I use it to charge my power bank, but you can use it to charge another equipment that requires 5V input.
However be aware that it's a PRIMITIVE charger, the output voltage might be not quite stable. So DO NOT charge your mobile phone or other fine electronic equipment with this charger.
The first picture is how I use it to charge my power bank.
On the second picture, I circled out all three materials I used.
Let's check the part list. To make one, you need:
1. a 3W solar panel
It's recommended that get the largest one you can access. You know the efficiency of solar power...
2. a 78M05 regulator chip
You can find it everywhere over the Internet. It's a regulator chip that convert the voltage of the solar panel into 5V, not very accurate, but enough to serve our power bank.
3. a micro USB cable
My power bank comes with a USB cable with a micro USB interface. To fit the charger with other equipment, just replace this cable with another spec that's fit.
You may notice some soldering is required. Yes, to connect the regulator chip with two other materials, a little soldering is unavoidable. But I have a Zoom-in photo for you. Check out the Third picture.
Strip out the coat of the micro USB cable beforehand.
Place the regulator chip flatly and keep the number on it upright.
Connect the red wire of the solar panel to the left lower pin, and the red wire of the micro USB to the right lower pin.
Then joint the remaining two pins together with the upper two pins of the regulator chip.
Yes, no more steps required.
Within 5 minutes, you done with an environment friendly solar charger!