Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: Will the USB ports power a device (iPhone) if the dock isn't connected to a computer?
Document: I really need a thunderbolt hub. Since one has to be connected to the computer, this device only offers one more. I would much prefer that the device had at least 3 thunderbolt ports instead of 3 USB 3.0 ports.
Note that while it does come with two thunderbolt ports, one is taken up by the cable coming from the computer. So unless your thunderbolt devices can daisy-chain, you will be limited to one thunderbolt connection. The dock comes with 3 USB 3.0 ports, which, likewise, is just a little limiting for my setup. I have a DVD drive, main external drive, a scanner, backup drive, Bamboo tablet, and iPhone cord that I would Iike to keep hooked up.
I just purchased this and connected it to my current-generation MacBook Pro Retina. I bought it mostly to leave my Apple external SuperDrive connected to it.When I connected the SuperDrive to the dock, I got a warning from the Mac that I'd just connected a USB device that needed more power than it was being given.
It works very good and i find it very handy, i just come back from work and plug just one Thunderbolt port to have 2 hard disk, iPhone, iPad, Display (Mini Display port), my headphone with mic all connected.To all, very important:[...]This enable charging iPads on USB 3 ports.
The Belkin Thunderbolt Dock is great if you connect a lot of devices to your Mac laptop. Some areas could be improved, though:- Only 3 USB ports! The thunderbolt cable can certainly handle a lot more, since not every device will use the full 2.5 Gbps that the dock offers. These devices include keyboards and mice. But it doesn't really make sense to dangle a USB hub off the Thunderbolt hub which is already dangling off my computer.- Doesn't negotiate higher charging speeds for iPads.
The drive would sometimes disappear from the desktop, requiring a reconnection or resetting the dock by power-cycle. Checked the cables and it seems to be the dock.- There's really only one thunderbolt connector available since the other one is required to connect to the Mac.- USB 3.0 speed throughputs aren't nearly as fast as if the drives are directly connected to the Mac itself. The difference is significant.- The USB ports supports standard 500mA current.
I'm using an external mike that's connected to my MacBook with optical cable via the Line In input. But this dock doesn't have replication of the Line In input - the have a jack for the mike, but it's not the same. So I was not able to hook up my high quality mike to the dock.3. When I plugged my iPhone charger to the USB on the dock the iTunes didn't see my iPhone.
If you need to expend the ports on your laptop, especially a macbook air or pro, this is awesomeThose are the ports you get access to with a simple Thunderbolt connectionI Gigabit Ethernet, Firewire 800, three USB 3.0 ports, headphone and audio input, and two Thunderbolt ports, one has to be used to connect the dock to the computer. I wish you didn't need the power supply as it would be cleaner on a desk. This dock is plug and play.
The Belkin Thunderbolt Express Dock combines 3 USB 3.0 ports, two Thunderbolt ports (one used for connection to a computer), audio in and out, Firewire and Ethernet. It offers a simple one cable solution to connect multiple devices to the Mac. It is clad in aluminum to match the look of other Apple products. It comes with a Thunderbolt cable and a sizable power brick. Installation is as simple as plugging in a cable; no drivers need to be installed.
Update:  I cannot hook up my iPhone or iPad via the USB on the Dock. iTunes does not fully recognize the content of the iOS device, so it gives false capacity readings and does not sync properly. That makes two USB devise types that do not work well with the Dock:  The USB superdrive, and now my iOS devices. Knocked to three stars.This is a great all-in-one dock, but maybe a little bottlenecked in connectivity for users with a lot of legacy USB devices.
Answer: Just tested this - once you disconnect the Thunderbolt cable from your Mac, iPhone charging stops.