DIY USB solar charger

Hungarian version.

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. :)

DIY Universal USB charger

Hungarian version.

UPDATE 1: I had to put a diode into the cable, because it seems a Chinese battery charger can push the charge back to the Nokia power supply. I used a 1N4001 diode to the cable of the power supply's "+" side, which can withstand 3A and it has 50V Reverse voltage.

I was having trouble charging my Smartphone. I do not have a wall outlet AC charger for it, so I always had to charge it from my computer with an USB cable. But in this way the charging was a bit slow, since the computer only supplies 500mAh of current through the cable. The computer had to be turned on as well. I wanted to change this. I have an older 2007 Nokia phone charger, which charges the phone with 5V. It is funny that Nokia has been since bought by Microsoft. In the beginning of the 2000 years Nokia was a leader in the phone market. So the Nokia charger has only a pin connector as can be seen on the picture.

I have cut the charger cable in two. I took an USB extension cable, I cut it in half as well, then I soldered the USB mother connector to the charger side, the father connector to the other side. As it can be seen on the picture. Now I have a universal USB charger which can charge with 900mAh as written on the charger. I can connect any USB cable to it and as it is a quality charger I do not have to fear from cheap chargers from ebay.

One more interesting thing I would like to note. There are some smart things what do not charge themselves with all the available power from the charger, if the two data cable in the USB cable is not shorted. I have a handheld computer (PDA) from 2007. If the two data line is not shorted, it charges itself slower than if they are shorted. This PDA has a car charger which charges with 1A, but I have bought another car charger which does not charge it this fast. It turned out that this is because the data lines are not shorted here. I simply shorted them on the charger side, so the units charge themselves faster.