Q: Will the PowerPack 10K charge my Pixel 3? If so, what USB Cable works with Pixel 3 charging?
A: Yes, it will charge the Pixel 3 at normal speed (no fast charging), which we have tested and verified. You will need a USB-C to USB-A cable to hook up the two devices. The USB-C tip goes into the Pixel 3 as usual; the USB-A tip (that is, the large rectangular USB connector) gets inserted into the USB port on the battery pack.
A side note: This battery pack follows Qualcomm's Quick Charge approach to fast charging, while the Pixel 3 adopts USB Power Deliver as the fast-charging method. So, the battery pack and the phone are not compatible with one another on fast charging. However, they will fall back to 5V/1.5A charging, which maxes out the charging power at 7.5 watts. The Pixel 3 won't register it as "Charging rapidly." You will see "Charging" on the lock screen.