GTrusted

Alternative chargers like the 27W based Softbank SELECTION USB PD USB Type-C Rapid Charging AC Adapter (2018) can be used to charge a variety of phones including the Google Pixel 3 XL using USB Power Delivery technology. 

Upon connecting the Google Pixel 3 XL to the Softbank SELECTION USB PD USB Type-C Rapid Charging AC Adapter (2018) over USB Type-C, we could see at initial voltage of about 5 volts almost no current was pulled by the phone. It took about 1 second for the voltage to rise up to a 8.8 volts rail where the phone finally pulled current which quickly ramped up to enable charging at around 20.2 watts (8.8 volts @ 2.3 amps). As the current kept on changing from 2.1-2.3 amps, the phone was charging in between 18.5-20.2 watts (8.8 volts @ 2.1-2.3 amps) with the Softbank charger. Click here to download the trace captured by the GRL-A1 power analyzer to see more details.

The Softbank charger managed to deliver above 18W to the Google Pixel 3 XL which is slightly more power than the phone can get from its own shipped 18W charger as observed here.

Download the A1 software from Granite River Labs here to view the trace.