I've read that one of the dangers of Y USB cords (if the two Y ends are attached to different devices) is that electricity could go the wrong way, frying a device.
So, in my case, I have the following issue. My Raspberry Pi doesn't have enough power to run itself and power an external hard drive, so what I was thinking of doing, is connect the Red and Black wires exclusively to the charger end, and the white and green wires exclusively to the Raspberry end.
Would this be safe? Do the Data wires and Power wires cross anywhere?