This does not need to be activated and is not activated as a selection function. Must be the original data cable and charger to support fast charging.
The Mi 8 supports the QC4.0 fast charge protocol, and the package is standard with 18W QC3.0 fast charge
In the charging time, the overall time of the Mi 8 fast charging QC4.0 charger and QC3.0 charger is basically the same, which takes about 1 hour and 56 minutes; When charging with the QC4.0 charger, the USB PD3.0 voltage will be preferred for charging, and the QC3.0 mode will not be selected