USB charging problems solved

Charging the Blackberry in the van is quite a lot harder than you would imagine. I bought several different PSUs that output ‘USB power’ including a very fancy digital laptop PC one, one that claimed to put out 2.1 amps for the iPad, and more.

Yet every time I would get a message on the Blackberry screen saying ‘This power source cannot charge this device’. Strangely, it worked fine on every PC I tried, even laptops, although it frequently wouldn’t actually charge worth a damn on a laptop that was, itself, running on batteries.

The clue came when I tried a friend’s fancy charge station at Fizzpop (the Birmingham hacking/making group) one night, and suddenly, it worked! This meant it wasn’t down to the driver(s), but the plugs.

It turns out that you can make a ‘charge only’ plug for USB, and that’s what I needed.

So, how?

I tried leaving the data channels open, and I tried shorting them, with no success. However, I found a reference online, and you need to put a 200 ohm resistor between them. Of course, how obvious.

Turns out Amazon sell special plugs for iPad, but only as the full sized USB plug, for about £6.

(I was walking through a street market, and saw a cigar lighter to micro USB charger and, for £5, I tried that, and it worked! So problem solved for me. But back to you.)

So, you need to split out the middle two of the four USB lines, and solder in a 200 ohm resistor between them. I’d suggest doing this on a USB extension or the like. Then, to charge your device, just put that lead in the line. The resistor will tell the hub/PC to supply lots of power, and the device will also know that it is a power-only connector, and to just suck up the juice, without worrying about handshaking or drivers.

This should work for anything – iPod, iPad, Android tablets, and you will probably also find that smaller stuff like Shuffles will charge faster too.

Obviously, hack at your own risk! Good luck.

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