Solar power is big these days, from power plants to rooftop arrays! This guide shows how to build your very own solar charger for small electronics. This charger will charge most small USB devices such as cell phones, mp3 players, iPods, and iPhones. These directions are designed to use parts from our Solar USB Charger 2.0 Kit though you can also find many of these parts elsewhere online. We have also included a circuit diagram and files for the laser cut enclosure (Step 1).

This project was designed for beginner Makers and students. It requires a base knowledge of soldering. While you can charge small gadgets, this project is not appropriate for camping or to be relied on for survival situations.

Difficulty: Easy

Cost: Low

Time: 30 - 60 minutes

Step 1: What You Need


Grab a Kit


Electronic Parts

1x USB Charging Circuit

1x 6V Solar Cell

3 x Rechargeable NiMh AA Batteries

1x 3 AA Battery Holder

1x 1N914 Diode

1x Toggle Switch

18 inches Stranded Wire

3 inches Shrink Tubing

Wooden Enclosure Parts

1/8th Inch Plywood

16 x 6-32 Screws

16 x 6-32 Hex Nuts

Double Sided Foam Tape


Soldering Iron


Wire Cutters

Wire Strippers

Screw Driver

Optional Tools

Electrical Tape

Hot Glue Gun

Helping Hand

Access to a Laser Cutter

Sourcing Your Own Parts

This section will be most useful for those sourcing their own parts, if you are building from a kit, feel free to skip ahead.

USB Charging Circuit

USB charging requires 5V at around 500mA of power to charge most gadgets. In order to meet these criteria in a small package we use a USB Charging Circuit, which boosts low voltage (2V) DC up to 5V DC. Nothing comes free though; we trade our increased volts for fewer amps. To avoid this tradeoff, we could use larger solar panels and larger batteries, but this would result in a larger, heavier, and more expensive charger. Take a look at our Lithium Heavy Duty Solar USB Charger 2.0 if you want something with some extra power!

If you're using an older Apple product, make sure your USB Charging Circuit is compatible. Typically a USB gadget requires just power from a USB port to charge. Most iPhone models, however, require a tweak to USB to work. iPhones will check the USB data ports in order to identify what kind of device it's plugged into and change charging speeds if it thinks the port can support it. Unfortunately if it doesn't see anything on the data tabs it will refuse to charge. This is a problem that plagues many generic USB chargers, especially older ones.

If you don't have an iPhone or iPod, then any old USB Charging Circuit will work. If you do have an iPhone or iPod you may wish to grab one of these charging circuits, as they're the only ones we have found that seem to work.

Our USB Charging Circuit needs a minimum of 2V to operate, so we need to choose power sources with this in mind.

Battery Power

We always advise the use of power storage when doing a solar project. Solar is inconsistent due to the inconsistent nature of the sun. Using batteries helps stabilize the flow of power, and also lets us hold onto that energy for later use.

In this project we use three rechargeable AA batteries. Rechargeable batteries put out 1.2V of power and using three in series gives us 3.6V. Using two batteries will cause our voltage to drop below 2V too quickly, and our USB Charging Circuit won’t be able to operate. Four batteries would require a much larger solar cell to charge.

Solar Power

Batteries require a minimum voltage in order to charge, but raising the voltage will not cause the batteries to charge faster. The general rule is to provide 1.5 times as much voltage as your battery needs (for us 3.6V x 1.5V = 5.4V), but with solar we want some wiggle room. We want our solar panel to meet the minimum voltage, even on days with a few clouds, so a 6V panel does well.

When charging AAs using a wall adaptor, we're able to charge them at high speed due to smart chips that constantly monitor the battery. Since our circuit is "dumb," with nothing to monitor the batteries, we trickle charge the batteries using the 10% rule. AAs can be safely charged as long as they don't have more than 10% of their capacity thrown at them at any one time. This means our 2,000mAh batteries should only get 200mA of current.

Our solar cell is rated for only 80mA, so we're completely safe! Different panels and batteries vary, so make sure yours work well together. One good aspect of the trickle charge method is that it will never over-charge the batteries. Once they're full they just stay topped off.


