If you own an iPhone 6s or 6s Plus and the battery percentage doesn't update while charging or while in use, there's no need to worry because it's a known problem which Apple is already trying to fix.
It seems that many users have reported the problem lately, and according to Apple it is only a matter of time zone and that is preparing a patch that will correct the problem in its last two iPhone.
According to Apple, the problem occurs when you set the time zone manually or as you change zones when traveling from one country to another. If you let the device automatically change the time and date the problem does not exist.
How to fix it
Go to Settings - General - Date & Time and select the option that says Auto Setup
According to the company, this setting fixes the problem in most cases. Otherwise, wait until the patch is released.
