Power adapter for USB 3 4-port hub

Toggle sidebar Toggle sidebar
I

igorjrr

Distinguished
Nov 8, 2011
25
1
18,535
Hello all!
I bought a USB 3.0 hub with an external power supply.
The hub has 4 ports, and one of them supports Battery Charging Specification. The power adapter has specs of 12V and 1.5A.
I contacted the manufacture regarding this power adapter. For me it seems it won't provide full power for the USB hub. See my math:
4 ports * 900mA = 3.6A - 1.5A (from power adapter) = 2.1A missing. Well, the USB port from computer (when on) could supply 900mA, so at the end I would miss 1.2A. Is it right?
And, I'm not considering the Battery Charging Specs above! Otherwise I think I'm missing even more power...
The manufacture replied to me saying that 12V at 1.5A can handle 4*5V at 900mA. So 12V provides more mA to 5V ports? I have no idea...
Could someone help me with this math?
Seems that this hub wouldn't support 4 peripherals drawing 900mA each. Or even worse, charging something at 1.5A and using other 3 ports at 900mA each.
Thanks!
 
Solution
S
Sort by date Sort by votes
I

igorjrr

Distinguished
Nov 8, 2011
25
1
18,535


Thanks, but my question is not about the USB 3 specs but if, having this power adapter, I'll be able to use 4 ports at 900mA - if my math is correct. Thanks for your help anyway.
 
Upvote 0 Downvote
N

noidea_77

Distinguished
Jul 28, 2012
6,527
0
19,960

And the answer is no.
 
Upvote 0 Downvote
S

Sammey19

Honorable
Oct 17, 2013
2
0
10,520





I know this reply is extremely late. But I'm looking into modding one of my HUB's and I can provide a bit more detail on this. Hopefully if/when you get this you'll be able to teach someone else this as well. Or perhaps someone will stumble upon this thread and my reply will help them... never know. (so, sorry for a potential grave dig.)

Okay so...

If the power is 12 volts and 1.5 amps you need not worry about the volts or the amps...

What you do is convert them to watts...

12 volts times 1.5 amps = 18 watts

What you do with that is pretty much obvious. Okay now 4*5volts at 900 mA is fairly simple to figure up (900 mA is only 0.9 amps):

There are 4 ports right? But we need to figure out how many watts is in 5 volts and 0.9 amps

5 times 0.9 = 4.5 watts

4.5 watts times 4 ports is still only 18 watts which leaves you with nothing left.
 
Upvote 0 Downvote
Solution
I

igorjrr

Distinguished
Nov 8, 2011
25
1
18,535
Thank you! Yes, I learned that it's not only the amperage that counts, but also how many volts... all together comes to Watts to do the proper math...
Your math is absolutely right, so 12V with 1.5A can handle a USB hub with 4 ports (5V each) with 0.9A.
Thank you! :)
 
Upvote 0 Downvote
You must log in or register to reply here.

TRENDING THREADS

Latest posts

Moderators online

Share this page

COMPANY
RESOURCES
FOLLOW
Top Bottom