Hello! welcome to my intructable:)
As the name suggests(in spanish) my motto is "something out of nothing" and in this case "nothing" is the energy source, which is the sun light, actually it is not really nothing, but because it is free I call it "nothing". Let's rebel against profit thirsty energy companies and harvest out own energy! Don't forget best things in life are free! ;) A charger for small portable devices like mobile phone is a good start. Very easy to make, suitable for beginners with very little knowledge in basic electronics. Keeping it simple!
Portable, lightweight, waterproof and can be positioned in 3 ways:
1. Position it in 45 degree angle ( I did not measure the angle just did it by the eye and please note that the leg should be shorter, then the panel) facing the window up to a meter away, if indoors. You just have to experiment a bit, if it doesn't charge, move it closer to the window.
2. It can be attached to the bag or ruck sack, by placing leg in a pocket with your phone plugged in, so you can charge while out and about…
3. Can be hung on the window with the string, so even in limited light you can still get charge, I would recommend silicon/rubber suction hook or you could simply attach the sucker to your panel, though this would be a compromise on minimal appearance.
Another feature is battery-less , this means phone is charged directly, so you have to remember to charge your phone at day time, although if you do forget it might still get charge from electrical lighting at your home, if it is bright enough. The idea behind this is to reduce unnecessary components to make it more lightweight for mobility as well as minimising damage to environment, and in my opinion it is bit wasteful to charge battery with battery and some batteries like conventional AA have short cycle, this can't be good for environment surely. And from selfish point of view this would add additional cost and consequently would take longer to pay off.
Update: Since uploading my tutorial, decided to improve design and reinforce for durability, the top pictures are of new charger and the last picture is of the old one. Now the USB box can be twisted up and down in 90 degree angle, which makes it easier to position on the ground and a lot easier to fit it in the bag. Added step 4 to explain how.
Step 1: Tools and Materials
What you need to have:
2 x Flexible solar panel 0.8W, 2V --- £12.98 (£6.49 each) got mine here: ebay.co.uk
DC-DC step up converter charger with USB female. DC 2.5V-5V --- £1.30 ebay.co.uk
6 x Sugru --- £8.25 (£1.37 each)
Total cost: £22.58
Tools and additional materials:
Red and black wire
Wire stripping tool
Tubing, like irrigation pipe or a straw, something similar, not too bendy as it needs to support the panel, 2 x 11-12cm long
When choosing solar cells for this application, make sure it has a decent current and voltage of 4V or 5V even better if you planing to use it indoors more, this way you can still charge in darker conditions, in addition to this to achieve 5V needed to charge, the dc voltage booster is necessary, I've chose 2.5-5V, so if your 4V panel only produce 2.5-3V its enough to charge, so it doesn't have to be in direct sunlight. To increase current you need to connect cells in parallel, to increase voltage connect in series. For the 2 panels I have I need to increase voltage, so if you getting same panels you need to connect them in series to achieve 4V and the current is high enough.
Step 2: Soldering
First measure voltage of your solar cells to check if its the same as in manufactures/sellers specs, this gives you a chance to check the distance from the light source ( window) and before soldering test polarity of the cells to determine the positive and negative (+ and -) when your voltmeter shows minus - you have it wrong way round, just switch it round and just like on your voltmeter you have black and red wire, solder wires about 15cm long in same way red to plus, black to minus and to connect your the cells in series you need to solder short peace of wire from + to - ( doesn't mater what colour) Then you need to connect solar panel to the charger module in the same way solder red to plus and black to minus and before you do that don't forget to stick tubing on wires, if you would be using this.
Tip: (if you are not familiar with soldering) put a drop of solder on the clean surface first then add wire, I would advice practice before soldering panels, I haven't solder myself for long time, but i did not practice, thats why my joints on cells don't look too good, so its good idea to practice before, but don't worry if it doesn't work out very nice, it will still work. Also you need to strip wire before soldering.
Step 3: Finishing
Prepare box, if your pill box same as mine AM and PM joint together, you need to cut half of it away with sizers, then open the lid, cut the hole for USB at the top, so it would just slide in and space for wires to slide in from sides. Unfortunately, the box is slightly too big for this module, so to secure it add some material inside at the bottom and back. when all done close the box. (if it does not close, adjust the insides and try again, it will close eventually;)
Now place sheet of cling-film on your preferably flat work surface and form some Sugru with your hands and apply, start from middle, make a thicker strip, add sides by rolling a thin sting and attach, thickness depends on the cell, they can vary dramatically, apparently made by hand, but the idea is cover white surface from the front and the back insulate wires and joints, attach string for hanging option. Eventually attach/secure ends of tubing to panel and the box. Leave it to set for 24h and the cling-film prevents it from sticking to surface, it can be easily pulled off.
Tip: If you find it difficult to do it all in one go, do it in sections, leave to set then do another section.
PS: you can attach string to the top rather than bottom, up to you...
Step 4: Improving
So to make the USB twistable in 90 degree angle you need to find very small empty plastic bottle (like the one in picture) and cut top and bottom off, only leaving the screw part and mount it on the wires from both sides before soldering (step 2) and adjust it accordingly as the bottle only opens to one side, this means one side has to be slightly unscrewed. Now apply Sugru and its finished!
TIP: Wash hands before applying different colors of Sugru, especially white can get quite dirty as you can see from my picture, I was going away the next day and wanted to take it with me, so was in the hurry...