Battery gets hot on iPhone SE After I updated my iPhone SE to iOS 10.2.1, the battery become really hot without changing it's life.

Are there some new functions that stress the battery? What should I disable to keep the battery from getting hot?
It could be somekind of software or hardware fault, if it's a software fault try this:

Reboot the phone, hold the home button and the power button at the same time till you see an apple logo

If it doesn't help, try to update the phone to iOS 10.3.1

If none of this help, try to bring your phone to the local Apple Store, or the place you bought it.