# Five minute solar phone charger

Need to charge your phone?  Have nothing but a clothespin and some P-N junctions?  Have no fear!  The (solar) power is in your hands!
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## Step 1: The Big Idea

So, what's the plan, stan?

Well, we're going to make a solar panel from scratch that can charge up a simple phone.

See, cheap phones like mine are real simple to charge--they just need 5V and they'll take care of the rest.  They'll draw as much power as they can (my little nokia will draw up to an amp while charging), but they're smart enough to limit their current draw to whatever the source can provide.

So, that means we need to make a 5V solar panel.  Solar panels are made by wiring up a set of solar cells--big silicon P-N junctions.  A solar cell puts out a very low voltage--0.65V open-circuit, or around .55V under an ideal load.  To get the 5V that we need to charge a phone, we have to wire up a bunch of solar cells in series.

But how many solar cells?  Well, a solar cell without anything connected to it will produce .65V in bright sunlight, but as I draw power from the cell, the voltage will drop.  This relationship is called an I-V curve.  The max current the cell can output is based on the area of the cell, the intensity of the sunlight and the temperature of the cell, but the max voltage is always the same, regardless of the size of the cell.
Every solar cell has a peak power point, a current-voltage combination that gives me the most possible power for that cell.  For my panel, I want to run my cells at their peak power point.  I happen to know that the peak power point of my cells is .5V at 130mA.  So, if I want to put out 5V, I need to stack up at ten solar cells in series, giving me an output of 5V.  If I'm drawing less than 130mA, my output voltage will "float" up, and if I draw more, my voltage will get pulled down.  Now, it so happens that phones are pretty smart and robust, so I can actually give them a bit more than 5V, and they'll be fine.  I'm actually going to add an extra cell, giving me a total of 5.5V coming off my cell.  This makes my panel a little more robust--the higher voltage means that, in lower light, it'll still put out enough voltage to charge up my phone, and it'll be less sensitive to shading or pointing it away from the sun.

So, I'm going to make a solar panel with eleven solar cells in series, I'm going to wire the output into a phone, and it's going to charge.  Cool, right?  It's pretty quick and easy to do, too.  Here's a video of the whole process:

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sanchitkhera7 says: Jun 4, 2013. 4:50 PM
Any chance of damaging the mobile phone? Does it work for smartphones too?
contactscolored says: Apr 4, 2013. 10:48 PM
I am fairly new to Instructables so I will have to take a look at putting it together. I definitely want to get a video up. I'll let you know when I get either up. (I tried replying but the captcha thing seems messed up)
Fhev says: Feb 14, 2013. 6:22 AM
sir, anu pa pwedeng ikapit sa clip bukod sa copper tape? anu ba pwedeng applicable bugod sa copper tape? pwede din q ba gamitin ang universal charger cable? iisa din lng ba xia? kung saka sakaling ganun gawin q, mas mgnda diba?
JensonBut says: Jan 25, 2013. 11:19 PM
I made these last night and the were delicious BUT the flattened out...
Gigean says: Jan 7, 2013. 8:14 PM
Is it possible to do make this for a smartphone? Is it recommended? I'm looking for a way to safely charge my Android phone
prank (author) in reply to GigeanJan 8, 2013. 12:05 AM
Sure! The charger I make in the instructable just outputs 5.5V at ~100mA. If you slap the appropriate USB connector for your smart phone onto the alligator clips, there's a good chance it'll power it up. It depends on your smartphone--some phones will be more finnicky about their power, but you won't hurt it. I say give it a shot!
prank (author) in reply to GigeanJan 8, 2013. 12:05 AM
Sure! The charger I make in the instructable just outputs 5.5V at ~100mA. If you slap the appropriate USB connector for your smart phone onto the alligator clips, there's a good chance it'll power it up. It depends on your smartphone--some phones will be more finnicky about their power, but you won't hurt it. I say give it a shot!
rimar2000 says: Dec 20, 2012. 10:15 AM
Very clever design!
lwillen says: Sep 26, 2012. 3:18 AM
jesus-i cannot see the clip because in germany it is blocked because of music copyright
prank (author) in reply to lwillenSep 26, 2012. 7:02 PM

It's the same video, but with creative commons music. Another guy, also from germany, had the same problem. I learned my lesson--all movies I put up from now on will have cc soundtracks.

--me
SelkeyMoonbeam says: Jul 17, 2012. 4:35 PM
Super cool!
Paulus44 in reply to SelkeyMoonbeamJul 20, 2012. 8:51 AM
Can't wait to do that tomorrow. Every day sun in the Philippines. (almost every day). But the problem the solar panel.

