Could a 12v 6w bicycle bottle generator be used to simultaneously charge two USB devices at 5v 3w?

I'm looking to power a few different USB devices while I ride my bicycle. Hub dynamos are typically 6v 3W AC, which makes them pretty conducive to USB which is 5v 3W DC, and there are some kits that do just that. However I've found a few bottle generators (the kind that run against the tire) that produce 12v 6W (I'm not sure, but I think they are DC). Now I'm no Nikola Tesla, but it seems to me that one of those could charge two USB devices at once. Either some kind of splitter or just a 12v battery with a USB hub. 

mrmerino4 years ago
I don't think you could charge two devices at the same time... You would need a generator that could supply the sum of the current each device requires, and have them in parallel. At that point the twelve volts is wasted, unless it is an AC generator, in which case hey lucky you, you can grab a small 1:2 transformer, step it down to six volts. Otherwise, use that six volt generator and a rectifier/regulator combo to charge your iPod.
iceng mrmerino4 years ago
You are correct, I chose not to muddy the water for a new member of
unknown experience with a minidown switcher that you know exchanges
voltage for current gain.

iceng4 years ago
Based on watts ... just barely ... 3w at 5v is only 600ma

But bottle DC generators can put out more power and
depending how hard you peddle it should be easy.