The Dell XPS 15 9575 (2-in-1) supports Thunderbolt 3 to rapidly charge using a USB Power Delivery 3.0 based charger like the Dell 65W PD Power Bank. When connected both the Dell PC and power bank over the USB Type-C interface, we observed how the PC charged through USB Power Delivery on 1% full battery.
As the voltage started off at 20 volts upon plugin, current was initially pulled up to about 3.4 amps resulting in around 68 watts of charging. The current then quickly formed a 2.4-3.4 amps band while at 20 volts allowing 48-68 watts power to be drawn by the PC. Click here to download the trace captured by the GRL-A1 power analyzer to see more details.
Other than fixed power levels, the Dell 65W PD Power Bank can also use variable power up to 68.25 watts (21 volts @ 3.25 amps) as advertised to successfully charge the Dell XPS 15 9575 (2-in-1) even though the PC may charge even faster with the Dell 130W USB Type-C AC Adapter that ships with the PC.