Question about adding external 2.5" drives that don't have their own power source

So I have a old laptop running as a harvester and I’m thinking about adding a bunch of external 2.5" that don’t have a external powersource (through a USB hub with its own power source). Basically I’m wondering if this changes the limit of drives I can connect compared to If I would use external drives with their own powersource?

Yes, you will be limited by your psu connections, or whatever psu you use to power them.

No these are external drives not internal, thye recive power from USB.

( twenty characters )

is it still unclear for you?

Well yes, unclear.

You first state that the externals will have no external psu.

You then state they will be powered by usb.

If they come with a psu, use it, that’s why they are provided.

What is the power output from a computer USB port? Most computer USB ports supply 5V of electricity with a maximum current of 0.5A . This amount of current is standard across the majority of computers and means the overall power output will be 2.5 Watts at best. Later USB designs bring that current up to 0.9A.

A hdd uses how many watts?
How many do you think you can power on a usb?

He said they will be USB powered through a hub with its own power source.

There IS a limit to the number of drives you can have via USB. It varies by system and USB hub. Power is a concern on a laptop. If the laptop only has a 65w power supply for example, you’d be passing less power to USB over the port (the power needed for data transfer, not the power physically needed to power the drives). As far as I know, the power supply on a USB hub only supplies supplemental power over USB and not data transfer power. That said, I use Belkin powered USB hubs at work and they are notoriously unreliable under heavy load.

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