Thanks.

"...or stay tuned for a DIY solar kit kickstarter my friend and I are launching soon"
when???????????
prank (author) in reply to Paulus44Jul 21, 2012. 5:35 AM
Saan nakatira ka sa pilipinas? Nakatira ako sa maynila!

Kickstarter kit is coming August 15.
filipeanut in reply to prankAug 22, 2012. 4:58 AM
Hey cool you're in the Philippines?

Where can I buy them here? I'm in Bohol but I'm willing to get to Cebu or Manila to buy a bunch of these and make with my friends and family here. What Filipino doesn't use these Nokia phones? lol

Salamat!
prank (author) in reply to filipeanutAug 22, 2012. 5:10 AM
Hey Filipeanut,

We're running a kickstarter right now, and kits of solettes are one of the rewards. Check it out at http://www.kickstarter.com/projects/alex9000/the-solar-pocket-factory-an-invention-adventure.

Salamat naman!
Paulus44 in reply to prankJul 21, 2012. 6:15 AM
Im from Netherlands and live here. Only english pls.
Thanks
JerryBYong in reply to Paulus44Jul 25, 2012. 6:59 AM
Translation of the above. "Where do you live in the Philippines? I live in manila!"
Paulus44 in reply to JerryBYongJul 26, 2012. 5:37 AM
I do live in Cagayan de Oro but this week we have a lot of clouds and rainy days. Anyway I have already the solarcells, but the coppertape was more difficult. But I found some scrapcopper and can use that. Tomorrow I make it and there are already some people from the mountains who will buy one.
I also read in the newspape that there there is a T-shirt what has a special procedure and it also work as a charger when you wear it. A wire from the T-shirt to your cellphone and your CP will be charged via your t-shirt.
Amazing.
JerryBYong in reply to Paulus44Jul 25, 2012. 6:58 AM
I live in Singapore! Sun everyday too!
gemtree says: Aug 6, 2012. 8:58 PM
The copper foil tape can be found where they sell stained glass supplies, usually in different widths.
brintxin says: Aug 2, 2012. 12:02 AM
Tremendous instructable!

Please does anyone know wher to buy these wafers ? - I just can't find an outlet on the net.

Thank you.
prank (author) in reply to brintxinAug 2, 2012. 4:04 AM
The ebay link from the materials page shows a bunch of places you can buy them. And we're releasing a kit on kickstarter in two weeks. Stay tuned!
brintxin in reply to prankAug 2, 2012. 4:31 AM
Thanks, but on the display I cannot see a materials page. I only see photos and the text and their are no links there.
I look forward to the kit.
prank (author) in reply to brintxinAug 2, 2012. 5:19 AM
Here you go--I should have made this an actual link. http://goo.gl/C25he

You can get the solettes from various guys on ebay, taobao, aliexpress, or anywhere else you search for "solar cell piece"
noahh says: Jul 27, 2012. 4:11 PM
If anyone is looking for copper tape, it's often sold at hardware stores in the pesticide section because it repels slugs.
mysss says: Jul 25, 2012. 2:27 PM
Awesome. So I take it a smart phone would likely be less robust?
chantie3 says: Jul 22, 2012. 7:04 AM
Do you think this would work safely and not break my iphone4? Thanks, Mary
JerryBYong in reply to chantie3Jul 25, 2012. 6:57 AM
Hi Mary,

This project won't "break" your IPhone as the iphone will simply say charging device not recognised. this project currently won't work for newer iDevices as they require a special circuit.

To quote Chunkyhampton
"Actually, charging Apple's devices is a little more complex than just supplying 5V on the USB port. You must also tell the device how much current to draw. This is done by supply a potential to the D+ and D- lines, using a couple of resistors.
This was reverse engineered by and is explained in detail by Lady Ada here:
and also a bit on my attempts at doing it here:
http://www.re-innovation.co.uk/joomla15/index.php?option=com_content&view=article&id=167:voltage-regulators-a-go-go&catid=48:blog&Itemid=75"

So yeah hope this helped
graghavendra says: Jul 22, 2012. 5:06 PM
actually these solar cell's are available which require for charging and all, at various sites,

dealsbookie.com, ebay.in also one of the sites where you can get solar cells
6v 100ma, 6v 200ma, 7v 100ma, 3v 100ma
resin laminated, cabinet, small kit, soldered with clip all available at just 4-6\$

can charge mobile phone by that, even can charge AA AAA batteries, can make solar lantern's and all
prank (author) in reply to graghavendraJul 23, 2012. 1:15 PM
You can definitely buy pre-made solar panels anytime you like. This instructable is about a different way of making them yourself. It's not a replacement--it's an alternative for anyone interested in what goes inside those pre-made panels.

