How to Fix an iPhone 6S/6S Plus that Suddenly Dies

Your battery indicator shows a cool 50 percent and then suddenly, it's dead.

With older iPhones like iPhone 6s or 6s Plus, it's a common problem. The years of use throw off the calibration while the battery's capacity dwindles. The issue, according to Apple, is that the battery percentage just isn't updating. As your battery drains, the battery indicator does not reflect the depletion. 

Restarting the phone seems to force the indicator to change, but stays frozen once again. Apple doesn't yet have an answer for exactly why this is happening, but we expect the bug to be fixed in the iOS 9.3 update. In the meantime, the company created a support page with a temporary fix.

Fix an iPhone 6S or 6S Plus battery indicator that won't update.

Restart your phone. Then go to Settings > General > Date & Time and make sure that Set automatically is turned on.