External portable hdd USB power question

I have a couple different portable external Hdd's. I have a kill-a-watt device which is a meter you plug into an outlet and into which you plug an electrical device to see what the device's power usage is. I'd like to see how much energy these hard drives are using while they spin. These drives have a single port that you plug into the computer. They are powered through the same USB connection which transfers data. Can I plug the drives directly into a USB "wall wart" power supply (such as the one that charges my phone) , which is plugged into the kill-a-watt, without harming the drive? Thanks!!

 

5 watts or less
http://www.cockeyed.com/science/power_use_database/portable_hard_drive.html
for a small portable with 1 USB plug, it uses under 500 mA (2.5W); with 2USB plugs 1A (5W)

 

My question was can I plug the drive's single plug (USB / power & data) into a USB wall-wart power adapter (such as my phone uses to charge) without doing damage to the drive. I want to compare power usage of the 2 drives I have.

 

Hi Jimbanville,


I would strongly caution against plugging a hard drive in your power adapter. The drives are not developed to be powered in such a way. Puling the drive in a wall socket will probably damage it and you could not only lose the data on the drive but not be able to further use it. What is more, such actions would probably void your warranty.
If you would like to know just how much power your drives are drawing you could check if the manufacturer of the devices has provided such information online, if not I would suggest contacting support and asking there before risking the drives health.


Hope it helps,
Frost_WD

 

Thanks for replying. I know you are attempting to help, but I don't I understand the rationale behind your caution. I was hoping to get more specific knowledge versus a general precaution. I know how the drives are powered… through the USB standard. A wall-outlet USB power supply and a computer's USB port both provide power in the same way (the outer pins are voltage and ground). I connected the drives to the wall powered USB power supply through the kill-a-watt device and both showed that they were using 3.3v and 1.5 watt. I've tested both drives and they both still function as they did before. I thought perhaps one was drawing more power because it tended to kill my laptop's battery faster, but perhaps there was another factor. I was playing full HD video files. That was probably harder on the processor and made it draw more power. The surface on the lap top above the battery got much warmer too. I tested laptop yesterday by playing standard YouTube videos for about eight hours, using the battery, and it never got warm to the touch.

 

The one thing that would be missing from your power experiment would be how much power each drive used while seeking and reading (or writing) data since those functions wouldn't be happening when plugged into the wall-wart. I'm not sure the Kill-a-watt device would be able to measure that difference anyway. It could also be that the additional power consumption of seeking, reading, writing would be negligible.

As you found out, USB power is the same whether plugged in to a USB port on a computer or a port on a wall plug. There are pins within the USB plug that supply power while other pins are for data transfer.

 

True. Thanks.