Powering Raspberry Pi B+ from multiple ports

Question

I am making a Cloud storage with own cloud right now. But when I was connecting everything to each other I found out that the Raspberry Pi is being powered from more ports than 1. I'll explain my setup here because it's very confusing.

I have a USB 3.0 Hub with an external power supply 5V. The USB hub is connected to a USB port from the Raspberry Pi. But in the USB hub I've connected another USB cable to power the Raspberry Pi in the original power port, the small USB one. I've also connected a HDD and a mouse to the HUB and in the Raspberry Pi USB's there are: Keyboard and the hub.

But here is the weird thing I want to make sure is safe and isn't hurting my RPI.

When I power on the PSU to my USB hub the RPI will power on because the HUB is powering the RPI. But when I disconnect the cable from hub to RPI the RPI stays on and I think that's because the HUB is connected to the RPI with the big USB cable.... Is this weird, yes it is. But basically the RPI is being powered from 2 ports: the original small one the mini USB, and from the cable from the USB HUB. Is this damaging the RPI in any way?

If you do not understand anything just ask me and I'll try to explain it better.

Answer 1

But here is the weird thing i want to make sure is safe and isnt hurting my RPI.

Generally it isn't safe to power from multiple sources, but in this case there is really only one 5V DC supply, the hub.

Ideally the microUSB power jack should be used since it provides the best protection against over-current/over-voltage; the circuit there includes a polyfuse and TVS diode (or something similar) so it may survive such incidents. This is not the case if you are "back powering" via the regular USB ports or 5V pins.

However, that your hub powers over the data cable is, I think, not a good sign, since this implies when connected to a normal computer there could be a problem. It should not do that.