Rejuvenating atv batteries?

[sparkwizard]

Haven't looked at it for a while but the last time I did it got topped off with distilled water, then charged.

Sitting there now with 11.6 volts. Charger is a Die Hard 12/2/75 amp, probably from the mid 80's.

11.6 means you have a dead cell. Get a new battery. I did not see that number yesterday.
A 12 volt battery at rest, no load should be close to 12.5 volts.