Dell XPS 9300 extremely slow when unplugged [solved already]

I have had an XPS 9300 for about a year and it worked just fine. However, since today, the laptop has become extremely slow, even opening the start menu takes a few seconds and whenever something happens the framerate even on windows is abysmal. Logging in with Windows hello also stopped working entirely (the fingerprint sensor works though).  Another curious thing: The laptop thinks it is charging constantly even when it is not plugged in. However, when it is actually plugged in it works at the normal speed. 

So far I tried restarting it but that did not change anything. 

However, just as I was typing this I did find the error: I opened Dell power manager and it installed an update and now it is all working again. I guess I leave this entry here in case someone else encounters the same issue.