Battery changed -- But,......

[PorscheFan]

Hi, maybe I need some help about this issue.

I just changed bettery yesterday. I drove for a while last night, I noticed the Voltage on my display is about 12.1 or 12.2. Today I drove from home to work , the voltage stayed about 12 or a little below. After parked the car for a while, I put the key in, the voltage is about 12.2. Should I worry about this? I searched previous thread, I also checked the cable and connector. I don't see anything abnormal. Before I changed battery (actually the battery died), I noticed the voltage while driving is below 12V. I tried to have battery externally charged, but it didn't work (5 years old, what you can expected...) . That's why I got a replacement.

So far, I don't have any problem to start the car. But searching the previous thread, it seems to me that this is a "non-charging" situation. Why should I do next? Your help is highly appreciated.

US-MY03, 996 C2 coupe, 6 speed

Edited August 6, 2008 by PorscheFan

[Loren]

Carefully measure the voltage across the battery (with a good voltmeter) while the engine is running 13-14 volts is normal. If it is below that then you either have a voltage drain or a bad alternator/regulator.

[PorscheFan]

Carefully measure the voltage across the battery (with a good voltmeter) while the engine is running 13-14 volts is normal. If it is below that then you either have a voltage drain or a bad alternator/regulator.

Thank you Loren.

I inspected the connection and followed wire to see if there is any leakage. I check the voltage before start and after start. It looks normal to me. Now I found a pattern of voltage change during driving. When the car is cold started, the voltage is about 13 - 14V. After driving about 10 minutes, the car warmed up, the voltage starts to decrease slowly. It stays above 12V all the time after that. If I re-start the car immediately, the voltage will go up to 13V and drop to 12V about 1 minute when the car is warm. If I re-start the car about 30 minutes later, the voltage is like cold start situation.

In this case, which one is more likely to be the problem? a voltage drain or a regulator ?

:unsure:

Edited August 7, 2008 by PorscheFan

[Loren]

Measure the drain by putting an amp meter in series with the battery and everything off. It should be about 40-60 ma.

If it is more - then start pulling fuses until you find the circuit with the drain.