Have you flashed a new ROM? Or is your battery life bad?
You would like to fix it? Then download and run this app!

The only things you will need are Android 2.3+ and root rights.

This app does it by removing the BATTERYSTATS.BIN file. The OS then generates a new and clean BATTERYSTATS.BIN so any invalid information (from the previous ROM) is removed. It is suggested but not needed to let the phone fully discharge calibrate and the let your phone charge to 100% without interruption.

Steps to do a good battery calibration:

1) Plug in your phone to the charger.
2) Charge your phone up to 100 percent.
3) Click on the 'Calibrate your Battery' button.
4) Unplug your phone.