In many threads I read it should charge 14.5 while driving or engine is on.
I have never seen over 13.8 on vehicle signals screen.
My Varta battery died after 15 days service and paint procedure as car lied down. It is only 1.5 years old.
It was fully charged and battery guys said it is ok.
I did drain test photo is here. It seems ok. But I always get the battery low warning easily.
 2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k

I had mine show 14.5v when charging after I haven't used it for a long time.

If it's not constantly charging at that or more with no starting issues, then I wouldn't worry.

It seems it decreases the life of the battery.
I don’t know if low charging value is the reason.
It lost 0.4 volts in 24 hours lying. 2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k