overcharging the battery HELP

I got my car back from the mechanic 2 days ago. I noticed the alternator gauge was pegged to the right + side. I called him and he said it was probably just because the battery was dead so I charge the battery with a trickle charger (battery is 8 months old) same problem. I was then advised to get a new voltage regulator and then a new alternator, and still the same problem.

Before I changed the regulator and alternator, the battery was getting 17 volts at idle. Not sure how much it’s getting now but I assume it’s the same based on the gauge reading.

I Don't think it’s the alternator gauge just giving me a bad reading because when I turned my lights on they immediately blew out from an over charge.

Ocassionly i hear a click (behind the dash?) and the gauge goes into the middle were it should be but 1 second later it hikes back up the the + side

Anyone know what could be wrong?