Comparisons? WattHrs/mi/lb. @ speed

Mathurin said:
Heh, you do realize he missed the point of the OP, WattHrs/mi/lb. @ speed?
No I didn't. You're not understanding my point. My point is that the relationship between weight and Wh/mile at a given speed is not linear. Therefore, dividing Wh/mile by weight results in a basically meaningless value.
 
CGameProgrammer said:
Mathurin said:
Heh, you do realize he missed the point of the OP, WattHrs/mi/lb. @ speed?
No I didn't. You're not understanding my point. My point is that the relationship between weight and Wh/mile at a given speed is not linear. Therefore, dividing Wh/mile by weight results in a basically meaningless value.
I agree
 
CGameProgrammer said:
My point is that the relationship between weight and Wh/mile at a given speed is not linear. Therefore, dividing Wh/mile by weight results in a basically meaningless value.

Easy enough to say... care to illustrate?

8)
 
Interesting thread. I'd love to see more data on other people's fuel consumption figures. Like Xyster suggested though, unless we can all meet up somewhere and test our bikes over a standard circuit (which would be fun), we need to describe the conditions under which we obtain our figures.

Weight is a linear factor in acceleration and hillclimbing, but has little effect on the power needed to maintain a given speed on level ground, assuming that our vehicles have roughly the same frontal area.

Maybe the simplest approach would be to agree on an "urban cycle" figure, in Wh/mile, that gives a picture of our general usage, quoting average speed and whether the terrain is flat or hilly.

This could be combined with acceleration times: say 0-20, 0-30 and 0-40 mph, plus maximum hillclimbing grade, to give a broader picture.
 
By using your battery to 60% to 80% DOD (a 12ah battery to 9.6 ah) is what is suggested on SLAs at a 1 C discharge rate = 12ah rate. Lithiums are usually rated at a .2 to .5 C discharge rate so you would need roughly twice the ah of lithiums for the recomended cycle life if discharged at the same rate as SLAs= 1 C.
As we all know or should know... there are no flat 20 mile runs with no wind that I know of..This is why I use many runs on the same course AND use the end ROUND TRIP AH FIGURES along with the AVRAGE speed on the complete 20 mile round trips tells your Watt hour picture clearly on YOUR Route.On days of plenty of wind, hilly routes, pedaling hard,moderate,or hard you will be able to see what your worst and best conditions are for your own peticular system and adjust your speed for making it back every time.just by looking at your ah consumption on the fly..For instance ... after 5 or 10 miles up hill you have used 6 ah.Coasting back you know you make it back eaisly.If at the first half of a trip your going down wind you may need twice the ah to get back but it may take half as much power to get to the half way point. Going against the wind or up steep hills CAN be done as efficiently as riding on the flats just by going slower and NOT exceeding your motors TRUE rated power(at the motors BEST efficiency) yet not exceeding the apparent head winds drag forces.(to try to stay in a no wind vacume comming down wind by matching the wind speed and not exceeding it.Of corse performance will suffer if you go too fast for your motor and batteries efficiencies.Other than that all is equal.EXCEPT WEIGHT!
There is a formlua for this topic as well.It takes X amount of POWER to lift 300 lbs 1000 feet in X amount of time.Then friction and efficiency of your system is added in..
Too much math for me! I tend to use what works best for my system.= 2 miles per amp hour on any round trip with no pedaling at any voltage from 36 to 72 volts on ANY trip.At 72 volts however I can ONLY exceed this ever so slightly= by climbing 20 to 30 % grades for a long time at full speed.
A fun weight test is too to do acerleration tests form 0 to ? in 5 seconds with different weights and gear ratios while checking the used AH or WH on each 5 second run.Also to my advantage I have a 1 mile run from my door step up hill against the wind at about a 15% grade that I have been doing many runs a day for checking the best combinations in motors, controllers, gearing,weights, bicycles tires and the effects of ducking the wind. 10 years of doing these tests tells me what to expect on any of above situtations or power systems available that are CREDITABLY RATED in the 1 to 10 KW range.
I have documented every trip with all the REAL WORLD figures for over 20,000 miles of testing and enjoying the rides and knowlege gained this last decade.Watching all the Evehicle Promises come and go has also been a learning curve.The thing I see most common these days in the forums is that most everyone wants to have lightweight bikes that go faster ,farther with good performance, easy to get, and at a good price with safe batteries that have a long cycle life. LOL It starts with a volume market that will afford the best! right now even though there is the X light hub motor for economy.There is little on the market that will peform efficiently at 1 kw for use with expensive batteries without spending twice as much for the batteries as you do for the ebike it self..
Do it youeselfers that can make packs cheaper can get great performance but without a WIDE range of efficiency there batteries WILL suffer if they are not matched to the motor systems requirements.
MOST ebike systems have so little of a range of efficient power that it does not take much to change there efficiency preformance.The factors included are.... no pedaling or too heavy of a rider,Up a small hill , againdt the wind. Adjustable gearing such as a sprocket change could allow any ebike perform to the best of its ability.If you want to use a hub motor at 40 mph or cruise at slow up a hill with a heavy person both cant be done efficiently unless you change the whole motor for each type of use.
Complete unedited Video trips you can learn a lot from IF you know what batteries are used And IF a map with the elevation graph is included Knowing the gross WEIGHT is also a BIG factor in ANY conditions. My standard of 2 miles per amp hour is for my ebike on ANY round trip WITHOUT PEDALING Carrying a 300 lb gross weight. This is my WORST case performance (I can also get bad performance like this keeping it too fast at 72 volts with 190 lbs of gross weight.)
This is only a decade of my real world results and knowlege from actual testing. What I see in forums are someones graphs that are pure BS. Show the graphs with your long , slow hill climbing Videos....
Ok now strat bashing me again LOL...
http://tinyurl.com/yvz4f7
 
