My "normal voltage" on the 86 5k runs 13.5 to 13.7 depending
on the load. From reading about different changing voltages for
different types of lead-acid cells, I feel that 14.2 would be
the best ( at 60 degrees F, make it 14.4 at 20 F ) if I could
make it happen.
My wife's dodge van runs 13.9, and the lights do much more
than hold a candle to the Audi's , even with the relay I added.
I had planned one day to perfrom monor surgery on the
voltage regulator in the Bosch alternator, but feel that
it would be good to have a spare alternator as backup in
case my surgery goes arwy. And the consequences if the
voltage really gets out of hand could be very expensive.
I am also quite convinced that sustained undercharging by
running 13.6 volts shortens the life of the battery, due to a
slow sulfation effect. So every two or three weeks I put the
battery on an overnight slow charge.