Hi rachel4291! Did you ever figure out your overcharging alternator issue? I have the same exact issue as you and the original poster of the thread haha I know very old thread revival. Ford Focus 2003 2.0L dohc. Thanks! Tony
Any alternator will charge 70-100 volts unchecked, high charging can be either wiring (grounds) or control, i.e., regulator inside alt. Load test the battery, one with faulty cell will encourage overcharge trying to fill the empty hole up.