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Over powering a Bafang geared hub motor - How much abuse can it take ?

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    Over powering a Bafang geared hub motor - How much abuse can it take ?

    I just purchased a Bafang geared rear hub motor . It is rated 750 watts at 48 volts . I will be mounting it on a 26' fatbike rim . I weigh around 240 lbs and my ebike weighs around 70 lbs .
    My Lifepo4 battery is 48 volts and can put out 50 amp bursts with a Lyen 12 Fet controller . This means I can go up to 2500 watts output for short bursts { 60 seconds or less} .
    Will this Bafang motor be able to take that type of wattage for short bursts without stripping the 3 nylon gears or burning up the motor ? I already shortened the 3 phase wires to 6 inchs in length
    and went to a much heavier gauge wire for the phase wires, on the outside of the axle { I did not open the hub motor up and replace the wires inside } .
    Last edited by rumme; 03-16-2017, 12:19 PM.

    #2
    On another note, I have been using a cheap YESCOMUSA direct drive hub motor on my fatbike for 2 years. It is rated at 1000 watts/ 48 volts, and I regularly pump 2500 watts to it, without it burning up the motor yet. I did drill 2 large vent holes to allow some air flow thru it. The problem with the yescomusa motor is it has about 25 Nm of torque and I wanted to try this Bafang which is rated at 80 Nm of torque.

    I assume if Bafang rates the motor at 80 Nm of torque, that is for the 750 watt power rating it has ? Would this mean that the torque would double to 160 Nm if I pump 1500 watts into it ?

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      #3
      Not neceserily:
      Amps * efficiency at instant rpm = Torque for propulsion
      Volts = Maximum rpm
      Amps * Volts * efficiency at instant rpm = Power for propulsion
      Volts * Amps * (1 - efficiency at instant rpm) = Heat into wires and motor.

      It will be close yet not increase 2 times.

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        #4
        Don't believe what the manufacturers say. Some specs are purposefully overstated, and other specs are purposefully understated. Start at a lower power level, and use a cheap watt-meter with a cheap temp sensor. Raise the power you are using until the motor is getting too hot (200F? 93C?).

        Your hills may not be as steep as my hills, so if it's hot when you use it, either add cooling, or swap-in a bigger motor...

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