Posted on: 2010-03-10
Note from 2024: This posting was written a while back. The power bank probably had the two pins like this because iPhones were expecting it this way. Don't modify a modern charger or power bank like explained in this posting as they are already designed for various devices be it Android, iPhone or your bike light
Most portable devices nowadays charge over USB. This is very convenient since whenever you have a PC nearby you can just plug the device in and charge it up. And if you don't have a PC nearby? Well, no problem there are wall chargers, chargers that plug in the cigarette lighter of your car and even portable USB battery packs.
But have you ever run into the problem that this stupid device just won't charge on your charger but only on the original charger that came with it? Until quite recently I got an HTC TyTN II cellphone/pda. Charging it worked like a breeze, you could just hook it up to anything that supplies 5 Volts and has a USB-Port and the phone would charge.
Power requirements of the TyTN are quite high, so it's battery get's drained quite fast. That's why I got myself a cheap USB-battery on eBay. It's the thing you see on the right side.
You can charge it from any USB-powersource using the mini-usb plug (in) and when it's full it can supply energy to anything you hook up to it's usb-output (out).
However now that I've switched to the Linux-based Nokia N900 the charger isn't working anymore! Whenever I hook up the cellphone the phone's screen switches on but that's it. No charging whatsoever…
So I thought, let's rip it open and see where the problem is!
(Needless to say, if you plan to "fix" your USB-battery make sure to be careful with the included Lithium-battery, don't touch anything you should touch with the soldering iron. If it's a wall plug disconnect it first, and so on... Generally you should know what you are doing and you are certainly voiding any warranty you might have on that thing)
Here is my battery, casing opened:
The thing in the red circle is the bottom part of the USB-Connector where the voltage comes out. The only thing that has to be done is soldering together the middle two pins of the USB output jack.
That's it. Nothing more, nothing less. It's probably one of the easiest hacks there is. The middle pins are the data lines, and the USB 2.0 specification says that a USB "host" that is supplying only voltage on a USB-port, not actually transferring data must have those two data lines short circuited. For some reason my charger didn't have them shorted, but it's easily fixed:
That's it. Now let's just put everything back together and finally the Nokia N900, among other devices, will be ready to charge. And that's a good thing because the N900 is an even bigger power hog than the TyTN II.