A sort of complex question concerning range and speed on an e-bike.

Discussion in 'Electric Bicycles' started by motorbikemike45, Feb 4, 2012.

  1. Late last Summer I finished my second e-bike using a Ping 48V, 15aHour battery and an e-bikekits.com direct drive rear wheel hub motor with a 7 speed cassett. The bike has great speed and power with a 25 miles per charge range running WOT. The e-bike kit comes with a 3 speed switch that cuts down the voltage the controller puts to the motor (24, 36, and 48), which is great for going slower on bike paths, in busy foot traffic on multi use trails, etc. In a little experiment to increase range last Fall I cut speed to the lowest setting on the switch and ran till the battery pooped out. It extended the range only 3 miles, from 25 to 28 miles on the same flat path I usually travel, though it took me about an hour longer to reach the range limit. This path allows for very few stops, so accelerating the bike from a stop is not a significant factor.

    I know that it takes a bit more work to push a bike and rider faster through the air due to increased air resistance, but the bike and rider take about the same amount of work to move the weight and overcome friction loads a given distance at a given speed. I understand that Watts are a measure of work, so I'm asking if going slower on an e-bike will make much difference in the range. A gasoline engined motored bike can get much better or worse mileage depending on how much throttle is used, but it doesn't seem to make a whole lot of difference on an electric vehicle at a relatively constant speed. In other words, for a given load over a given distance will the Watts required be the same at 24V, 36V, and 48V at WOT in each voltage? Will the amps increase at different voltages to move a fixed weight a fixed difference and use the same Watts. Volts X Amps = Watts
    Last edited: Feb 4, 2012

  2. HeadSmess

    HeadSmess Well-Known Member

    i think the problem is the voltage switch itself. how does it work exactly? does it just dump excess voltage through a regulator or resistor? so the current available remains constant? the rest becoming merely wasted heat?

    or is it a fancy switching dc/dc convertor, that with roughly 95% efficiency, will basically double the current while halving the voltage?

    the former will give proportionately less watts as the voltage is reduced, whilst still placing full load on the battery... not good, and what is happening i feel.

    the latter will give approximately the same wattage output regardless of output voltage... but as the motor can only DRAW so many watts at a certain voltage, or amps(e=ir), the watts used at a lower voltage is less, you go slower, but theres less drain on the battery... mileage increased :)

    that make sense?

    i may be overlooking something major and be completely off track... such as it maybe being a PWM type voltage reducer...which wouldnt give the current gain of a converter either... but would place less load on the battery and improve mileage somewhat...
  3. Thank you for your input, HeadSmess. I don't know how the 3 position switch works. It is small and the wires to/from it are very small, so it can't be carrying much current. It seems to me it simply sends a signal to the controller and that alters the voltage to suit. I somehow assumed the range would greatly increase as I clicked lower settings, though I'm not so naive as to expect it to vary as much as two or three times as long. It is nice to increase the throttle sensitivity range at lower speed when on a crowded multi-use trail. The latest kit I ordered had a geared 350Watt hub motor and it came without the 3 way switch. I was completely underwealmed by the geared motor, so I returned it and my new 500Watt direct drive hub motor should be delivered Monday. I'm curious if it will have the switch, or if it has been deleted to save cost/complexity.
  4. DeathProof

    DeathProof Member

    e bikes dont belong here lady we are men we are about the gas engines :smile:
  5. MikeJ

    MikeJ Member

    Easy there, DeathProof; be respectful of everyone in this motoredbike forum. Negative comments are of no value. We all seek advice from others who know answers. That DOES include electric bikes. I recognize a distinction between electric motors and fuel-fed internal combustion engines. Most everyone uses the term motor for both types of devices; I have yet to hear the term electric engine.

    I assume Motorbikemike45 knows there are other electric bike forums. But I hope he stays in touch with this forum, for someday, I may ask him for assistance with an electric bike. I am looking into one now. If he can get more mileage out of a given charge, I certainly WILL be interested.

  6. Deathproof, please return to the infant's nursery. This is a forum for grownups and immature children are not welcome. There are some 14 year olds on the site, but they are mature for their years and we welcome them. Grow up and behave or we will take you behind the woodshed and teach you some manners.

    I have built 4 gas engined motoredbikes, and while they were fun and semi-practical transportation, my interest has now been drawn to electric powered motored bikes. I still have some interest in ALL motored bikes, which is why I remain here instead of going over to Endless Sphere entirely. Perhaps, if you live long enough to mature a little you will put your childish prejudices behind you and realize we motored bikers are all in this together and wish to help everyone who share our hobby responsibly. With adulthood will(usually) come maturity, compasion, responsibility, and, with luck, wisdom. Be very careful, I have a friend in Winnipeg who would gladly put you down as a favor. She owes me and she's tougher/meaner than any man. :)
    Last edited: Apr 15, 2012
  7. Ypedal

    Ypedal Member

    I own both types, gas and electric, from 36v to 100v, geared to DD, the gassers get run once in a while to prevent the carbs from gumming up, the eletrics get me to work daily.. :cool:

    the 3 position switch regulates the throttle signal, these kits almost all use Hall sensor throttles, it's a 1 to 5v signal telling the controller to go partial or full PWM ( pulse width modulation ) .. the motor will always see full battery voltage, the controller simply regulates the pulses to adjust the speed from the throttle position.

    below 20mph, there is no big advantage, once you get going above 30mph wind drag really shows a range difference.. the rest depends on tire pressure, rider weight, terrain .. etc..