I haven't dug into this yet, but I do have a lot of experience with getting full motorcycle electrical functions out of an Enduro bike with only 40W output.
So, headlight and taillight are powered by 12v AC directly off the charging coil which has a 12v (14.7v AC) voltage limiting shunt regulator to limit the voltage. There is a second 12v DC circuit that powers a battery, the blinkers, horn and a small LED safety bulb in the headlamp housing (in case I dump the bike at night and the engine dies. The battery is 8 NiCads taped and soldered together. Weighs about 1 lb. Li battery would be wonderful.
So, my dream is a hybrid bike weighing under 50 lbs with a China Girl supplying speed, range and charging when I need it, and a 250w electric supplying 20mph city/parkland/bikepath power to not offend the population. All I've done so far is build a few CG and electric bikes, but not combined them of got the CG charging.
The flywheel turning 6000+ rpm is a great potential for power, but we know tapping it off the present coil will kill spark or timing (and power). Options are:
- Use more powerful magnets on the flywheel (glue on rare earth magnets?)
- Use a separate coil for charging off the flywheel, ideally at 90 degrees to ignition coil
- Use a discrete coil and glued on magnets in another location (wheel rim? Clutch housing?)
The goal would be to charge a LiFe battery in 20 miles that would run the electric motor for 5 miles or similar.
I believe at all times keep the weight down, keep it simple and remember that this is at heart an assisted pedal bike.
I really think the China Girl has the advantage for a lightweight durable power source with a bit of prep.
I should mention: if you are cutting the laminated coil core or flywheel magnet be aware the sheets of the laminate are varnished to insulate them. This is to avoid eddy currents, heating and improve efficiency. Cut slow (no grinding), keep cool and re-varnishing might help.