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I have a Raspberry Pi 2 Model B and a 2,5 inch HDD that I want to connect via USB. The HDD also powers itself over USB. Does the Raspberry Pi 2 Model B provide enough power? Can I safely run the HDD without breaking any of the two devices?

Socrates
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2 Answers2

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You SHOULD be able to power a HDD from the Pi2 (provided you use an adequate power supply AND set max_usb_current=1). The max USB current is 600/1200mA depending on max_usb_current

Unfortunately adequate power supplies are not common. See the comments in https://raspberrypi.stackexchange.com/a/47642/8697 Even though this is Pi3 the issues are the same and the power circuitry very similar.

Community
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Milliways
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  • Any quick hint where to set (and as well check) max_usb_current to 1? How much mA does Pi 2 Model B provide without this setting on USB? – Socrates May 28 '16 at 02:32
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    @Socrates add max_usb_current=1 to your config.txt file. you can access this file by connecting your pi's sd card into a laptop. also it will raise the current limit from the usual 500ma to approximately 1200ma – Mohammad Ali May 28 '16 at 04:00
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No, it does not! You can harm your RPi board seriously if you will power your HDD from it, even attaching a 5Amp PSU : the RPi board is simply not designed for such currents. Use a USB hub with external PSU and it will be OK, or - if you're about to use just a one more PSU for your HDD, make sure you've connected it's GND(Ground) with the one supplied to RPi

Alexey Vesnin
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  • Some 2,5" HDD for USB2.0 do run with a single connector and thus presumably with <= 500 mA which would most likely ok for the Pi if the power supply could handle it. – Ghanima May 27 '16 at 15:40
  • What is the maximum current for USB devices on Raspberry Pi 2 Model B? – Socrates May 27 '16 at 16:11
  • @Ghanima I don't doubt a PSU - it can supply even a 10 amps... The problem lays on PCB's current ratings: take a look here and keep in mind, that NIC+4USB is a single USB outlet – Alexey Vesnin May 27 '16 at 16:15
  • @Socrates I do recommend you not to exceed 200 miliAmps per device. On my RPi2 250+ mA did caused problems: tested it on hi-power USB WiFi adapters – Alexey Vesnin May 27 '16 at 16:17
  • other answers claim otherwise e.g. http://raspberrypi.stackexchange.com/q/27708/19949 – Ghanima May 27 '16 at 16:28
  • @Ghanima tried, not working: not in Raspbian, not on latest Git kernel – Alexey Vesnin May 27 '16 at 20:27
  • What rubbish! Why do you think the Pi2 has a 2A polyfuse (and the Pi3 2.5A) if the board was not designed for it. – Milliways May 28 '16 at 00:17
  • @Milliways actually - it can be fused even for 3A per USB output - a form-factor and a standartds does not prohibit it... But it is not - I agree, I learned this lesson in a hard way by attaching a various hi-power USB WiFi dongles that worked just perfectly on a regular PC. I actually don't understand why the RPi makers either make a proper soldering or make just one USB outlet... – Alexey Vesnin May 28 '16 at 00:23