Bob, that's a really good idea that never crossed my mind. I was thinking a single 3mA LED for low drain, but with a 'test' switch, I could put a descent brightness LED on there, or maybe a few SMD indicators to see how much the panel is producing and I no longer have to worry about the loss. That would definitely increase my options without sacrificing any performance (other than a few grams of weight). Plus brighter LEDs could be easier to see in bright light, which by definition is the condition that I'd prefer to use the panel! Thanks! BTW, I am using a 12V spec'd panel, the 7.2V was just an example. It was actually cheaper to buy this Powerfilm 5W unit rather than 5W of 6 or 7 Volt Panels. I'm not sure why that is. All the wiring in the panel unit is inside the stitching so I can't really see how they are wired to guess what spec panels they are and series vs parallel design. BTW, the quality of the build on the Powerfilm is fantastic! High quality wire, Brass rivets (non-corrosive), electrical parts are sealed with silicon and routing and wiring is taped in place to minimize stress. I was very impressed when I took it apart! The little circuit board has two diodes on it and only one is being used, so it must be a generic PCB that they used for their 10W version as well, which is basically 2 of mine in parallel.
Jerry, battery charging is freakishly complex! Luckily the iPhone has alot of built in protection so as long as I stay in the USB 4.75-5.25V spec, I should be ok. You can actually charge batteries at a fairly wide range but it will affect their lifespan and cause excess heat. One of the huge advantages of Lithium Ion batteries, besides their low weight, is the ridiculous # of charge cycles that they can go through. Technically each charge takes a little bit of their capacity away, but poorly designed/spec'd chargers make it much worse. Lead Acid batteries are much more forgiving except that they can heat up and be damaged if overcharged, especially at high (quick) charging voltages. But obviously, the assumption is that if you're charging your car with a solar panel, your battery is dead, and you just want to up the juice, not replace your alternator with a solar panel :)
Jack, think I'm into this one for $100 bucks already :) I'm not sure how well they would sell at that price! But maybe this project will give me some insight into building another one much cheaper. NOW TAKING ORDERS!!! (MUST PAY UP FRONT!!!)