18600mAh Wireless Portable Phone Charger

I
was selected for the Governors Honors Program (GHP) and for a display project I decided to bring something that could possibly become a commercial product, if produced economically (a bit Shark-tankish).

What I decided on was a portable power pack that could be charged wirelessly, but could also charge your phone wirelessly. Lucky for me the wireless battery charging problem had already been solved so the process was not as difficult as it sounds.

The first step was to select the batteries.

Lithium polymer batteries while energy dense were too volatile and could burst into flames if improperly charged.

Lithium Ion was the way to go. The cells are more stable, store lots of power, and are fairly inexpensive. 

The debate was now between cylindrical cells or rectangular cells. 

Round cells tend to be more robust, while hard to mount. Flat cells are easily pierced if scratched with a sharp object, but are thinner and better for mounting.

 The volume wasted by the round batteries meant less energy storage. The rectangular shape was just too good to pass up. I went with 3 6200mAh cells which would be wired in parallel for a total of 18600mAh. The best supplier of the batteries I have found is this guy on eBay: 3X Li Ion Pouch cells

The next step was finding a project enclosure. After a long search, I found an ergonomic enclosure (rounded rubber grip) with some style (the last aspect was very hard to come by).

My measurements of the cells were off by around 10mm and the enclosure couldn't hold the cells, so I had some clearing out to do. I used a Dremel to take the inside from this:

To this:

 The battery problem was solved, but now came electronics. The power transition would be inductive and required a decent efficiency so I decided against making my own. I found  a transmitter receiver pair on Deals Extreme for around $13.  

The output of the receiver was 5v, but I didn't trust the power to be clean enough for charging a battery. I instead bought a 5v booster circuit. This added the ability to charge the batteries with usb and allowed usb devices to be charged with a cable.

After installing the cells I began packing in the electronics. The process was messy and beautiful, everything fit.

I put together a quick plexiglass box and drew a curcit on a copper clad board with a sharpy for the 12V power supply, I had to see this thing work. I etched the board and populated it with all of the components. 

I glued in the power transmitter, the transformer and the new board then I closed the box.

Then for the almighty test.

The first problem was a shorting usb contact, then the transmitter started humming. The batteries got warm, but I put my phone on the power bank anyway.

I heard a satisfying "blom". It worked! Now all I had to do was get into the GHP. 

There is joy in work. There is no happiness except in the realization that we
have accomplished something. -Henry Ford.