Hi @lukashfn,

Try running an ePSA/Diagnostic test on the system, click here to view a Dell article that explains how to run this test. Let us know if you receive any errors. 

This could be related to the video card. When it is connected to the AC it is using full VC (nvidia). When it is in battery it wont get full performance, therefore, does not fail.

Send me a private message with the Service Tag so I can review your account. 

Hi, already did this test alot of times, never gave me any error. Sending the service tag for you.