If some school's oval running track is available nearby,
there we find the equal circuit for running level ground comparisons.

Although the speeding may be limited to the low twenties,
often such tracks are clear of users in the small hours of the night.

In my area, at least, I can easily do this in windless conditions
(it's often dead calm at 3 or 4 AM).

And so--while the figures would be idealized,
by others making oval track runs under similar conditions,
we have a way to get very close comparsions.

When you think about it, Wh/mi or Wh/km at speeds above 20 are not very meaningful for universal comparisons--because the wind resistance will begin to overrule any possible level of "efficiency" inbuilt into the bike;
and owing to our wide variances in body sizes, stances and clothings, the wind drag varies so much as to become a large question mark against
fair comparisons of the bikes themselves.

So, high speed is sort of out of the question. for equilateral comparison purposes.

Besides, standard speed runs of say 20mph steady will show with accuracy and repeatability the relative efficiencies of our bikes
-under those narrow conditions- (level ground, still air, moderate speed).

And I just about bet that most set-ups will draw almost identical Wh/mi Wh/km figures, for the work function is the same,

and bike motor system efficiencies don't vary much more than what?
Perhaps ten to twenty percent between best and worst cases of electro-mechanical set-ups running for comparison within these narrow conditions

And if the bike is free-rolling, the differences in electrical efficiency, say I,
will be on the order of ten percent or even less.

It's when the bikes are strained by load and high speed that the superior efficiency will most show up.

But strain of high speed on level ground is all in abeyance to wind drag,
which varies so widely between bike styles and riders' shapes.

Only the strain of grade climbs is repeatable, and only in still air, and only for bikes run on the identical grade, really. And identical hills are not found at high school running tracks around the world.


In other words: posting Wh/mi Wh/km comparisons in other than flat oval track runnings in stillest air, will always show up as a melange of conflicting and seemingly incredible, irreconcilable results.

Reid
 
And I just about bet that most set-ups will draw almost identical Wh/mi Wh/km figures, for the work function is the same,

and bike motor system efficiencies don't vary much more than what?
Perhaps ten to twenty percent between best and worst cases of electro-mechanical set-ups running for comparison within these narrow conditions

And if the bike is free-rolling, the differences in electrical efficiency, say I,
will be on the order of ten percent or even less.

