Instructables

Can i use a solar panel to charge a cell phone?

I made a call phone that looks like a calculator so i can use it in school and what not and everyone thinks its super amazing but the battery dies really fast, i checked my connections and nothings touching so i think the batteries defective but my friend gave me the idea to use the solar panel from the calculator the charge it. I get about 1 volt under normal lighting about about 2.25 volts under a bright light (directly under a light bulb).

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It aint gonna work bro..........lololololololol
-max-3 years ago
you would need a solar cell about 3 inches square. my best answer would be to get your hands on a old (working) phone with a good battery inside. the bigger the better.

my other idea id to make a crank for it, of a "shake N'go" mechanism (which is not very practical for many obvious reasons.)

if you know how to make an inductive charger you can hide in your desk, and a pickup in your gadget, that may work, but you might destroy the sensitive circuitry inside.

disclaimer: do this at your own cost. their is a reason why phones are banned.
Jimmy Proton (author)  -max-3 years ago
well as you can see there is no room for a bigger solar panel or battery then the one i got. I was just hoping that this could keep the battery going longer, no need for a full charge. The only thing i was worried about is over charging cause i was going to hook it directly to the + and - terminals on the battery.
well with a small solar cell you definitely will not need to worry about overcharging. but consider using a blocker diode (not any old silicone rectifier, but a germanium diode. [or at least a scotchy diode] these are recommended.) a diode will stop current from flowing from battery to the solar cell.

with a standard diode you will have a significant voltage drop (0.6V). get your hands on a few germanium diodes (they have a voltage drop of about 0.2V).

you mentioned earlier your cell puts out about 1V. well a fully charged lithium ion battery holds about 4.2V if it goes below 2.25V, (amusing its protected) the internal circuity will cut off power.

so math time!
1.1V - 0.2 = 0.9V that is way too low. if you get super lucky
2.5V - 0.1 = 2.15 still too low.

im sorry it didnt work out for you. all i can say is more solar panels, or better battery.
-max- -max-3 years ago
sorry, anywhere i said "silicone" i meant silicon. and if you get very unlucky,
0.9V from little solar energy minus
0.6 or 0.7 voltage drop equals
0.3V or 0.2V

there is more energy in a radio antenna than the limitations (small cell, large load, voltage drops). but its best to try! numbers (especially mine) don't say everything! you might get lucky, who knows?!
Jimmy Proton (author)  -max-3 years ago
So just hook the cell up to the battery with a germanium diode and that should be it? all I'm looking for is something to keep that battery lasting longer.
Jimmy Proton (author)  -max-3 years ago
also this phone cannot be activated because it is an altel phone so its no good for communications but i can take pictures/video and play music on it and some of the teachers already know about it and they think its cool.
Mudbud3 years ago
You need a stronger solar panel and/or a new battery... It also depends on the battery type like if its Lithium or NiCad, etc

Short answer: Yes

Jimmy Proton (author)  Mudbud3 years ago
That's the only working solar panel i have but despite its small size it would still work at least a little, right? Its lithium-ion....like every other cell phone battery.
even if it did work, it won't charge the battery high enough, plus you need to have a regulator in there so it will stabilize the current and whatnot