Instructables

Solar Powered USB Charger (phones, MP3 players etc)

Picture of Solar Powered USB Charger (phones, MP3 players etc)
IMAG0229.jpg

This is my take on a already well documented little project. Very simple to make and a good introduction to electronics and solar powered stuff. Works just fine too. You need to generate 5-6V to charge a phone.
You will need:
Solar panels. I used 2 panels. (3V I think )
5V voltage regulator
USB female jack/connector
Insulated wire
Soldering Iron
Epoxy or hot glue

 
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Step 2: A series of solar panels

A USB port from a computer puts out 5.5V for charging of phones and mp3 players. So you need to get about 5-6V from your solar panels. In this case I need to solder the solar panels in series in order to double the voltage output. (3V each panel).  Solder the positive of 1 panel to the negative of the other. (Its just like putting 2 batteries in a flashlight)

Step 5: It works!

Here it is charging my HTC.
I have it under an incandescent bulb as it was dark outside when I finished....but it works!

Schmidty162 years ago
Will this work for an iPod touch4th gen
No, you need a data connection on the USB to charge any apple device
mabster9252 years ago
can anyone tell me why my phone wont charge this is all i get (solar panel is 6V 1W)
can anyone tell me why my phone wont charge this is all i get (solar panel is 6V 1W)
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MattCP (author)  mabster9252 years ago
In theory all should be working...
Maybe LG like the evil Apple empire and the phone needs a data connection in order 'to know' its connected and will then beging charging??
mabster9252 years ago
what should the wattage on the solar panel be? (6v solar panel)
will a 0.5watt panel work?
MattCP (author)  mabster9252 years ago
Should work, but slow...
A guy on youtube said (and I agree) that if you want a fast charge that wont take all day get a 1.5w or higher.

I just got five 3.3 Watt 6 Volt Solar Panels for 20 bucks. Granted there not small and light like the ones listed but there great for starting and testing a DIY project before spending a lot on these nice little ones.
I think a point most people have missed is that while the charger unit DOES charge, especially in bright sunlight, and the voltage regulation is a NICE idea - very good actually, there is a fundamental problem in that MOST devices, unless in standby or off, they will draw more power than the cells charge the batteries up at.

I mean this is nice if you want to leave your phone or the charger in a sunny position and only use the phone for like 10 or 15 minutes a day - great.

But the sheer lack of "current" in milliamperes is it's fundamental limitation.

I use a similar set up with a 10W 12V solar panel, to keep 3 big car batteries charged up or protected against self discharge, as they only get about 3 watts into each individual battery for about 4 or 5 hours a day.

But if the batteries were used to supply any real power to anything - it's going to take MONTHS to charge them up, that being the rate of self discharge and the amount of power needed to be put back into them.

But as a float charger - it's a good set up.

Same goes for this - mainly OK for low use products or low power use products.
MattCP (author)  Wroger-Wroger2 years ago
Thoughtful comments...cheers!
Another thing is that some charge displays, show voltage but not amperage.

So while the charge bars show "charging" that is the device is hooked up to a higher voltage supply than the voltage level of the internal battery, it may not actually be showing that the battery is really charging relative to the amount of current being drawn and the amount of current going into the battery.

This is an effect I noted with inverters running from 12V batteries, in that they stop drawing power when the battery voltages drop to 10 or 10.5V, but by adding a small charger to the battery, it raises the voltage of the cells while putting in hardly any power, and the voltage sensor in the inverter reads the batteries as being fully charged.

So you can keep drawing heaps of power from a partially discharged 12V battery, by the super imposition of a voltage over the batteries real voltage.

Not recommended to do this - but this is what you may be getting on the charging bars, reading in that the battery is charging when the device is pulling more power from the battery than the charger is putting in.

It may be a case of simply slowing the discharge a little more than anything.

Again - not volts, but milliamps - how much does the device draw when fully active, in stand by or when off - vs. the amount of current actually being put into it.
kilofeenix2 years ago
i've hooked this up to my phone and it says its charging but when i check back my phone has less battery. I've tried up to 1 amp since thats what my voltage regulator is rated at. I've put an 2n4001 diode on but still no luck. Any idea's?

5.25 v input
5v output
1amp
MattCP (author)  kilofeenix2 years ago
Diode around the right way?
yep, checked that
1n4001
For those asking where to get the solar cell, why not salvage some from dead solar yard lights?
Hey, thanks for a great instructable but I have a problem.
I built the charger but I don't think I am getting enough voltage. I am using two 3 volt cells and I put them under a bright spiral CFL bulb and it can hardly light a very bright LED. My phone and other devices are not being charged. Any tips?
I am going to try putting it under the sun tomorrow.
MattCP (author)  ababypenguin3 years ago
Solar panels won't work under a CFL bulb. Needs an incandescent to test indoors.
How did it go in the bright sun?
Leave it on a sunny window sill.
Thanks for the reply,
Okay, I'll stick to incandescent bulbs. I am using a USB hub with a bright blue LED as my load. On a sunny day, the LED was much brighter than indoors, but not as full as when the hub is plugged into a USB port. Even in the sun my phone isn't getting charged. I am currently using two 3 volts cells but I own four. Do you think it would work if I used three or maybe all four cells? (My only worry is that the regulator will not be able to handle 9-12 volts and it might get fried.)
SWV17873 years ago
I don't know if the voltage regulator chip does it but I always thought you needed a diode to prevent power back flow from just killing your devices battery in low light.
iPodGuy SWV17873 years ago
I was wondering about this as well. Could the author clarify, please?

