Your looking or 12vdc when the car is off and nothing is turned on .
Your looking for 13.8-14.6vdc when te car is running (depending on load )
If you have a voltage load tester you can test the battery's performance when the car is off
Specializing In BMW, Audi, Mercedes Benz ,Volkswagen, Volvo
"Burning 2nd is a lot like vitamin tonic. Overly harsh, tastes like crap, but somewhere in all that there's good intent......just have to learn to read between the lines, actually you have to squint really hard to see the good, but its there somewhere"