Your regulator is what keeps your charging voltage
from over charging. This may have ruined that battery that won't accept a charge. You probably need to have it checked at your local shop.
Your alternator and regulator should be checked
at your local shop that repairs alternators, starters and generators. Be sure to remove the battery ground before removing the alternator and mark all your wiring. If that alternator has an internal regulator you may be better off to get a rebuilt alternator. Hal