Testing a 4TB WD Elements USB Portable on a Raspberry Pi 3 draws 420mA
(photo in the link below)
But, it’s extremely important to have a good quality power supply. (best to buy official RPi branded ones)
So, if you have a good quality power supply and don’t exceed 3A (which 2 WD Passports wont) you’ll be fine.
I have a Raspberry Pi 4 (4GB) but, am using the 4x USB Inputs for LED Lights which draw a lot of amps (more than a WD HDD) … but did the calculations with my tester to make sure the total amps did not exceed 3A and everything works fine.
