iPhone or iPad, including iPhone 6 and 6s users complains regarding issue with iPhone battery. The iPhone shuts down while some battery is remaining in it. The battery indicator shows that iPhone have battery around 30-40 % but all of sudden the iPhone keeps shutting down inexplicably. The issue is reported by many users as this can happen at any time when a user is expecting some important calls, the iPhone can keeps shutting down and turning off while the battery still reads 20%, 30%, or even 50% . Even the iPhone asks for recharge, after plugged in the phone turns back on, but it keeps shutting off unexpectedly.
This is very strange that why iPhone, iPad, or iPod suddenly turns off when you still have 30%, 50%, or any other percentage of battery remaining. The problem can be due to faulty battery or some software glitch. Software issue can be with battery indicator as well which may point to wrong battery status or sudden drop in battery level.
So long as it's not a problem with your phone's battery or any other internals, fixing it could be as simple as completing a couple quick steps.
Fix 1: Recalibrate your iPhone battery
This step will help to reset the battery indicator issue with actual battery level. The first step to take to solve this problem is to calibrate your battery.
-When the phone shuts off above 1% charge it for a short time (1-2 minutes), the turn it back on.
-Run the battery all the way down to 1%, then until it shuts off.
-If it shuts off above 1% again repeat the first step.
-When you finally get to a 1% shutdown charge it for 4 hours with the wall adapter.
If the battery is not defective this should fix it.
Fix 2 : Let Battery discharge completely
As the battery starts charging normally from the point it turned off iPhone, means it does not fully Discharged so it is possible that problem of wrong battery indication.
So most simple step let the battery drain full (as it switch off at 30%) "After it switch off by its own then keep it as it is for 1-2 days. This will results in totally battery discharge and after that wait, you will find the problem is resolved. "Just need to wait for it to work"
Fix 3: Hard Reset or Upgrade to latest iOS version
You may also try to hard reset your iPhone to see if that fixes the issue, other wise keep updating iPhone to latest iOS for the fixes released by Apple