I want to attach a generator to a door handle and have the output charge a battery. My system needs to provide about 3 Watts. A similar question was asked here and I referenced it to get an idea of what kind of force, torque, power, and energy are needed to turn the door handle. These values, however, were calculated without the generator attached to the door handle. My question is, how would attaching the generator to the door handle affect these values? I know that the generator will also require some torque to turn it. What I'm confused on is if I should just connect the generator directly to the door handle or use gear ratios to figure out some gear system? The gear system would be to increase the angular velocity of the generator based on the gear ratio and the angular velocity of the door handle. Generators that I have looked at usually have some rating where they say what voltage and current are produced based on the rpm, so I figured I could get these rpms with gears, but gear ratios also relate the two torques.
I know there is more than one question in here, but if you could help me with understanding any of this I would really appreciate this. Even if this isn't quite feasible, what would be the major constraints?