases can then recombine within the battery itself, sometimes with the help of a catalyst, and no topping-up is needed^[3][1]. However, if the pressure exceeds safety limits, safety valves open to allow the excess gases to escape, and in doing so regulate the pressure back to safe levels (hence "valve-regulation" in "VRLA").

I always wondered myself what a VRLA battery was and if they had catalyst or not. Because the catalyst is usually some hyper expensive precious metal (like palladium or something), I would bet that the mfg of the small/cheap batteries just hope the Hydrogen and Oxygen bump into each other and eventually recombine--And that this may work for batteries that are not subjected to high levels of gassing (charging current into a "full battery").

Batteries that go "dry" in storage--If the water can out-gas, and then oxygen can come. Once the plates are dry and exposed to oxygen, they are oxidized and ruined (again, as I understand).

Similarily, once a battery has sulftated (for a sealed battery, stored for more than 2-6 months without charging, sulfation will begin), there is no (known to me) in-battery process that the hardened sulfate can be reversed.

Here is a thread how one company (Concorde) recommends to "recover" their AGMs... Not supposed to apply to any other brands of AGMs:

Sulfated Lifeline Concorde AGM Batteries

And here is a great thread from DapDan with information on how one place recommends to restore AGM batteries (new catalyst caps, adding water to cell, etc.):

Low rest voltage on GNB absolyte IIP cells

In the end, trying to do "extreme" things to batteries should be done in a safe area and always under some sort of supervision/monitoring (don't want to overheat the cells and blow acid around) and performed while wearing appropriate safety gear/gloves/face shield/water/hose/baking soda nearby/etc.).

And--if the cells are otherwise scrap--if you can try some of the above things (if done safely)--you are not loosing much anyway.

-Bill

MarkC

Bill - the Concorde thread is what go me starting thinking about this again. I've tried many combos of desulfating techniques with similar results - sometimes good, but always temporary. I could not call up the GNB IIP cell reference - I'll do a search. These "inexpensive" types are very simple - If they have catalyst, it's not visually evident. They are very easy to disassemble and reassemble with a PVC/ABS combo pipe glue (light green stuff). I tried about every combo of water/electrolyte in various amounts - usually negative results, but not scientific enough to draw concrete conclusions. Many of the "cells" were obviously under a pretty good vacuum - would suck air in when removing the little soft rubber caps. Never had a bad cap - they would reseal under a newly glued down top very well.

To me there is a bottom line here - that the networking industry wastes lots of resources relative to these small VRLA batteries - both in replacing them every two years (they stay on the charge cycle ALWAYS and likely dry out much too early, and also in letting them sit in unused UPSs for way too long and sulfate. The industrial applications should have a programmed charge routine - bet they can significantly extend the life. Going Li technology with good BMS might be a good solution - the weight of these things is always an issue (battery packs can weight upwards of 50 pounds).

The question is mainly about those VRLA's that never had a load on them and have died due to self discharge - does that slow, low stress process lend itself to a recovery technique? My guess is not!

inetdog

MarkC wrote: »

The question is mainly about those VRLA's that never had a load on them and have died due to self discharge - does that slow, low stress process lend itself to a recovery technique? My guess is not!

I think that sulfation is sulfation, no matter how slowly or quickly it happens. The normal soft sulfate, which is part of the active element of the plate when the battery is discharged, slowly converts to hard dense sulfate crystals which are not as susceptible to the reverse reaction involved in charging.

zoneblue

From what ive read "Gel cell" AGM batterys rarely get sufated (unless abused) and certainly not those in float service. They just dont last long enough to see it. The typical 7Ah type UPS battery while techically now of AGM construction ( we used to call them gel cells), dont have catalysts at all. Nor a pressurised vent. Hence they lose gases and thus water fast. That is why you see so many youtube videos showing people "restoring" them by adding water.

However an AGM battery without pressure sealed vents, or catylyst, means they will never last no matter what you do (positive grid corosion/negative plate depolarisation). And that..is why you have to replace your UPS battery every 2 years. Even on a supposedly brand name UPS like APC.

MarkC

Bottom line for me is that I've stopped attempting "recovery" of any of these UPS type AGMs. Any that have ~12 volts or better, I give them a few days charge on a pulse type desulfator/charger and load test them in their battery cage (typically 4 or 8 in series depending upon the type of UPS). Any that lose voltage substantially quicker than the others, I replace. Again, as I use these UPSs as an emergency backup inverter only, and don't leave the batteries on the UPS charger continuously, I find that the resultant battery cages will pass the UPS self test and hot start the unit. However, I do periodically (every 2-3 weeks) recharge them by leaving the unit on for several hours. So far these "leftover" batteries have been useful for over 8 months.

PNjunction

MarkC wrote: »

Bottom line for me is that I've stopped attempting "recovery" of any of these UPS type AGMs.

Proper maintenance is key. As a note of interest, those that muck around with sealed AGM's by popping the caps and finding them dry inside (they are supposed to be - only the separator has the electrolyte wicked in it), and then filling them with water don't realize that they have changed the chemistry from AGM to a poorly-performing *flooded* lead acid. It now follows the rules that flooded does, such as no more than .10C charge rate, etc, no more than 14.4v max etc... Hence the videos of rescusitated cells bubbling over with the agm charger...

Typical non-savvy corporate types may errantly substitute gel for agm when it comes time for replacement, not knowing the charge rate and voltage differences between gel and agm. Get it wrong, and you cook the gel, and undercharge the agm, depending on what the oem ups is based on.

Either way, home grown recovery solutions for old abused cells rarely goes well for the unknowledgeable.