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I'm planning to attach multiple portable 2.5" hard drives to a Raspberry Pi 2 Model B. These hard drives are powered each by a single USB cable, which is a problem, because the Pi does not provide enough power to run all of them.

My idea is to connect each drive to an external power source using an USB Y-cable.

Can I do it or will I run into problems? Did any one try that approach?

I got that idea, because I have seen other USB devices using such cables for their power supply.

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    Wouldn't a powered USB hub be a simpler more full proof solution? – Steve Robillard Feb 3 '16 at 1:53
  • You mean I should take a powered USB hub, connect it to one port of the Pi and connect both drives to the hub? – Rotareti Feb 3 '16 at 1:56
  • Yes, that is exactly what I am suggesting. – Steve Robillard Feb 3 '16 at 1:57
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    It doesn't matter. There's only one USB bus and everything goes through it. You can connect two drives to two ports or via a hub to one port, the bottleneck is the same. BTW, the ethernet jack also shares this port. – goldilocks Feb 3 '16 at 2:02
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    I don't know how they do the pass through, but I'd assume the hub itself adds no overhead. Note there's the implication here that if you were going to use two drives for added performance, don't bother. They will compete with one another no matter what. – goldilocks Feb 3 '16 at 2:11
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Yes you can, or better use a 10Amp-powered USB hub

UPD: I'm using this one with a 10Amp block(the one which goes with a hub is 3.5 Amps). I've opened it and seen a VERY good base board with huge reserved potential with it. I'm using it for 5 years with 10Amp DC block, not a single problem or heating(checked with pyrometer).

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You can connect to the B+ or Pi2 as the improved power circuitry will protect the Pi from the external power.

It is not, however, recommended. If you really must use Y cable you do not need to connect the +5V lead to the Pi, although this requires custom or modified cables.

As others have suggested a powered hub is a better solution.

The reason some older drives come with a Y cable is because they require more than the 500mA which a compliant USB port can supply. Very few modern drives with improved motors require more than 500mA. If you are contemplating using such an old drive you are unlikely to be successful.

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