Battery Low [Q] Nexus 7 Battery issues

I recently flashed two different ROM's on my N7 (cm11 offical nightlies and Codename KITKAT) and both of them cause my N7 to die at like 40 percent battery or so. When I charge my device after it goes dead it takes about 1-2 hours to get any sort of response but when it comes on it has 50+ battery. I need suggestions, should I flash a JB rom? Get a new battery? Re-calibrate my battery?