Picture of DIY Solar USB Charger - Altoids

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.

Step 1: What You Need

Picture of What You Need

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

Soldering Iron
Tin Snips
Melt Glue Gun and Glue

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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I purchased a cell phone battery pack extender and was not impressed so I'm looking into making my own. I first tried connecting one of those cigarette lighter USB converters into a 12V power point adapter connected to a 9V battery but the phone would not constantly charge. If that makes sense.

But charges perfectly fine off the 6V car battery on my Trabant. The only thing I can think of is the milliamp per hour rating of the 9V battery I was using was too low to support charging.

georgeyhere1 month ago

By 'USB charger' do you mean the cable or a wall adapter?

koby71 month ago

i love it

dr_amazo1 month ago
the OP mentioned that you can take the circuit out of a phone charger and use it for this project. what I'm wondering, though, is that the project calls for a DC to USB circuit, whereas the wall chargers would be AC to USB circuits, right? if this is correct, do I need to do anything to alter the chip I take out of the charger in any way to fit with the project, or can I use it as is and just insert it into the new circuit?
Nice build. Do you think if you placed a mirror in the lid you could use it to refract more light onto the solar panel?

Have a great day! :-)
JoshuaZimmerman (author)  Just4Fun Media3 months ago

Nah, it would be a super duper tight fit then, and you're better off just angling the panel at 45 degrees.

justForFun's idea [ i think ] was to have direct sun on the panel PLUS reflected light from a mirror to increase output LOL i think you misunderstood the idea trying to be conveyed. JustForFun did not mean for the mirror's light to be the only light applied to the solar panel. personally i thought it was a fantastic idea!!!!!! be well my friends

ThomasW202 months ago

Could this be done using an 18650 battery? I am thinking this way I could set it in a window to charge all day and get a full charge or 2 to my cell phone off it.

Di Immortales2 months ago

have you thought about using super capacitors? they charge in seconds

JoshuaZimmerman (author)  Di Immortales2 months ago

Super caps are nice, but they hold very very very very very very very little amperage compared to even the cheapest AA. Sure, you could get giant soda bottle sized super caps (and spend hundreds of dollars per cap), but thats a bit above and beyond the scope of this. With current technology it's not financially or practically a good solution.

Azzurro3 months ago

nice and simple, i like it. a question: why don't you add a switch for solar charging? just because when there is no sunlight, the panel will slowly drain the batteries. better to open the circuit when you don't use the panel.

JoshuaZimmerman (author)  Azzurro3 months ago

Thats why there is a diode, to prevent drain. A lot of people add switches to this project, no reason why you couldn't. Just not necessary.

ah well okay a diode is a lot better of course :)
Elmercab4 months ago
I got this circuit board off an LG travel charger . Trying to figure out where I would put the negative and positive wires. I also wanted to add a switch I'm not sure if that would makes things more complicated. Wondering if any of you could help

those looks like a step-down? If they are they will work if you have a big solar panel to step the voltage down to 5vdc. You can get the battery powered usb charge at the Dollarama if you live in Ontario, they are like three bucks!

What the guy above me said. You have a STEP DOWN. You want a STEP UP. Two completely different things.

GaetanoM3 months ago

sorry, where have u find the usb charging circuit

JoshuaZimmerman (author)  GaetanoM3 months ago

My website, browndoggadgets.com

BilalK23 months ago

Does this work with 18650 battery cells?

JoshuaZimmerman (author)  BilalK23 months ago

No, you'd need a charge controller in the mix. At the start of the write up I link to my Lithium Heavy Duty 2.0 project, which uses 18650 lithium battery cells. It's not too much different from this write up.

this instructable was posted in 2011, so this guy made it about 4 years ago.

Edbed3 months ago
These look awesome!
SeanC57 months ago

What was the problem with this kit? what batteries did you use?

JoshuaR8 SeanC57 months ago
aa batteries
SeanC5 JoshuaR87 months ago

Lithium aa?

Those would explode.

Lithium batteries are NOT rechargable. Lithium-Ion batteries are, but with special controlling hardware. He used Nickel Metal Hydride batteries (Ni-Mh), your standard rechargable ones.

use NiCads if you are not concerned about their self-discharge rate, they have a much higher mAh than their cousin NiMh.

JoshuaZimmerman (author)  waterlubber6 months ago

Rechargeable 1.2V AA batteries. Nothing special.

RodneyMori5 months ago

what happens when the battery is fully charged, nothing is connected but the panel is left out in the sun?

given the cell panel's low amperage, it should be safe to leave them in the sun once they are fully charged.

JoshuaZimmerman (author)  RodneyMori4 months ago

Nothing. It just kind of tops off. Thats why we keep the amperage low enough as to not harm the batteries.

SeanC57 months ago

What was the problem with this kit? what batteries did you use?

JoshuaZimmerman (author)  SeanC56 months ago

Not enough battery power, not enough solar power. Newer gadgets require more amperage and 2 AAs just doesn't do it any more.

will energizer rechargeable batteries work they are 1400 mAh

they would work, but it will give your device about a 10-15% charge before they drain.

So if i make this will it charge my galaxy s4? Because other comments arent specific

It would charge it but since the energy density of the two AA batteries aren't that high, it would charge your S4 to about 10-17% before the two AA batteries drain.

every time i plug my phone in it shuts off

whats wrong

Probably you've done something wrong with the connections and either there's a short circuit or the voltage is too high/low. Recehck all the connections and/or use another converter.

Will this work for the converter I took it out of a car charger
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