Solar Powered Cell Phone Charger

Power you cell phone via the sun.

Step 1 Materials/Tools

You don't need much to get this project up and running. I actually bought everything I needed at Radio Shack, and will provide the SKUs for each item in case you want to do the same.

Solar Cell (I used a 6v 50mA one)
SKU: 277-1205
Project Box (I used a 5x2.5x2 and it fits perfectly but any small enclosed box that you can cut holes into will do fine)
SKU: 270-1803
12VDC Car Power Outlet Socket
SKU: 270-1556
Vecro (or your adhesive of choice)
SKU: 64-2345

You will also need a soldering iron (15 watt. SKU: 64-2051B), solder (62/36/2. SKU: 64-013), and something to cut 2 holes in the project box (I didn't have anything available designed specifically to cut holes, but I just used my CRKT knife and it worked fine)

Comments

[SpeakNoEvil]

Great device! I'm curious about the input voltage from the solar panel - did you have to match it to the car charger or the phone?

[kenshi07]

I would guess that the car charger device would regulate the voltage for him.

[Knuxz]

Incorrect. The car port is just that. A port. All it does is allow power to flow through it to the charging device. It, itself is not electronic in any way, except having power flow through it.

Example:
If you have twenty-four instead of twelve watts run to it, it will output at twenty-four, not twelve.

[lloydrmc]

Incorrect. The car charger itself has voltage regulation circuitry in it.

[Pale_Flyer]

kenshi, there still needs to be enough power for the charger to knock it down to the correct level

knuxz the PORT is just a contact, as you stated. there is nothing else there.

lloydrmc, you are right in the charger, but technically Knuxz is also right, as he specified the PORT, not the CHARGER. the charger would be expecting 12V at like 10 Watts (i am not sure on the wattage, if i am wrong, i appologize) the charger probably has a transformer in it set to about 2.4:1, so if 6 volts go in, you will not have the 5V the phone is expecting, or what every the phone wants. i am going off current phones which normally go straight from USB at 5V.

[Pale_Flyer]

with the system he designed, he could connect anything under 6v to it. as currently configured, he has to have it as a car style plug... if he spliced in another power port, say to screw terminals, or aligator clips, he could direct charge just about anything, and maybe use the terminals for a battery, with diodes so the panel could charge the battery, and the battery could power the port. WARNING! WARNING! WITH OUT VOLTAGE REGULATOR ON BATTERY RISK OF FIRE, EXPLOSION, DEATH! Some capacitors in a bank with some resistors and diodes may work better, and through a friends, ahem... experimentation... ahem... in electronics class... caps don't appear to suffer from overcharge problems... he plugged some 2000 mA caps into breadboard power supply at much greater than recommended voltage/amperage, and they did not suffer problems after multiple charge/discharge cycles. i know small caps can power small circuits depending on drain for at least a few seconds. So with the right circuit, and the right cap(s) you could build this with a decent "charge" capacity. and ultracaps would be even better, but have not seen any other than online.

[lloydrmc]

2000mA, or uF? I'm not aware that caps have an amp rating at all.

Look - this would make a LOT more sense with more/better solar cells, and some NiCD or NiMH batteries to store the juice. Set it up so you have nor more than C/10 or maybe C/5 at about the correct voltage, in optimum sun conditions, and you will be fine.

"C" is the capacity of the battery. So, with 3000mAh AA batteries (which are available cheap as dirt on ebay), you set it up so you have no more than 300 to maybe 600 mA output from the solar cells.

You'll note that the specified solar cell has a current rating much lower than that. No problem, except that it would take proportionately longer to charge any given battery. It would also help to orient the solar cell properly, at the correct heading and angle (rather than have it just sit flat on top of the box.

I'm pretty sure someone has a solar-assisted minty-boost project on Instructables..

[Pale_Flyer]

that was supposed to be Farads in my comment... i wonder how i messed that up...

i looked at your comment, and yeah, you could go for a battery bank, but that would as you said, take a while to charge. The other thing is, i think i was suggesting more along the lines of smoothing the charge, or maybe a quick emergency charge, like 5-10% of a cell phone batt to allow for a call to a tow truck... i am not 100% sure, as it has been over a year and a half since i have looked at that.

[Jr Hacking kid]

how about adding a battery and charge that so u can leave it to charge in the sun and when you come home you can charger you fone =)

[rangerman2889]

you could find a way to hook it up to a spare phone battery that way you charge your extra battery in the sun while you use the other one, and then when you need more power, just put the full battery in your phone and start charging the dead one.

[lloydrmc]

I would be VERY careful about hooking any sort of solar cell to any kind of lithium (e.b. LiON) battery, which is what most cell phones have nowadays. Overcharging a lithium battery can result in a rather spectacular fire and/or explosion. Check YouTube for video of what this looks like.

[DualPhase]

Thats actually a better way to go. You might want to add some sort of voltage regulator to it too.

[lloydrmc]

You don't need a voltage regulator if you're using a car charger. The car charger takes care of that.

