The Google Pixel 2 18W USB-C Power Adapter that came with the Google Pixel 2 XL can deliver nearly up to 18W charging to the phone using USB Power Delivery 2.0 which we observed in this review. Here we can also see how well the phone works with the Google 45W USB-C Power Adapter which clocked in about 140 minutes for entire USB Power Delivery charging.
When connected over USB Type-C, the Google Pixel 2 XL immediately pulled current while on a dead battery as the voltage initially started up at 5 volts. In less than a minute after plugin, the voltage has risen to a 9 volts rail where the phone was pulling close to 1.5 amps to charge to around 13.6 watts (9.12 volts @ 1.49 amps) with the Google 45W USB-C Power Adapter. The current then dropped quickly after the first 10 minutes of charging to stay along a 0.7 amps rail, only allowing charging at 6.37 watts (9.1 volts @ 0.7 amps). Upon reaching 44 minutes, charging then reset which caused the phone to trickle charge which also briefly pulled up to about 2 amps @9 volts. The current later settled out to about 0.8 amps in the next 38 minutes of charging which then progressively ramped down to below .2 amps followed by residual charging as the battery filled up. Click here to download the trace captured by the GRL-A1 power analyzer to see more details.
The Google Pixel 2 XL was switched off during the initial stage of charging when it started drawing up to 13.6 watts. When the battery has charged for a bit after the first 10 minutes and the phone was switched on, it pulled lower current below 1 amps at around 9.1 volts. While the phone was inactive, it briefly pulled higher current to draw power close to 18 watts (9 volts @ 2 amps) but when actively used, it pulled lower current to charge at only about 7.3 watts (9.1 volts @ 0.8 amps).
The Google Pixel 2 XL supports USB Power Delivery well with the Google 45W USB-C Power Adapter since the phone also charged similarly with its own shipped 18W charger even though 18W of charging only happened for a brief amount of time.