I'm looking to build a 40 port USB Charging station / dock.

I found this product available online but with only 12 ports and at $16.50.
http://www.aliexpress.com/item/12-P...sktop-Fast-Charger-for-Smart/32582794696.html

I also found a seller that sells a dedicated 5v 40a power supply:
http://www.aliexpress.com/store/pro...dio-Computer-Project/2028081_32600468404.html

I discussed with a friend of mine about taking the 5v 40a power supply and hooking it up to a group of female usb sockets and charging multiple devices at once. My friend says that each usb socket will need it's own charging circuit so the phone can properly charge. My understanding from reading online is that no matter how many amps are applied to the phone the phones internal charging circuit will only pull so many amps.

Am I completely off on my understanding with this? I am rather out of my depth but would rather build something and learn how it works than buy a product. Thanks.

 

Your right. The device that's plugged in will only take the current it needs.

Do you really have USB 40 devices you need charge at one time or is this a just to say you have one sort of project?

Also, many devices can pull up to around 2 amps so you might as well step things up to an 80+ amp 5-volt power supply or maybe a 140 amp being there are 3.5 amp rated USB chargers now.

The downside is how do you plan to feed power to that many USB ports without having lots of voltage drop? You will either need to have lots of smaller leads feeding to multiple points (2 - 4 ports per feeder set) or have some pretty heavy circuit board traces to handle that much current.

 

There is so much USB information available, but it keeps changing and for the most part, I think it's misunderstood. Then there's Apple stuff.

I think you should look at this http://www.edn.com/design/power-man...IC-speeds-adoption-of-universal-USB-charging- article first.

it's not so much that the device takes what it needs, but the complex signalling from the device requests a certain amount of power. You really want to emulate a DCP or Dedicated Charging Port.

tcmtech has the other issue nailed. I think you really will need a per port based regulator.

Then there is the quiesient power consumption issue,

 

Your right. The device that's plugged in will only take the current it needs.

Do you really have USB 40 devices you need charge at one time or is this a just to say you have one sort of project?

Also, many devices can pull up to around 2 amps so you might as well step things up to an 80+ amp 5-volt power supply or maybe a 140 amp being there are 3.5 amp rated USB chargers now.

The downside is how do you plan to feed power to that many USB ports without having lots of voltage drop? You will either need to have lots of smaller leads feeding to multiple points (2 - 4 ports per feeder set) or have some pretty heavy circuit board traces to handle that much current.

Thanks for replying. At the moment I have a need to charge up to 8 - 10 devices at one time. Future proofing and trying to scale up before the need arises.

 

There is so much USB information available, but it keeps changing and for the most part, I think it's misunderstood. Then there's Apple stuff.

I think you should look at this http://www.edn.com/design/power-man...IC-speeds-adoption-of-universal-USB-charging- article first.

it's not so much that the device takes what it needs, but the complex signalling from the device requests a certain amount of power. You really want to emulate a DCP or Dedicated Charging Port.

tcmtech has the other issue nailed. I think you really will need a per port based regulator.

Then there is the quiesient power consumption issue,

Thanks for replying. That's what I was afraid of. I am out of my depth here. I figured I could simply wire together the power source in parallel and the amps would be dispersed evenly depending on the usb connections present. Probably best to just purchase usb charging hubs. Thank you.