Picture of How I built a Solar iPhone Charger for under $50.
To see my personal site with these tutorials and news, please visit http://www.BrennanZelener.com


I am not responsible for any damage that you may cause to your iPhone or any device that you use with this charger. I can not stress the importance of checking your circuits with a multimeter enough, and I can assure you that I've done so at every step in this build process. Your phone is a very expensive device. Treat it like one!

Intro and Design:

Over the past month or so, I've been working on designs for a stationary solar iPhone charger. By stationary I mean a charger that will be kept in a fairly permanent place. I bring mine with me if I'm going to be camping or staying somewhere for a while, but it's really not meant to be portable.

This isn't only a solar iPhone charger. You can use it with any device that will charge via USB. I just happen to use it to charge my iPhone. Also, this design doesn't include a battery in the circuit - which means that you'll have to charge your iPhone when the sun is out and shining. I know it's a serious inconvenience, but adding a battery makes the circuit much more complex - and is a bit more costly. I'll be following up this design with an update on how to add a battery conveniently into this circuit.

The idea behind this panel is that it's simple (and cheap!). You don't have to have any prior circuit knowledge,or familiarity with electronics. I'm really just stepping out of the novice stage as far as soldering is concerned, so this is a great beginner project for just about anyone!
akbrennan (author) 5 months ago

Hi folks, thanks for all of the comments! It's been over five years since I posted this tutorial. Since 2009 a lot of great solar cellphone chargers have been released. I really like the ones made by a company called Goal Zero.


When I made this tutorial I had very little electronics knowledge. This charger will work, but with the solar panel I used it's highly likely that you could burn out your 5 volt regulator (and possibly fry the charging circuit on your cellphone). The solar panel is putting out way more power than is needed. Please look for newer tutorials with more thoughtfully designed circuits.

Very creative , but don't you think it would just be too big. This might be very useful . But is it okay if I use this lightning usb data cables that is still compatible with iOS 7 or iOS 8 something like this one

http://ezrd.me/r/?rd=083K7OGCE ? It is my extra one so that I don't need to buy another one. I will let my husband do this and will keep you updated. Thanks!

I use a 1m long data cable so that my phone can still be put indoor without being exposed directly under the heat of the sun.

SparkySolar10 months ago


It is interesting, but maybe a little too big

Hi, can you give some info about how you connected the diode.

It is very dark in the photo.

... or buy the parts separately for about the same price (no soldering, wiring, or work needed)

solar panel : http://www.gomadic.com/solar-panel-10.html

charge circuit: http://www.gomadic.com/svc.html

tips to charge your mobile device : http://www.gomadic.com/cabletip.html

... or get one with a carying case and more already built : www.gomadic.com/sunvolt-standard.html


jscript2 years ago
What happens if the regulator gets too hot and burst? Will the iPhone get 20V? That is a dangerous voltage for a smartphone, right?
Sassah1222 years ago
This is waaay to expensive and complex. You can buy small solar panels for your car and modify them. I got a cheap sunlight - 12 volt soler panlel for $16. Then you just get a car power to usb adapter and attach it to the solar panel. Then just plugin your iPhone usb into adapter and you are good to go. I had my charger up and running for about $20 and in about 2 hours.
you don't need to manage or buy all these tools!!!
look at this DIY Solar Panels Blog
you can simply buy it at the cheapest rate from here
punith4202 years ago
dude you get a solar charger in e bay for Indian rupees 800 tat will be 20 dollars
get 4 of these http://www.siliconsolar.com/6000ma-3w-commercial-solar-cell.html there $7 a piece 3 watts each
A better alternative would be a LM2949 or 2954 low dropout regulator, 7805s are very wasteful
won't help too much, since it's not an app needing low dropout. It's not that the 7805 is particularly inefficient, it's that LINEAR REGULATION is going to be inefficient in this case. You could use a switching regulator module like http://www.dimensionengineering.com/DE-SW050.htm, but it would add to the price. Or you might be able to find a ~6V (nominal) solar panel (cheaper) and use that with an LDO...