Reid[/quote] Reid what you and others are failing to except is that most ebike systems ARE Rated at the best efficiencys of 450 watts or less.And hub motors are NOT efficient with slow speeds and a heavy load.Unless you pick out just the right winding and voltage to maintain only 1 good top speed say at 12 mph for climbing hills with your wattage staying under 450 watts.If you have a hub motor that will do 30 mph on the flats it will certanily NOT climb a hill that the higher turn motor will provide power for more efficiently.UNLESS you pedal HARD!
What you may fail to relize is it does a lot more power to run any hub motor outside of its efficiency range.With out pedaling this may be most of the time at all start ups untill you reached your desired speed and even maintaining it at 20 mph without pedaling.Over the intire trip your best effiency range is very limited if you do NOT pedal.
A system that has broader efficiency range maintaining a 90% average (from a 94% efficient motor/controller ) range on most trips using a more powerfull motor that has a efficient ebike speed range from 0 to 40 mph 200 watts to 1.5Kw all in the 90% efficiency zone your overall efficiency will be upwards of 90%. Sorry to say some of the uses I have seen here with Hub Motors cause there efficiencys to drop below 40%.Using over 30 amps? Now see how that equates to your expensive battery usage drawing over the .2 C ratings most Chineese batteries are rated at.Sure they suggest a 1 C with 10 C max but the fine print by the manufactures say rated at a .2 C untill 80% didcharged.How many ah battery is required for a 15 to 35 ah discharge using a .2 C rated lithium battery ? How efficient are hub motors going slow to match small packs ? Would it be cost effective to pay $200 MORE for a more efficient system ( if it were available) of spend TWICE as much on batteries to keep up and risk motor/controller/battery dammage? all at a larger expence in the long run.. IF you have such luck ?
 
Reid Welch said:
If some school's oval running track is available nearby,
there we find the equal circuit for running level ground comparisons.


In other words: posting Wh/mi Wh/km comparisons in other than flat oval track runnings in stillest air, will always show up as a melange of conflicting and seemingly incredible, irreconcilable results.

Reid
No... Average round trips do fine! for Real World Testing.Oval tracks are mostly dirt and the radius of the track adds trie resistance you will incure.This is not a real world comparison.Nutons law! in my terms lol.
"Power spent going up gives a fee ride down" How fast you want to go up only depends on how much power you use efficiently with the available sorce and how much wind resistance you fight. Yes the amount of weight is only limited by time.The time it takes you to come down is limited by the grade, and wind resistance, turns, traffic, hub motor drag drag and amount of power used if any. How fast you safely go down hill is the most important! If you DO NOT have a efficient system with WITH efficient SLOW hill climbing power ALL THINGS ARE NOT EQUAL.. as on flat land in a vacume.Either is riding into a 10 MPH head wind unless you have efficient power to do so without pedaling.
NoT a Moped but a ebike that you don't have to pedal to get more efficiency going would be nice to see available some day.For public use I must say.Think about power going up having the equal and oppisite reaction comming down. Visa versa. X speed/weight or power and resitance @ Efficiencys! = how much you will spend on batteries.
 
(N)eiither is riding into a 10 MPH head wind unless you have efficient power to do so without pedaling.

Exactly, Randy


I spoke of the LCD, the lowest common denominator, which most all of us have access to:

an oval, quarter mile paved asphalt (not dirt) running track, found in nearly all communities.

And here, a practical idea for adding LOAD, Randy:

to simulate the load of a steady grade, substitute a wind load instead:
open a drag chute, a small one, tied to the back of the bike.

And here, semi-serious, if we had standard sized wind-loading drag chutes
for e-bike testing, and temp. and barometric and humidity equalization,

there you go: a genuine LCD test for still air level ground PAVED oval track load testing for efficiency.


You know, it's only common sense: Load is a load whether it comes by wind or by grade.
It's the same retarding force.

And in case of a whisper of breeze,
the back and forth nature of an oval track tends to cancel its effect.
Multiple identical laps make a fine real-world averaging.
And this is what we what: a repeatable set of test conditions.

Retarding forces. Think about them. And if we're all running 15 mph* circuits around boring oval tracks
around the world, why it's all the same for all testers,
even in Australia where (jk) I presume the oval tracks run backwards.
Yes, right. So the OZ tester's result will be in a minus sign.
To correct make a vertical mark through the - :lol:

And then we can in this way truly test relative efficiencies,
no mountains needed.

*why 15 mph? Because then the drag chute is the major, standard wind resistance and the bike style/rider type hardly matters.


___________________
_________

For Paul:




Regarding Cultured Good Manners
versus the Wet Blanket:


It requires an awful,
awful lot
to piss an Englishman to blow
--to blow away a fog.

So if you fog an Englishman
he'll likely tolerate....

Yet if you keep on rotting damp,
he's really,
really good at hate.


 
Jeepers, Randy!

PULEEZE Try clicking on the post reply button at the bottom of the page...

Re-Reading all these quotes is croossin my eyes!!

:!:
 
(soft-chimes are heard)


We interrupt this food-fight in order to bring you a message from the OP...


HI KIDDIES!!!

