Calibrating your Android Battery won’t make it last longer, but report its status more accurately:
Whenever you flash a new/custom ROM or you feel your battery is mis-calibrated, follow the steps:
Install this app from the Android Market: Battery Calibration~ GOOGLE PLAY
Completely discharge your phone battery; either let the phone shut down on its own, or multi-task/play music/videos, etc to make the process faster. After the phone is down, try to start it up after 5 minutes. If it starts up, drain again, if it doesn’t then it is completely discharged.
Charge your phone using a wall outlet, USB charging is not recommended. And do not switch the phone on, just let it charge, it will display a battery indicator as soon as you start charging. Let it charge for 8 hours continuous.
After 8 hours, switch it one, while still plugged in(charging). Stop charging and remove the connecting wire. Use the phone until battery drops to around 98-97%. Plug it in again, let it charge while being switched on. (Till 100%)
Open up the battery calibration, remove the phone from the wall outlet(stop charging) and hit the big Battery Calibration button immediately.
Your battery is now calibrated.