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Step 5I think your done
Stick the solar cell in the lid, plug in your cell phone and point it at the sun.
You can now toss it in your bag and forget about it. Just remember about it when your almost out of juice and need to make some calls. I found I can even charge it under strong indoor lighting.
You can now toss it in your bag and forget about it. Just remember about it when your almost out of juice and need to make some calls. I found I can even charge it under strong indoor lighting.
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It is not likely you will build this to 850ma using a pair of lawnscaping panels... but worry not, you do not need anywhere near 850ma if you are patient.
There could be a low-current cutoff in your phone - say 200ma (just a guess) under which the phone will not charge. I think phones with smaller batteries can get by on less charge, whereas something like a droid or iphone would be more picky.
If your cells can not maintain 5v reliably, you will want to run your power (whatever you get) through a MintyBoost circuit.
The Minty design is now at v3, but a Minty v2 (I think there is a tutorial here) would be more efficient for this application, and you can get the MAX756 chip sampled free. :-)
.. and if it does not work with your phone no matter what, use the cells to charge a NiMH AA batteries which are pretty forgiving. Then use the AA batteries to charge your phone (4 rechargable AA's directly will charge your phone, or 2-4 rechargable AA's through a MintyBoost will give you a nice flat 5V output curve until the batteries are completely empty).
Personally, I would not buy landscape lights to try this out. If you have some already, great. If you are going to buy something, I would go for one of the newer better solar cells from Adafruit or Sparkfun, etc.