Instructables
Picture of DIY Solar USB Charger - Altoids
finished2.jpg

I've been reading a bunch of blogs this fine Earth Day morning and have noticed that most of them are posting little write ups about green solar powered USB gadget chargers. They're all quite nice, but also quite expensive. I don't think I've seen any for less than $60, and I've not seen one that really suits my style.

Instructables has quite a few guides on how to make Solar USB Chargers, including the very well done guide on how to combine a Lady Ada Minty Boost circuit with a solar + lithium ion battery. Great, but a bit expensive to make and not a very simple project for the weekend DIY person.

Well luckily for us I know how to make one for under $20 that is better in nearly every way and also completely fits into an Altoids Tin. Covert style.

*** Update: I've since retired this kit. It's not held up over time very well. I've done an updated version called Solar USB Kit 2.0 and a more rugged version called Lithium Heavy Duty 2.0. If you're looking for something pre made, especially for camping or emergencies, you should try out one of our Folding USB Solar Cells. They're inexpensive and much much more powerful than what you'll find here.

 
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Step 1: What You Need

Parts:
USB Charging Circuit
Solar Panel 4V or greater
AA Battery Holder
AA Rechargeable Batteries
1N914 Diode
Altoid Tin (or whatever)
Wire

Tools:
Soldering Iron
Solder
Tin Snips
Melt Glue Gun and Glue
Tape

Cost is less than $30. I can make one for under $10 when I buy parts in bulk. I have a kit available at my website BrownDogGadgets.com which has everything you need to make this project. Also, if you're lazy, I do sell made versions in a variety of tin styles.

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Rip that puppy open.

Find that that turns 2 or 3 AAs into 5V USB.

(Not a wall one. Bad idea.)
Can I use an AC to USB converter? I ripped apart a kindle charger cord; would this work?
Did you ever find out? I'm wondering the same thing, I have an MP4 charger cord
TheArtVark1 year ago
Hi,
If I understand correctly, if I leave the batteries in and place it in the sun it will use BOTH the solar panel out and the batteries ate the same time if I want to charge anything, right? No need to take out the batteries? When the it's less sunny the batteries drain faster, when it's scorching the batteries drain slower?

