Can a single USB port power a 7200 RPM 2.5" HDD?

I was about to buy an external HDD enclosure. I've seen many that come with cables with 2 USB ports on one end (for power). I do not want to have to use 2 USBs to power this drive, but I will be using my ST9320423AS 7200 HDD inside.

Now I'm thinking that since its a 7200 RPM drive, I will need 2 USBs to power it...is this the case? What would happen if I purchased an enclosure that was powered only by one USB port? I am not worried about speed, I just need it to work. Seagate has these specs for the drive:

Startup current, +5V (max): 1.0 amps
Seek power (typical): 2.2 watts
Read power (typical): 2.1 watts
Write power (typical): 2.2 watts
Idle mode, low power (typical): 0.69 watts
Standby mode: 0.20 watts (typical)
Sleep mode: 0.20 watts (typical)
Voltage tolerance (including noise): +5V ± 5%

From my understanding, USB 2.0 has a max wattage output of 2.5W. If this is the case, it looks like the drive wont be able to spin up... Can anybody shed some light on this? Thanks.

 

Basically your drive wouldn't start. As it shows there your startup power is 1AMP. USB 2.0 only provides 500mA max (.5A). So When you plug in the drive you will hear the drive try to start but nothing, once you plug in the second cable it will spin up.

This is the reason most external drive are 5400RPM too since USB 2.0 will be the limiting factor in the drives speed anyways. SInce you already have a drive it's kinda tough but you basically will need 2 USB ports to power it up. They have USB 3.0 now, those ports provide more power so that's a plus there.

 

Most external hard drive enclosures usually have 1 USB 2.0 (eSata/Firewire, etc.) for PC connection and a power adapter for power.

I wonder, what kind of external hard drive enclosure are you looking at? Can you post a link? It is not very common for hard drives to be powered by 1 USB 2.0 (USB 3.0 might change this though) excluding several low-powered notebook hard drives. 2 USB 2.0 to power a hard drive works, but it will not as efficient as the enclosure having its own power adapter.

Even my USB 2.0 switch needs a power adapter to function properly with only 3 basic USB 2.0 devices hooked up to it.

EDITED: jakejm79 corrected me.

 

That isn't even close to true, there are numerous external HDDs out there that are powered by one USB port. My WD passport does quad duty between my Wii, X360, Nettop and Notebook and performs flawlessly with only one USB plug.

 

No, it isn't. It depends on the HD. Some are a lot more power hungry than others. Also, USB 3.0 provides twice the power output as it's 2.0 predecessor.

 

For the record, I've now amassed 3-4 SATA 2.5" Notebook Hard Drives all in their own enclosures:
250gig 7200rpm Hitachi
320gig 7200rpm Hitachi
500gig 7200pm Seagate 7200.4

Early on, I selected one enclosure brand and stuck to it for no other reason than a) it works and b) collectively offers a uniform look. I went with the NipponLabs #USB-25SATA-BK SATA-to-USB Enclosure.

It came with a cable typical in cheap enclosures like this: one end has a single USB (type A) connector, the other end has a double connector presumably to draw power from TWO adjacent USB ports on the computer.

All my external hard drives power-on and work fine plugged into just one of the notebook's USB slots. There's never been any indication of the drive faltering from lack of power. If it did, I don't think I'd be capable of cloning around 400gigs of data.

I've since shelved the original hydra-head cables and bought a shorty USB(A) to USB(A) cable for occasional access to any of the drives.

 

Huh, (s)he said, "There is no way 1 USB port can power a hard drive" that statement is simply not true. It can and has been done numerous times. I'm not saying that ALL hard drives can be powered by 1 USB, but some can and the fact that some can renders the statement (s)he made above completely untrue. Maybe (s)he should have written, "There is no way 1 USB can power THIS hard drive." That would have been a true statement.

 

I was just simply answering his question on why most "custom" HDD enclosures (with only 1 USB 2.0 & no power adapter) might not work for his specific hard drive which runs at 7200RPM. Most likely the HDD will need more power than 1 USB 2.0 can supply. If it does work then good for the OP.

Pre-built notebook enclosures like the WD Passport are custom made to handle slower hard drives that draw less power. I doubt a WD Passport enclosure will supply enough power for a hard drive like the ST9320423AS.

I admit, I forget to put "THIS" hard drive.

 

Thanks guys.

 

The enclosure does not limit the power that the USB port supplies.

What can happen though is that the electronics of specific enclosures are not as power efficient compared to others - this can make it look like the enclosure is 'limiting' the power to the drive, but the enclosure itself has no reason to limit what voltage/amperage the HD recieves from the USB port it is plugged in to.

 

I mentioned the WD Passport enclosure because it doesn't use 2 USB 2.0 or a power adapter, but 1 USB 2.0 to power the hard drive. Earlier, I mentioned that the specific hard drive might require more power than 1 USB 2.0 can supply. Anyways, OP gets the main idea. Just leave it at that.

 

To be sure your external HDD are powered USB-2.0 better buy 5400rpm device. I have 320gb-WD and 250gb-Toshiba HDD.
Not all HDD 7200 are working.
Maybe on desktop are OK but on USB notebook port NO. Too much power hungry.

 

What abt the current portable 1tb external HDDs that are available in the market..Are they working because the rpm is 5400?

Please comment!

 

They should. A lot might ship with dual cables "just in case".