I would like to show you my solar USB charger what I built in 2009. I have ordered from Ebay from China 6 solar panels for 64 USD. It would cost 72 USD today if we calculate inflation. I have put the panels into a DVD case, which is getting a bit worn in the past 7 years. I want to build a new case for them. By the way, who watches DVDs these days?
The Diode is hidden behind the duct tape.
These are 6V 133mA panels, so 0,8W per panel. So the six pieces I bought together is 4,8W for 72 USD. Today I could buy more than 35W power rated panels for the same price. In 7 years their price dropped to seventh of the original price!
I was thinking that 6V would be good to charge USB devices, because the USB specification suggests 5V. As it can be seen on the picture I used three panels and I connected the in parallel, so theoretically they will give out 400mA current. I have also put a diode in front of the USB connector to prevent the current flow to the panel direction.
The solar panels supply the specification ratings at ideal conditions and without any load on them. I was curious how much power they give under load. I have used my magic KEWEISI usb capacity meter to measure the voltage and current. It seems the three solar panel supply around 4.6V with 0,2A current. It is interesting that they supply around 10% less power if I used them in a horizontal position, not in an ideal angle. In horizontal angle they supply 4.5V with 0,15-0,17A.
As it charges very slowly, I barely used this charger. I usually use it if I go to a bicycle excursion and I am charging my PDA.
The funny thing is that, I have sold the three leftover solar panels on an auction site for double the price than I have paid for them, so the three I am using were for free. :)
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