Like the author said (sorta), the most efficient setup (price-wise) may not be the same as the most efficient setup (electrically.)
car charger are usually of the switching kind and are far far cheaper.
billgeo westfw3 years ago
Switching regulators are the way to go with those small panels.
You want to squeeze every last mA out of the whole circuit there!
mrdudej3 years ago
Is there a way to make it work with this ?


Also, is there a cheap way to implement a maximum power point tracking algorithm? Because the phone will draw more or less the same current (0,5 amps if you use usb charging), regardless of the irradiation. When there's not much irradiation, the voltage will lower and can prevent the voltage regulator from doing it's work properly. The charging rate should be limited when there's not much sunlight. How can i do this? Thanks!
ou're regulator wastes 75% of the power coming from you're panel as it's, but you bought it because it's cheap, right? I've bought this one: http://www.ebay.com/itm/270959601119?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649#ht_3676wt_1192

i did not care to check if this is a buck converter which won't waste energy because i thought every regulator works like this :) By closer inspection of the spec sheet, i assume this is a buck converter, but i'm not sure. Can someone confirm this? Thanks!
mrmerino3 years ago
I wonder if you could transform the output down to 5 volts, and then you could connect like four devices in parallel.
ASCAS3 years ago
The 7805 only limits the regulated power supply by 1 ampere, probably this wouldn't work with the iPhone 4S nor the iPad. But it's a good guide though :)))
garren113 years ago
Im planning on downsizing this and including a battery for it. My concern is what would be the chance of it potentially short circuiting the iphone if there is any chance at all. All help is appreciated.
Asmodeo5 years ago
Nice instructable!
I was thinking about something like this to recharge my cellular phone....
The regulator goes "hot" because the formula to calculate the disipated power is:

P=(Vin - Vout) / Iout
In your circuit:
P = (20v - 5v) / 0.5A = 15v / 0.5A = 30Watts!!!

Go get a heathsink for your poor regulator!

You possibly could use a 12V solar panel, with 0.5 Amperes output current, and the dissipated power would be

( 12v - 5v ) / 0.5A = 14W ...still in need of a heathsink...

I don't know if there are 9v solar panels.....

Wrong. P=IE, not P=I/E, so P out(max) is 7.5W
Hello Asmodeo, just a quick little blurp about you wondering if there were any 9 volt solar panels out there. Harbour Freight sells a neat little solar charger with battery power as well for around $12, not bad.
Yo! I just picked up the "1.5 Watt Solar Panel w/Auto Lighter Adaptor" from a Harbor Freight store for $14.99. My plan is to build a USB charger as well, however I'm going to desulfate a 12 volt hobby battery (7 amp hour) and use that to capture the daytime sun, and then charge my USB devices at night.

After I make my prototype, hopefully I'll buy another to put together an instructable, but a sneak preview includes me using 5 volt switching regulators instead of 7805's (linear regulators). You can get the switching regulators from Dimension Engineering. Another problem I need to work around is moving the solar panel "smarts" from the "auto lighter adapter" to the inside of the actual solar panel.

Lookin' great, keep it up!
Mouser.com has the Murata switch mode regulator
Just so you know, 15v at 0.5A is 7.5W, not 30. You multiply, not divide.
OUCH! YES, you´r right!!! but....I made you think. huh!
You should have spotted that since it's only a 10W solar panel. ;-)
Darn, I thought that he had cold fusion or something going there.
akbrennan (author)  bananafred5 years ago
Yes it is! I wondered where he was getting 30W, from calculation of a 10W panel... Thanks for pointing that out! Brennan
Sorry, I forgot to mention that it has several different settings for different voltages. They are as follows, 3, 6, 9, 12 volt configurations. I got it just to tinker with, works pretty well for my purpose and curiousity.
akbrennan (author)  Asmodeo5 years ago
Thanks guys! @Asmodeo - There are 9V panels. However, this was the best one that I could find for the price. As I mentioned, it's certainly not the most ideal for charging via USB, most likely it was made for charging 12V batteries. I was considering building my own custom panel, which would be the most efficient - but this was the easiest and fastest method, which makes for a good instructable for beginners. I'll continue to document my projects. Thanks for your comments!
monkyDJ3 years ago
Do you need more then 10 w???
monkyDJ3 years ago
I hope this works man, because I doing this for a project and I need to get a good mark!!! lolz
ginbot864 years ago
Instead of a linear regulator, you could pick up a switched-mode PTH08080W from Texas Instruments. They offer sample parts free of charge, and even shipping is free. These offer over 2 amps of current compared to one of the linear regulators, and is adjustable with a simple potentiometer.

