Default Problem battery and reboot android

Hello,
I have a fake iphone 5s, and i have problem on my battery, i have try calibarte it but its worse now. Now my phone power off around 30-40% and after its wont charge (after many hours i have the icon of charging) and it's reboot with no reason if it have less battery. How to fix this ?
Thanks
I'm French, sorry for my bad English