Users of iPhone 6s and 6s Plus are experiencing an issue where their battery percentage is not updating, so they’re unable to tell how much power they actually have.
Apple says it’s connected to changing the time on your phone manually or switching time zones when you travel.
The suggested solution is to go to Settings on your phone and then choose General, then Date & Time. Make sure you switch your time settings to Set Automatically.
Apple says they are still working on a permanent solution to the problem.