Picked up a charger with the desulfate function in it not too long ago. Tried it on a car battery that wouldn't stay above 12.5 volts for more than about 3-4 days.
After 3 sessions, it improved to about a week before it dropped the same amount.
So... work? Yes, definitely not snake oil.
But miracle worker? No, unfortunately even a week isn't enough to be a useful battery.
I bought the CTEK (56-353) off Amazon several years ago after seeing how much Jay Leno liked that model.
Its worked pretty amazingly well for me...brought some batteries back that I thought werent ever gonna make it back. It gets used constantly around the homestead for topping different vehicles up that have been sitting through cold snaps, etc.
I'll definitely buy another if this one craps out some day (knock on wood).
To be clear
We did this with the salts, not using a gizmo.
The time we spent we could have at the time gotten an equivalent battery for $120. I think he slant $20 on the chemical kit and it was nasty dealing with the chemicals and we spent an hour or more understanding what got do and doing it.
My brother got into solar power for his house. he bought second hand refurbished solar batteries for his set up. The seller had desulfecated, (if that's a word), the batteries and tested them so they were holding around 90 -95% or more of new batteries. Cost wise to the holding power gave them value for money.
My understanding is it also depends on how bad the damage is to the battery. with a vehicle it needs to be done before the battery has got to the point where the output is reduced. if a battery is 3 year old and still working then it would be a good time to do it.
I've used these a few times with limited success. First time was for wet cell batteries in a camper trailer. Ran it about three times, didn't work at all.
I used another a few months ago on the TX650 AGM battery. It seemed to work alright, held it's charge overnight, but cranking power still wasn't enough to crank over the engine.
I did a post on it here not that long ago.
I think these are best used regularly on new batteries to prevent sulphation, not a lot of use on old batteries that have stopped performing.
I have read you can put baking soda, caustic soda or Epsom salts into a wet cell to revive it, but I think you can take that with a pinch of salt. Perhaps one of these in conjunction with a desulphater might work. I wouldn't stand to close though.
But where on earth would you find a wet cell these days.
Yeah mebby, notice those pulse desulfator chargers that were all the rage a couple years ago have mostly disappeared.
I keep an old non automatic charger around to bring back seriously discharged batteries but I never trust them again.
I have a charger with a "doctor" feature. I thought about using it on my rv's deep cycle battery that is currently (no pun intended) mostly dead. I'm not even going to try. It's 5 years old and doesn't owe me a thing. I'm not going to get fancy with it (as in Li-ion replacement Expensive, much?), just a plain old (new) battery. It should last me another 5 years...