Run power troubleshooter from Control panel  Set display brightness to a level where it's readable but not too dim In BIOS > performance > Disable turbo Boost  Most important : I reimage my Dell computers as soon as I get them out of the box. Clean Install using Microsoft Image, No Bloatware from dell.    Windows 11 is expected to be make battery life even better.  I would suggest not to spend more in a new battery, While it's in warranty contact Dell for a battery replacement after a Clean OS install. 
Well, big disappointment. Going from Dell 13XPS which would last almost 8 hours to 15XPS which lasts barely 4. Sure there is an 84Wh option but I opted for the standard 56Wh battery. I see battery reviews online that sound a lot better than mine, however, some tests are done with wifi off and low power settings. Anyway, don't fall for the 56W battery, life is way too short if you're on the road.
Dell XPS 15 9500 i5 ridiculously short battery life