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[ZeroMark]

Just put 1300 miles on my new 2014 DS 11.4 riding a nice 4 mile commute down one long street to get to work and back each day.  Flat, lights all timed pretty nicely, weather is Las Vegas heat.  My question is: at what speed in MPH is the motor on my Zero operating most efficiently?  40MPH?  50MPH? 30MPH?  I have the stock/standard everything with the belt drive and wanted to hear someone chime in on the specifics of the motor.  Is it designed for a certain RPM to be most efficient?

I've read other posts regarding efficiency, and overall, my app says i run approx 88 watts/hr over the life of the bike so far.

-Mark

[Doug S]

EVs in general, and the Zeros specifically, are designed to achieve a very high "efficiency" across a wide speed range. But the answer to the question I THINK you're really asking is, "as slowly as possible".

When I use the term "efficiency", I'm talking in the purely Physics sense; the ratio of the energy consumed over time to the amount of work done. "Work" done by a vehicle is dominated by three things: wind resistance, rolling resistance, and potential energy gain/loss by gaining/losing altitude. The first two always increase as speed increases; wind resistance in particular rises VERY fast as speed increases. Someone said in another thread that wind resistance rises proportional to the FOURTH power of vehicle speed.

So if you ride faster, your actual "efficiency" won't change much -- a few percent unless we're talking about extremely high or low speeds. The amount of energy expended/gained by climbing or losing elevation will rise directly proportional to your speed, as will rolling resistance, but since you'll finish the ride faster, the total amount of energy lost to those two things will be nearly a wash.

It's wind resistance that makes the big difference. Since it rises so fast as speed increases, and is dominant above very low speeds, the faster you ride, the more work has to be done to split the air, which isn't an efficiency loss per se (the bike IS doing more work), but it will reduce your range dramatically.

So the technical answer to the question you asked is, it doesn't make much difference in terms of actual EFFICIENCY except at very low or very high speeds. But the amount of energy it costs to make a trip will rise as your speed rises, at any reasonable road speed, so you'll always pay less, and have more range, if you ride as slowly as possible.

[Richard230]

If your are trying to travel as long as possible, follow the government's standard city routine.  It averages 19 mph, is performed on a dyno in an enclosed room with no wind or elevation changes.  You will get great mileage, but will be bored to death.

My guess is that the best speed to travel the furthest distance in a reasonable amount of time would be around 40 mph, before wind drag starts to be a major factor. 

[protomech]

The trip average speed for the UDDS is 19 mph, but there's a lot of sitting still there. Much of the actual travel speed is between 20 and 30+ mph.

http://www.epa.gov/oms/standards/light-duty/udds.htm

[biolife]

If you want absolute distance then pretty much the slower you go, the better. But as noted above, it gets a bit boring cruising along at 20mph for an hour or more.

[ctrlburn]

What if the question was asked "At what point does efficiency largely break from linear?"  which is really the goal - to travel below the speed at which losses in efficiency become dramatic rather then trundle along shackled by pure mathematics.

[krash7172]

If your are trying to travel as long as possible, follow the government's standard city routine.  It averages 19 mph, is performed on a dyno in an enclosed room with no wind or elevation changes.  You will get great mileage, but will be bored to death.

My guess is that the best speed to travel the furthest distance in a reasonable amount of time would be around 40 mph, before wind drag starts to be a major factor.

Agreed. I stick to 35 mph roads (40mph max) when efficiency matters.

The most efficient speed is how fast you can push it without it turned on

[NoiseBoy]

If your are trying to travel as long as possible, follow the government's standard city routine.  It averages 19 mph, is performed on a dyno in an enclosed room with no wind or elevation changes.  You will get great mileage, but will be bored to death.

My guess is that the best speed to travel the furthest distance in a reasonable amount of time would be around 40 mph, before wind drag starts to be a major factor.

Agreed. I stick to 35 mph roads (40mph max) when efficiency matters.

