You can increase your battery life by taking the following measures until a real solution is found. Then you can take back what you have done by undoing the changes:
1) Turn off background app refresh
Settings>General>Background App Refresh ( Turn off those apps that you do not constantly need to be refreshed )
2) Turn off Auto-brightness
3) Reduce Screen brightness
Settings>Screen and Brightness> Bring the slider to halfway
4) Reduce visual effects
Settings>General>Accessibility>Reduce Motion ( Enable/Turn on the setting )
5) Turn off "Hey Siri"
Hope this helps.