One random question: Would it make sense to power the system from an RC NiMH battery? I found one that outputs 1700mAh of 4.8V for the same price or less as a bunch of eneloops to do the same thing with less mAhs here.
How do you charge these batteries, though?
BTW, I don't think I'll want an in-bike charging circuit, as I have read that Nickel batteries should only be charged at room temperature, and, well, winter's coming. I am thinking just to be able to alternate between dynamo and battery mode, without ever connecting the battery to the dynamo itself, instead taking it to my room to recharge.
Another thing I'm considering is using a hub dynamo, since apparently they don't cost extra effort while pedaling, therefore could always be engaged, and the need for batteries would be eliminated. I could use a supercap to power the system during stops. And the cost is about EUR 30 (40 dollars). Any comments?