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  1. #1 E-bikes batteries and Power, what's the real world? 
    C-Moto Not-so-Noob
    Join Date
    Jun 2010
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    Suzhou
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    Has anyone any further knowledge/experience around this subject? Just throwing it out there; e-bikes and e-bike power.
    Bit of a novice when it comes to e-bikes; brear with if these are considered to be stupid points.
    Looking to get me a high power e-bike, notionally 3000 watt and voltage in the 72 to 96 kinda range.
    90 to 100 kph and a range of 100km.
    Nearest Iíve come across (in reality, not just questionable web ad) is Bikerdocs e-bike on these very pages.

    Bear with me, Iím getting to the point now; in the midst of web trawling for info on e-bike power construction etc.

    It would seem to be;
    Power (expressed in watts) for a motor doesnít have too much bearing on actual (real) power output of the motor.
    It can be higher or lower than actual power output. This is along with power being expressed differently, peak power and constant running power.

    Actual measure of power of a system is dependent on the maximum power output of the control unit and the voltage.
    Eg: (old school physics) V=IR
    Maximum wattage= total voltage x maximum controller current.
    So: 72volt batteries x 20 amp (max rating) controller (72*20) = 1440 watts max power.

    So a system above could only put out 1440 watts, regardless of the size of motor.

    To achieve 3000watt maximum power, would require a 42 amp controller @ 72volts or 31 amp controller @ 96volts. Do such controllers exist?

    Back to physics again, using a higher voltage/lower amp would increase motor speed the inverse for lower voltage/higher amps.

    Has anyone any further knowledge/experience around this subject? Either to add to, to clarify my musings or tell itís a load of bolox Iím talking.

    My next hunt is for knowledge of batteries, Nicad vs lead acid.
    This seems to be a bit harder to find out, so Iím still looking.
    The main question is. Are Nicad significantly better than lead acid? Nicad weigh a lot less, are quicker to charge and last longer.
    But, are Nicads the poorer in an e-bike application? Where very high current deliver would be required (for acceleration) for shorter periods of time.
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  2. #2 Re: E-bikes batteries and Power, what's the real world? 
    C-Moto Senior Asymptomatic's Avatar
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    Changchun China
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    I am not really sure about the physics so my information may not help you. You might want to contact the company called Evoke in Beijing. A foreigner named Nathan Siy owns it and they build custom E-Bikes. He is always happy to chat with others who are interested in E-bikes. He is also part of this forum so you could shoot him a private message. Or send me your wechat and I will send you his. I personally bought a custom E-bike but it has Lithium ion batteries not the terrible lead acid or NiCd. Lithium Ion Phosphate battery tech is what all the big E-Motorcycle companies are using.Nathan is running Lithium Ion Cobalt's and getting over 150km range and over 120km/h. What I can tell you is, I have 4 72 volt lithium ion battery packs, not sure how many cells each. I also have a 5000w rear hub motor and my bike is a modified motorcycle. It does 85km/h with a distance of right about 80km as well. I can tune the controller for more speed and acceleration but then I lose distance and I need at least 80. With a better controller and if you are willing to cough up the expense for more cells, you could build or buy what you are looking for.

    My E-Bike
    12509281_10201214129470778_8478337018190670780_n (1).jpg
    ďI have never been lost, but I will admit to being confused for several weeks"
    Triumph Speedmaster, Di ping xian da pao che 5000W, KTM Duke 390, Dayang DY150, Jencheng 150 Razkull Clone
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  3. #3 Re: E-bikes batteries and Power, what's the real world? 
    Senior C-Moto Guru MJH's Avatar
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    US
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    Quote Originally Posted by Davie View Post
    Has anyone any further knowledge/experience around this subject? Just throwing it out there; e-bikes and e-bike power.
    Bit of a novice when it comes to e-bikes; brear with if these are considered to be stupid points.
    Looking to get me a high power e-bike, notionally 3000 watt and voltage in the 72 to 96 kinda range.
    90 to 100 kph and a range of 100km.
    Nearest I’ve come across (in reality, not just questionable web ad) is Bikerdocs e-bike on these very pages.

    Bear with me, I’m getting to the point now; in the midst of web trawling for info on e-bike power construction etc.

    It would seem to be;
    Power (expressed in watts) for a motor doesn’t have too much bearing on actual (real) power output of the motor.
    It can be higher or lower than actual power output. This is along with power being expressed differently, peak power and constant running power.

    Actual measure of power of a system is dependent on the maximum power output of the control unit and the voltage.
    Eg: (old school physics) V=IR
    Maximum wattage= total voltage x maximum controller current.
    So: 72volt batteries x 20 amp (max rating) controller (72*20) = 1440 watts max power.

    So a system above could only put out 1440 watts, regardless of the size of motor.

    To achieve 3000watt maximum power, would require a 42 amp controller @ 72volts or 31 amp controller @ 96volts. Do such controllers exist?

    Back to physics again, using a higher voltage/lower amp would increase motor speed the inverse for lower voltage/higher amps.

    Has anyone any further knowledge/experience around this subject? Either to add to, to clarify my musings or tell it’s a load of bolox I’m talking.

    My next hunt is for knowledge of batteries, Nicad vs lead acid.
    This seems to be a bit harder to find out, so I’m still looking.
    The main question is. Are Nicad significantly better than lead acid? Nicad weigh a lot less, are quicker to charge and last longer.
    But, are Nicads the poorer in an e-bike application? Where very high current deliver would be required (for acceleration) for shorter periods of time.
    R is the Resistance measured in OHMS

    I is current measured in Amps
    V is voltage

    Ohms= I/V

    If you are interested here are the derivations,
    http://simplemotor.com/calculations/

    I assume the controller is a combination of a battery charger/monitor and a rheostat. The current flow to the engine is a matter of the calibration of the rheostat, basically the throttle, which of course effects the rate of discharge of the power source, the battery bank.
    It’s a variable speed motor it has its engineered limits, its hp output linear to what it gets from the controller as a rate. The loss is inherent in the design efficiency a lot of the energy gets lost. Fans and other methods can reduce the loss.
    Last edited by MJH; 03-04-2016 at 08:10 PM.
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  4. #4 Re: E-bikes batteries and Power, what's the real world? 
    Senior C-Moto Guru MJH's Avatar
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  5. #5 Re: E-bikes batteries and Power, what's the real world? 
    C-Moto Not-so-Noob
    Join Date
    Jun 2010
    Location
    Suzhou
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    Thanks for the info fellas,
    Checked out the Evoke website; fine looking machines. One day maybe, but a scooter is more what I'm looking for, to use for day to day running around. I'll drop Nathan there a line though, see whats what.
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