Originally Posted by luigi90210

is that with the stock gauge or a multimeter?

either way if you are getting 15.2 with a multimeter check terminals and make sure they are clean(you can clean them with a wire brush and baking soda mixed with water), make sure everything is bolted up right(no loose cables)

dirty terminals can cause resistance and that can create an overcharge senario

if the battery terminals are spotless and connections are perfect check your alternator, take your multimeter and attach it to the alternator itself and checking the voltage coming out of the alternator, it should read 14.7 or somewhere around that area, if you are seeing more than your alternator is the problem and it needs to be replaced

EDIT if you can take a pic if battery before cleaning it if it needs to be cleaned