I truely think its not the battery. Relay or fuse most likely. Does anyone have a diagram of wiring from alternator to the battery? Thx

 

Next best thing to the wiring diagram - https://www.porsche.com/all/media/pd...PA_KATALOG.pdf

 

This is for the 2006 model year but it should apply to all years up to 2010. If there is a bad cell the charge voltage will drop to a lower value.
I never uncovered a wire diagram with the sense wire mentioned here.

 

Thanks for the info. BTW, I scanned that Amazon listing above for this product a few times, searching carefully, and found absolutely no description of what the product actually does. Really. Check it out. If you can put some content into that Amazon page, it might help others.

 

It’s strangely compulsive - I keep looking at mine. New toy I suppose!

I wonder if it would work with a dual battery setup like on the early 955s. (Like mine).
i can’t see anything about that anywhere.

 

Work..yes...but also depends on what specific info you're looking for and how it's connected, if you have one for two batteries the voltage will be accurate but it wont' be able to differentiate between the two if for example one is lower than the other. You could of course run one directly on each battery.

A couple of direct links for those looking for the info as well.
BTR-1 Lithium Battery Tracker
BTR-2 Lead/Acid Battery Tracker

 

It would have to be two units - one for each battery.
How would that be displayed/how would I switch between the two, or are they superimposed in the graph (which would be better).
serious thread creep - sorry!

 

Each Tracker can be custom labeled in the settings so you would then select which battery to view in the app, no superimposing so each would be viewed independently. The app allows for up to 5 trackers in the app. Done this way originally so you can basically be monitoring up to 5 vehicles via the same app

 

Thanks very much.

 

Thank you very much!

 

Thank you for the info. I suppose mb23 is a fuse? Looks fine on the left side of the dash. Gp25 relay looks ok too. I swapped it with another one to check. I can not seem to find the alternator relay from the diagram! Do you happen to know where is it? Thx in advance.