coasting (vs complexity) sepex vs pm brushed

Hi, I'm thinking through a KISS ev conversion for a motorcycle. regen seems complicated (and not as efficient as coasting) so I want to focus on being able to coast well, but would like to leave out the mechanical freewheel/sprag clutch if the motor will freewheel on its own well enough.

Do PM motors, even if they are not connected to anything, create significant drag when overrun? With more rotational mass and/or rpm would the cogging effect cancel out (the pull into cogged position is canceled by the pull to stay in position on average?). I have heard that they do create drag with the magnets there, perhaps with some very fancy controller (and position sensing) it could be canceled out, but that doesn't sound simple.

Do sepex motors freewheel nicely by de-energizing the field (and the armature of course) ?

Thx!

hmm, wonder if looking at a common unversal motor would give me a clue (i.e. take the motor out of a 120v drill and see how it spins). I do recall at the local science store a magnetic device that slowed down a penny when dropped, probably something like that going on in a pm motor as well as cogging when de-energized.

From what I recall, Sepex can allow regen, but series wound DC motors don't.

With the right controller, it is possible to regen a series motor too, but I am not aware of any that do it yet (unless the Soliton1 or it's descendants have finally implemented it--it was discussed back during it's development, but I don't know if they ever ahd time to do it).


Regarding freewheeling, the only thing I know you'd have with a non-PM motor is bearing drag, and if it is a brushed motor, the friction of commutator and brushes.

Any PM motor I'm aware of will have some drag on it when spun without power.

There is the cooling fan too. It would be simple enough to bolt on an electric blower and temp controller and remove the internal fan. But I don't know if there is much energy to recapture there, though certainly there is some if you only cool as needed independant of rpm + improved coasting.

I might consider regen later, and sepex makes that a little simpler, but I'm considering shelling out for lithium and don't know how to match recharge current and not break stuff cost/time effectively yet. I do know how to coast and stay off the brakes alltogether though

PM motor detent drag depends heavily on the design of the motor. Some will turn over easily and allow for easy coasting, while some would take a torque wrench to turn over and will add vibration and drag. Looking at the particular motor design would be needed.

I think the cogging is a bit of a red herring now that I look into it, it would not be noticable if the poles were not ferrous, the issue really is eddy currents (a magnet passing by a conductor). I would be looking at an EMC-ME0909 (or two) if I went pm, so how many hp does it take to spin a disconnected EMC-ME0909 at 4500rpm would be the $39.74 question.