Many iPhone users after upgrading to iOS11.2.6/iOS11.2.5 and the latest iOS 11.3.2 are facing serious battery drain issues. iPhone users are experiencing fast battery discharge and mobile heating up once they upgraded to latest iOS software release. Even resetting the device does not seem to help for the issue. For many users it is like the battery drain 80% in 6hours normal usage. This was never the case with older iOS releases. Even new iPhone X and iPhone 8/7 users a facing battery drain issue in iOS11.2.6/ iOS11.3.1 and battery performing very poor.
It seems that iOS11.2.6 has been causing problems for many users and overheating and battery drain is one of them. The issue is not widespread but significant users are affected by this. Apple have not released any comments on battery drain in latest release. Even the iPhone 6 battery life iOS 11.2.6 has become worst performing as iPhone 6/6s are already reported with poor battery life issue with iOS11.
How to fix battery drain issue in iOS11.2.5/iOs11.3.1
First thing to do is check which thing is causing this much battery drain of iPhone. GO to Settings->Battery and check the list for highest usage app or services. If any obsolete or unused app is causing battery drain please uninstall that immediately.
Fix 1: Turn Off “Hey Siri”
While your data is ON, Siri does consumes data for “Hey Siri feature” and it is reported that Siri sometimes causes battery drain in iOS11. So please try by turning off this feature : Goto->Settings > Siri & Search and disabling Listen for Hey Siri.
Fix 2: Reduce visual effects:
disable the “parallax” effect in your iPhone which support 3D animation of wallpaper, iMessage from auto playing.
Fix 3: Turn off location services:
Head to Settings > Privacy > Location. You should turn this off if not using regularly or if you know which app is taking too much battery you can at least to try that off.
Fix 4: Turn off Bluetooth and WIFI:
You must be aware that turning off Bluetooth and WIFI from control does not completely turn these features off. In order to avoid battery drain please turn them off by going inside Settings menu.