What's the typical Boxster voltage while driving?

[Dale_K]

I've got some battery charging questions.

First one in the thread title - what should a voltmeter read on a properly running Boxster while driving? I get 14.2 for about 1 mile then tapering off to 13.75 after about 15 minutes. The readings didn't change when I put on a new voltage regulator. I'm used to seeing 14.3 - 14.5 on my GM vehicles and with no variations during the drive.

Second - which measurement is more meaningful - battery voltage or hydrometer reading? My 2000 S is showing 12.6 volts with the motor off, measured with a digital gauge throught the cigarette lighter. This measurement was taken after holding back the flash-to-pass headlight switch for 10 seconds, to burn off the "flash charge" whatever that is, per the voltmeter instructions. I think this is considered a good reading. Yet the hydrometer reading is in the fair to low range - about 1.175. The battery is a conventional unit from O'Reilly and is only about 2 months old. When I put it on a 6 amp charger it briefly starts out reading low on the charger gauge but moves into the green 60% charged region within 30 minutes. The digital voltmeter reads 14.6 while charging.

Basically I want to know whether I should replace the alternator and if that will give me the 14+ volts that I see on other vehicles. Or whether Porsches are different somehow and my Boxster readings are normal for the car.