[ElectricMotorcycles] generator efficiency question

[john fisher]

I am thinking through a high-powered 3 wheel elec-bicycle. For packaging reasons, using the human-powered drive 
component through direct drive is awkward. So what I am wondering is how much efficiency would I give up by pedalling a 
generator/alternator and charging the battery.
assuming:
the human produces about 150W steady
a few pounds of extra weight is acceptable.
the direct-drive efficiency is basically 100%
any opinions? is it a 50% loss? even greater?


John