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I have a rpi4 with the default 5v 3A charger. However, when I hook up all my usb peripherals (2 mechanical hdd and a cc2531) I run into power limitations and things do not work properly.

I am thinking of a solution as below where the pi is hooked up to the power adapter on its own. I happen to have a usb c hub that has a power in option. So if I hook in another power brick to the input of the usb hub, connect the hdds to the hub,and connect the usb c end of the hub to the pi with a USB C to USB A cable would it work without issue? I'm a bit hesitant to try without confirmation as I don't wanna burn out devices ;)

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There are many Q&A here in RPi SE that discuss various technical aspects of USB hubs. In your case (based on your question), it seems the key feature you need is a self-powered USB hub - vs a host-powered hub. In summary, the self-powered hub will provide power to the drives that are plugged into the hub, thus saving capacity of your RPi power supply.

If you can find a self-powered hub that supplies 2 amps at 5V in a single port, that will probably be sufficient to power your RPi 4 under most scenarios. Note that the "official" recommendation for a supply for the RPi 4 is for 5V and 3 amps., but the basis for this recommendation has never been disclosed. In other words, 5V and 2 amps will cover you in most situations.

The RPi 4 is the only RPi that uses a USB-C connector. However, there is no electrical advantage to powering the RPi 4 with a USB-C power source because the RPi 4 will take only a 5VDC (nominal) input - same as USB-A. The RPi 4 is "wired" such that it will not allow power delivery at any voltage above 5 V (nominal). So yes - if you have a self-powered, USB-C compliant port, it is safe to connect it to the RPi 4.

But once again, having the ability to source 2 amps at 5VDC is the key. Note that some USB-C power sources will claim the ability to serve as a 100 Watt charger for laptops, etc. Know that this jargon is irrelevant to powering an RPi 4. That said, if you wish to delve deeper into the USB Power Delivery Specifications, you could start with this excellent Q&A.

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  • Thanks for the detailed answer. I am thinking of a setup like this: ibb.co/XXpnZ7S. The concern is if the 2nd power source will cause issues with the Pi? (which from your response feels like a no?) and the second is if the USB hub (which is a mobile OTG style hub) suitable for this purpose?
    – jamie
    Sep 9 at 8:55
  • The setup/block diagram in your picture looks reasonable, and should cause no problems for your RPi. I'm afraid I can't offer an informed opinion on the hub itself, however, assuming it meets USB specifications, I can't see any reason why it should not work.
    – Seamus
    Sep 9 at 9:20
  • Awesome. Thanks!
    – jamie
    Sep 9 at 11:58
  • This is the usb hub that I have, and believe it should be usb compliant. amazon.de/dp/B07MY1X9T9/…
    – jamie
    Sep 9 at 12:01

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