I have a PIC-powered desulphator, built as a kit from Courtestown Marine. Works good and does indeed rescue sulphated batteries (but not ones in which the plates have warped). This design was from the desulphator forum (now linked from the Courtestown web site) and when I started with the design I had the source for the PIC. Somewhere I lost it. Courtestown then fell out with the designer and they lost it as well, but had a copy of the hex file so could continue producing them (I think that they have stopped that product now). Obviously they also blew the security fuses... So if anyone can find the source that is a good starting point. Porting to Arduino then a short step....