iOS 11.4 and iOS 11.3 is reported with poor battery life by many users who upgraded their iPhone to latest iOS 11.3. The battery life is very poor in ios11.3 as the battery drain really fast. It is surprising that even with iOS 11.3 update, all of a sudden caused battery to drain at least 3-5x faster than ever before for some users. This is really annoying from apple that for every new iOS release the battery life becomes poor for many iPhone users.
Almost all phones including iPhone x and iPhone 8/7/6 have been reported to get affected with poor battery with upgrade to iOS 11.4. And the battery drain is immense and consumption is too high by system. It’s like in 3 minutes users is losing 5% of battery.
How to fix battery drain in iOS 11.3 and iOS 11.4:
To save battery of iPhone first please check which app is actually consuming too much battery .Go to Settings > Battery. To see how long each app has been open and running in the background. If it is some third party app uninstall it and check the performance. Or
1. Turn wifi off: to make sure any major sync (like photos would stop). Please check that any major cellular updates are also turned off.
2. Turn off Siri & Search indexing in Photos - to minimize the "risk" of lots of background activity that might drain the battery. It is quite possible that iOS 11.3 will be reading in the background the photos to try indexing and clustering them in order to offer better search options
3. Try setting Auto-Lock to a new value: system update might have set Auto-Lock to Never so the screen never turned off.
4. Turn off iCloud Drive in iPhone settings as this can be a potential battery consuming task to sync all data of your iPhone
5. General setting :Clear the safari history. Turn the iMessage off for about 10 seconds then back on. Now Goto-> cellular settings and toggled ALL settings either off then on or on then off again depending on how they were originally set. Now hard reboot the iPhone and check the battery performance.