If you’ve noticed that the battery life on your iPhone is not what it used to be, it’s likely that the problem isn’t with your iPhone or some setting or app, but a bug in iOS 11.4.
Apple’s support forum has been blowing up with complaints from users that battery life has been seriously curtailed since installing iOS 11.4. The problems seems to be reasonably widespread and affects the iPhone line up across the board.
I’ve seen this issue on the iPhones that I use. It seems to be accompanied by the device running unusually hot. Below is a photo I captured when I used my thermal camera to check the temperature of my iPhone 8 Plus.
It is also unclear if the latest iOS 11.4.1 update fixes the problems as the release notes make no mention of a fix.
The bottom line is that if you’ve yet to upgrade to iOS 11.4, you might want to wait it out for a fix. If you have and it’s killing your battery, then maybe try installing the latest iOS 11.4.1 update.