Quote:
Originally Posted by zjrog
I'm thinking I can add a second sprocket to the rear axle, which would be a freewheel. So I don't think there would be much regenerative charging.
Budget, less than $100. Batteries aren't a real issue, I might be able to get some freebie recycle turn-ins.
Speed, 10 MPH or less. Would like a range of 15 miles, but less isn't bad. I just want the thing to get up hills around town here, and with it freewheeling when pedaling, be almost transparent (minus the battery weight...).
I'll get and post a pic or two of the rear axle and drive stuff later.
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Use a 500w or so motor geared for high torque, so it tops out at 15MPH or so. You'll get plenty of regen going down the hills, especially with the motor geared for torque. Like you said, it should neither accelerate nor regen by default, but just freewheel. That's easy since all it needs to do is leave the PWM off. You'll have a potentiometer to adjust PWM power (amount of acceleration or regen) and a switch to select between acceleration and regen. (As unusual as that sounds, someone on a hybrid bike site actually uses that "sign magnitude" setup daily. A more usual center position for freewheel is actually more complex to design for a brush type motor, but merely a software setting for brushless DC.)