You can reset your battery calibration inside of your recovery. Usually, you get messed up battery #s after a new ROM install, so I wouldn't worry just yet. I'd run your phone until it shuts itself off due to low battery. I've had my battery report 1% left and then run for another hour, after a fresh ROM install.
If this just started with in the installation of a new rom, I would immediately reflash the rom. Anytime I have an issue with a new rom or new kernel and the issue is not widely reported by others, I reflash. If the problem persists, I go to a different rom. Before reflashing you might want to redownload the rom and be sure to check the md5 to assure you've gotten a good download.
Baton Rouge, LA