The problems seem to be reasonably widespread and affect the iPhone line up across the board.
"My iPhone 6 was working perfectly fine until I updated to iOS 11.4 and ever since I did that my battery is draining rapidly even without me using it at all. I used to go a full day without charging it now it may last half a day. I am just wondering if something got turned on with this new update that I have to turn off to save battery life. It is just weird I have not done anything other than updating the iOS and now this happening ,"one user moaned.
"I have the same issue with my 6S+. It was fine before the update. And my battery health is at 90 percent yet I just watched my battery % drop from 50 percent to 20 percent in a matter of minutes while not using it. I’ve looked through all the settings and can’t see anything I’ve previously had turned off turn back on with this new update in regards to saving battery life. Whatever it is that’s causing it they need to fix it ASAP", moaned another.
Apple released another update but there is no mention that it fixes this issue and the moaning as still continued. Not enough to think "shall I get a phone which has not been programmed by the finest minds in the Apple spaceship".
For those who came in late, Apple got into hot water for throttling the battery life of older phones in the hope it would encourage fanboys to upgrade.