I have iPhone 5S with 10.1.1 iOS. I have experienced few situations where my battery life was about 30-40% and iPhone immediately turned off. When I tried to turn on it indicated low battery and kept doing this for about 2 hours everytime I tried to turn on. And then suddenly turned on and was back at around 30% battery life and I did not use charger in the meantime (I did not have it). Then this situation happened to me again when I had my charger with me, so plugged in and after while iPhone turned on charging but already had about 40% of battery charged. This happened to me like 5x in last 3 months. The scenario is always very similar, battery life about 30-40%.. (never happens when the battery is more than 50%) and then few hours idle until comes back. Does anyone has any suggestions? Many thanks for help

  • Was it in cold weather or similar? - You could try simply recalibrating the battery (i.e. let the battery drain completely, then charge it to 100% and leave it in the charger for an hour extra... repeat that cycle again - and hopefully it will be better at knowing the real capacity of your battery)
    – jksoegaard
    Commented Nov 13, 2016 at 20:02
  • Anecdotally, some people have reported this being a software issue and not hardware. Up to iOS 9 this was classic "battery" or "failed chips" internally, but I've seen this on several generations of hardware (5 and 6 - both S and not) for me to think it's all hardware related. It could still be hardware though.
    – bmike
    Commented Nov 13, 2016 at 21:16
  • I have this problem too on iPhone 6s, the phone started switching itself off around 38%, it's happened around 20 times. It seems to have cleared up now. I agree it must be a battery calibration issue as I didn't have the problem with iOS <= 9.x. Commented Nov 16, 2016 at 1:18
  • Thinking of closing as dupe to apple.stackexchange.com/questions/239878/…
    – bmike
    Commented Mar 31, 2018 at 20:53

4 Answers 4


When I was a Genius at an Apple Store about two years ago, this issue was relatively common. Most likely this is a hardware issue with the battery itself, but there is a chance it could be a battery calibration issue. It's best to troubleshoot calibration first.

Calibration Issue

The battery itself keeps track of how much battery life it has, and reports this back to the phone, which it then displays on the screen for you. Sometimes, the battery may be fully charged, but the battery or phone instead reports a different charge percentage.

Fixing a calibration issue is relatively easy:

  1. Use your phone until it completely runs out of battery power and shuts off.
  2. Plug your phone into a charger, and leave it plugged in until it is fully charged. Ideally, do this overnight so you know to be sure it gets completely charged.

This process will tell the phone and battery where its lowest and highest charge points are.

Hardware Issue

If you continue having the issue, it is almost certainly an issue with the battery itself. If you have an Apple Store nearby, make a Genius Bar appointment there and bring your phone in. They can replace your battery there the same day, and it usually takes less than an hour.

If you don't have an Apple Store nearby, there may be an Apple Authorized Service Provider near you that can help. Go through the prompts at Apple's support site, and they will help you find a good option.

  • If the problem is an iOS one around lower limit of the battery charge, lets say iOS computes a level of 0 % when the battery level is 33 %, then a user will never be able to reach this lowest level of charge. ↵ In this case it is not possible to make a correct battery calibration.
    – dan
    Commented Nov 16, 2016 at 14:42
  • I understand what you're saying, but in my experience, that's not the case. If the phone's battery is at 33%, but it's telling the phone that it's at 0% (and that's what's shown on the phone's screen), the phone still will not shut off until the batter actually runs out of power. I've seen phones sit at 0% for hours before actually shutting off. But you are right that sometimes it is not possible to make the battery calibration. In that case, the fix is to replace the battery.
    – hisaac
    Commented Nov 16, 2016 at 15:23

Battery percentage is usually an estimation as it can be quite difficult to work out actual percentage.

A great way to see the health of your battery is by using a tool such as CoconutBattery (Mac, free) which will allow you to view the cycle count, current capacity and how much it can store of its original design capacity.

Remember, batteries are considered a consumable and once they've been cycled too many times will need to be replaced.

This could also be a software issue as some other users have mentioned, so your best bet is to backup the device then restore it through iTunes, setting it up as new to test.


I'm experiencing the same problem and believe iOS 10 software is the cause and not hardware.

If iOS 10 is not registering the correct amount of battery power. Occasionally prior to my iPhone 6S going to sleep it's registering a decent amount of power to wake from sleep (as much as 50%). The phone will not wake from sleep and is effectively useless. However connect it to a power source or a computer, the power issue resets and the phone will wake reporting over 30% power and more. It seems to reset some flag that tells the phone that the battery is dead. It has happened too many times to be a coincidence. iOS is not registering the correct battery level, mistakenly thinks it does not have enough power and will therefore not power up. Once connected to a power source for a few seconds, the phone will reboot normally and show power levels correctly.. This has occurred through all iterations of iOS 10 including the latest betas.


Problem solved, I have my battery changed and the issue hasnt occurred (well for 2 weeks so far). I first tried this calibration mentioned above, but it didnt help. Then I restored the iphone completely, didnt help either. I didnt expect the issue to be in battery as it has been just 2 years since I bought the device new and previously I had iphone4 for 4 years and there was no issue with battery but apparently it is not same, battery itself seemed to be the issue.

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