What are you guys showing you your battery voltage gauge while driving? I think my alternator may be a bit weak. I am generally around 13.0-13.2. On initial start up its about 13.7-8 which is still a little low. My car never has any issues starting even with a small Braile battery. Just curious.

 

When my car sits for a while, the voltage stays fairly high . . . like you, high 13s, but after I have driven it for a bit, it drops to low 13s. I have a fresh battery, but of course this does not speak to the health of my alternator.

I have been meaning to notice what it does with the headlights on, but I usually am distracted . . . HaHa, best-- KH

 

Sounds about right to me, put a load tester on it.

 

I see 14V gradually creeping down to mid 13's V throughout a drive...all depends on the regulator spec and freshness.

 

I live in AZ and I am always watching the voltage when I cold-start my car its always right at 14 volts as soon as I start driving with radar detector on, A/C on, and radio on it starts dipping to around 13.5-13 volts and if I run in to get some grocery's while car is still idling after 10 minutes or so it drops to around 12.3 sometimes 12 depending on how hot it is. Soon as I start driving it starts to creep up to 12.8 -13 ish. Also when I do my 2 min cool down the last 30 seconds I turn everything off A/C, Radio ect to take load off and by time I am ready to turn car off the voltage goes back to 13.8-14. BTW If I keep it on a battery maintainer all the time never get in the low 12's.

 

Check voltage regulator , cheap fix

 

About the same for my Turbo. Remember that gage is probably not the most precise instrument around.

While the voltage level starts out high, up around 13.7/13.8V (guessing from where the needle is on the gage face) after an engine start the voltage levels drops over some engine run time -- call it 15 to 30 minutes (depends somewhat upon how long the car has sat unused) -- as I guess the battery gets topped up. Adding electrical load can have the level down to around around 13V.

 

Hi Mac. I am not going off the dash gauge which is heavily dampened (just like the other gauges). I am going off of my Motec dash data which tripped a low voltage alarm while at the track this past weekend. The alarm was preset at 12.8V and I have since backed it down to 12.4V and no longer get the nuisance alarms. When I pulled the data which is posted below, I can see that the voltage momentarily spikes down to 12.5V from roughly 13.1-13.2V. These spikes are very brief lasting only fractions of a second, roughly a tenth or so. They are not perceptible on the dash gauge. Interestingly, when looking close at the data, these voltage spikes correspond to coming off full throttle and jumping hard on the brakes where you see deceleration of -1G or so. You can see this by looking at the voltage spikes (Bat Volts C125) and correlating them to throttle pedal position (Pedal Position 1 %) and longitudinal G force (G Force Long). The whole graph corresponds to selected data over the course of a 1:55min lap. As you can see, during this lap my average voltage was 13.1V with a low of 12.49V and a high of 13.25. This data is pulled off CAN bus by the way.

As I said I have zero issues with the car starting or anything else but after looking at things close I felt that battery voltage should be closer to high 13s while driving, not low 13s. My Cayenne for example shows just under 14V while driving, and that car has a huge battery in it. This car only has a small Braile 21. The spikes are something that I need to figure out. I would be interested if someone could log their Voltage data while driving the car and going from full throttle to full braking. Maybe these micro spikes are normal under these conditions? I doubt it though.


[url=https://flic.kr/p/xBKNRg]

 

^Did not know you were getting info from Motec?

 

Yes, every parameter on the car is automatically logged via MOTEC and can be downloaded at a later time for analysis.

 

I have replaced the voltage regulator last spring and even loaded with all the electrical components I never got voltage lower than 13.4 volts (indicated bu the cluster). At start it reach 14. I did the switch of the regulator after seing the voltage going close to 12 volts....I purchase a Bosch because I was not too confortable with all the different manufacturer that I saw on Ebay for less than $15.00. Bosch part#vrb254 or # F-00M-145-341 ...

 

Thanks JP. I'm assuming the voltage regulator is part of the alternator which has to come out for the swap? Any DIYs?

 

Of course there are some DIY :

Alternator removal, very good one from smistry007: https://www.6speedonline.com/forums/...e-replace.html

regulator replacement from Aerkuld: http://forums.pelicanparts.com/porsc...placement.html

Happy wrenching John!

 

I haven't pulled mine yet but have done regulators on others= not bad at all.

 

very easy job, I use HUCO #130570 regulators which have been good for me so far.
Make sure to inspect the copper rotors (which the brushes swipe on) for excessive wear.