Screen flicker and battery drain

Hi,

I have a problem with my phone, whenever I install a stock rom Jb example (GalactusRom or other) and I started playing without plugging in the power, the screen starts to flicker and after the phone turns off and restarts the battery when it rises from 70% to 15%

What do you think? and how to resolve this problem ?

Sorry for my bad english.

Thanks !