Barrel-style charger to USB adapter - really?

[workinwifdakids]

I was browsing newegg or somewhere similar and found some adapters that go from a barrel-style on one end, except instead of terminating at a wall plug it has a USB on the other. The idea being, I guess, one could charge a device that takes a barrel connection (laptop, camera, whatever) and charge it via a USB. I know there are different USB connections (wall plug, cigarette lighter/car, computer), but my understanding was that they all push out the same power once the power goes through the USB port.

Setting aside the "why would you" for a minute, would a USB charge reasonably provide any sort of power to the kinds of larger devices that charge from a barrel connection and a wall port?

[randy]

It all depends on the Current and Voltage requirements of the device in question. USB specs provide (IIRC) for a Max of 5v, and a max current of (again IIRC) a max of 500mA.

I doubt many of the devices that use the barrel plug will run on a USB power connection, but you might be able to recharge their batteries. How long to charge and how well, again depends on the device, but many of them probably require 12v input.

The only to way to be certain would be to check the specs of the factory power supply/wall wart/charger etc.

[Greg]

I suspect you have it backwards. Is the barrel plug male or female? If it were a device that took a wall plug with a barrel end connector, and then supplied power out through a USB port that would make a lot of sense. (Same concept as how wall wart evolved into brick with a detachable power cord.)

[Greg]

I suspect you have it backwards. Is the barrel plug male or female? If it were a device that took a wall plug with a barrel end connector, and then supplied power out through a USB port that would make a lot of sense. (Same concept as how wall wart evolved into brick with a detachable power cord.)

I have several devices with barrel connectors on one end, and usb on the other. relatively low powered rechargeable devices for the most part, but also a couple of portable hard drives.

I have such an external hard drive. And I know which connection is for power, and which is for data.

[workinwifdakids]

Well, I can't find the one on newegg. I'm tired.

Here's one on Amazon:

Here's another.

Thanks btw for all the answers. This stuff is pretty interesting.

[randy]

It all depends on the Current and Voltage requirements of the device in question. USB specs provide (IIRC) for a Max of 5v, and a max current of (again IIRC) a max of 500mA.

Nope.

USB does provide for a 5v +-.2v voltage, but allows for up to 2.4a

Minimum is 500ma, allowing for 1.5w but it will accommodate up to 13w.

Thanks Chris, I was dragging it out of memory. Apparently I remembered the min current as max.

My biggest experience with USB power (other than plugging devices in) is making sure that the voltage is stepped down to 5v when wiring USB power ports in from the RigRunners in our vehicles. With a 40a capacity, I don't usually need to pay much attention to the current draw on our USB devices.

[Cybrludite]

Speaking of USB...

:jacked:

[mekender]

Well, I can't find the one on newegg. I'm tired.

Here's one on Amazon:

Here's another.

Thanks btw for all the answers. This stuff is pretty interesting.

The general view in the consumer side is that the device should regulate what power it accepts. So I have a car charger that has a max of 2.1A per plug, but if the device can only handle 500mA, it should not draw more than that.