Take the following with the appropriate grain of salt.
While tinkering with my 70 340 Duster this week I checked my factory shop manual on alternator output, it showed a charge voltage of over 15 volts at max output.
I've always believed a longer,lower voltage/amp charge was better for long battery life but I suspect in the real world charging a battery at 16 volts for 30 minutes that had the correct level of electrolyte ain't going to hurt anything. That voltage I do believe will boil the electrolyte if left too long, so I'd definitely check it before charging.
JMHO
RonR
