Battery going dead
 

I have a 2007 q7 and it has an issue with battery going low while driving
I have changed battery and alternator ( used one)
The battery is a 950 cc battery and the used alternator charged the same as the original
I just had the battery monitoring system reprogrammed and it just happened again
Go for an hour drive and just ac and radio on then come back home ,turn it off 10 min later try to start again ...no start battery too low

Any ideas ....?????????

If you crank it up and put a voltmeter on the battery terminals, what reading are you getting? It should read between 12.5 and 13.5 volts. Sometimes as high as 14volts just after cranking since the voltage regulator is recharging the battery from the start up drain.

I know you said it's charging but it doesn't sound like it's charging enough for some reason. How old is the battery? More than 5 years old, it could be developing a dead cell and not being able to deliver the amps for starting.

What he said. May be it is time to get a new battery.