I paid about $125 for a batteryminder, 12248. It claims to desulfate batteries. Yet to see it take a half dead battery and fully restore it. Manufactor claims it may take up to 3 month to desulfate a battery. I'm not totally sure that it can or if there is any charger out there that really can.
I use the batteryminder to charge batteries and keep them topped off in the winter. It has a 2a, 4a, and 8amp setting. A setting for gel, flooded and AGM batteries.
I have about 25 batteries: mowers, tractors, trailer, car, truck, and trolling.
Currently, I have 4 lawn mower batteries on a bench connected in parallel and will leave the charger on them for a week or so. Then move it to other batteries. It's very important to keep batteries topped off, especially in the winter when you may not be using them. When I can, I top off more than one battery at a time. I try keep the charger working year around.
I really don't know if I were to spend that much money on a charger again. I can say that the charger hasn't damaged any battery, so that a good thing. It does good job charging batteries at a slow rate and not cook them.