Alternator Overcharging

When checking the wiring on my under dash gauge lights I found the voltage with the car not running was a little over 11 volts, which seemed to match the volt gauge. I checked the battery and it read 12.4, with the engine running the gauge read around 13.5 but the voltage at the battery wad 15.2.
I check the ground at the voltage regulator and it was good, I also ran a ground from the battery to the voltage regulator case, and there was no change in the
a new voltage regulator and still no change.
The gauge mismatch is less of a concern that the over charging, any suggestions of what to check next.
Thanks
Mike
reading. I installed

gauge eng off.jpg

gauge eng running.jpg

battery eng off.jpg battery running.jpg

Volt Reg.jpg

Alternator.jpg