Battery Dilemma Update
 

So I spoke to my mechanic... and also said with an output of 15.5 volts (engine running), it's over charging the battery and is ruining it. He said the correct voltage should show around 14.1 volts. He also mentioned that depending on the model year... there's also another part that is suppose to regulate the recharge voltage (I didn't get the name of the dang part... anyone have any clue)? It's possible the battery, this mystery part, and the alternator needs to be replaced.

Any clue from people a reasonable cost to replace all three with labor @ $90/hr? $700? $1000?

I'm dropping the car off after work. He'll have a look at it.

The voltage regulator is internal on the alternator. Replace the cheap part first. (battery)
 

A bad battery can cause all kinds of weird stuff.

Given the numbers that you posted about the car at rest, I'd make sure the gauge is right.

The voltage regulator is external, bolts to the back side of the alternator. A cheap part.

Oops. Sorry... meant that it was attached to the alt.

Yeah, like it will be the cheap part that is causing the problem...
 

(just keeping in line w/ the Nat'l Sarcasm Society). Don't you know that Audi over-engineers the cheap parts and makes sure that only the expensive ones fail?

Thanks for all your input over the years, don. You are one of the reasons why AW is such a good place to hang out and just about the best damn place on the web (well, that doesn't have nekkid pictures on it, anyway). ;-P

check voltage across regulator with car running - if 15+ volts, replace it?

You can simply check the voltage across the battery terminals with car running and all accessories
 

off, using a multimeter or voltmeter (don't go by the one in the dash cluster). If it is pushing more than 14.2V or so into the battery, it is likely that something isn't right. Too high a voltage can fry the battery, too low is also bad as it will not charge properly. You want the voltage regulated within a prescribed range that is best for the battery, which is like 13.6 up to 14.2V. Outside that range will eventually kill the battery.

The gauge looks to be right... the needle is pushing pretty close
 

to the 16 marker.

The multimeter shows 15.5 with the engine running (no accessories on). Interestingly... with the engine running and all the accessories turned on (AC, Radio, lights, windows, seat heaters), the needle still sits around the white marker between 12 and 16. I always thought it's suppose to drop.

Soooo.... if it's the alternator or regulator that is fried... what are the chances my battery has been damaged beyond using since discovering the problem about a week ago?