Above is a circuit diagram for this project. It's designed so that the solar cell is always charging the batteries and the toggle switch turns the USB circuit on/off. A diode has been put in place to prevent power from flowing the wrong direction into the solar cell. This is a very common design for solar chargers.

Our kit comes with a wooden enclosure made from 1/8-inch laser cut Baltic Birch plywood, with holes cut for wires, switches, and ports. Wood works well because it is non-conductive and easy to paint or decorate. We have included the files here for anyone who has access to a laser cutter.

If this isn't an option for you there are more simple ways of making an enclosure. Inexpensive and easy to find, plastic food containers or bins work well. If possible find one with a rubber o-ring, which helps keep moisture out. These makeshift enclosures are also are easy to modify with a box cutter or exacto knife, just watch your fingers!

It s also possible to find "Project Boxes" at many online stores. These also work quite well for enclosures, but tend to be more expensive. However, we advise against metal enclosures. Altoids tins and metal project boxes may look nice, but they are difficult to modify and can easily short out projects if left uninsulated.

<p>Is it possible to replace the batteries with supercapacitors? i heard they charge up faster.</p>
I made one that was this, then I am currently, soldering 5 seconds ago, making one that also has a crank charge too :). the advancement abilities to your project here are amazing and easy as pie.
<p>If you added more batteries ie. enough to make it to 5 volts would it still charge on apple devices</p>
I realIy liked your project idea :) . So I wanted to ask if you can charge the phone battery when you have your solar panel and the batteries connected/active? Or can you only firstly charge AA batteries with your solar panel then turn off the solar panel and then charge phone battery from AA batteries?<br><br>If you can have all the components active at the same moment wount the solar panels 6v be too much for the charging circuit? The charging circuit can take voltage between ~2,6v and ~4,8v ( correct me if I'm wrong) . Would using a solar panel with lower voltage but with higher amperage solve this for example?
<p>Hi, I just finished making the Solar USB charger and put in a new pack of rechargeable batteries. But when I charged it into my iphone 5s, it could only charge for about 7% before the small coil on the <a href="http://www.browndoggadgets.com/collections/charge-controllers" rel="nofollow">DC to DC Boosting Circuit with 5V USB Output</a> (the red one not the Apple one) started to get really hot and made very weird noises. Does anyone know whats wrong with it? I checked my wiring and it doesn't seem to be wrong to have caused a short. Any suggestions?</p>
Will this charger work with an iPhone 6?
<p>I am using a 4.7V, 500mW, 120mA solar panel. This is supplying three 1.2V(x3=3.6V), 2100mAh AA batteries through a 1N914 diode. The output of my battery pack is supplying a DC-DC boosting circuit with USB output. I am getting an output of 5V. But when I connect my phone to the USB port, the charge percentage goes down. What can I do about it? Is my current or power not enough?</p>
<p>how many amps does the apple circuit produce</p>
<p>also, when i charged my iphone with the apple circuit, it didnt charge. But when i used my android, it worked BUT it only showed that its charging but the battery actually went down, please help</p>
<p>Make sure your batteries are all charged up. Also, some phones draw more power than the USB circuit puts out. They are CHARGING but their percentage goes down since they're using more power than you're putting in.</p>
<p>Does this work for iphone5 also because its a USB?</p>
How did you make the board? Can I ask for a guide? Sorry im new
<p>hi, i was wondering what are the dimensions for the laser cut box. If you can reply, thanks</p>
While it is off does it still charge the battery
Awesome! Looks like the ghostbusters ghost trap; ) we need more solar stuff! more more!
<p>We're working on it!</p>
If i wanted to buy one of these could i purchase one from you?
<p>Thats the idea. We have kits, and we highly recommend you building one on your own. It was designed for middle school students to learn how to solder with.</p>
<p>so i have 4x 1.2v (= 4.8v)solar panels from those yard lights you buy from walmart they suck as lights but they come with a solar cell and rechargeable batteries so it can last all night (they dont) so im using them would they work or since you need 5v do i need to add another</p>
