Fake, it can't handle the currents when it's below a certain % (somewhere around 30-40% depending on the temperature) and when you try to open a camera or something else resource-heavy, the phone restarts.
Very inconsistent as well, the phone can shut down at 15% or at 1%, you never know. Meanwhile, if it shuts down at 15% for example and you turn the phone back on in TWRP, it shows 15% again and lasts several hours there, but not in the OS. I guess due to low consumption? But on the other hand, I tried it with always-on screen in TWRP to totally drain it off and it literally lasted hours and hours like that at 15%. ¯\_(ツ)_/¯
The phone might say 20% and in 5 minutes drop to 1%.
I've had it for several months and I've done everything: endless power cycles, I've reset it, I've cleared the battery cache with root, I've changed ROMs. And of course, the overall battery life is worse than the previous one, which was 4 years old.
I would have been better off paying double and getting an official one from abroad.