Thanks for the instructions!
The temperature of the air doesn't matter as much as you might think. The panel will output more mA when it is 60 degrees and sunny...compared to 110 degrees and mostly cloudy. But yes, leave the batteries in.
Ah, thanks for your answer. No hassle charging then, just stick it out in the sun. With 'warm' I actually meant 'sunny', but good to know that temperature is not an issue either :-)
No problem...but as another user mentioned I would add a small circuit to prevent overcharging the batteries.
Schmidty161 year ago
I was wondering if I could use another usb connector if so can I fond 1 at RadioShack if so what is it called and if I can where can I find one in stuff ling around my house
This has a "USB Type A" for charging electronic devices, you shouldn't need anything else because it's the industry standard. To use anything else would be over-complicating things or risking damage to your equipment. Your best bet is to buy the kit: http://www.adafruit.com/products/14 and add a solar panel to it.
I don't have access to your store
xJValx1 year ago
is it somehow possible for the charger itself after it is complete, to pull juice out of the phone that its supposed to be charging?
There should be diodes in the device and on the USB-DC converter to prevent that from happening.
Snakera1 year ago
Do you know if this will charge the iphone 5?
The iPhone5 and iPad4 both require more wattage than their predecessors (that's why Apple changed the plug). I'm not exactly sure of the iPhone5 power requirements, but my iPad4 requires 12W of power (12W/5V=2.4A). Thus I cannot charge it in my vehicles, laptop/desktop computers (500mA max), etc. If the components of the USB-DC converter can handle it, then yes. But, you'd have to check the appropriate datasheets. I would send an e-mail to AdaFruit and ask her.
rsantos241 year ago
I have a 6 VSolar 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.
One of the IC's could be bad or there could be a bad solder joint.
rweiss1 year ago
Hello,
I am wondering, if we're using some internal batteries (ie. AA in your case), that are wired directly to the solar cell, are they at risk of overcharging if the device is left in the sun?
Thanks for the great tutorial.
Electronics should never be "left out" in the sun long enough to overcharge the batteries and you should be able to find a solar panel that will fit in the tin. However..."stuff" happens! So I do plan to incorporate a protection circuit in mine.
cnephew1 year ago
When you say "You can rip one out of a cheap USB charger" what exactly do you mean by that?
Some wall warts and car chargers have a USB connection on them. I assume that is what he's referring to. I'm going to build my own USB-DC converter using AdaFruits Instructable. It calls for a 22uH inductor and I did find a 20uH inductor in a Motorola RAZR charger.
jayc1601 year ago
I tried making with with two recharchable 9v batteries and im not making any headway does it only work with the AA's ? Or do I need to add something in the line to make it work ? im also going to use a plastic pelican case instead of an altoids can just seems a little more rugged.
Pelican cases are awesome! If you are using 9V batteries you need to add a LM7805 circuit or you risk frying your electronics. But you will be wasting a lot of power and therefore, money. To know more, read AdaFruit's Instructable: http://www.instructables.com/id/MintyBoost!---Small-battery-powered-USB-charger/step2/The-Process-Come-up-with-an-idea/
Fashiondez2 years ago
Hey, does anyone know what to do when you hook everything up, and it is working/shows that the Iphone is plugged in, but it doesn't charge it? Should I cut all the wires and re attach them?
Ever solve this? Same problem.
gowtham771 year ago
If I rip out a USB Charging Circuit from a cheap charger would it work. I mean the transformer in the circuit is designed to reduce 230volts into 5 volts required for output. But when the input is just 6 volts would it work
henryd1061 year ago
Just how many devices at once could this support?
Is the USB constantly putting out charge? Because a switch would be needed to turn on and off the output, right?
Schmidty161 year ago
can I find another dc to usb converter that is cheap on RadioShack that will work on my iPod or is there a cheaper 1 that I can find in an old device if there is 1 at RadioShack what would it be called?
Schmidty161 year ago
cool thx I have a few questions
Houghie721 year ago
I have got the USB charging circuit from a USB car charger that turns 12v into 5v. Does this mean in order to charge, I have to have 12v going into the USB charging circuit?
On the brown dog gadgets website I found a 6V solar cell, and a 1.5V cell which would be best? I don't completely understand the voltage situation.
ccc21 year ago
I made this, and I am able to charge my simple keypad phone, but I can't seem to charge my ipod touch. I keep getting the message, "charging not supported with this accessory." I am guessing that this is because my ipod needs more power to be charged, but 'm not sure. Any ideas on how I could fix this?
ttawi1 year ago
Hi~ u said "just connect all the red wires with all the black wires", but u r actually connect the red wires to the red wires. i dont know what to do. i think i should connect the postive wire from the solar panel to the postive wire from battery, right?
yoji1 year ago
hello, i have a question. how can we know if the battery is fully charged? and is it possible that battery may explode due to overcharging? how to prevent it?

thanks.
lg902211 year ago
i have a question im new to this but i was wondering can you use the usb circuit found in car chargers? because those are 1.99 compared to the 8.99 dc to usb circuits. i know it takes 12v and drops it to 5v volts but if it receives 6v wont it just drop it to 5v? not really into the whole elctronic thing. or where can i buy cheap dc usb
rev5121 year ago
Hey so it started charging for a few seconds and then my phone said something about my phone is not comparable with this accessory and now it won't charge!?!?
Sorry if this has already been asked, but will this one work with an iPhone 4s?
bulletbkr1 year ago
just a note, if you use hot glue to secure and insulate the connections and wires on the back of you solar cells, be sure to put something under them when you put them in the sun to charge. I now have a ruined dashmat in my truck because the hotglue melted into the fibers as I was charging my batteries. Boo for hot glue. I thought it had a much higher melting point than that.
BillMetrey1 year ago
Hello, I tried to access y our website several times with no success. Are you still accepting requests? I would like to buy at least one of your solar chargers. Thank you!

Bill Metrey
kldtia1 year ago
I attempted this project. I have one question I'm charging a samsung Gs2 phone and I pluged it in. It says it's charging but when I look at the phone it seems like my battery is losing charge. What did I do wrong.

Thanks
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