Whoa, hold on here... don't run away with my thread here guys!
It is not common for computer controlled cars to run 15 volts. Just because there are a lot of accessories on board, does not mean it needs more voltage to run. Voltage =/= capacity. Current = capacity. Hence the threads about bigger capacity alternators to run cars with a big stereo system. I only have the 105 amp alternator, but might try to get a 140 if it will fit.
Electrical load like lights, heating elements, etc, are rated to perform under a wide range of voltage. But they work as designed under a narrow range.
I've had my share of computer controlled cars. Even dating back to my 87 Regal. It has a 3.8L turbo, and has never seen voltage top out above 14.6. It had a system in it, with one regulated power amp for mids/highs, and an unregulated amp for the subs. Just about every piece of wire in that car has passed through my hands, down to the wiring for the custom fan, and 8 gauge fuel pump feed and ground.
I have my dads Subaru Forester out here, with power moonroof, rear defrost, heated seats, foglights, front defrost, heated wipers, heated washer fluid, etc etc. I bet you it isn't running at 15v. I know my 01 Cruiser parked out here, with custom LEDs, reverse lights, stereo setup, moonroof, heated seats and foglights, etc etc has never seen voltage that high, even on a nearly dead battery that needed a jump. My sisters 00 Regal LSE doesn't see 15v either. Its running a stock 3800, with power roof, seat heaters, stereo, digital climate control, etc etc. It still has all original switches, no dash bulbs or switch backlights are out. Seat heaters work great. Hasn't needed a new tail or headlight bulb in the last 2 years, and she used to drive 3 hours a day or more with it.
15V may be a normal at the "extreme" ends of the charging spectrum (for very short periods of time), but 15V all the time is not.
2004 Buick LeSabre Custom FE5 GXP suspension conversion. 170Kmi
2001 Silverado 4WD 5.3L, 33" BFG ATs, Z71/Z82 pkg, 147kmi.