Advice on buying a mini solar panel for a solar powered usb charger

[jstriker]

Hi

I need some advice please. I am making a solar powered usb charger to . It is direct powreddso there wont be a battery connected.

The advice I need is about what type of solar panel that I need. I have the usb charging module and I plan to mount it in a box probably about the width of a breakfast cereal box. I know that most mobile phones need 0.7 ma to 1 amp to charge but most of the solar panels thst I found are not that high powered. What wattage /voltage /milliamperage mini solar pwnel would I need to be powerful enough to charge a mobile bearing in mind that it need to be portable?

I have fiund this one but it is only 100 ma? http://www.selectsolar.co.uk/prod/265/powerfilm-mpt6150-100ma-6v-mini-solar-panel#overview

Also will I need a blocking diode to avoid damage to the solar cell?

Thanks

-James

 

[BobK]

To charge a cell phone, say 2000mAH, it takes 5V at 1A for two hours if 100% efficient. That is 5W. So to get that kind of performance you need a 5W solar panel minimum, and realistically a 10W panel. A 1m² panel puts out about 100W, so you would need about 1/10 of that or about a 31 cm (or 1 foot)
square.

Smaller panels could be used to charge the phone a proportionately longer time.

Bob