My iPhone 6s is turning off at around 20-30%. I've tried multiple times to calibrate the battery using Apple's method by plugging in to turn on until the device is at 0% but with no success.
The phone was bought at launch (September 2015). I never had these problems with the 2 other iPhones I had before.
Seems like this is a common problem with multiple models.
How can I fix it?
iPhone 6s, iOS 10.1.1
Try to reset your device. This won't delete your data stored on this device.
Alternatively, you may go to Settings - General - Reset - Reset All Settings
If this does not help, restore your device to factory settings. Note that this will erase the data from your device.
Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.
As a final step, try the recovery mode. Turn your device off, then plug it to your computer with the home button pressed. Keep the Home button pressed until you see the iTunes logo on the screen of your device. After that on your computer you should see the iTunes window saying your device needs to be restored to factory settings. Click on the restore button.
https://support.apple.com/en-us/HT201263
If these steps don't work, contact Apple and ask for help.
Try to reset your device. This won't delete your data stored on this device.
Alternatively, you may go to Settings - General - Reset - Reset All Settings
If this does not help, restore your device to factory settings. Note that this will erase the data from your device.
Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.
As a final step, try the recovery mode. Turn your device off, then plug it to your computer with the home button pressed. Keep the Home button pressed until you see the iTunes logo on the screen of your device. After that on your computer you should see the iTunes window saying your device needs to be restored to factory settings. Click on the restore button.
https://support.apple.com/en-us/HT201263
If these steps don't work, contact Apple and ask for help.
The same issue with my 6s 64 gb. And Apple support service in Kiev(Ukraine) told that there's no issue
And
I visited my local shop and did a diagnosis. They did not fix anything however they managed to pull out a big chunk of fluff from my iphone's lightning port.
The fix has happened last Friday (4 days so far) and my phone is working perfectly, so far.
I'll give it some more time.
iPhone 6s turning off at around 20-30%
