The Battery calibration needs to be done after flashing a new ROM, but you can calibrate any time you think your battery is mis-calibrated. This program does it by removing the battery stats.bin system file. The OS generates a new clean battery stats file soon, thus any fake information from the previous ROM is removed.
It's suggested, but not necessary, to let the phone fully discharge after calibration, then charged to 100% without break.
NeMa developed a Battery Calibration tool for Android. It will help to delete existing battery stats.bin system file. Personally, I do not calibrate battery after flashing new Android ROM but some said it really help to improve their phone battery life. No harm to try it right? It might help to improve yours too.
You can do the same thing if you have HTC HD2 ClockwordMod Recovery installed. Just go to ‘advanced’ and then ‘Wipe Battery Stats’. It should do the same trick. Just make sure that your phone battery life is 100% before wiping the battery stats.
you can download Battery Calibration for Android here.
Good Luck
:)