My iPhone has been using huge amounts of battery power for almost 2 weeks now – ever since I upgraded to iOS11. It can drop 20% of it’s battery percentage in an hour and it’s using so much power that it takes 5 hours to charge! I’m keen to see who else is having this problem and whether it’s resolved itself for you.
After some reading I am hoping that this increase in power usage on iOS11 is caused by Spotlight reindexing. This would also make sense as to why all the power saving measures such as low power mode etc make no difference. It also makes sense as to why the battery drain doesn’t seem to be tied to any particular application. If this is the case, all we need to do is wait a few days and the iPhone should finish indexing and eventually return to its normal self. If however it’s some kind of a bug in iOS11, we may need to wait for a fix from Apple. If it is caused form Spotlight indexing, waiting should eventually fix it. If you are camping or in a situation where you you need the phone and cannot put up with the battery drain you have 3 options:
UPDATE: It’s not caused by Spotlight indexing. I turned off all indexing and the problem is still there.
I’m contacting Apple Support and will keep you updated.