weird Jailbroken iPhone 5 glitch

I jailbroke my iPhone on the first day that it came out and added a few tweaks, the normal stuff nothing crazy. The last two nights around 20% battery the phone just shut down and was unresponsive for about half an hour. last night it showed the dead battery when I tried to turn it back on even though it was at 20%, I tried again some time later and it turned on. I couldn't turn on or reboot tonight and it showed no dead battery on screen... any ideas, comments suggestions? happening to anyone else?