Gnex automatically turn off when unplugged with battery remaining

This issue is somehow weird. When I do something with my phone for a while, my phone just turns off suddenly. It doesn't really power down, it is just off. Then I remove the battery and put it back, turn on the phone. Sometimes it boots successfully, sometimes it doesn't. The phone is bootable and works reliably when it is plugged in. :confused: I've tried flashing some ROMs but the issue still occurs. I don't know whether there is something wrong with battery or mainboard. I accidentally increased voltage for my Gnex via Trickster mod some days ago. I think this is the reason causing this problem.

Could you please give me some advice? Thanks.

Zenfone 2 ZE551ML switches off suddenly despite 20 percent battery remaining

My Zenfone 2 (Z551ML- 4GB RAM) turns off at 20% battery life! I tried turning it on but no luck. I need to connect the charger before the phone will boot up. But when I turn on the phone with charger connected the battery shows as 20%. I have tried to calibrate the battery but still no luck! Any suggestion regarding this will be very helpful... Thanks a lot in advance...