Hacking the power: using USB Y cables

Hi All,
As someone who knows nothing about electronics I really welcomed the guys at Dexter publishing http://www.dexterindustries.com/BrickPi/getting-started/power-up-the-brickpi/ .

One option is not described there though: would there be any advantage in using USB y cables like http://www.amazon.co.uk/StarTech-feet-Cable-External-Drive/dp/B0047AALW6/ref=sr_1_2?ie=UTF8&qid=1383646542&sr=8-2&keywords=dual+usb+micro , providing the Raspberry Pi with double the power?

E.g. can double the USB power - without the battery pack - provide enough power for the motors?

Or: in the scenario in which we used both the battery pack and USB power, would a Y USB cable make the battery pack last even longer?



A USB Y will put the two USB power supplies in parallel. Unless you’re trying to use under-rated USB power supplies, this will have no benefits.

This will increase the current available, but it’s still 5V, and still through the RPi uUSB power jack. This will not allow for running motors.

When using both USB and a battery pack, this will only increase the battery back’s run-time if the USB power supply can’t provide adequate power (if you’re using an under-rated power supply).