<p>each of my solar cells puts out 2.2v +- 0.2v so with the 4 i get 9v</p><p>so do i need all 4 and all 4 batteries or can i can i do with the 3 like you</p><p>oh by the way my batteries are the 2/3 aa the weird short ones but normal sized around </p>
<p>The big issue isn't the voltage, it's the amperage. Thats what will determine how fast things charge up. Typically the ones out of garden lights are super low amperage. You'll be waiting weeks to charge up the internal batteries.</p>
I like the bleach wallpaper on the phone in the pictures
<p>Ha, not my phone!</p>
Thank you for share your project. I think you will be right to use a boost up from the Solar power to the USB. Anyway, you use the diode to drop the voltage from the solar power to the battery and not to let the current flow from the battery to the solar power, isn't it ?
<p>It's to prevent the solar cell from sucking power from the battery, which would destroy the solar cell.</p>
<p>Do I have to use this 1N914 diod, or can I use (nearly) any other? Go some electrical waste here..<br>What do I have to care when choosing the diod?</p>
<p>Pretty much. 1N914 is super common and cheap, and has a low voltage drop. Thats why we use it for a lot of our projects.</p>
<p>Great instructable and a fun build. The only mods I made were hot glueing the battery holder, USB connection and solar panel on.</p>
<p>Hot glue is the way to go. Looks nice.</p>
Or anyone if they could answer
I promise I am not a narc
Hey guys i need to know ASAP... I have created my own model of solar charger, i have searched up the patents on solar chargers and Tsann Kuen Enterprise Co Ltd seems to hold a patent for solar chargers have you guys received any threats since you sell your products?
<p>they just say this charger is not recognized and then charge anyways or atleast thats what mine did</p>
<p>How long should it take to charge? I left it in the window for about a week and it charged my phone (galaxy s3) for maybe 5 minutes before cutting out . While it isn't super sunny out, I expected a little more. Is that normal?</p>
<p>Depends on many things. I've found that Galaxy S3 phones are tough to charge due to the fact they want 1A or more of power, plus they have huge batteries. For those phones you really need to use a Lithium Battery instead of AAs (plus the right protection on it).</p>
Instead of foam two sided tape, i used a hot glue gun
<p>Yup, that works just fine as well. Hot Glue is not conductive, though it is a tad messy.</p>
<p>Would a DPDT center off toggle switch work? If so, are there pros and cons? </p>
<p>Thanks for putting this together! Can you please tell me what the the voltage across the USB pins before hitting the voltage booster would be? </p>
<p>Hi, if I used a 12v lead acid battery would it be necessary to use a charge controller? How many AHR would be sufficient?</p><p>Thanks</p>
<p>You'd want to build a much much bigger setup if you were using a 12V Lead Acid. You'd want a big old 12V charge controller and a big 12V solar cell (18V actually).</p>
<p>Would i do any changes if i do it for charging an Iphone 5?</p>
that's understandable, but in my case I need something lightweight and easy to pack around so its perfect, but to each his own.
<p>They're just limited in size and metal. A small plastic container would work far better and be far easier to waterproof.</p>
if i change the battery with battery size D 1.5v and 6000mAH. solar charge still works?
You need to have rechargeable D batteries, regular ones won't recharge. If you have rechargeable ones it would work just the same, only it would take a much longer time to charge up as their capacity is greater than AAs.
As I am in the army and need to keep in contact with people this is absolutely necessary for me I switched out the small solar panel for a 5w one and I fit everything into an altoids tin and it fits very nicely, as long as you layer the bottom of the tin with electrical tape you won't have any problems with shorts.
True, I do love Altoids tins. They're just&hellip; not my medium of choice any more.
I made this and I absolutely love it the efficiency rate I have calculated at ~90% +/- about 3% for error on my part

About This Instructable


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Bio: I used to teach middle school science, but now I run my own online educational science website. I spend my days designing new projects for ... More »
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