The Xiaomi Mi 8 is among the latest phones to adopt Qualcomm Quick Charge 4+ technology to offer USB Power Delivery 3.0, PPS (Programmable Power Supply), and Qualcomm Quick Charge 3.0 based charging over USB Type-C. Despite this, the Mi 8 still ships with the Qualcomm Quick Charge 3.0 based Xiaomi 18W QC 3.0 Charger which we used to fill up the phone's battery in about 110 minutes.
Once we connected the Xiaomi QC charger to the phone with its battery fully discharged, we could see charging initially went up to around 16.7 watts (6.2 volts @ 2.7 amps) which later dropped slightly to about 15.4 watts. The current pulled continued to decrease along a 5 volts rail towards the end of charging to eventually settle close to zero when the battery was almost full. To see more details on the entire charging cycle, click here to download the trace captured by the GRL-A1 power analyzer.
If given a QC4+ based charger instead of just a QC3 charger, the Mi 8 could have taken advantage of the more advanced QC4+ charging to charge even faster.