While playing around with my exercise bike and F&P motor/alternator I have discovered that an old PC power supply is quite happy fed directly from an unmodified F&P turning at various  RPM.  I have tested this particular old power supply at about 80 to nearly 300 volts and it produced regulated voltages 12 and 5 volt right through.  I didnt bother measuring the negative voltage outputs whatever they are supposed to be.

I suppose there is a tweak somewhere in the power supply to up that 12 volts to something adequate to charge batteries.