Q: battery percentage does’ t update and reset not help.(iphone 6s with ios 9.2.1)

Mehdi,

Try the steps in: If your iPhone 6s or iPhone 6s Plus battery percentage doesn't update - Apple Support

mehdi keshtkar,

When you state that you reset the iPhone, Did you select these options?

Back up your IPhone to Icloud or ITunes then Select Settings>General>Reset>Erase All Content And Settings.

Then setup the IPhone as "NEW"

Step 1 Tap "Settings" on the Home screen

Step 2 Touch "General" and tap "Usage" to open the Usage screen.

Step 3 Scroll down the screen and tap the "Battery Percentage" switch to change it from "Off" to "On." The percentage of the remaining battery power will appear next to the battery icon.

Setting up the iPhone as NEW rules out any contaminated data that may cause this.

If your issue is resolved then it may appear that something in your backup was causing the issue.

I hope this helps