This magic box should restore almost EOL batteries up to 90% original condition.
Lead acid batteries (e.g. car batteries) gradually develop sulfates (PbSO₄) on their electrodes that may dramatically reduce their performance (low capacity, low voltage, slow charging etc.) This may happen quite soon if the battery is repeatedly discharged under 12.4V (applies to 12V AGM batteries) and/or kept in this condition for some time (days).
Sealed batteries can't be opened to remove sulfates from electrodes mechanically but this box should do the trick - it returns Pb back to electrodes and SO₄ back to electrolyte.

It can be used for 12/24/36 and 48V batteries - the display is activated after attaching terminal to the battery and the value can be changed if the battery supplies very low voltage so the desulfator wouldn't stop at the correct voltage.

Technical data:
Operating current: 20mA/40mA
Peak current: 2A/4A
Peak voltage: 60V-100V
Pulse frequency: 10kHz

The pulses are soft, not wearing electrodes like old style desulfators.

Some modern (more expensive) chargers have desulfation as a part of charging process but most of them don't.

Now I'm restoring a 12V/7.2A CSB battery in a really poor condition (the charger even rejects it) so let's see how it succeeds. Sharing to anybody interested.

Lead acid batteries are some of the most recycled items in the world, but it is nice that things like this are available to the consumer so that they can rehabilitate batteries at home without needing to buy new ones and recycle old ones.

If the battery needs this to "get revived", it is already practically dead and never be reliable in any way. It may prolong its service a bit, but first not for that long, plus it will die soon anyway (beside others, the desulfation pulseng does severely accelerate corrosion of the healthier parts of the electrodes, so they will break apart very soon).
You may get a bit gentler desulfator, but that won't be that much effective anymore. It is a tough dillema to make: Either insufficient desulfation, or corrosion damage. The battery gets damaged either way...

So really the only thing that remains is to prevent sulfation in the first place (e.g. never leave the battery discharged for more than really unavoidable).
Maybe adding a bit of desulfation pulsing as the battery is aging (when the sulfation becomes greater life limiting factor than the corrosion), but for that to work well it would have to be integrated part of the battery management (like in modern cars where the charging control is in the engine computer and not in the alternator alone - where you have to reset the ecu battery management once you replace the battery, as otherwise by the "keeping the old battery on life support" way of charging it will destroy the new one within few months).

So yes, desulfator may help, but I doubt it is worth spending the resources (here I mean both money, as well as the environmental damage manufacturing one) for such gadgets instead of accepting a bit shorter battery life. Mainly with the level of recycling of the old ones. And don't get it wrong, the high recycling level is such high not because of environmental concerns, but juts because getting the materials for new batteries by recycling the old ones is and has been the cheapest way to get it for all the century these batteries are in widespread use...

After a couple of hours desulfation, at least the damaged battery started charging again. No discharge test yet. It might not be fully recoverd yet - according to some sources, the process may take several days on heavily sulfated batteries.

My short internet research haven't yielded any direct relation between desulfation and corrosion buildup - what's the source for your claim? The corrosion will appear anyway - I don't expect keeping a battery for 20 years just with the desulfator help. Anyway, why would expensive chargers do pulse desulfation with every charging if the benefit was at the cost of significantly faster corrosion?

The box with a 1/3 price tag of a 12V/60Ah AGM battery weights probably less than a standard 10W GLS LED and probably doesn't contain anything particularly environmentally harmful. Most of current smart gadgets, wearables, air pods... you name it, powered by a lithium battery and not expected to last for long (actually out of fashion very soon) are much worse than this box.

Well, over many years I have not seen a single small lead battery restored by a simple slow trickle charge or whatever snake oil they sell as 'desulfatizers'. You are probably just wasting your time.... Once dead, VRLA batteries ultimately go to trash, sorry, recycle ))

To desulfate, you need to apply higher voltage over tye cells, so you electrically break down the sulfated layer. But on a healthy part of the cell the same elevated voltage causes overcharging (even happening just locally - so happening even when the cell as whole is still practically discharged) and this overcharge is, what accelerates the corrosion.
Now desulfators are designed to reduce that problem by using just short pulses for the desulfation, followed by drawing the charge back. This reduces the rate of the overcharge corrosion significantly, but does not eliminate it completely. Plus the shortened time means the desulfation gets less effective (thebreakdown needs some time to accumulate enough traps), but still the net outcome is way better "more desulfation vs less corrosion" trade off than with just plain severe DC overcharging. But there is still an extra corrosion damage resulting from desulfation attempt.
But that is not the point why I think desulfators to not be worth, with a battery that would be dead by sulfation now you kinda don't care if the corrosion makes it to die two months from now instead of a year, in such case you still get at least those two months of useful life.

The point is, you should avoid "desulfating" batteries, which do not need it "just preventively", there the life loss from the extra corrosion is more severe than the eventual gain from sulfation, so the result would be quite significant net loss of battery life.

Unless there was really an accident in battery management leading to significant sulfation of an otherwise good battery (so the desulfation may bring back significant amount of the useful life), the sulfation tends to happen on batteries which are about to die or dead anyway (by the way most often the cause is high selfdischarge leakage, usually from the mess released from the electrodes by the corrosion), so desulfating may "bring them back to life", they will die soon again. So what you get is just a week till the performance of such battery would become so low it won't be sufficient for the application. So when speaking about "saving the environment/money", we are talking about just a small fraction of the battery lifetime (so that could be translated into extra bit of battery to be manufactured/recycled/paid for; the high recycling efficiency reduces that impact further), vs not spending the cost/environmental impact on making an extra gadget. Or traveling to and from a shop where they have it. So according to me net loss, include the extra hassle with the extra attention that battery needs.

Yes, you may say "lets start with an oversized battery, so it may degrade deeper so last longer", but this completely ignores the fact that a larger battery has higher environmental/cost impact to start with, so by oversizing you will be net loss there as well. The only thing you will gain is the convenience - not having to worry about the battery for a bit longer time. But for the convenience, the use of quality batteries and a scheduled maintenance so a dying battery gets identified and replaced before it fails within the well ahead plannedout maintenance intervals saves a lot more of the convenience/reliability than just oversizing it to "just allow deeper degradation".

The snake oil lubed the electrodes so that the small battery not only started charging again, but with other 40 hours of desulfation its fully-charged voltage increased from 12.0V to 12.8V. We'll see how long it lasts.

With typical use for this kind of batteries (i.e. starting battery in a car), the deeper discharge shouldn't happen except cases when the car is used as a "shopping bag" once a week to a supermarket around the corner. Typical life of an AGM battery in a car is about 4 years.
Other applications (like powering electric fence generator in my case) asks for better monitoring so that the half discharged battery is replaced and recharged early and the sulfation risk is minimised.

Actually may be ok for such un-demanding application like electric fence. There is a need for some kind of battery monitor to shut down the load at ~1.8V/cell or so...


Car batteries often go completely flat if the car is left for a storage (like in winter) or someone just forgot to turn off the lights.