peppero4 years ago
i have a problem my phone not charge but discharge and the same for the mp3 player how it's possible?
sdobbie4 years ago
There is a much quicker way to do this. If you got a usb car charger and connected it to the solar panel you would have a more efficient charger. Car chargers accept voltages from 12 to 24 volts usually.
Phoenixmill5 years ago
What works for some good low voltage Solar panels are the Garden lamps that people use to line their driveway. you can ghetto rig those together to get really low voltages, or really high ones. you would be surprised at how many people have broken garden lamps they are willing to get rid of.
if you decieded to use one of those, would you need the same parts and everything?
Good idea!
ReCreate5 years ago
I recommend you strap the Voltage regulator to something, It may overheat while the i-phone sucks electricity through it. Though they do have thermal shutdown to prevent them from burning themselves up.
7805s do indeed have heat overload circuitry, as do, no doubt the murata switching version that's a drop-in replacement.
This seems awesome! I am not sure if someone already mentioned this in the comments, but isn't it bad for electronics to be exposed to too much light? Someone told me that once and you can even read it on the back of the packaging. Simple solution: cover up that iphone with an empty dark container (as house to keep it cool)?

I am gonna try tackling this project this summer!
Uhh - if I wanted to keep something cool outdoors, I might use something white or even reflective.
krimb15 years ago
 What a great guide! Really sturdy, and the built-in blocking diode is really awesome.

One question though: this setup won't trickle charge the iPhone after it's fully charged, right?
lloydrmc krimb14 years ago
I seriously doubt that an iPhone counts on the charger to do anything. The charge circuitry is going to be in the phone.
lloydrmc5 years ago
Try the Murata 78SR regulator.  It's a drop-in replacement for the 7805, except that it's switch mode, can handle two amps, and is much more efficient than the linear mode 7805, to the point that it doesn't even need a heat sink.  I wouldn't sweat the higher current - the unit will draw what it needs.  I would do the resistor hack, though.
WOw I never heard of that part -- sounds great
It's not even expensive. Try Mouser.com
senor taco5 years ago
For some reason my iPhone won't charge from this. I tested all the connections, and everything should be working, but when i plug my phone in nothing happens...
Once again, build this circuit.
dizingof5 years ago
Are you sure it's charging your iphone? :) A simple usb connection wont do it for the iphone, you need to add 2 resistors to the D- and D+ of the usb connector to let the iphone "know" it can start accepting current and start charging.. Note this, an icon for a REAL charging status is a small lighting and not a 'concected to usb' icon... google for more info on how to charge an iphone using USB . Good job!
It is not actually charging his Iphone. For it to charge he needs to build this circuit.

 +1 on this comment. Apple stuff (and other picky devices) really need the USB signal in order to charge. (Hm, since yours charged anyway, it's not an absolute requirement I guess...)

For more info about this (or how to make your picky device charge with your custom charger) check out this instructable: 

Could you be a little more specific about those resistors? I think that is the problem I'm having with my charger, so if you could help me out that would be great.
akbrennan (author)  dizingof5 years ago
Thanks dizingof! The charger seems to work beautifully - but occasionally my iPhone will refuse to charge from it. I just blamed it on the sun, - but your suggestion sounds much more plausible :D. I'll definitely look at adding the resistors on the next circuit. By D- and D+ do you mean the data cables? Thanks! Brennan
akbrennan (author) 5 years ago
 Hi guys!

