I have absolutely the same problem! Got my cube i7, all the time shows 4% and doesn’t charge.
Geekbuying wrote me to send it back to fix. I can’t fix it by myself but I think it is a bios problem, becouse in diagnosis it shows that there is no driver for charging (in bios).
After some search in forums, i am thinking that it can be drivers or bios update problem. I bougth tablet from GearBest, and since day one i am trying to return it but seems that they delaying return on purpose.. So im kinda desperate at this point.
Had the same problem when I ordered mine.
The battery wasn’t connected to the device.
Solution:
Disassemble the back cover and connect the battery to the device.