I figured I can't go too far wrong at 2 bucks with free shipping. It uses the TP4056 IC which is a constant current voltage limited charger, resistor programmable from about 50 mA to 1A, and can be connected to a USB port or a wall wart supply. http://www.tpmicro.com/goods.php?id=47
I think it might be possible to put a diode in series with the output so that it might work with LiFePO4 cells. It should drop the 4.2V to about 3.5-3.7. I have some 18650 cells of both chemistries that I got for testing but this should be an easy way to charge them. I'm not sure I trust it enough to plug it into my main computer, so I might use one of my older spares (a Vista and a Win XP laptop).
It'll be awhile before it arrives, so I'll report on my own results.
A forum community dedicated to DIY electric car owners and enthusiasts. Come join the discussion about electric vehicle conversions, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!