In this Instructable, students learn about basic electronics and renewable energy sources by building a solar powered cell phone charger. While existing chargers run from $70 - $90, the components for this project only cost around $20. This is by no means the best or most effective charger - it is cheap, and can recharge in the sun. For a much more elegant, well designed, and well documented solar charger, you should really check out the materials on adafruit.com.

This project is of course, derived from the work that Limor Fried did in her MintyBoost Altoids charger, and from several other instructables, including this project from Joshua Zimmerman. The main differences for this project are cost, and durability. I found that his embedded iPhone charging cable was particularly fragile, with the wires exposed. These issues should be addressed in this instructable.

Here are the components you will need:
- $4.00 - Emergency iPhone charger - via Amazon
- $2.00 - AA battery holder - via RadioShack
- $3.99 - Solar Cell. I used this cell, from Brown Dog Gadgets, but you may be able to find them cheaper.
- Solar Batteries (AA)

- Wire, solder, soldering iron
- Altoids Tin
- Double stick tape
- Electrical tape

Step 1: Disassemble Emergency Charger

The emergency charger is a nice cheap little piece of electronics, but we want to extend its capabilities by adding solar power. To do this, we will need to remove it from its housing. I find cracking it along its length is best. Once this is done, remove the chip you find at the top.

Step 2: Solder Some Wire Onto the Solar Cell

You can either mount the solar cell onto the outside of the Altoids tin or keep it inside as a hidden treat. Either way, you will need some wire on that solar cell. Hopefully you have red and black wire (although any color will do so long as you keep track of which is positive and which is negative). Solder about 6 inches of the red wire onto the positive lead from the solar cell, and the same amount onto the negative end.

Step 3: Connect the Wire to the Battery Pack

The solar cell will provide power to the battery, which will in turn charge your device. Connect the red wire from the battery to the red wire from the solar cell. Do the same with the black wires. I recommend lining them up, and giving them a twist . You can then add solder, or cover the ends in electrical tape. If you are feeling saucy, do both. . .

Step 4: Ready the Container

Depending on your design, you will need one or two holes in your Altoids tin. One hole is for the USB port to stick out of. In our case, the students drilled holes in the side, and expanded it to size using pliers and tin snips.

The other hole is only necessary if the solar cell is to be mounted on the top or bottom of the tin. If this is the case, you should create a hole large enough to fit your wire through comfortably. Again, a drill and tin snips work well for this job.

Step 5: Assemble the Final Components

At this point you should mount the battery pack and USB circuit inside the Altoids tin using double sided tape. You can also use hot glue to ensure they don't move around once they are in place. The same should be done for the solar cell.

With the components mounted, the last wiring that needs to be completed is to attach the solar cell and battery pack onto the USB circuit. The clamps in back of the USB circuit are where you want to do this. Look on the circuit itself for a + icon next to one of the clamps. This is the one to attach the red wires to. The - clamp is for the black wires. I like to add a glob of solder onto the clamped wires to help them stay in place.