UPDATE The response for this item has been so phenomenal that I've started my own company dealing in Altoids-tin DIY electronic kits. Check out The Electroids Co or go straight to the Altoids 9V USB Charger Kit.
There's a small tradition for people like me with my (mental) faculties to go about building their own slick iPod accessories. Other people have designed battery-powered chargers for their iPods, from Altoid tins, and I wanted in on the action.
But the problem with these designs is that they use Firewire ports to power their iPods, which renders them pretty much only for charging their iPods, whereas USB can power iPods, cell phones, air conditioners, little robot guys, rubber duckie lights, personal cooling fans, air purifiers, Christmas trees, and essentially anything that requires 5 volts or less. So I figured I'd make a battery-powered USB charger that I could use to power my cell phone or my iPod in a grind. I hate not having a full charge on my devices, when my cell phone's battery is anywhere under 90% my heart starts racing and I get on my hands and knees and look for power outlets.
So if I had a small, compact USB charger that I could throw in my backpack or slide in my pocket that could be powered by inexpensive little 9v batteries, I'd be a happy camper. Problem was, I had no idea where to start. There were no decent tutorials out there, and Radio Shack's prices were insanity (and they didn't have USB sockets). So I had to do my own research, and I had to make contact with electronic parts manufacturers in order to actually get resisters, USB sockets, and voltage regulators for decent prices (or at all).
My final design is pretty sweet, I think. I used an Altoids Gum tin.. it's a perfect fit for a 9v battery and it slides right into the little key pocket on a pair of jeans. Since I wanted to maximize the battery's life as much as I could, I added a toggle on-off switch so I could physically cut power from the socket; and to accompany that I added a small red LED light that would turn on to show that it was turned on (and that there was still a charge to the battery).
Good news is, it works perfectly. One cheapo battery put out a steady 5 volts through the socket for over 5 hours, and then kept going over 12 hours with a steadily decreasing voltage output.
I've got a usb charging cable for my cell phone, iPod, and PSP. A fresh 9v provides about 5 hours of playback time on my iPod, 60 minutes of talk time or 4 hours of standby, and I don't have any idea how it would fare for the PSP, but 9v batteries are like a buck so who cares?
Click here for more pictures
Since I went through all the effort to learn how to do all this crap and to get the parts, I thought I might save some other people the effort and start putting out kits and instructions so the people who see these things and say "cool.... now how do I make one?" will have an answer.
That's right, I'm selling the things. That is, after PayPal fees I'm pretty much selling them at cost, but I sure wish someone were selling these things a week ago.
So click here for my electronics kit storefront. If you want to learn how to design circuits and get started with the underappreciated world of electronics, check the kits out. I'll be adding some more kits (flashlights, bigger chargers) sometime later.
Edit: Ok, I'm getting a lot of hits, a lot of buys (thanks, guys), and a lot of complaints from people who just want to know how to build it and don't want to buy one..
What I'm primarily selling is the parts to build one of these. If I put up the how-to instructions, you'd just have to go out somewhere and buy the parts yourself at around double the cost (my first prototype with RadioShack parts cost around $22.70 not counting the usb socket which was impossible to find). If you buy a kit, you're buying it for the parts as well as the instructions to get you started in electronics making.
Anything that can power via USB can power via this. I'm getting too many emails asking if it can power your sony/samsung/motorola/gatorade whatever. This thing emulates a usb port, so it will power anything that charges over usb. The end.
If you want a pre-built charger!!!!!!! Click here