You dont need an app for battery calibration. Charge your phone to 100% like over night 100%, then reboot into recovery, go to advanced, and go to "Wipe battery stats" confirm it and reboot and then unplug the phone and dont plug the phone back in until the battery completely dies. Dies as in completely dead. Then After it dies and the phone shuts off plug it in, and dont turn it on or anything and let it charge to 100%. Again overnight 100%. And your battery should last ALOT longer. Its not so much the battery its that stats folder that gives a false reading from flashing. On stock 2.2 my battery would last like 4-5 hours. Now on CM7 after doing this, my battery will last up to 8-10. CM7 in general actually gives you a better battery life but that battery stats file will screw you up. So wipe it.