The RAVPower Xtreme 26800mAh Portable Charger with Type C Port + 30W Type-C AC Charger has both a USB Power Delivery based portable battery as well as a USB Power Delivery charger to supply power to other USB Type-C based phones, tablets, and small form factor notebooks. We'll use the AC charger portion to charge the USB Power Delivery enabled LG G6 phone over USB Type-C.
Looking at the USB Power Delivery negotiations between the RAVPower Xtreme Wall Charger and the LG G6, the charger declares its source capabilities of 15 watts (5 volts @ 3 amps), 27 watts (9 volts @ 3 amps), and 45 watts (15 volts @ 3 amps). This is a problem since this charger is only rated to up to 30 watts and from testing that Benson Leung has done, is potentially dangerous since the AC adapter eventually overheats.
The LG G6 then requests to pull 27 watts (9 volts @ 3 amps) which is accepted by the charger.
The RAVPower Xtreme Wall Charger later advertises not only the 15 watts (5 volts @ 3 amps), 27 watts (9 volts @ 3 amps), and 45 watts (15 volts @ 3 amps) it initially declared but also an additional power profile of 45 watts (20 volts @ 2.25 amps). The LG G6 still continues to request 27 watts (9 volts @ 3 amps) which the charger complies.
The LG G6 can be seen to start pulling around 0.5 amps at 9 volts but the charging current drops down before increasing to charge at about 18 watts (9 volts @ 1.9 amps).
Be careful though about using this charger with any notebook that tries to draw more than 30 watts. As can be seen from the above power delivery protocol negotiations, the RAVPower Xtreme Wall Charger actually advertises it can supply 45 watts rather than the 30 watts that it's rated for. From testing that Benson Leung has done, the AC adapter eventually overheats when providing 45 watts which creates a potentially hazardous situation.