Cell phone battery charge from solar energy

i need help... i want to charge my nokia cell phone battery... i want to charge it by using solar energy...how i will do it by using solar energy? plz help me what i will need to construct solar battery charger...and what will b the circuit?

Start with a solar panel which delivers an open-circuit voltage about double what is marked on the plug-in charger which came with the phone, i.e. 5V on the charger means get a 10V panel. The panel should be capable of delivering a short-circuit current of at least 100mA in bright sunlight. Use an LM317 as the regulator (**broken link removed**, you will need two capacitors and two resistors). Set the output voltage to match what is printed on the plug-in charger which came with the phone, i.e. 5V. If the plug-in charger is rated at 500mA, a panel rated at only 100mA will take five times longer to charge your phone.

Although in this case, if the panel delivers 100mA at 10V, you should be able to get 200mA at 5V, right ?

TechnoGilles said:

Although in this case, if the panel delivers 100mA at 10V, you should be able to get 200mA at 5V, right ?

Click to expand...

MPPT. Requires a sophisticated switcher. My 20Voc, 1Asc panel only puts out ~ 0.7A at 14V, so it is not a straight line...

Gotcha. Thanks !

find out the voltage of each of the solar cell and its current. you need atleast 350ma at 5.7 volts to use it like a charger. no switcher required. see nokia charger specs. just give the voltage and current and plug it in the charging socket like you plug a charger in it. the pins are readily available. u need satellite grade solar cells those are expensive. put 10 of them in series and see.

I doubt you can do it directly if you're going pocket size. You would need some form of a energy storage device to store your energy harvested from the panels such as a li-ion/li-po/nimh battery. I used a MAX1555 from Maxim, set at 100mA using the USB setting and taking input from a 6v 100mA panel. I used a 18650 li-ion battery with a capacity of 2200mAh. From there you can use a variety of step-up regulators to step your battery's output to 5v which most wall warts use. I used a TPS61071 from TI. You need not use another charger ic to charge your phone's battery as the charge ic is embedded in the phone itself.

Solar panel -> Charger -> Battery -> Step-Up Regulator -> Phone

Hope this helps!