Are you sure the charger is working?
Another thought, and I know I'll catch a whole poop pile for saying it, but have you thought of trying EDTA?
I've brought back batteries that were so sulfated that they wouldn't show a charge.
I've even used it in the batteries in my bus which are between 7 and 8 years old and have been in 2 semi's and 1 other bus.
Here is some information at Home Power Magazine: http://www.homepower.com/search/search_result.cfm?search=EDTA&CFID=403866&CFTOKEN=f52e65507e7ac18f-EC155F6A-2B3A-CE71-B02D8E26E0832D55&jsessionid=8630e52b7bf27b2b6927
It costs about $16/lb plus shipping, but that is enough to do a whole bunch of batteries!