Start problems with my A3 3.2

Hello, I was just about to get something. So I activated the heater by FFB, about 10 minutes later I was in the car. I turned on the navigator to insert the SD card (which also worked without problems) and then tried to start the engine. It didn’t work, the engine stuttered briefly but didn’t work (similar to an empty battery). I tried it again directly, the same result: stuttering. Then I waited a minute and it again The idle speed stood SOFORT at 600 rpm (normal idle speed with me 700 rpm), normally the idle speed after a cold start is increased for about 30 seconds at approx. 1200 rpm. This increase of the start speed remained completely out. Now the question: If really *only* an empty battery should have been the cause (why, was yesterday still on the AB with high Moto rspeed on the road, actually the battery should be sufficiently charged as a result ?!?!), then at least in the FIS a warning should appear that the battery voltage is too low. But there was absolutely no warning message in the FIS, neither regarding the battery voltage nor any other error. What could this have been about? Did anyone else have this problem with their 3.2r? Is there a way to query the battery voltage somewhere? Thank you in advance and Gru ß, test winner