Neat i'ble! I love solar gadgets!
MattCP (author)  iPodGuy3 years ago
Yeah...you are absolutely correct. A diode would prevent any charge being dissipated back through the solar panel when there is not enough sunlight. (dark really). I thought of this charger being tossed in your backpack and pulled out to boost your phone or iPod on nice sunny days...
I don't think the reverse flow will damage the phone's battery...just drain it. (?) But to be on the safe side, a diode connected to the positive from the panels could be a safe bet. Isn't there a bit of a voltage drop tho? I'm working this stuff out as I go.
Cheers for the comments!
The drop across a typical silicon diode is ~ .7v
juanjomf3 years ago
Hi sorry my English.
I'm from Uruguay .. If you know that maximum solar cell gives 5 volts. not ever require anything.
I put my cell 5 volts directly with a 1N4007 diode or similar just for safety.
I saw that the solar cell without the diode calienta.Lo another bear in mind that we have 5 volts but the amps?. Minimo 100 or 150 milliamps need to show that the loading, the majority of small cells are only 80 milliamps, my advice is cell buy 8 or 12 volts and 150 milliamps or 200 or put 2 ceeldas of 5 volts and then put 5 volts regulator LM7805. Greetings ..
i really really love the project!! can i have the circuit diagram?? please.. please.. please.... thank you... thank you... thank you...
i really love the idea.. and i like to create one.. how can i view the circuit diagram of that project? could you help me?? please.. thank you...
mark565003 years ago
Hey i love the idea and i just made one of my own, i tested it and i get 5v out of the usb port but when i plug in my phone it just lights up and does not say charging. Does this mean its not charging or i just dont have enough current for it to work? I'm using a 6V 100mA solar panel
dtommyd3 years ago
Since there isn't a battery as a buffer doesn't it start and stop charging with every cloud? I have some of those I may need to try it out.
rpvanpatt3 years ago
So, I have a panel that puts out about 8-9volts...I put a 5v regulator on it and a blocking diode, which brings it down to bout 5.5v in sunlight. I hook up the usb female port, then test it by plugging in a phone, and it will say charging for about 10 seconds but then cuts out....any ideas? I am going to hook up 4 chargeable batteries to it, so it will charge the batteries, then batteries will put out for the usb charger...think this will work better?
tank10003 years ago
I made one of those chrger to but i put mine into an old book i had abound my desk. i used i 6v 100ma solar panel. how many amps does the one you made put out?
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MattCP (author)  tank10003 years ago
Awesome...mine is a at work, so I will hook it up and let you know the amperage.
jcgeorgia3 years ago
When I check the usb with a meter, it gives out 2.5vdc and 6vac. Is it safe to say that I don't need the voltage regulator? I don't get anything on the meter when I have the voltage regulator soldered in. And I have paid close attention to keep from wiring it wrong.
MattCP (author)  jcgeorgia3 years ago
Might want to be certain of the max voltage output from your cells. I like the safety net of using the voltage regulator. The amount of photons hitting the solar cells has a direct relationship to the voltage output. Getting enough light?
jcgeorgia3 years ago
after unsoldering the voltage regulator, i soldered the usb directly to the solar panels. I put it in the sun light and my meter reads almost 5vdc. I borrowed a digital meter and it reads .39mA. My guess is that the solar panels just arent generating enough power to charge anything. I tried my bluetooth earpiece and it didn't show it was charging. Oh and nobody in my house has an iphone. I did try it on a Droid X but that was before I pulled the voltage reg off.
MattCP (author)  jcgeorgia3 years ago
Yeah, there can be a huge difference in voltage output from the cells. Depends on the amount of light and the max output from your particular cells of course. The voltage regulator prevents it from exceeding 5v...safer for the device.
jekan68613 years ago
a warm hello from a cold Japan. Could you possibly tell me where I can source the cells in your picture. They look as though they have a resin of plastic cover? Many thanks
Je Kan
MattCP (author)  jekan68613 years ago
I got these particular ones from http://www.technologysupplies.co.uk/ a few years ago and they have been in my spare parts drawer for a while.
You could try http://www.solarbotics.com/
I lived in Tokyo for a few years, Tokyu Hands dont carry solar cells? (It is the greatest shop on earth after all!)
AMP6783 years ago
Tried it with an iphone? I've heard they're picky. and how many amps does it put out?