The car is turned off after 10 seconds then I get a message that it is the battery icon, but it surprises me that the big screen does not go off and all lights are on just the engine that is closed? Could it be the battery? Could it be that there is a spare battery for just lights, etc. Could it be that I fully refueled the car and it came in dirt into the tank work? I tried to clean the tank, but it does not work. Could it be the battery or alternator or engine?
It is an Audi A8 04th

Please answer. Thanks.

 

test the battery and alternator.

check the connections.

Check the accessory belt.