Speed vs Range

Discussion in 'Electric Bicycles' started by DrkAngel, Feb 21, 2013.

  1. DrkAngel

    DrkAngel Member

    Everyone likes more speed!
    Well ... most everyone.

    What most don't realize is the cost of more speed.
    Pulled from the ebikes.ca simulator, I noted the various ranges supplied at different speeds.

    Generic Mountain bike - motor only.
    665w peak output motor w/48V 10ah battery = similar to a 24V 450w peak output eZip motor - pushed to 36V 675w peak output motor.

    10mph = 46 miles range
    15mph = 30 miles range
    20mph = 20 miles range
    25mph = 13 miles range
    30mph = 8 miles range

    Wow! ... calculator click click click ... Every 5mph increase in speed decreases range by 33%!

    Most are shocked at the affect wind resistance plays.
    Wind resistance is the major factor, but road load, tires, drive train etc. also contribute.

    Makes me reconsider a lot!
    Do I need 30mph capability? Nice to have it but ... don't need to use it! - OK! - Still a go.
    Road Style bike with high pressure tires and crouched position? - Working on one!
    Motor only, crouched behind an Aerodynamic fairing? Sounds almost essential - for sustained 30mph! - Battery pack mounted between bars and fork is a partial fairing. I'm sure I could easily enhance that!

    Fortunately, I tend to cruise at 15mph, commute at 20mph with only very limited bursts nearing 30mph.

    I'm even considering not upgrading (choke) my latest eZip Trailz LS.
    OEM configuration is limited to 15mph in TAG (Twist And Go) mode and ~10mph in PAS (Pedal Assist System) mode.
    Well, not upgrading, till after I run a range trial with my prototype 22.2V 40Ah pack.
    I will add high pressure 1.75" tires for less rolling resistance and comfort seat and suspension post ... <15mph range trial might mean 5+ hours in the saddle! :cool2:

  2. Richard H.

    Richard H. Member

    Good summation of the facts and IMO really not a problem since a sustained 30 mph is too fast for most bicycles unless custom made for it. By that I mean running the gamut from cheap dept store bikes to mid level LBS bikes. 15 to 20 mph is more realistic on several fronts from component durability, brakes systems not to mention legal compliance. Want more speed than that, get a motorcycle.
  3. schulze 123

    schulze 123 Member

    Hi Guys,
    Here's another interesting observation for you in that once you start opening the throttle on your E Bike above the 2/3 mark, just watch those amps start to climb. If you can gear your set up (bit hard with hub motors) so that you can achieve your desired cruise speed between 1/2 and 2/3 throttle, you will get the best range and torque.

    Cheers BJ
  4. bromoto

    bromoto New Member

    Great job DA,

    After seeing those numbers and the decrease in range at 33%, also makes me wonder if I should re-enforce my build to handle two batteries or If I don't getting 8miles at 30Mph......
  5. wheelbender6

    wheelbender6 Well-Known Member

    It looks like for commuting to work, 15mph is a good compromise between speed and range. That is about the speed you would go on human power alone. The electric kit allows you to do 15mph without having to change out of sweaty clothes when you arrive. You can further increase range by pedalling along with the electric boost.
  6. LR Jerry

    LR Jerry Well-Known Member

    Hybrids are getting very popular with systems which recharge while using gas only.
  7. rawly old

    rawly old Member

    Anyway you look at it, it would take forever going coast to coast on
    electric alone.
  8. LR Jerry

    LR Jerry Well-Known Member

    People have done it on peddle power alone.
  9. rawly old

    rawly old Member

    Quite true,
    when I was a young man, I'd pedal as much as 140 mi. in a day,(60 uphill &
    80 down). Now I'm a fat old man whose had "major' traumatic injuries to both
    legs. I could still make 140 a day with the Tanaka if my hind quarters held up.
  10. darwin

    darwin Well-Known Member

    Back in the day I'd walk 7 miles to school in a blizzard with no shoes on and then run 26 mi marathon in PE class. You whipper snappers are spoiled today.
  11. rawly old

    rawly old Member

    Golly! ...At least I had shoes.
  12. DrkAngel

    DrkAngel Member

    20mph "Legal" Limit (USA)

    The 20mph USA "legal" eBike speed begins to look more "reasonable" than it did originally?

