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Solar cell to recharge a cell phone

 
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purifier



Joined: 30 Nov 2004
Posts: 219
Helped: 1
Post06 Feb 2005 5:57   Solar cell to recharge a cell phone
I'm trying to build a small project that involves a solar cell charging a cell phone battery... It this possible without making the equipment bulky...
The output of the solar cell should be given to the input of the cell phone... The cell phone required a voltage greater than 3.4V for it to charge...
I could get only the above info...
But,
1. Can a solar cell be used for this purpose?
2. What is the formula used to calculate the voltage and current given out by the solar cell having a surface area of S?
3. What is the current needed to charge a cell phone?
4. Do i need to know the internal circuitry of the cell phone?
Can someone please help me...
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IanP



Joined: 05 Oct 2004
Posts: 6346
Helped: 1505
Location: West Coast
Post06 Feb 2005 6:12   Re: Solar cell to recharge a cell phone
Some answers to your questions you can find in sites like this:
http://www.ebigchina.com/ebcps/4/pd/480988.html
There hundreds of these devices on the market..

Unfortunatrlly small cells don't produce enough current for this purpose and as you know some of phone battries should not be re-charge unless they are almost fully discharged..
How big should be this cell?
You can estimate its size from manufactures data sheet v power it can generate..
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purifier



Joined: 30 Nov 2004
Posts: 219
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Post06 Feb 2005 6:29   Solar cell to recharge a cell phone
Thanks a lot for the link... Regarding the size...Palm size...will that be enough or will it have to be better...
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IanP



Joined: 05 Oct 2004
Posts: 6346
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Location: West Coast
Post06 Feb 2005 6:37   Re: Solar cell to recharge a cell phone
Quote:
Power is equal to current times voltage. The power rating of a photovoltaic module is typically quoted as the power output of the module when the incident solar radiation is 1000 watts/meter squared and the temperature is 25º C. This is a typical value of solar radiation around the middle of a clear summer day. A one-meter square module that is 15% efficient would therefore have an output of 150 Watts on a clear day near noon.

From the above you will be able to calculate the required size of the solar-cell..
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purifier



Joined: 30 Nov 2004
Posts: 219
Helped: 1
Post06 Feb 2005 6:43   Solar cell to recharge a cell phone
And, by the way...if i increase the size, will the current increase? If yes, then is there any formula to calculate this...?
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usernam



Joined: 09 Mar 2004
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Post06 Feb 2005 6:46   Re: Solar cell to recharge a cell phone
They can wired in series to increase voltage, and in parallel to increase current.
Increase will be more or less equal to the number of cells.
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purifier



Joined: 30 Nov 2004
Posts: 219
Helped: 1
Post06 Feb 2005 6:55   Solar cell to recharge a cell phone
That's exactly what i needed...thank you very much... i'm open to suggestions... if you can help me further as to how to design a circuit...i'll be grateful...
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IanP



Joined: 05 Oct 2004
Posts: 6346
Helped: 1505
Location: West Coast
Post06 Feb 2005 6:58   Re: Solar cell to recharge a cell phone
The voltage of the electric current from a single or multi-crystalline silicon solar cell is 0.5 volts.
AS far as current is concerned it varry from manufacturer to manufacturer for the same size. Some claim that from 6cm diameter they can have 0.5V @ 0.5A. Maybe???
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purifier



Joined: 30 Nov 2004
Posts: 219
Helped: 1
Post06 Feb 2005 7:33   Solar cell to recharge a cell phone
Oh...i don't think that can be used to charge the battery... unless ofcourse we connect many cells in series or parallel...what do you say?
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usernam



Joined: 09 Mar 2004
Posts: 693
Helped: 129
Post06 Feb 2005 8:47   Re: Solar cell to recharge a cell phone
You can get upto a current of around 2A from a solar cell (about 4cmx4cm) but in general the voltage will be around 0.5 V. So you will have to probably connect cells in series for your application.
Of course which cell you buy depends on your budget.
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Sputnik



Joined: 19 Oct 2004
Posts: 150
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Location: South Africa
Post06 Feb 2005 11:34   Solar cell to recharge a cell phone
Have a look at this, perhaps you could tailor it to your needs.

Sputnik Idea

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