Instructables
Picture of Cheap solar powered iPhone charger
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 
 
 
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Step 1: Disassemble emergency charger

Picture of Disassemble emergency charger
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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

Picture of Solder some wire onto the solar cell
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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.  

Can I use Ni-Cd batteries? (1.2v rechargeable 2/3 AA 150mAh battery)

Mrdewdew10 months ago
Cool project!
nodoubtman1 year ago
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?
can you explain me ?

thanks!
marC:)
What size blocking diode was used?
rsantos241 year ago
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.
How do you connect the battery/solar unit to the USB? It it with the two wires that you soldered together in step 3
mking011 year ago
why, it just so happens that i AM feeling saucy this morning, how convenient!
JCG51 year ago
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?
DoctorDv2 years ago
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.
-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.

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.

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.

-Doctordv
Do you connect one diode to the red wires? and how would you connect the red wires to the usb chip?
MyTopFan2 years ago
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.

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.

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.)

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??
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.
pauleway (author)  TheQuestioner8682 years ago
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.

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
Watch out though. The ones from my $1 Store only put out around 3V at 20mA.

They're great for many projects, but they really don't have very kick.
Hey! Thats my solar cell! Cool beans!

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.

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.