Charge batteries with a bike dynamo?
I am experimenting with ways to charge batteries while cycling. Standard bike dynamos produce 3 watt 6 volts. That's not a lot of power but 12 hours of cycling should charge a 36 watt hour battery. I am thinking about about making my own battery pack. It needs to be 4s1p 14.4 volts.
What I need help on is what sort of battery chemistry to get: lithium ion, LiMiNi, lithium poly, etc. The batteries I need should charge efficiently at low current (about .25 amps).
The other thing I need help with is how to turn the dynamo power into charging power. I know I need to rectify it and smooth it. I have heard about Zener diodes. They are used in solar applications because they are more energy efficient. Should I use those? Lastly, dynamo power varies depending on the speed of the bike (Between 0 volts and 12 volts.) Lithium ion cells need a 4.35 volt charge. Would it be better to use a regular voltage regulator you get a radio shack or a switching voltage regulator. I have an anyvolt 3. Maybe there are PCBs you know of which automatically regulate a vacillating input voltage.