USB charging of a single protected 16340 3.7v LION?

http://media.digikey.com/photos/Tens...G_10-00240.jpg

This got me thinking about using a USB wall wart or powered hub to recharge some of my lower mAH devices. In reading Azmaria's battery pack sticky and some of the recharge port threads, it seems that the conventional wisdom is to buy a smart charger and use unprotected, matched lion cells. Perhaps because of the analog nature of the protection boards, and also because of the high capacity making USB non-viable.

I don't have a battery pack, just a single 16340 at about 550 mAh. It is protected. Could I safely plug it into a USB wall wart charger, say one with output of DC5.00±0.02V DC300±50mA? Would the PCB of the battery do the work and cut itself off? Is 5V okay voltage to feed a 3.7V cell?

Most Li-Ion batteries are designed to be charged at or around 5v for that exact reason. USB has set a ubiquitous standard for low power consumer electronics, and because of that almost ANYTHING can be charged via USB if you're handy with a soldering iron.

sweet. I thought lions were supposed to blow up or catch fire if you left them charging too long.

the pcb should prevent that, as long as you're charging from the pcb pads, and not the battery terminals directly. Regular old charged carbon Li-Ion is pretty stable. It's the Li-Fe (iron sulfide) and Li-Po (electric polymer) that are super volatile.

Thanks for the help. The PCB is not exposed. It is shrink wrapped to the battery. The terminals are the only thing exposed. They are Ultrafires if that gives you an idea.