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Overheating problem -- please help

  1. Aug 4, 2015 #1
    i have read in some places that the max recommended temp of a brushed motor is 150-160f (correct me if i'm wrong)

    My electric bike has a 540 watt battery with a 500 watt motor and it gets to 147f when i rode it 3 miles. I thought this is a bit close to 150f so i was wondering if i could buy a 600watt motor to replace my 500watt one and my neighbor said that it might still overheat because 540watts is less than 600watts. It doesn't seem right by common sense but i'm a 9th grader so I can't be sure. So will a 600watt motor still overheat with 540watts going through it? (the battery and the motor are both 36v)
     
  2. jcsd
  3. Aug 4, 2015 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    There is no such thing as a "540 watt battery". Is this a production electric bike, or something that you custom built?
     
  4. Aug 5, 2015 #3
    the bike is custom built
    the battery is 36v 15amps and i think it is 10ah
     
  5. Aug 5, 2015 #4
  6. Aug 5, 2015 #5

    davenn

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    That will depend entirely on the make and the model of the motor which you have told us nothing about
    do you have a link to the motor spec's ? ( tho 150 deg F sounds quite high)

    it doesn't work that way ... the motor will draw a certain amount of current depending on how much load it had ( that is weight (mass) of bike/rider, if its going uphill downhill, flat ground etc etc)

    when starting off from a standing position, the motor will draw high current, once up to a steady cruising speed ( whatever that may be) the current drain from the motor will drop.
    so for example
    at moving off it mite be briefly drawing 20A @ 36V = 720W till its settles down for cruise speed and the next variation in speed or load
    at cruising speed it may be drawing 10A @ 36V = 360W

    A lot of guesses here without knowing the specifics of the motor etc

    my other suggestion is that the motor cannot handle the load and that is why it is overheating
    consider how you mite lessen the load aka stress on the motor so that it isn't working so hard


    Dave
     
  7. Aug 5, 2015 #6

    sophiecentaur

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    Perhaps lower gearing and a lower running speed would solve the problem.
     
  8. Aug 5, 2015 #7
    here is a link to my motor https://www.amazon.com/ScootsUSA-36...=1434777590&sr=8-4&keywords=36v+500watt+motor
     
  9. Aug 5, 2015 #8
    how can i lower the watts of my battery to solve the overheating?
     
  10. Aug 5, 2015 #9
  11. Aug 5, 2015 #10
    it would be better to be at 13.8 though (i think)
     
  12. Aug 5, 2015 #11

    berkeman

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    That is not your problem. And your battery does not "have watts".

    You are stressing the small motor too much, or it would not be overheating. Either take it easier on the motor (slower, lower gearing as already suggested), or add fins to it to help cool it when you are riding the bike, or get a bigger electric motor that is sized for the load you are placing on it.
     
  13. Aug 7, 2015 #12
    so if i get a 600watt motor will that fix the problem?
     
  14. Aug 7, 2015 #13

    berkeman

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    Switching from a 500W motor to a 600W motor will not make a significant difference. Doubling the size of the motor would help a lot more. What motors are typically used on motorized bicycles?
     
  15. Aug 9, 2015 #14
    Should also consider cooling, is there proper airflow going towards the motor?
     
  16. Aug 11, 2015 #15

    NascentOxygen

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    You might find that in some states a bicycle fitted with a motor rated at more than X watts will be classifed as a motor vehicle, and as such require that it be registered and be ridden by a motor-vehicle-licence-holder. It would be worth checking whether this applies where you live.
     
  17. Aug 22, 2015 #16
    thank you guys so much! i figured out it was a brake problem
     
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