I had a set up with a powered external hard drive, and a wifi dongle. It worked fine.

One day, the wifi dongle decided to cut out—it would restart every time I inserted it into the Pi, and after the restart, the Pi would not recognise it. I since replaced this with another one that works.

I wanted to replace the powered external hard drive with a portable one, that does not use an external power supply. I have three of these, one of which can use an extra USB port for extra power. All three of these restart the Pi, even if the one requiring extra power is powered from a port separate from the Pi. After the restart, the Pi will not recognise any of the devices, nor will it recognise the wifi (working dongle).

One hard drive has a power light that is easy to see, and when it is restarted with the Pi, the light oscillates between off and on. It will do this for around 30 seconds, after which, it remains off.

I read that the Pi can have issues providing the initial power to such devices, and that it can be fixed by adding a capacitor. However, I also read that the devices should work if started up with the Pi, which they don't. Is the issue likely to be that my Pi has somehow become faulty, and won't give enough power, or is it worth adding the capacitor (or another solution)?

Thanks for reading!

  • 1
    you cannot replace a powered HDD with an arbitrary portable one exactly because of the issues you have just listed. try to find the portable with a very low consumption current, something in the 0.5-0.55A range.
    – lenik
    May 28, 2014 at 17:51
  • What about the one that used external power from another USB port?
    – Jacob
    May 28, 2014 at 18:46
  • Most portable HDD require almost the max power the USB can give it to spin up. Technically on newer PCB this shouldn't be a problem but a POWERED USB HUB is recommended, never the less.
    – Piotr Kula
    May 28, 2014 at 21:03
  • if you want I had just written a blogpost for RaspberryPi stack Exchange which addresses almost the same issue and to overcome it. PiAdHoc
    – Shan-Desai
    Jul 26, 2016 at 12:33

1 Answer 1


I had similar issue. However, i used a 2 A charger to power my pi and then connected my hard disk (WD 1TB) to it. Everything was fixed then. I was able to use my hard disk and even use wifi dongle in parallel without any issues. Most of the USB powered external HDD's require atleast 500 mA of current and if your charger doesn't output current of more than 1 A, then it would be hard for Pi to share the current with the hard disk and so your pi would turn on and off at times. Hope it helps.

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