Will a single USB 3.0 port have sufficient power (via a non-powered hub) to run two external 2.5" platter hard drives (the type that don't require an AC power adapter)?
The hub is a Sabrent 4-Port USB 3.0 Hub with Individual Power Switches and LEDs (HB-UM43).
The hard drives are Western Digital "My Passport" 1TB USB 3.0 drives (several years old), product # WDBBEP0010BBK-01. Plugging either drive into a USB 3.0 port, does not show any power consumption via Win7's Device Manager (strange). Plugging a drive into a USB 2.0 port shows 500ma. The labels on the hard drives do not reveal power consumption information.
Best Answer
If you had some ultra low power mechanical drives (I'm not sure they exist), you could, but not two of your drives or any I'm aware of.
The hub, itself, uses some power, then the drives would have to share what's left from the 900 ma connection to the laptop. At 500 ma for each drive, you would exceed what's available.
This would not work even with a special laptop charging port designed to deliver high charging current to an attached device. USB power is in "unit loads" (each unit load for USB 3.0 is 150 ma). USB devices have to negotiate for power beyond the first unit load. Hubs make a standard USB connection, which carries a maximum of 6 unit loads (900 ma) for USB 3.0 drawn from the laptop's port. USB 2.0 has a unit load of 100 ma, and a maximum of five, for a 500 ma limit.
With a powered hub, you could connect both of your drives. The combined data transfer rate for two USB 3.0 mechanical hard drives should still be well within the bandwidth of the hub's USB 3.0 connection.