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I bought a powered USB hub from Maplin, just something cheap, but the guy assured me that it would work fine.

Anyway, plugging it into the raspberry pi (with the microusb power lead out of the rPi) powers on the rPi.

Will this cause any damage to the rPi? It seems to work fine with it plugged in this way (I believe - but don't quote me - that I have one of the newer rPi's, something about something in the USB has been replace with something else, I don't know).

Can you overpower the rPi? I've read loads about underpowering the pi, but nothing about overpowering it. e.g. If I use a 5.2v 2amp power lead? Or perhaps two power inputs (one from the hub via the USB and one into the microusb port.)

If its plugged into the hub twice it seems to work fine. But if its plugged into the hub via the USB port and into the mains via the microusb port then it seems to be jerky and unresponsive.

Thanks!

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First of all, you should check which hardware revision do you have. This question may help you if you don't know how.

If you have board revision 2.0, then you don't have polyfuses on USB ports. This means it is safe to power your RPI from USB powered hub, as long as you don't provide more than 2.5A of power. Now to do this, you would have to do some shortcut on the board or something like this and of course HUB' power adapter would have to be able to provide so much current. So it's better to use HUBs that can't.

If you have board revision before 2.0. It may or may not be safe to do this. Most of the boards before rev 2.0 do have polyfuses on USB ports and then you can't power your RPi from USB ports as they will quickly "blow" and cut your power off. It's not permanent, after couple seconds, when they cool, they will be working almost the same as before blowing.

So if your RPi seems to be working OK being powered from USB, it seems that you don't have polyfuses and it should be safe to continue using this method.

You can't overpower your RPi by using power adapter that can provide too much current. The 2amps you see on the adapter is maximum current it can provide. But in order to do this, something would have to consume that much power. And RPi won't do this unless there is some shortcut in the circuit. And even then it won't do this when powered from microUSB because there is some protection circuit there (1.1A polyfuse and TVS diode).

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  • Brilliant, a clear and concise answer. Many thanks! :)
    – Thomas Clayson
    Commented Oct 3, 2012 at 10:03
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    There is a polyfuse to protect overcurrent near the micro usb. This polyfuse is still present on the rev2 boards, but won't be protecting anything if the power is coming from the other usb ports. I wouldn't worry too much unless you are experimenting with the GPIO, etc. Even then if you kill the Pi it's not such a big deal now as it was when there was a long waiting time for them.
    – John La Rooy
    Commented Oct 4, 2012 at 2:54
  • I think the original question was about supplying power to the microUSB power input from a USB hub, rather than directly from the mains, and not about supplying power to the RPi via the USB peripheral slots.
    – spookylukey
    Commented Nov 19, 2012 at 17:48
  • @spookylukey: I don't think so. And Thomas, who asked the question, seems to be happy with the answer. But anyway, of course it's possible to power RaspberryPi from USB hub which it self is connected to it. It's the setup I'm currently using.
    – Krzysztof Adamski
    Commented Nov 19, 2012 at 19:16

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