I have an Audi A6 2.7 Quattro. Our first issue was the radio stopped working. It would light up, but I couldn't turn it on. It wasn't that big of a deal, so I didn't pay too much attention to it. It was like this for about 3 weeks. This morning when I went to turn the car on, it would barely start. It acted like the lights were left on. I checked my light switch and it was in the off position. My son likes to mess with the overhead lights in the back, so I checked those and they were off. The only thing that was plugged in was a phone charger. When the car did turn over, the CD player started to cycle. So I checked to see if the radio would turn on and it did. I drove my car about 1/4 mile up the road and left it on while going into the mini mart. Drove it home and there didn't seem to be any issues. Turned off everything and went inside my house. I was at home for about 15 minutes and started the car with the exact same issue. I popped the hood and checked to see there was any corrosion or anything physically wrong with the battery, but didn't see anything. As I began my 25min trek to work, I kept an eye on the battery gauge and it seemed to stay charged, which to me seemed like a pretty good indication that the alternator was doing its job. I had the radio and the AC on, which only the dipped the battery level a little bit. My guess is either coils or a starter...am I on the right track? Not a car guy, only know the little things I pick up along the way. Appreciate any advice and help....Thanks \m/

 

Sounds like you have a parasitic drain. It might be that the radio is not completely turning off and is draining the battery.

Do a google search on "parasitic drain" and look at some youtube videos to help you try to do the diagnosis.

(After re-reading your description of the problem, my advice would be to take it to someone who knows auto electrical systems.)