There is not really any GOOD way to refurbish a lead acid battery. They will eventually quit working. That guy may have good feedback but what about 6 months down the road? (ebay feedback doesn't work that way.) With that being said....do a google search for "
Epsom Salt + Battery". All the guy on ebay is doing is selling the info on how to do it.
Hopefully, I just saved you and a bunch of other people $6.