High voltage

It's a new alternator only 3 days old.
Reading 15.3 voltage out of alternator but
still running high voltage through my
truck.the battery is getting a charge but
when my Rpm goes up my battery gage
goes up to high. All my Gage's start acting
up my lights in side cab quit working only
my dim lights will turn on and my dash
lights get brighter windows doesn't have
power to them. When I come to an idol
everything comes back to normal. I've
changed the regulator out of the first
alternator i put in there still had the
problem. I bought a brand new alternator
the one that is there now. Only been in my
truck for 3 days. Still having the problem