Check the battery usage under
App/Device full usage since last charge.
For more battery saving tips, see
How do I save battery power?.
For phones with Android 5 Lollipop or higher, Device Protection may be enabled, which means that after the factory reset, you'll need to sign in using the same Google Account that was logged into your phone. If you forgot your Google Account password, use your computer web browser and go to www.google.com/accounts/recovery to reset your password first.
To perform a factory reset:
If you have a security lock on the device, you'll need to enter your security information as well.
The phone will reboot and reset.