I started experimenting with making my own small solar panels after I was dissatisfied with the existing resin-laminated panels--I was finding panels with shorted solettes, putting out a lower voltage than I needed, the resin would yellow in the sun after a couple years, making the whole panel unuseable, and after looking into how the panels are made, I started wondering if there could be a better way to make them.

Now, I'm not claiming that this instructable is a better way to make solar panels. There are plenty of flaws with the fanned design I used here. But it's just cool to make your own solar panel from scratch, and I put this instructable up to share that coolness.  Because making something yourself is always more interesting than buying it.
graghavendra in reply to prankJul 23, 2012. 11:20 PM
its nice to hear back from you..

i wish to say, resource and knowledge availability is very important, which always vary from country to country..
think about the country which are growing, knowledge they have towards solar
even now, millions of people seeing solar only in books, they think its complicate, unreachable, misunderstanding concept. because of above.

and all of sudden, u can except all to do as u said, level of knowledge, understanding capability and resource and patience and support all these must required to do it.

i suggest to buy resin, cabinet at 1st, test it, be practice, become friendly with the subject, then go deep to make ur own..

and the place where i mentiond, u get cabinet one. so no worries about disadvantages of resin..

who cant do all for themself atleast let them do this, i hope if they start slowly they reach goal for sure a day, a person who dont know anything, cant get satisfactory results when he done such deep experiments

let me say some info, i m a deep hobbyist, done many plenty.. still availability of these solar panel is tuff, and u mention copper tape, that too..

most are copy cat at beginning they dont use their brain to find alternative, so they think we cant do these. and drop their idea/wish
Brian996 says: Jul 23, 2012. 3:18 PM
Just a thought: You could rivet the solettes with a plastic non-conductive rivet and attach the conductive tape to each side of the solette pack. No clip needed. Then the charger would fold up to a pocket size.
prank (author) in reply to Brian996Jul 23, 2012. 6:47 PM
I dig it. I actually started this response about how hard it is to put a hole into solettes, and then it crossed my mind that I'd never tried circuit board drill bits.

I tried one, and after fumbling and breaking my way through ten solettes, I got it! I actually drilled a hole in silicon, to my utter surprise. I'm using a ~1mm bit that's meant for fiberglass circuit boards--it's a rando bit from an electronics store in manila, so I'd bet against it being a fancy-schmancy diamond bit or anything like that.

I dig the rivet idea--my recommendation after a bit of drilling is to do it on a perfectly flat, hard surface. If the surface can compress at all, the solette will bend, build up stress, and snap where the drill bit is pressing into it. I like drilling from the back, too--the drill bit centers in the metal screenprinted layer before it starts cutting into the silicon, and it's easier to get the hole where you want it.

With the rivets, I'd use a nice wide rivet or a washer to spread out the force, otherwise it'll be snap city.

Now I want to build a solar necklace with magnets to hold everything together!
xenobiologista says: Jul 23, 2012. 9:35 AM
LOL...mouse AEDs. Your captions are hilarious.
marymac says: Jul 23, 2012. 7:58 AM
As clueless I am I might vote to buy a solar charger for USB devices for as little as nine bucks or a fancier one for about twenty and all in a case. The iPhone wants a lotta beef for a charge but will it ever get enough?
blancast says: Jul 23, 2012. 7:54 AM
On the fan design: How about adding an axis to the fam pivot...a hole through each segment and through the jaws of the clothes pin with a plastic rod running through the lot. The rod could just be mushroomed on each end with a hot piece of metal or glued.
Not only would this solidify the thing a bit and make fanning it out easier, the extra security of the attachment would make it easier to fan the pieces out for maximum exposure.
nof-z says: Jul 23, 2012. 5:17 AM
is it possible to use an iphone charger?
JerryBYong says: Jul 23, 2012. 2:11 AM
Hey is it possible for me to use a few of those solar cells from solar powered calculators?
prank (author) in reply to JerryBYongJul 23, 2012. 3:15 AM
Hi Jerry,

You can use those solar cells--those are amorphous cells, which means that they're lower efficiency than the crystalline cells I use in this instructable, but they put out higher voltage in low light. A calculator uses a string of those cells--four or five cells in series, and to get to five volts, you'd need the panels from two or three calculators in series. It's definitely worth an experiment!
gibi24 says: Jul 22, 2012. 8:43 AM
i'm now bidding for the items needed, can't wait for the items to arrive, you know how slow post to manila can be at times. thanks! finally a diy project i think i can finish.
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