I have a A6 3.0 2002. Yesterday after I had been driven the car to work, I came back home and after 30 minutes wanted to start the car again but it didn't. It made a sound like it wanted to start. it had lights, sound and all. the battery indicator showed about 12V, initially but this morning showed like 6V. Is the main problem the battery or is it something else that is killing it. Thanks

 

If you have lights and voltage it may not be the battery. If it makes a clicking sound as you're trying to turn it over it will be the starter.
Good luck

 

Do the starting problemsONLY happen after the engine has been running for some time? If so your coolant temp sensor could be bad.

 

it could be the battery is dead or the alternator isn't charging it, a failed alternator will fry the battery through over voltage or simply not charge it up at all so when you are driving your using the battery to keep going and when that's dead you are where you arealternator would be my guess