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Thread: Speed vs Range

  1. #1
    Senior Member DrkAngel's Avatar
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    Lightbulb Speed vs Range

    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.

    Anyway
    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!
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  2. #2
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    Nice write-up, DrkAngel. I've been using ebike.ca's simulator as well. I've been meaning to send the guys at ebike.ca an email with a request to put the Papamotor 48v 1000w hub motor on the list of options.

    Absolutely, wind plays a huge factor the faster you want to go. I noticed a considerable change before and after installing my front fairing. Even with it, the wind if directly blowing at me takes a big bite out of my performance. I've seen a drop of 5 mph in the extreme conditions I've ridden in and the 48v 15Ah Ping battery really gets a workout.

    I can easily get over 20 miles at 30+ mph with my current setup assuming the wind is between 0-5 mph, the road surface is smooth, and I'm not carrying any cargo in the panniers. Of course, the terrain here in Florida is mostly level which also helps.

    I've been using Schwalbe's Big Apple tires in the 26" x 2.35" size and so far they've performed flawlessly. I've got a new rear 7-speed cog with an 11t so I'm looking forward to pushing my max distance to 25 miles using just the 48v 15Ah Ping battery.


    If we don't make changes to our use and abuse of energy, Mother Nature will make it for us.
    Be a part of the solution to Global Warming instead of a contributor.

  3. #3
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    Quote Originally Posted by DrkAngel View Post
    Everyone likes more speed!
    Well ... most everyone.
    Well, I dislike waiting around for my battery to charge almost as much as I like more speed.

    Nice work DA.

    My 17mph 10ah 450 watt geared hubmotor "mtb" conversion sips energy as long as I keep it under 16mph (most of my riding is on level ground). I'm pretty sure that you could get well over 25 miles out of it if you wanted to (I tend to pedal most of the time). I don't think I've ever pulled the battery down to less than ~ 40%. Meanwhile, I only get about 18 miles or so out of my 20mph 10ah 750 watt direct-drive Worksman based "board track replica" (the low bars and seat height are, of course, much more suited to "e-power" riding than my more sedate mtb conversion).

    I've given some thought to converting my DD BTR over to a 48-52 volt 22amp 25+ah lipo battery in an effort to reach 28-32mph (I already have an upgraded controller that will handle the amp and voltage increase). This level of performance would also (imo) require a powerful drum or disc front brake. Projected range on this upgrade will be...well...let's just say that range will be at the bottom of the performance chart...

    However, I'll probably spend the money on a solar battery charger before I upgrade the BTR.

    Wait a minute (or hours)...didn't I just say that I don't like waiting around for my battery to charge?

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    Sometimes I wish my bike another 5 MPH's in it , I learned this last year when a Pit bull broke free from his leash, he kept up with me easily on my 26" wheel 20 MPH E-bike, he chased me into a main street & I threaded through traffic until he broke off the chase if I was on my Raleigh Grand Prix road bike I bet I couldve out run him. Then theres the times when riding on busier roads & you have to overtake a bunch of parked cars @ once then tuck back into the side of the road .
    But having said that I notice with my bike when I'm going flat out downhill a little over 25 MPH's it gets a little squirrley more so then my Road bike a lot more so. I hink you need a bigger frame/tire maybe some Schwable Big Apple tires for a safe well engineered 30 MPH ish EA-Bike { notice I said EA E-Assist , LOL ** . When I'm able to get off long Island one day to a more rural area I'm going to score me a Stealth Bomber or maybe build a beefier faster bike but for now very content with the miPower & it's capabilities.
    It is important to note that by cutting your top speed & pedaling a little more you can greatly increase range
    Good E-Biking 101 lesson
    Last edited by Scaliboy62; 02-21-13 at 10:21 AM.

  5. #5
    Transportation Cyclist turbo1889's Avatar
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    It should be noted that going slower does not necessarily extend your range. A whole lot depends on how the bike is geared between the motor and the wheel and the power and efficiency characteristics of the motor used. Motors running at less then their ideal RPM are less efficient and the inefficiency can catch up with you and negate the gains achieved by the reduced air drag of lower speeds depending on the gearing. Usually there is a sweet spot when going just barely fast enough to keep the motor in its efficiency range but no faster so as to keep the air drag down to a reasonable level. Things get even more interesting when calculating hill ascent because the energy used to climb becomes just as much of a factor if not more so then air drag. And if you want to get really picky there is a third factor, that being rolling drag which isn't calculated the same as air drag but usually its so much smaller of a factor that it doesn't effect much.

    Check out the calculated range graphs in my design thread to see what I'm talking about as far as "the sweet spot":

    http://www.bikeforums.net/showthread.php/858245

  6. #6
    Senior Member DrkAngel's Avatar
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    Lightbulb Air Resistance vs Road Resistance

    Below 15mph RR (Road-Rolling Resistance) is the major resistance factor.
    Somewhere above this speed AR (Air-Wind Resistance) becomes the major resistance factor.

    While RR increases at a linear rate -1, 2, 3, 4, 5, 6, 7, 8, ...
    AR increases at a geometric rate - 1, 2, 4, 8, 16, 32, 64 etc.


    This graph shows the resistance transition occurring near 18km/h (~11mph)
    This appears to be a road or race bike.



    Air resistance is such a factor that at near 30mph ...
    An electric bike with lowered seat and crouched rider is faster than a bike with a "properly" positioned rider applying substantial assist.
    A Mountain bike requires 255w of pedal effort to maintain 18mph.
    I chose 18mph because most cyclists are familiar with the effort required to maintain this speed.

    This graph demonstrates the additional speed available from adding the effort required to power a bicycle at 18mph.




    From 10mph, assist will double speed to 20mph (10mph).
    From 20mph, the same amount of pedal assist will increase speed 5mph.
    From 30mph, the same amount of pedal assist will increase speed 2.5mph.
    From 40mph, the same amount of pedal assist will increase speed <2mph.
    However at 50mph, the same amount of pedal assist will increase speed ... barely ... 1mph!

    On the other hand ...
    This degree of pedal assist will more than triple range (300%) at 20mph and almost double range (200%), cruising at 25mph.
    At 30mph assist increases range, possibly 33% (133% total).
    Pedal assist contribution percentage declines quickly with speed.
    Near 30mph, a more aerodynamic position outperforms even substantial pedal assist from a "proper" pedal seating position.
    Last edited by DrkAngel; 11-13-13 at 03:58 AM.
    "Best of all! ... I get to play. ... http://www.bikeforums.net/attachment...&thumb=1&stc=1
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  7. #7
    Senior Member DrkAngel's Avatar
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    Cool

    Watts needed at more typical speeds.

    Last edited by DrkAngel; 07-23-14 at 12:21 PM.
    "Best of all! ... I get to play. ... http://www.bikeforums.net/attachment...&thumb=1&stc=1
    Sorry! ... I'm addicted to improving enhancing.
    With side orders of inspiring enlightening!"

    Acronyms

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