    I have multiple "compliant" eBikes:

    Comfort Cruiser
    2009 eZip Trailz LS (Low Step)
    No pretenses, 20mph limit on a big tired, big low slung suspension seat, full upright position.
    Typically I "cruise" at 15mph and "meander" even slower.
    Designed for motor only, but I do apply some assist getting up to speed and on hills ...
    Dumped the 24V 10Ah SLA batteries and packed 25.9V 25.92Ah LiPo into the oem eZip battery case.
    The battery upgrade, combined with the 16T upgrade provides a reasonable ~20mph.


    The Commuter
    2008 eZip Trailz
    Designed to commute at a sustained 20mph.
    29.6V 31.2Ah homemade Li-ion battery pack.
    16T upgraded drive gear.
    Smaller, higher pressure, Kevlar belted, low RR tires.
    Proper pedaling position seat.
    Designed for continuous pedal assist, motor only 20mph+, reasonable pedal assist provides better range or a comfortable 25mph.
    Safety gear includes reflective tires, strobe headlight tail and turn signals, (mirror is mounted on helmet).

    Snow Beast
    2008 eZip Mountain Trailz
    Winter only, designed to mush through slush, snow and ice.
    OEM 20T gearing but upgraded from 24V SLA to 33.3V 31.2Ah Li-ion for a ~20mph capability with a substantial torque increase. (1st upgrade 37V 20.8Ah Li-ion battery replaced for better durability and 20mph legality)
    Homemade studded tires ... front tire swaps between mountain tread and sheet metal screwed mountain tire, dependent on road conditions. Rear tire is a used carbide studded tire, drive wheel wears steel studs too quickly. Home made studded provides better traction than the carbide.
    I do assist for extra umph, when needed,
    When really icy-nasty ... I lower seat and ski my feet.


    Might have gone overboard with this one ...

    Then I went way too far ...

    So 20mph is OK by me ... though I might push the limits.

    By tuning motor wattage, amperage and gearing, I can limit motor only speed to the "legal" 20mph, but provide substantial motor assist above 20 mph.
    Even modest pedal assist might provide 25mph+ speed and some assist is available right through 30 mph!

    I do have a Haro 700C 24speed I intend on gearing for 22.2V 43.2Ah battery that provides 20mph capability ... might be a switch that "TURBOs" to 44.4V 21.6Ah (providing 30mph+ capability), 48-11T sprockets allow 30mph+ pedal assist at 90rpm.
    Last edited: Nov 14, 2013
  13. DrkAngel

    DrkAngel Member

    30mph w/assist from a 20mph "legal" eBike?

    30mph or run down ...

    I live in a small city with every street within several miles limited to 30mph.
    Most anywhere there are multiple routes available ... most everywhere ...
    In particular, there is one ~5 block stretch of 4 lane, no shoulder, that I must traverse on a daily basis.
    Usually I hop on from a side street at their red light and hump it up to 25mph+ to stay ahead of them.
    Sadly, motor assist declines from about 12mph and is nothing at 25mph.

    Ideally, I could fine tune a bike for motor only 20mph but supplies substantial pedal assist to 30mph.

    With the proper voltage and amperage "fine tuning" this is possible.
    Using the ebike.ca simulator I "built" this example ...


    Overvolting, while reducing amps, provides less assist below 20mph but gives substantial assist past 30mph.
    Ideal for the cyclist looking for a sustainable "keep up with traffic" speed.
    Even moderate drafting should greatly reduce required assist effort.

    Added benefits are:
    Higher efficiency, especially at lower speeds
    Less overheat potential in spite of the higher voltage
    A perfect alternative as an eaBike as opposed to an eBike
    Find a truck or van for substantial drafting
    Find a car of proper height for good overall visibility, use it for moderate drafting, and as a "blocker"
    (Drafting, especially with larger vehicles, does not require being dangerously close)

    Graph is for a Mountain Bike, Road or Race bike should benefit even more!

    3 shunt Controller "switchable" by cutting and adding switch to one or more shunts?
    1 shunt - 11.7Amp - 350w - 20mph motor only = legal
    + shunt - 23.4Amp - 620w - 28mph motor only
    + shunt - 35.0Amp - 820w - 28mph motor only = full power! (Substantial acceleration increase)
  14. rawly old

    rawly old Member

    I'm sure as technology progresses, we'll be seeing electric bikes with
    greater range for extended travel in spite being hobbled by wattage
    limits. I can't only hope they become more affordable as well.
    As it stands now, 150 mpg with my 35cc honda on a $15 bike is still
    the most practical option for me, but then I'm a dirt poor old man.
    I like the notion of an electric bike, but I suffer from 'range anxiety',
    and am skeptical since, to my knowledge, those expensive batteries
    seldom if ever survive to the touted 2000 charges.