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Are these "Amperage step up" adapters safe to use?

post #1 of 5
Thread Starter 
I was looking around on ebay/google for a usb charging solution for my HP touchpad when I found this:

http://www.amazon.com/Switching-Charging-Charger-Adapter-Convertor/dp/B006JXOROC

Pisen is one of the better china brands, but I'm wondering if these are safe to use? It apparently steps up the 0.5Amps from a usb port to 2A, enough to feed an iPad etc.
$3 shipped on ebay for those who are looking for one.

Cheers


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post #2 of 5
I thought USB (from a computer) could deliver 0.5A max @ 5V--I'm confused by this contraption--how does it allow a draw more than what the port can supply?

If you're using a higher-current source (like a wall plug or a car plug), they should be capable of delivering 2A already, right?

What device is this for?
    
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post #3 of 5
Thread Starter 
Quote:
Originally Posted by guyladouche View Post

I thought USB (from a computer) could deliver 0.5A max @ 5V--I'm confused by this contraption--how does it allow a draw more than what the port can supply?
If you're using a higher-current source (like a wall plug or a car plug), they should be capable of delivering 2A already, right?
What device is this for?

It's supposed to somehow make your usb port supply 2A, but wouldn't that lower the voltage?

I'm hoping theres someone who knows how this might work as my electrical knowledge is next to none tongue.gif
 
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post #4 of 5
Quote:
Originally Posted by cgg123321 View Post

It's supposed to somehow make your usb port supply 2A, but wouldn't that lower the voltage?
I'm hoping theres someone who knows how this might work as my electrical knowledge is next to none tongue.gif

Witchcraft I tell you!

But I don't understand--since it's passive, you can't increase the amount of current.

Okay, I just looked around, and found this:
http://androidforums.com/samsung-galaxy-nexus/500497-1a-2a-car-charger.html#post3946933

Devices recognize something as either a "USB" (data) port, or an "AC" (technically DC, but whatever) connection. Apparently if the port is configured like a computer USB data port, the device itself will recognize that and only draw up to 0.5A. If the port is configured NOT as a "USB" data port, the device can draw up to 2A. It seems to just be a slight change of not shorting the two data usb pins on the usb port which tells the device it's not a usb data port, but rather a strict charging port.

Don't see why they wouldn't be unsafe in that case--the device will still only draw as much current as it is allowed (by the circuit in the battery--batteries are pretty smart these days).

edit--But if you're plugging the device into a computer usb port, you will still only get 0.5a since that's all the computer port can supply (I think technically usb 3.0 can output up to 0.9a)--this is probably more for wall chargers that are still only putting out 0.5a
Edited by guyladouche - 3/28/12 at 9:25pm
    
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post #5 of 5
Thread Starter 
That's what confuses me, the theoretical max current output from a USB port is 0.5A (as I have been told). It doesn't seem to make sense that an adapter would somehow allow it to output more, without drawing power from an external source.

Anyways, thanks for the reply. I ordered one earlier for $3 shipped so I'll see if it actually works and report back:thumb:
 
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