I have designed them, several decades ago, for very heavy AH battery banks.

I am quite familiar with the present available desulfator sold in Internet which is a copy of a simple pulser ( LM555) with a 330 Uh choke with a 2200 microhenry choke to isolate the 330 uh choke pulse from the power supply for the pulser section.

They are available from 20 to 120 dollars and most of them have the same basic principle and it seems that they have not discovered the circuits for high power which implies to have a lot more of technical knowledge to make them.

alot of folks think that sulfation is a bad thing, when the reality is it is a normal chemical process that takes place when a battery discharges. What drives me nuts about the hype surrounding desulfactors is the claim that sulfation is bad for your battery.

hard and crystallized sulfation is what you get if you allow partially charged plates with their normal sulfation sit for an extented amount of time, harden and crystallize.

a desulfator should only be sought when someone has neglected their batteries to the point that normal charging, and equalization cannot break down the hardened or crystallized sulfation,, even then my bet is most of these units are worthless
and don't do anything that a controlled equalization would not have done anyway.

this is a classic case of "create the crisis (where one does not exist) and provide the solution (a solution you can make money with).