Originally Posted by
Arcanum
2old, etc.: The BBSxx drives use a cadence sensor for pedal assist. If the pedals aren't spinning, there's no power. Possibly worse, if you're pedaling slowly you get less assist than if you pedal quickly.
Many of the better integrated systems use torque sensing pedal assist: The harder you press on the pedals, the more assist you get.
That explains at least part of the worse pedal assist behavior with DIY hardware.
Once the pedals are moving on the BBSxx the controller takes over via dashboard .. so however it's programmed at say 'level 1' that's the power/assist you are going to get.. won't matter how fast you spin the crank . the motor will try to get to the programmed rpm .. it'll get there faster if you put more effort into it .. but the power delivery will be based on % of programmed voltage and speed cutoff.. time between motor start and motor stop via the crank are programmable as is ramp up % of power .. using drivetrain gearing makes it easier or harder to get to the programmed rpm .. so there are some variables to play with to fine tune the BBSxx series... but as I said, no substitute for good torque sensing, which apparently is now available with the newest Bafang mid-drives, but they require a special frame ..