I thought I have this weird problem, but when googled I found this is quite common.
So your iPhone 4S shuts down even when it hasn’t gone as low as 20%, 10%, 1%? Bad news is you will not find an official solution to this problem. Good news is this trick that I tried might just work for you.
- Install a free app called battery doctor on your iPhone.
- When the phone shuts down connect your laptop to your computer to charge, not to an A/C wall outlet.
- Once the phone boots up, open battery doctor. Continue charging until battery doctor says “no charging necessary”.
That’s all. That should solve the problem.
In case it doesn’t…
When I read through numerous articles online I noticed some suggested a hard-restart (press and hold power + home buttons together for few seconds until the Apple logo comes up). I did that few times just after the charging was completed while battery doctor running in the foreground. And my phone started going all the way down to 1% again before shutting down.
It is not a guaranteed method to solve this problem, but then there isn’t one. Rather than trying to take a backup and restoring factory settings etc, this is a simpler solution that can be tried first.