Hi!
I've noticed a bit alarming voltage at idle on my 2013, vrs, mk3, 2.0tdi.
It casually floates at 15.1 and yesterday after a 45min trip, it went even as high as 15.9v, at idle.
Drives and starts just fine.
Its winter time here and temperature is 5celcius outside. Battery is 6months old, brand new Exide Agm, also coded in car.

Is it normal behavior or should i be worried?

Edited 30 November, 20241 yr by VenomVrs

19 minutes ago, VenomVrs said:

It casually floates at 15.1 and yesterday after a 45min trip, it went even as high as 15.9v, at idle.

This makes me thing that the voltage regulator is FUBAR. I have no idea what @PetrolDave is trying to say, but I've never seen an alternator and regulator in good order output more than 14.4v.

14 minutes ago, Paws4Thot said:

This makes me thing that the voltage regulator is FUBAR. I have no idea what @PetrolDave is trying to say, but I've never seen an alternator and regulator in good order output more than 14.4v.

I was thinking the same. And i really dont want to cook the new battery, agm is pretty expencive. 
 

@VenomVrs What are you measuring with?

 

Voltage regulators are controlled differently in start/stop cars, and AGM batteries may be charged at higher voltages than conventional ones.

Dave is showing max charging voltages per cell for these batteries at different temperatures. 

Multiply by 6 to get voltage between battery posts.

 

 

General upper limit for charging AGM batteries is stated at anywhere from 14.8 to 15.0V. But this is often quoted for a standard - maybe 20 or 25C. Below that the absorption voltage rises for each degree C drop. That gives us some pretty high theoretical voltages for charging a cold AGM battery - but it's the battery temperature we are considering here, not the ambient temperature. Self-heating during charging will bring the battery temperature up.

 

A very smart charging system would have some form of temperature measurement on the battery to take account of this. A step too far for car use.

 

So your "high" voltage may be normal and you are sensitized by having to fork out recently for a new battery. Are you reading the car voltage values from the ECU or are you using one of those cigarette lighter plugins? Or something else?

Guys, i'm embarrassed. Turns out all seems to be good. My ObdEleven main paige was showing 15.2 and sometimes 15.9v. But at the battery terminal with tester it was actually 14.7v at idle. And ironically when you go deep inside ObdEleven menu, it also shows real voltage. Dont know why the main paige of the app is so off.
Sorry guys but thanks for answering!