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 - 10.4wh/mile
15mph = 30 miles range - 16wh/mile
20mph = 20 miles range - 24wh/mile
25mph = 13 miles rang - 37wh/mile
30mph = 8 miles range - 60wh/mile


If you travel the same long route on a regular basis ... make a friend along the way.
Stop in for a quicky ... recharge.
eBike forums, clubs or registry?
Help set up a recharge network.

Metricilated 'er up fer ya ...
Generic Mountain bike - motor only.
48V 10ah Lithium battery = 480wh
10mph = 46 miles range ........ 16kph = 74 Kilometer range - 6.5wh/km
15mph = 30 miles range ........ 24kph = 48 Kilometer range - 10wh/km
20mph = 20 miles range ........ 32kph = 32 Kilometer range - 15wh/km
25mph = 13 miles range ........ 40kph = 21 Kilometer range - 23wh/km
30mph = 8 miles range ........ 48kph = <13 Kilometer range - 37wh/km

Remember ...
It's not just, how far you go ...
It's also, how go you far!

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.
(I use 3 eBikes + latest eZip, + building a road version and an eTrike ... also.)
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!

This is part of the reason I ended up building a trike. The aerodynamic factor on these is sooo great I can cruise along @ 27mph with way less power than my mtb requires.

Something like this would really increase capability for range at higher speeds.

You could even build a two wheeled streamliner which would only need around 1hp (~750 watts) at 60mph!

The only thing I like about upright bicycles is the added visibility. You would realistically need some sort of a tall flag on a low recumbent in order for trucks not to merge on top of you

Visibility is a major reason I never completed ReCycle, my lowracer 'bent bike, and instead built CrazyBike2.

migueralliart said:

This is part of the reason I ended up building a trike. The aerodynamic factor on these is sooo great I can cruise along @ 27mph with way less power than my mtb requires.

Click to expand...

As far as taht goes, any lowracer 'bent would have similar aero. A bicycle version would be slightly better aero than a trike.


As for the topic itself, and DrkAngel's comment:

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

Click to expand...

This is similar to how I use CrazyBike2--I cruise at 20MPH as much as I can, between the many traffic control stops I pass thru on my commute to/from work, reserving any higher speeds for emergency GTFOOTW maneuvers (which don't happen all that often, but sometimes come up, when it is safer to speed up to get out of the way than to try to brake and risk skidding into the problem instead). If I am on lower-speed paths like the canal, I go slower, partly because I'm usually going on longer trips and doing this will increase my range some. (not having to stop very often also increases my range).

But if I need the speed, it's there, and becuse it *could* do up to 30-35MPH, it still has quite fast acceleration past 20MPH to GTFOOTW if I have to.

30 mph has been my target speed.
Everything within several miles has a 30 mph speed limit.
I have viewed that safety dictates that I be capable of blending with traffic, not hindering it or outrunning it.

See - Bicycle Safety - The Math of Speed

My "main" eBike, 2008 eZip Trailz (5500 miles), runs at a modest <500w but I regeared it for motor only 22mph with some assist past 25 mph. Since I push this bike to near 30mph daily, for a 5 block stretch, regearing for assist past 30 mph is advisable. See - Re Gearing the EZips - Simple Mods Oh yeah! - I do provide a substantial burst of pedal assist, motor assist ends near 25 mph, so it is all me pushing to near 30mph! DNP 7spd 11T freewheel required.

I did mod another eZip for 30mph capability, I pumped it up to 37V and regeared for +30mph capability. In fact I've maintained 30mph plus for multi-mile test runs. Sadly, not too efficiently and requiring much effort. Of course that was a fairly upright stance with a heavy bike and 2.1125" tires at a sagging 40lb pressure.

My 30 mph project is a 32lb Haro Express Deluxe.
With 700C 35mm tires, @ 85lb, road load is minimized!
48 - 11T 8speed drive train pushes 90rpm crank speed well past 30mph. See - Sprocket Ratio = Pedal Assist MPH
EZip motor pushed to 44.4V (830w peak output) and geared up 25% pushes some assist to near 40mph, providing substantial assist at 30mph.
Perhaps most importantly, It has a 17" frame ... that means I can lower my butt to rear tire level and take advantage of the fairing-shrouds I intend on building-testing. I suspect that a lowered aerodynamic position might outweigh any sustained pedal contribution that I might be able to contribute. See - Haro Express Deluxe Build

Why eZip drive trains? Easy to regear for different speeds voltages and torque! See -
Re-Gearing the eZips - Simple Mods!

