Originally Posted by
calyth
I've tried those before, they don't really charge well, not unless you leave a modern smart phone turned off and let it charge up slowly. The best it does is to hold a certain battery level.
Poor choice for those who use phones as GPS, but then phone GPS typically use data, and that's probably not a great idea if any carrier charges roaming for going out of the area (don't know if that applies anymore)
The guy I talked to said it worked, however it might have been another brand. I will ask him again, next time I see him. If it works, it would be extremely handy.
Here's a Youtube video of a guy making his own using a 9 volt battery. He says at the end of the video that it takes and hour and 15 minutes to charge his phone.
http://www.youtube.com/watch?v=nuo3bOrqn5I