You seen on the gearbox picture how David had a motor on it. That's what I want to do with a 24 volt 350 watt motor. Then under the seat in the mid frame mount a 24 low rpm alternator; it would be driven off the left side of the rear wheel. From what I was seeing these alternators can have different size regulators put in them. The more voltage the higher the rpm that's needed. However by calculating a high drive ratio the wheel wouldn't have to spin very fast to get a desired voltage with this type of alternator.. I'm only wanting an assist motor to the engine. The motor would be used on battery only for low speed things like riding on green way trails. Where I live the green ways allow electric at low speed but don't allow combustibles because of the noise levels.
I think what you're were trying to tell me before is a charging system has to have a minimum and maximum regulation.