Mains Powered USB Charger - Do They Make These?

A question about whether Mains Powered USB Chargers for MP3 players existed.

I am sure I saw this question asked a while ago and the answer was it couldn't be done because the beast was getting more than just volts down the line.

However having had a quick Google I can't find those posts now. I have seen that some MP3 players come with mains chargers.

Also these sites .....

Maybe someone else has the definitive answer.

Does this look like what you want?

Thanks both, but they seem to be for particular models. Why I dont know as surely a USB port is a USB port?

Or even

Ahh, now that looks worth a go at =A312.95!

Cheers wattie

There is also someone on ebay selling usb mains chargers for i-pods at =A39.99. Didn't check out the shipping charges though.

Try a USB hub with a power supply but not connected to the host PC. If it OK charges then any powered USB hub will do, though a 2.0 hub should cost about £10-£12 and the hub itself could come in handy sometime.

cheers, Pete.

In article , Pete C writes

I don't think that would work if not connected through to the PC, USB hosts are not supposed to supply power unless the slave device asks for it.

Tim said, "USB hosts are not supposed to supply power unless the slave device asks for it."

As most usb devices are powered off the host, they would need power first before being able to request it ! The powered hub idea should work fine. You can also get a device that plugs into a car lighter socket which has a usb plug on the back which is meant for charging pda's.

In article , Pete Cross writes

Yes that's true... I'm sure I've read it in the USB spec somewhere...

You can get (IIRC - it could well be less) 50mA until you enumerate. Then (if you ask for it) you can get 500mA. HOWEVER many PCs aren't this strict and will give a lot more. Laptops are normally more strict to conserve battery life. Hubs vary in their behaviour IME.

Chris

I thought it was 5mA, anyway...

Some devices are even conservative, and won't simply charge from a USB port, without an active host controller to tell them that they can use 'high power' mode.

Which practically means it needs connected to a PC.

Hi,

This is the kind of thing:

The spare ports could be used for a phone charger etc.

There are smaller hubs that are not much bigger than a large postage stamp.

cheers, Pete.

AIUI, the power control is done from the root hub, not the leafs. So, some very conservative devices won't work from a standalone hub. IIRC it was a sony camera that wouldn't charge from a USB port not connected to a PC.

Hehe, that's sony for you, either their love of non standard ways or get you to use their pricier kit. Just cos' it's not charging doesn't mean it's not powered.

AFAIK a USB port can't deny power unless it's overloaded, to do otherwise would complicate things with no benefit.

cheers, Pete.

Actually, their kit is doing the right thing, it's just it'd be nice to be able to switch it to doing the wrong thing.

Not quite true. Plugging in a 'dumb' peripheral that draws 0.5A, without bothering to enumerate, while doing a backup to a USB HD, or doing a long sound recording, would both be bad.

I don't see how needing a connected PC for the charger to work benefits the user in any way.

I think we'll just have to agree to disagree on that one :)

cheers, Pete.

It's intended to plug into a USB port, not a portable charger. It's not unreasonable in that case to comply with all of the specifications for that port, and indeed is good practice.

Use a cheap & portable mains powered USB Hub perhaps? I have a tiny 4 port one I bought in Singapore 18 months ago. Very handy.