[sdiy] USB power (slightly off-topic)

[Rutger Vlek]

Dear list,

I hope you don't mind me tapping into our collective list wisdom for
something slightly non-synth related. The case is as follows:

I'm building a NAS at home from a Raspberry Pi 4B and a couple of SSDs. The
SSDs are connected to the Pi via a SATA-to-USB converter. They work, but
stop working when used intensively. Not to my surprise, because the power
requirement of the drive is 1.7A at 5V each. The Pi USB ports can only
deliver 1.2A at most (and shared between 2 ports). So I need a more beefy
supply. My initial idea was to buy a couple of these USB Y-cables that have
two USB-A connectors on one side, allowing the user to provide the
paralleled power of two USB ports. However, even on a single port, the Pi
already reaches it's limits. So I thought, why not plug the second USB-A
plug of the Y-cable into a USB-charge, so that it can provide all the
current needed by the drives. However, I have a bad feeling about this...

I don't have a clue about the internals of a typical USB Y-cable, and have
not been able to find any datasheets on them. In the worst case, power from
the Pi's USB port would just be connected directly to the power output of
the USB-charger, and that does not sound like a good idea. They might not
be at the exact same voltage, and I since both of them are SMPS's, I don't
know if they'll somehow start interfering with each other. If only there
would be some series diodes internally present in the Y-cable, but I have
no clue if there are... Does anyone know (or can measure)?

Plan B was to buy a powered USB hub, but I struggle to find one that can
deliver the required 1.7A at 5V on multiple of its ports at the same time.

Plan C, that just came to mind, is that I might be able to find a beefy USB
PSU with multiple ports, that I can use to feed the Pi from, as well as the
drives via Y-cable. The Y-cable would then be combining the power from Pi's
USB output with the direct output of the same PSU. Would that work?

Plan D would be to make my own power distribution board, where USB
connectors pass data between the Pi and the disks (but no power), and power
is injected from a DC barrel plug (and some filtering)

What do you think would be the best approach?

Rutger
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