I fitted a new Exide battery to my 98 A6 2.5 TDI in March (correct spec BTW).
The problem is that before I start the engine in the morning the voltmeter shows the voltage as just over 10v. Once the car is started (a struggle sometimes in cold weather) the voltmeter shows about 13v. If I stop the engine and go back after an hour or so the voltage shows over 12v.
My feeling is that the battery is not holding the charge as it should, but on both occasions that I have taken the battery back to the shop I bought it at, it tests OK (well it would as I have just driven there). The alternator test shows it is charging OK.
I would appreciate some feedback on what batteries should show on the voltmeter before starting, after being left overnight.
TIA