AA Battery cell phone chargers

[Stonent]

A local store had some of those on sale for $2.42 each with battery so I bought 3 (one for me, my wife and mom)

I figured it was just a joule thief and I'm pretty sure I'm right.  The device itself appears to be a AA battery based flashlight housing made out of Aluminum. The end is just a end for a small flashlight with a 2.5mm 2 pin jack sticking out.

It also has about 10 interchangeable tips for different phones.

The tiny little board is about the size of a penny and has on the bottom what appears to be 2 transistors, a small capacitor and a resistor.  One the top it has the jack, a larger cap, an LED, a big diode, and a coil. It is silk screened HF-05AJ.

The box says it can supply 400mA but I've managed to plug my HTC Droid DNA (HTC Butterfly or Deluxe for those outside the US) and it says "AC Charging" on my battery widget which would make it seem it was drawing a full amp. But after a few minutes of charging, a warning comes up saying that the phone won't charge as fast and please use the genuine charger.

Also it did successfully boot my Raspberry Pi from just the AA battery inside. Overall I'm pleased.  Now the coolest hack I think would be to add a USB input into this device so that it can charge via USB.

The only down side is the 2.5mm jack is very touchy. If you move the cable the LED tends to shut off and stops charging.

Now that I think about it, this device is small enough that you could potentially squeeze it inside a car charger. That would be cool. Just unplug it and take it with you and keep charging.