I can charge the Gemibook by the USB C port using a charger. Using a powerbank, 20 w output, i can’t. Specifications for this port, please ?
20 watts is not enough. The power banks can usually not provide 12V or only 12V 1.5 A. The power bank should deliver at least 45 watts, better 65 watts. So also deliver the USB-PD profiles with 12V 3A, 15V 3A and 20V with at least 2.25A.
Important: The USB-C cable must also support 65 watts. Otherwise it won’t work!
It should work with this one.