I found a cheaper solution to charging my iPhone by solar. I use two solar arrays, very similar to those found here for $23 each:
http://www.batteryjunction.com/12vsopabachs.html
They deliver 150 mA max, but I've found they can easily deliver 175 mA each, and not even when angled directly at the sun. I use this with a simple car power inverter that has a USB charger port on it, but you can always make your own 12V to 5V regulator with a 5V regulator from Radio Shack, see here:
http://www.radioshack.com/product/index.jsp?productId=2062599
I've used this with my iPhone a couple times and found that it is able to charge my iPhone. There is one trick though, the iPhone is picky about its power supply, and so you need to trick it by making a simple circuit with two resistors. See the post below for instructions (you need to scroll down a bit in the post to get to what I'm talking about, it involves making a voltage divider on the data channels):
http://forums.macrumors.com/showthread.php?p=5447947&posted=1#post5447947
Also, it charges the iPhone even while playing music. The first time I tested these was in my car, and I had the panels directed in the windshield. After driving for 3 hours it charged my iPhone from about 60% to 90%; and this was with the panels not angled towards the sun. I haven't taken account of how it charges since, but know it does.
Also, if ever the power goes out for several days, you can always pull the battery out of your car when needed (or buy another car battery specifically for this use), and use the power inverter (if it has a USB port) or the 5V regulator to charge your USB electronics. You can then keep the car battery charged with these solar cells, so you don't need to waste gas running the car to charge the battery back up.
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I found a cheaper solution to charging my iPhone by solar. I use two solar arrays, very similar to those found here for $23 each: http://www.batteryjunction.com/12vsopabachs.html They deliver 150 mA max, but I've found they can easily deliver 175 mA each, and not even when angled directly at the sun. I use this with a simple car power inverter that has a USB charger port on it, but you can always make your own 12V to 5V regulator with a 5V regulator from Radio Shack, see here: http://www.radioshack.com/product/index.jsp?productId=2062599 I've used this with my iPhone a couple times and found that it is able to charge my iPhone. There is one trick though, the iPhone is picky about its power supply, and so you need to trick it by making a simple circuit with two resistors. See the post below for instructions (you need to scroll down a bit in the post to get to what I'm talking about, it involves making a voltage divider on the data channels): http://forums.macrumors.com/showthread.php?p=5447947&posted=1#post5447947 Also, it charges the iPhone even while playing music. The first time I tested these was in my car, and I had the panels directed in the windshield. After driving for 3 hours it charged my iPhone from about 60% to 90%; and this was with the panels not angled towards the sun. I haven't taken account of how it charges since, but know it does. Also, if ever the power goes out for several days, you can always pull the battery out of your car when needed (or buy another car battery specifically for this use), and use the power inverter (if it has a USB port) or the 5V regulator to charge your USB electronics. You can then keep the car battery charged with these solar cells, so you don't need to waste gas running the car to charge the battery back up.
As of 5:00 PM EST it's pretty much the same thing. It's good to see people check the facts.