Solved ✅

UPDATE 03/02/17:

Since Apple performed the repair we have had no further issues.

However, since talking to an Apple technician regarding the case, I understand that Apple updated the repair procedure soon after starting the battery replacement program.

If you’ve had your battery replaced but are still having issues, you may need to do a DFU restore to recalibrate the battery with iOS.

Two things of note;

1) Ensure you have a backup before attempting the procedure.

2) You need a computer with iTunes for DFU restore.

The procedure is detailed here.

It has also been suggested that a DFU restore may help users of older devices, such as the iPhone 6, with battery issues introduced that have become prominent since iOS10.

UPDATE 01/12/16:

It’s now possible to check your serial number to see if your device is one of those affected.

Simply head over to the Apple support page to find out.

UPDATE 21/11/16:
Apple has acknowledged a hardware fault with a limited number of iPhone 6S devices, specifically those manufactured between September and October 2015.

A free battery replacement program for iPhone 6S devices has been created for those customers affected by the ‘unexpected shutdown’ fault.

For details of the program, and to arrange your repair, please go to the following Apple support page.

Over the past two weeks i’ve heard from lots of people who are experiencing battery issues with their iPhone 6S.

The charge (pun intended) is that since Apple released iOS 10.1, the battery percentage indicator is drastically out of sync with the actual amount of charge remaining.

As a result, affected devices have been turning off unexpectedly.

Telling tales; the iOS10 battery percentage indicator.

After hearing from family members and a couple of colleagues about the problem, I realised they were all using iPhone 6S.

I turned to twitter to try and verify that the problem was specific to iPhone 6S, and concluded that iPhone 6 and iPhone 7 are unaffected (and that iPhone 7 users seem to report real improvements in battery life!).

Alas, the iPhone 6S seems to have a problem with iOS 10.1;

With the issue comfortably confirmed, and having it in our own household, I took the opportunity of trying various solutions. In short;

  • Factory resetting & restoring using iTunes backup.
  • DFU reinstall of iOS & restoring from iTunes backup.
  • DFU mode update from 10.1 to 10.1.1 (which was not previously released)

The last update was particularly useful, as one symptom of the unexpected power losses was that the phone ended up being unable to boot beyond the Apple logo. Only ‘updating’ the phone to the newer release in DFU mode managed to snap it out of the boot loop.

After both the original factory reset, and the DFU update to 10.1.1, the phone did behave as expected, but reverted to the unexpected shutdown behavior after just a couple of days.

I engaged with Apple Support, first via twitter, and then via web chat. On both occasions the agent ran remote diagnostics and verified that the battery (hardware wise) was OK.

Because I had already tried a factory reset and the DFU restore, their ultimate recommendation was to DFU reset the phone again and notrestore it from backup, effectively setting it up as a new iPhone.

I wasn't convinced that this would actually resolve the issue, because the agent had already hinted that this was a wider problem;

Apple Support chat transcript

I also didn’t want to risk losing any data or particularly want to reinstall and reconfigure very app, setting and preference on the iPhone.

I then questioned the agent about the likelihood of a reset without a restore actually fixing the issue, and received a fantastically honest response;

Apple Support chat transcript

To say this kind of response was refreshing is an understatement, especially when like me, you’re used to completely robotic responses from other companies on web chat support. Bravo Apple.

I persisted with the view that a full reset would prove fruitless (pun intended again) as the issue is likely related to iOS 10.1.x rather than within the user data itself.

Based on the advice above, and my tendency to be stubborn and unbeaten, I decided not to proceed with the reset and looked into the other options.

Well aware that iOS 10.2 is currently available via public beta, it seemed unlikely to me that Apple would plan to release the update without fixing this issue, so back to twitter I went, and found this;

Chip is a tech guy who works for Microsoft’s bing search engine, I chanced that he wouldn’t mind helping me out, so asked the question;

Chip replied within 2 minutes and confirmed my suspicions;

For Chip at least, iOS 10.2 has kept his battery working reliably for at least six days, much longer than i’d previously achieved with my resets/restores.

As a side note, what a completely amazing community of helpful strangers twitter can be, thanks again Chip!

As a result of this conversation, I installed the public beta of iOS 10.2 today (and am open to the possibility of other bugs arising) on our affected iPhone 6S.

Hopefully this will resolve the battery percentage issue though, and if it does I will be feeding back to Apple (as is the point of the public beta) so that iOS 10.2 can be released to production ASAP and the battery issue can be resolved for everyone.

At the time of writing we’ve had no further problems, but I will update this line in a few days to confirm either way.

What if I have the battery issue and want to try the beta myself?

Firstly, think long and hard before installing beta software on your primary device. Beta software is unfinished to some extent and has been subjected to limited testing, it will likely solve some issues whilst introducing new ones.

If you’re not 100% prepared to encounter issues, don’t install beta software.

If you still want to try, you can enrol your device at

iMore has written an excellent article detailing how to enroll your device, which I highly recommend you reading in full.

In particular, it tells you in detail how to archive a device backup before proceeding, which I would highly recommend you do!

Good luck!