If your iPhone has been shutting itself off, even when you clearly have a reasonable amount of battery left, try the following fixes.

1. Hard Reset

Hard resetting usually takes care of this issue. Hard resetting is the equivalent of “have you tried turning it off and on again” but on a much deeper OS level. It usually resets the defaults.

To do a hard reset on your iPhone with a physical home button (any iPhone before iPhone 7), press and hold both the “Sleep/Wake” and “Home” button for 5 seconds. The iPhone will reboot, you’ll see the Apple icon flash and the iPhone will come to life.

On the iPhone 7 and iPhone 7 Plus, press and hold the “Sleep/Wake” and “Volume Down” buttons to do the same.

2. Are You Running The Latest OS?

Users first reported of this issue when iOS 9 was new. The effect was random and no actual source for this issue was found.

But users have reported that updating the OS to the latest version usually solves the issue for them. At that time it was iOS 9. At the time of writing, it’s iOS 10.1.

So when your phone is booted and running (presumably after you did the hard reset), go into “Settings” -> “General” -> “Software Update” and update to the latest software.

3. Charge Up

If your phone just isn’t responding and nothing is working (even the hard reset), just put your phone on charing. And keep it there for an hour or so without meddling.

If that doesn’t work, try using a different cable, a different power adaptor or try charging it from your Mac.

4. Drain To 0% Then Fully Charge

If the issue is related to the battery indicator (as in, the battery stats are not displayed properly in the system), the fix is to drain the battery to 0% (actually use the phone till it powers off because there’s no charge left) and then charge it up all the way to 100%.

5. Restore via 3uTools

Step 1: Connect your iPhone to your Mac/PC and open 3uTools.

Step 2: After your iPhone is recognised, go into the section and first click on “Backup/Restore".

Step 3: After the backup is complete, click on “Restore Data“. This will start the process of downloading the latest iOS software, wiping your device completely, and installing the new OS on your device.

Once this is done, your phone will be restored to as it was when you first got it. Once the process is done, you’ll be asked if you want to restore the backup you made before. Once that’s done, all your apps and data will be back on your iPhone.

6. Contact Apple

If you did all of the above, we’ve taken care of any software issues that might be responsible for randomly shutting off your iPhone even when you had charge left.

But we can only do so much. It’s possible that your iPhone has a damaged battery, or any other component. If your iPhone is 3-4+ years old, that’s a very real possibility (I’ve seen it happen to a year old iPhone 6 too).

The best option is to contact Apple (call them on 1-800-694-7466) or to go into your nearest Apple service station or Apple store. If you’re under warranty or have Apple Care+ (always a good idea), Apple might just give you a new device or you’ll have to pay for repairs.

Source:iPhonehacks