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.  

Can i use 6V, 200mA solar panel???pls reply fasy<br>
Should be fine.
<p>I need a better step by step! There's no talk about a diode and a better wire to wire description. Im new to this and I need a &quot;solar charger for dummies&quot; HELP?</p>
What size blocking diode was used?
<p>You should be able to use an easily available (US anyway) 1N4001 diode.</p>
<p>Can I use Ni-Cd batteries? (1.2v rechargeable 2/3 AA 150mAh battery) </p>
Cool project!
Hi! Nice instructable. But i don't see why you are adding the solar panel, i have 12v 90 mA solar panel. If the circuit is actually working without the solar panel? <br>can you explain me ? <br> <br>thanks! <br>marC:)
I have a 6 V 50 mA Solar panel wired to 2 rechargeable batteries, and the battery wires and solar panel wires are soldered to the USB connector. The USB connector is lit up so there is some power going to it but the device is not charging.
hi rsantos24 as you mentioned you are using 6v 50ma the 6volts part is fine but 50ma no..you see a single rechargeable battery requires more than 900ma do the math and you require 1800ma a 50ma solar cell is not going to do the job.However it will recharge the batteries but to slowly you will have to keep the solar panel facing light for like 36 hours or more.so my suggestion is you try a different solar cell. <br>
How do you connect the battery/solar unit to the USB? It it with the two wires that you soldered together in step 3
why, it just so happens that i AM feeling saucy this morning, how convenient!
When I was working with my chip, the switch on it cracked off and it is hard to work. I have an extra switch and I was wondering if I can take out the old switch and solder in a new one, would it still work?
Wouldn't you want a diode between the solar cell and the battery pack? Also, I'm thinking about building one of these and I'll just use the battery pack the charger comes with. Lastly, I'm going to add a switch between the battery pack and the circuit so I can switch between charging the batteries and charging the device. <br>-Doctordv
Yes you do. If you don't use one you'll end up destroying your solar cell. A simple 1N914 diode will work. You can find them everywhere in old electronics, or just spend $2 and get a 10 pack from Radio shack. <br /> <br />Also, you don't need a switch. It's unnecessary. If you wire it all up in Parallel you'll have no problem. Without a gadget plugged in the batteries will charge, with a gadget plugged in the USB circuit will activate and you'll charge the gadget. <br /> <br />Without anything plugged in the USB circuit will draw no power. (You need to cut off the red LED though. No loss there as it's a useless status light anyhow.)
Where would you put the Diode? between the 2 red wires?
Yes that is what I would do.<br><br>-Doctordv
Do you connect one diode to the red wires? and how would you connect the red wires to the usb chip?
Hi, I'm planning on doing a similar project with a larger solar panel that will charge 4 1.2v AA's. From there, I will solder that to the USB to charge my ipod. <br> <br>My question is: will the 4.8v from the AA's be too much for the USB charger to handle? If it makes any difference, I'm using the same USB from the same emergency charger as you. <br> <br>THanks in advance.
Wire up two sets of AAs. As in two sets of two. Then you'll get double the capacity at 2.4V of power. (You could wire them all up in a series, but you don't need to.) <br /> <br />The 4.8V should be fine if you're insistent about going that route. Though it works best between 2-3V.
Would rechargeable batteries work instead of solar batteries?? <br>Thanks for sharing this 'ible! :D
Any AA rechargeable (or AAA even) will work just fine for this project. Most garden lights out there use low capacity AA or AAA NiMh rechargeable batteries. They're just like what you buy in the store, only cheaper and with a lower capacity. Only the really expensive garden lights use Lithium batteries.
This is a bit beyond my expertise, but I'll give it my best shot. I believe that they probably would, but my understanding is that solar batteries may be better engineered to take a low or variable charge rate when they are charging. The thing about solar power is that, while it is free, it doesn't produce a ton of power, and can cut at any moment when a cloud passes by. Batteries tend to do better with a steady charge. I might recommend LadyAda's tutorials, kits, or instructions, which I believe have more info on this. <br> <br>http://www.ladyada.net/make/solarlipo/
If you want a really cheap solar cells, go to your local dollar store and look for the solar garden lights. They arnt the most efficient, but some are quite nice :)
thats a great tip thanks <br />
Watch out though. The ones from my $1 Store only put out around 3V at 20mA. <br /> <br />They're great for many projects, but they really don't have very kick.
Hey! Thats my solar cell! Cool beans!<br><br>Also, I do in fact have a USB kit with all those same parts on my website (browndoggadgets.com), as well as an instructable that is more or less the same as this one.<br><br>Also, if you put a wholllllleeee lot of hot glue over the exposed wires it cements them in place. In case you ever have a problem with them.

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