Thanks for all of your comments, they are all thoroughly appreciated. I'm sorry that it has taken so long for me to fully respond.

This solar charger was a very fun project. I am going to be working on a more efficient and smaller charger this summer.  - If you are interested in contributing to the project, feel free to email me at brennanzelener at gmail.com.

As the charger stands right now, if you are planning on building your own, I would recommend checking out the MightyMintyBoost. My charger, while simple, can run into problems with the 5V regulator being the only circuitry.

I'll be updating my blog and instructables with a new iPhone solar charger design, as well as a MacBook solar charger in a couple of months. I hope to talk to you all then!

knektek5 years ago
would 3 X 4v 80ma solar cells work if i connected them in series?
thepaul935 years ago
Nice Job
But I was wondering if I could use a 2W 12V Solar Panel?  As 10W panels in Australia are expensive.
Johenix5 years ago
Cheap (perhaps even free) solar panels can be obtained at your local Volkswagen dealer. The panels are plugged into the cigarette lighter socket of cars in transit to keep the battery charged. They produce 12 volts at a few miliamps and have suction cups for attaching to the inside of a window. Or look for VW Solar on EBay.
is there any other alterations u have to make if u use the vw solar charger.
akbrennan (author)  Johenix5 years ago
Thanks for the tip!
mediaburn5 years ago
So what type of charge times are you getting with this set up?
akbrennan (author)  mediaburn5 years ago
In full sun, the amperage is exactly what a computer USB port puts out. ' The charge time will depend on the solar insolation, but if you have good sunlight - about the same amount of time it takes to charge when it's plugged into your computer.
A switching DC-DC voltage regulator would be a better choice. You'll be able to regulate the 20v (unloaded) panel down to 5v at 90% efficiency. I made a 20w panel that charges a small SLA battery, and I run a 5v regulator to charge all of my USB devices. You can get them on ebay for < $20. Don't listen to people saying to rewire the panel to lower voltage and higher current. You want the higher voltage so it can still put out power when its cloudy. Remember everybody its 20v unloaded. If you throw a 5w load on it, the voltage should drop to 13-14v.
akbrennan (author)  1dot21gigaflops5 years ago
Thanks for pointing that out Hitokiri!
pieplay5 years ago
Every voltage you send to the shunt-resistor (voltage regulator) will be a loss (current X Voltage= Watt) in that case using just enough solar panels to reach you voltage is cheaper. or you can use a Chopper to regulate your voltage output. choppers don't use any current(nearly) and can also increase the current
tristantech5 years ago
You should seriously protect the leads on the voltage regulator. If those touch when you're charging, I could damage the iPhone beyond repair!
bananafred5 years ago
Rewire the panel to get higher current and lower voltage, if the wires are accessible.
dmeierhofer5 years ago
What a great photo. Good job!
p0g0685 years ago
thank you ! nice and clear cant wait for the upgrade to using a battery!
akbrennan (author) 5 years ago
Thanks for all of the input guys! @RazorConcepts - I'm really an amateur when it comes to circuits. Thanks for the suggestion! I'll take a look at the LM2949 and 2954 for future revisions. @thecheatscalc - I love shrink tubing too! I'll definitely make the next circuit more professional. This one was made for simplicity, but using a 7805 with a 20V panel wasn't the most intelligent idea. Redesigns are underway! @Berserk87 - after thinking about it more, I agree. However, the nice thing about the 10W is that it manages to charge the phone even in the shade.
I was thinking, if you're getting 20v out, at .5A and all that is coming to your phone is 5v at .5A... isn't that a bit wasteful? there's at least ~1.5A you could still recover.
Nice job though! looks pretty nice! Although I'm personally a fan of shrink tubing... I like the simpicity.
Berserk875 years ago
a 10W solar panel is overkill, and pricy. the most you need would be 2.5W or 5W if you want to be able to charge 2 devices.
Kaiven5 years ago
Very clean! Nice job!