re battery issues – as an example, the action centre toggle does NOT disable bluetooth if you find that re enabled upon updating as I did despite never using bluetooth products)- go into settings and you’ll find it still on. Its worth googling/ youtubing battery tips for ios11- I’ve always done that and there’s a bunch of things to turn off that you genuinely don’t need (looking at you ad tracking location etc) take a moment and look them up, you’ll be surprised what is running you don’t need. And no, it doesn’t cripple the phone. Never found anything unusable after turning the majority of location and background tasks off etc.
Battery calibration is NOT the solution, unless your phone is only 24 hours old. Proactively look up the tasks that use battery resources and turn them off.