By supporting USB Power Delivery, the Apple 10.5-inch iPad Pro can be charged using other compatible non-Apple chargers that support USB Power Delivery technology other than its own supplied 12W USB power adapter. Here we try charging the 10.5-inch iPad Pro with the USB Power Delivery based dodocool 30W USB Type-C PD Charger connected with the Apple USB-C to Lightning Cable.
Using Granite River Labs GRL-USB-PD-A1 test software, we can see that the dodocool 30W USB Type-C PD Charger displays 15 watts (5 volts @ 3 amps), 27 watts (9 volts @ 3 amps), and 30 watts (15 volts @ 2 amps) USB Power Delivery profiles after a hard reset.
Starting with a battery charge level of 1%, the 10.5-inch iPad Pro starts to request 15 watts (5 volts @ 3 amps) and gets accepted by the dodocool charger.
After responding to a Discover Identity request by the dodocool charger, we can see the 10.5-inch iPad Pro follows up to request max 30 watts (15 volts @ 2 amps) which the charger also complies.
Upon plugin from a 1% dead battery state, the 10.5-inch iPad Pro initially pulls a quick current spike of about 2.7 amps at 5 volts when reaching 10 seconds.
After the iPad starts booting up, USB Power Delivery negotiation occurs, resulting in charging at around 10 watts (5 volts @ 2 amps).
As Vendor Defined Messages are exchanged, after few seconds, the iPad makes the 30 watts (15 volts @ 2 amps) request during which the voltage quickly rises to 15 volts with current at around 2 amps. This results in the iPad to eventually achieve charging at about 30 watts (15 volts @ 2 amps) with the dodocool 30W USB Type-C PD Charger.
The 10.5-inch iPad Pro is able to use around 30 watts (15 volts @ 2 amps) to get the fastest charging from USB Power Delivery chargers like the dodocool 30W USB Type-C PD Charger which is more that the 12 watts that you get when charging with its own Apple 12W USB Power Adapter.