Making a Solar Powered USB Charger

Thread Starter


Joined Jun 17, 2011
So I'm trying to make a solar powered usb charger, below is my circuit diagram. With it set up this way, it charges up fine to about 4.9v but then when I plug my ipod into it, it shows it's charging for a few seconds then the voltage drops to about 4.5v and then drains at a constant rate from there about 0.1v every second or two.

I tried adding in another AA to give me about 6v to try and counter the voltage drop, but when I plug in my ipod nothing happens. Thinking that 6v may be too much for devices that are supposed to use 5v, I tried some different resistors going from the batteries to USB with no luck, the ipod does nothing.

Last edited:


Joined Sep 9, 2010
The drain begins when the iPod sees what it thinks is a valid charger and then starts asking for more current than your charger can continue to supply. If you've got the batteries to play with, you might try putting 3 in series, and then 3 more in parallel with the first 3, 6 in all. That would double the current flow while keeping voltage hopefully in the working range. But, even double might not be good enough to keep the iPod happy. It's looking for 500mA and maybe more.

It's possible you could use different resistors to tell the iPod not to ask for so much current. Not sure that's possible but maybe worth a little research on your part.


Joined Nov 16, 2007
You've given us no specifications on the solar pannel, the Voltagge and current ratings.


Joined Sep 9, 2010
I assumed - especially from the OP's results - that the panels were far too small to charge the iPod directly, only the AAs over long times.