[s0mnath]

would this work for an iphone 4?

[lloydrmc]

iPhones can be tricky, as they require voltages on other USB pins to be convinced to charge (which is accomplished by resistors between the 5V lines and the other pins). Look for the instructables on minty boosts (there are a number of versions), as they have info on how to make this kind of thing work with an iPhone.

[Pale_Flyer]

if you use a 12V car to USB thing, and plug the Apple USB cable into the USB Port, then the cable handles the resistors, and all you need to do is make sure that you have 5V at about 2.1 A ( if i remember right) for optimal charge on the iPhone.

[deeannabe]

do i have to use a soldering iron? will it work without it?

 

[thepaul1993]

you could get away by just twisting the wires together, then just cover with some tape

[rkulkarni3]

ya that's right

[Fxnite69]

Could A USB Added To This Instead Of A 12VDC Socket?

[nirav.telang10]

yes why not you can use usb also

[DualPhase]

Totally.

[vpittman]

I have just built this and had a few questions:

1) what type of capacitor should be used for this circuit? I have tried looking into it at radioshack.com but couldnt get myself up to speed enough to understand what uF meant in relation to what is needed/required
2) I was thinking about adding in a AA batter "box" to hold two rechargeable batteries, where would I need to splice that in to this circuit and would the one panel be enough to charge this. Ideally I would like to use the solar panel to charge the batteries and use the batteries to charge the device. To go along with this, would I need to install other items (ie blocking diodes, voltage regulators, etc)?


If anyone can help I would appreciate it, thank you!

[cindi59]

I got hubby to use this to show me how to weld the wiring. It really worked! My first solar build rofl... It will charge my DS and my cell phone. I wanted something like this to take with me fishing.

Of course the sun has to be out rofl...

[stregoi]

nice device, i could totaly use one of these

[snailtrail]

This will not work for a iPhone if some made it work let me know
It will work for other phones

[corky1333]

iPods and iPhones require at LEAST 500ma. the solar cell you are using is only 50ma. Find a 500ma solar cell and if over 5v, use a 5v regulator. resistors on the usb are also required to charge. (http://www.instructables.com/id/How-to-get-your-iPod-to-charge-with-your-homemade-/step1/Schematics/) My homemade solar charger is 500ma and it has capacitors to smooth out the output.

[gabe009]

The only time i would use this is if I'm stranded on a island.

[alreadywife]

hmm, nice gadget!

[kostya]

Last summer I built 2 small solar panels (each 3V/80mA).connected them in series,added a cable with minijack and blocking diode 1N4007 and tried to charge my Nokia. At full sun I read on the screen 'No charge.Disconnect the charger".What's the problem?

[lloydrmc]

Lose the diode. If you insist on using one, get one with a lower forward voltage drop. A 1N4007 is not a good choice for this project. I'm pretty sure that RadioShack has a reasonably high current germanium diode.

[niranj_1994]

See the charger adapter of our cell phone,I think its output is 3.7v(old model),5v(new model).So add a regulator to it,it will work.I know this by making a cellphone charger which is powered by a9v batt.So,try this it would work.

[silver912targa]

Well if I read my charger's details, it gives a 5.3 volts and 500mA. Your panel doesn't even come close to it. You need to connect more panels to gain more amps..... Michel Portugal

[Eirinn]

It should still work. The amperage, as i know of, only controls how fast it charges.

[january.30.2008]

To be completely honest kostya, I don't have a clue. I am not that talented when it comes to this sort of thing. I designed mine as a simple trial and error basis that ended up working for me. Hopefully someone else on here can lead you in the right direction.

[notaguitarhero]

Thanks for this! I made it and it works! I would very highly recommend using a diode so the phone doesn't discharge. Also, using a 6V 50mA solar panel requires putting it in direct sunlight, meaning you have to leave it outside. Putting two solar panels in series will help to increase the voltage and then you can MAYBE bring it indoors. Putting solar panels in parallel will decrease the charge time too. Anyways, thanks for the inspiration! You got me on a "solar-craze"

[lloydrmc]

There is no need for a diode! Try this yourself - hook an LED or a light bulb or even a DVM to the charge contacts on your phone. You will get nothing!

[Colonel88]

1st of all:

You must use a 7805 voltage regulator, which brings the voltage down to5 volts because it might be too much or too little voltage from thesolar cell.

2nd

You might overcharge the cell phone and power surges will definitely fryit; put in capacitors.

3rd

Radio shack solar cells are frickin expensive.

[lloydrmc]

1st - the car charger takes care of that

2nd the phone takes care of that, capacitors won't help, and where exactly are the power surges coming from? Just exactly how clean do you think car electrical systems (which the car charger is designed for) are?

3rd Expensive compared to what? What other store is everywhere that has them available? Can you really get something like that, in single quantity, elsewhere for all that much less?

[Wild Blade]

 I'm curious, does the car charger for a cell phone usually act as a diode blocker? Does is keep the circuit from sucking up the phone's energy while the sun isn't out? Also, this was a very fun project, great work!