So I wanted a portable way to charge my MP3 player so I wasnt SOL if the internal lithium battery died... Also, I just felt like messing around with making something, so off I went browsing maxim's website, and then digi-key to get the parts on the way. After I designed the PCB I cut a blank. Then I used some scotch brite to polish it up. I used the toner transfer process to mask off the board for etching the masked off board, with some extra sharpie on it to make sure I didnt get any eat-though. I sharpied the whole back to keep the etchant from having to eat the whole unused back side. my etchant reactor The warm etchant works a bit quicker then if it were cold. and the crock pot provides a nice glazed ceramic container that isnt affected by the etchant. after etching, rinsing, and then a rinse in a baking soda solution to neutralize any etchant on remaining on it. After using acetone and a paper towel to get the sharpie off, and scotch brite to get the toner off, the finished PCB Solder up the boost controller IC (MAX608) solder up the small SMT componets ( current sense resistor, diode, transistor, and a ceramic cap) add the SMT aluminum electrolytic caps (which I went overboard with... only need ~150 uf input and output, I put 660 uf each ) soldered up the USB port, the SMT inductor, and the battery holder, which I also superglued to the back to make sure it wasnt stressing the solder joints too much. There you have it, battery powered battery charger in an afternoon. Ive seen smaller ones online, but I think they were only made for ~100mA. This can output a full 500mA, and if I changed the current sense resistor, it could probably output more without a problem, up to about 1000mA or so. With an upgraded mosfet, from the tiny SOT-23 one currently to a larger one, I could increase the output even more. EDIT: oh and if there are any bridged pin on any of the ICs that isnt a mistake, they all got connected together, so I just soldered them like that.