The most efficient speed is how fast you can push it without it turned on

Maybe not if you factor in the calories you burn pushing it!

I'm sure the most efficient speed would be even lower if you disconnected the lights as they become a significant power draw at very low speeds but are barely a concern at motorway speeds.

[Doug S]

I'm sure the most efficient speed would be even lower if you disconnected the lights as they become a significant power draw at very low speeds but are barely a concern at motorway speeds.

Not intended as a correction, but for anybody who hasn't done the calculations, I did: The 50W headlight on my 11.4 SR drains less than 0.5% of the battery capacity in an hour. To be precise, a 50W load will drain an 11.4kWh battery in (nominally) 228 hours. That's not too much of a drain if you ask me.

I don't know how much the rest of the bike draws, however (running lights, misc electronic modules, etc.) but I can't believe it's anywhere near 50W.

[NanoMech]

Put another way, my average usage of 104 watts/mile indicates that turning off the 50-60 watts of headlight and running lighting for 1 hour would enable me to travel approximately 1/2 mile, assuming I am not at the nonlinear end of the battery power (last 3%?).

On a hypothetical 3 hour ride that would consume 95% of my battery capacity, leaving the headlight and running lights off the entire period would enable approximately 1.5 additional miles of motoring.

[ctrlburn]

Recognizing one optimum speed is not a specific vehicle speed - but an Air Speed, which most can get a general awareness as we ride (riders like Terry gets a more subtle awareness).
I'm thinking along the lines of a Dwyer windspeed meter (calibrated tube which floats a ball) would better indicate for hitting or staying below a wind resistance target - for those of us without a live torque readout (I've got a phone, (but  not a mount and a disposable phone)). I'll try rigging a clear tube and calibrate on windless days against the speedometer.

Going higher tech - a Kestrel will even data log.

[NoiseBoy]

Going higher tech - a Kestrel will even data log.

But you have to feed it mice all the time or it would just fly away. Hardly practical for long distance motorcycling.

[RickSteeb]

Just put 1300 miles on my new 2014 DS 11.4 riding a nice 4 mile commute down one long street to get to work and back each day.  Flat, lights all timed pretty nicely, weather is Las Vegas heat.  My question is: at what speed in MPH is the motor on my Zero operating most efficiently?  40MPH?  50MPH? 30MPH?  I have the stock/standard everything with the belt drive and wanted to hear someone chime in on the specifics of the motor.  Is it designed for a certain RPM to be most efficient?

I've read other posts regarding efficiency, and overall, my app says i run approx 88 watts/hr over the life of the bike so far.

-Mark

Doctorbass posted this data... YMMV


http://roulezelectrique.com/wp-content/uploads/2014/08/Optitrip-EV-by-Doc.jpg

http://roulezelectrique.com/quebec-la-sarre-quebec-en-moto-electrique-2000km-pour-0/

English translation!:  http://goo.gl/nYs2k5

[trikester]

I added a kill switch to my FX (& e-trike) headlight, on low beam only, for dirt riding. Often my average moving speed will be between 8 & 18 mph so over the long riding time the light could make the difference between riding back or pushing the last mile or two.

By only disabling low beam I can quickly flip the light on high beam if someone is coming toward me.

Trikester

[Doctorbass]

in general the best speed to use with the zero is at around 80kmh ( 50mph)

This is teh best for great speed, efficiency and confort all at a time.

The max efficiency speed is for sure a very low speed. overall it seem that the slower you run the best efficiency you get but this is not totally true.

we have to see not just the motor consumption but also teh reat like mentionned about the headlight exemple.

when you power on the Zero the controller, the DC-DC and all electronic components draw some power, not only the headlight. I have not measured that power yet but i would assume that it should be at about 100Watts of power

This mean that  at a given speed if you go too slow that 100Watts will get more important compar eto the motor power and the efficiency will drop. this mean that there is a speed that if you go slower you loose efficiency due to the continuous constant 100W power consumed by teh rest that is independent to the speed.

Doc

Doc