Your range chart pretty much agrees with my experience over 10,000 or so miles.

I've been amazed at times at the range increase you get from cruising 18mph vs 20. For me that has been the compromise long range speed. 15 and under just seems like such a crawl, but by 22-25 mph you just blew your range. 18 mph has been tolerable, yet gets me some real range.

One thing often overlooked by people when calculating battery size for a certian distance is that you rarely ride in no wind. By afternoon, if you must ride upwind, you'll need a lot more wh. 15 mph into 15 mph wind is the same as riding 30 mph.

I typically take a 10 mile morning ride (weather dependent), around a circuitous MUP.
Dependent on wind direction, I ride through the forest into the wind and take the wide open path, with the wind at my back. Sunglasses and visor needed upon occasion!

DrkAngel said:

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

Click to expand...

So we can approximate battery size required for distance at speed ...
48V x 10Ah = .480 kWh
15mph = 30 miles range

example - 50 miles at 15mph = .480kWh /30 miles x 50 miles = .800kWh
or ... if 48V
50 miles at 15mph = 10Ah /30 miles x 50 miles = 16.67Ah of 48V

Note! Do not use this to estimate if you are using SLA batteries!
SLA batteries often output less than 50% of rated Ah!

DrkAngel said:

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

Click to expand...

If 15mph gets you a 30 miles range, then 30mph should only gets you 3.75 miles. Same thing with 10mph vs 20mph. The required power increases 8-fold when the speed is doubled.

DrkAngel said:

DrkAngel said:

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

Click to expand...

So we can approximate battery size required for distance at speed ...
48V x 10Ah = .480 kWh
15mph = 30 miles range

example - 50 miles at 15mph = .480kWh /30 miles x 50 miles = .800kWh
or ... if 48V
50 miles at 15mph = 10Ah /30 miles x 50 miles = 16.67Ah of 48V

Note! Do not use this to estimate if you are using SLA batteries!
SLA batteries often output less than 50% of rated Ah!

Click to expand...

That's draining the battery full right? which is not recommended. Shouldn't we do MAX 90% DOD

migueralliart said:

That's draining the battery full right? which is not recommended. Shouldn't we do MAX 90% DOD

Click to expand...

That would be how much battery capacity you would "need" to get that far.
You would probably "want" much larger to save battery life and as a safety margin.

alex12342011 said:

Something like this would really increase capability for range at higher speeds.

You could even build a two wheeled streamliner which would only need around 1hp (~750 watts) at 60mph!

The only thing I like about upright bicycles is the added visibility. You would realistically need some sort of a tall flag on a low recumbent in order for trucks not to merge on top of you

Click to expand...

Oh yeah - try fitting this in the back of your compact SUV and then bringing it on the Staten Island Ferry - range ain't everything...lol

SamTexas said:

DrkAngel said:

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

Click to expand...

If 15mph gets you a 30 miles range, then 30mph should only gets you 3.75 miles. Same thing with 10mph vs 20mph. The required power increases 8-fold when the speed is doubled.

Click to expand...

I believe that you are referring to a rule of thumb and that maintaining 30 mph would require 8x the power as maintaining 15mph?

That concurs nicely with my posted information!

?

You forgot to realize that while you are using 8x the energy ... you are traveling 2x as fast ... for a 4x energy usage per mile.

Below 20mph wind resistance is reputed to be a minimal factor?
That might be a reason that the rule of thumb doesn't fit for 10-20mph?

also- at 10mph it is easier to contribute a lot of the power by pedaling,sometimes using no throttle at all. So the distance would increase even more. at 15mph not as much increase by pedaling.

DrkAngel said:

You forgot to realize that while you are using 8x the energy ... you are traveling 2x as fast ... for a 4x energy usage per mile.

Click to expand...

You're right. 8 times the power, 4 times the energy consumption. 30 miles range at 15mph and 7.5 miles at 30mph. So your estimation is almost exact.

