I am wondering if magnetic pedals would induce current in mid-drive ebike motors or batteries. I am assuming for theoretical purposes, they would, because all oscillating magnetic fields induce a current in everything conductive within their lightcone, but for all practical purposes, the effect would be so negligible as to be unmeasurable, but I don't really want to do the calculations myself. Is there any research out there on this, or can anyone do any napkin calculations?

  • Magnetic pedals weren't something I'd come across before - they're an interesting concept for foot retention though I can't see me ever trying them – Chris H Apr 2 at 14:14
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    If you're using the word "lightcone", you're required to do the math. – ojs Apr 2 at 14:31
  • I'll just comment that magnetic pedals have been tried as many times as there are reasons they haven't been widely adopted (i.e., many times and reason). – Paul H Apr 2 at 15:47
  • Some e-bikes have a reed-contact, activated by the a permanent magnet in the spokes and possibly an similar sensor to detect pedal motion like bike-computers had. The cleat retention might interfere with these. – Carel Apr 2 at 17:22
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    For those not in the know, en.wikipedia.org/wiki/Light_cone – mattnz Apr 2 at 19:33

They won't interfere with the batteries (which aren't sensitive to magnets) or the motor (which contains stronger moving magnetic fields). Anyway even in the worst case both are a good few cm away and magnetic fields reduce quickly with distance.

Even wiring run along the downtube is reasonably well separated from the pedals, and it takes a lot to induce a measurable current in a straight wire with even a strong permanent magnet (I've tried - even a coil has trouble picking up much unless far closer than your setup would suggest). A problematic current would be even harder to induce.

There's a slim chance they might interfere with a magnetic cadence sensor in the cranks, which some electric bikes use to sense pedalling to know when to assist. You may be able to whether a particular model uses that sort of sensor.

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    Maybe they could interfere with Shimano’s electric shifting system which uses wires for the signals. – Michael Apr 2 at 16:19
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    @Michael I'd be very surprised. You have try quite hard to sense a magnet. If electronic shifting was that sensitive it would have trouble with the field from the current in the motor wiring,which is much closer as well as stronger (and pulsed faster as the motor uses PWM to control the speed) – Chris H Apr 2 at 17:14

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