The 8x power requirement for twice the speed is not a rule of thumb. It's physics and it applies to all cases. Air resistance is part of the equation so it's already accounted for.

aroundgube is correct. The slower you go, the more your pedaling efforts contribute to the total wattage. For example, if you put out 50w by easy pedaling and are traveling 20- 25 mph, you are likely contributing 50w added to 500w from the battery. Assuming for this example that you waste 20% of the 500w, your wheel sees 450w. Your 50w is not much of the total.

But if you ride slow, and only 100w is reaching your wheel from the motor, your 50w of pedaling is now 1/3 of the total of 150w..

Below 15 mph, you can really extend your range by pedaling. But as a nit pick, it's NOT better efficiency from the motor. It's just using pedal power for a third. The over all combined efficiency is just simply a result of less drag.

Well "a picture is worth a thousand words" so ...

Graphs built from ebikes.ca motor simulator

Notable improvements include:
All data from dual motors displayed on normal screen
dual motor performance combined via "ADD" button
Pedal assist watts option
"Race bike" load line replaced by "Mtb Tuck"

Mapped performance of an old hub motor.
26" wheel outputs a continuous 23mph.
For evaluation purposes I compared to the same rig in a 20" wheel.



Full throttle:
drops speed from 23mph >> (legal) 20mph;
improves efficiency from 72% >> 80%;
improves hill (below 12mph) and starting (35lb >> 45lb) torque;
increases range from 23 miles to 32 miles!!!

Partial throttle emulates, only partially, better range and efficiency.
This exemplifies one shortcoming of hub motors, the lack of variable gearing or ratio options.
Purchase of a specific capability motor might be optimal, but best for a specific use.
Mid drive through pedal drivetrain looks to give best multi-use or multi-condition capability! ... ?

DrkAngel said:

Mapped performance of an old hub motor.
26" wheel outputs a continuous 23mph.

Click to expand...

System A is showing 36 inch wheel in the screen shot???!

Buk___ said:

System A is showing 36 inch wheel in the screen shot???!

Click to expand...

Some factors were altered to match actual motor's performance!

DrkAngel said:

Based on oem specs, real life observation and a bit of imagination ...
I created a reasonable map representation of the BD36's power curve.
Though some values were altered, (most notably controller amps and tire size) ...

• Power curve matches:
• top un-loaded speed
• observed top loaded speed
• rated watts
• Max controller drop-off speed

Click to expand...

Wheel size was chosen to match 26" performance and 20" estimated by percentage 36" / 26" x 20" = 27.7" for B.
See original thread - Rescue Motor BD-36

DrkAngel said:

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 - 10.4wh/mile
15mph = 30 miles range - 16wh/mile
20mph = 20 miles range - 24wh/mile
25mph = 13 miles rang - 37wh/mile
30mph = 8 miles range - 60wh/mile

Click to expand...

Finally made up a Wh/mile graph ... using above data.



Might have time to add Mtn Bike Tuck, Recumbent and data for higher speeds ... later.
Closer sample rate and fractional miles range should smooth curve nicely, did some rounding up\down from gathered data for "cleaner" numbers.

.

Are the assumptions in these numbers steady state cruising on relatively flat ground with no pedal assistance?

In bashing them against my own experience, they seems a to lean toward being a bit pessimistic. Since I seldom cruise less than 20 mph and often 25mph or more, I figure my average is about 22.5mph as a "typical" speed. Given that, I'd expect to consume about 30 wh/mi.
But I think my real consumption is closer to 25 wh/mi. But then it is hard to put your finger on what your typical speed is given how slowing for stops and accelerating figure into average moving speeds. My actual average measured moving speed is typically about 20mph - which includes slowing for stops and accelerating from a stop. If we go by that, then your estimates are pretty spot on.

OTOH, if I add 5 wh/mi for my pedaling efforts, things jibe better with my finger to the wind typical speed of 22.5 mph.

Motor only, level road cruising.

Be aware that my graphs and charts are based on level travel on good surface travel.
Not factored are:
acceleration, getting up to speed;
climbing hills (might use >5≫10X the energy per mile;
coasting down hills (down hill uses much less≫0 energy, but full throttle even under no load can still uses noticeable energy! - regen enabled?);
Poor road surface (dirt, mud, snow, slush etc.)