There was a thread here once... let's go WAAAAAY BACK and check in with cGameprogrammer's illustration:

CGameProgrammer said:
My point is that the relationship between weight and Wh/mile at a given speed is not linear. Therefore, dividing Wh/mile by weight results in a basically meaningless value.

OOPS: CGp was unable to find any real-world ebike examples of the relationship of weight being significantly NON-linear.

(12hrs later)

BZZZZZZZZtttt. Sorry.... gonna have to call "time".

Check the graph below and notice the extreme curvature to the slope. Especially notice the curvature at the steepest grades.


:roll:


(Sorry to steal yer gameshow gag Math... felt perfect here)
 

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Right I misread the Op, how to measure performance/efficiency

Combining wh/mile with weight and speed takes into account metrics I can think of measuring easely. Speed, weight and energy consumption all affect a bike's performance, so it's fair to account for them. Just as the candidate who took 3h to ace a test is not as well suited to the job then the guy who aced it in 15m, a heavy bike penalizes it's usability. As with aero, it won't affect it in a way that's easy to measure, but the difference is that a bike can be taken on a scale to yield a number.

From experimentation, I've found that weight on the bike hurts a lot more then weight on the rider. I'd say around 2-3X worse. Also weight isn't linear in how much it hurts. If you start with a light bike and add 5Kg to a rack, it'll make things a lot worse. Add another 5Kg and it won't make as much difference as the first 5kg.


Adding max range to the equation would be nice.


Bike de merde:
As measured per the op's formula

IMG_5216.jpg



Motor only benchmark, slightly powdered glazed road:
28.8wh/m / 250lb = 0.115 @ 15.6Mph


Real life usage:

Glazed roads w/slight powder, soft weather:
32wh/m / 250lb = 0.128 @ ~19Mph average, ~25Mph peaks.

Snowed in roads, wind, bitter cold:
48wh/m / 250lb = 0.192 @ ~16Mph average, ~20Mph peaks.


This bike used without assist in it's element would have given ~13mph top cruising speed on the flats, average ~10mph. On a bad day, it would have taken around twice longer to get somewhere then on a good day. So, the motor turned bad days into something equivalent to summer commute times. I was very happy with it, but next winter I'll use something better.


Weight breaks down as so:
Hub motor ~6 Kg
Battery ~14 Kg, three 12Ah lead bricks
Cro-mo Giant Yukon ~16Kg.
Tires, rack, front rim >4 Kg
Me ~68 Kg
Clothing ~6 Kg
 
TylerDurden said:
Check the graph below
Thanks; this proved my point exactly. The gray line (0% grade) is almost exactly flat. That means that if someone is using 280 W weighing 280 lbs, someone who weighs 140 lbs can NOT expect to only need 140 W; they will need 280 W, according to your own damn graph! That's what I mean when I say the relationship is not linear. This is true even for a 10% grade, according to your own graph.

That is why expressing the value "per pound" (or unit of weight) is worthless. You can't multiply that value by your weight to estimate your Wh/mile. On the other hand, energy required is linearly dependent on distance traveled, so Wh/mile is a meaningful value. Someone traveling twice the distance will need twice the energy, all other things being equal.

Do you get it now?
 
My typical 34km commute, overall average speed of 52-56km/h, top speed 87km/h. 37Wh/km = 59.6Wh/mile. 178lbs + 103lbs (bike) + 10lbs (backpack) = 291lbs.

0.205
 
CGameProgrammer said:
That's what I mean when I say the relationship is not linear. This is true even for a 10% grade, according to your own graph.

That is why expressing the value "per pound" (or unit of weight) is worthless. You can't multiply that value by your weight to estimate your Wh/mile. On the other hand, energy required is linearly dependent on distance traveled, so Wh/mile is a meaningful value. Someone traveling twice the distance will need twice the energy, all other things being equal.

Do you get it now?


OOOOHHHHHHH.......

You mean directly proportional?


I get it now.


Why dintja say so in the first place?



:lol:
 
So are we in agreement here that the Wh/mile is the main number we should be focusing on?

I thought of another reason not to divide by weight. If you inverted watt hours per mile, you would get miles per watt hour-- which is similar to miles per gallon in a car. Nobody talks about gallons per mile per pound of vehicle because the weight and general efficiency of the vehicle is already considered in miles per gallon. The same is true of watt hours per mile. The weight and efficiency of the bike is already a part of the Wh/mile number so there's really no reason to divide by weight.
 
Excellent point, jondoh.

So are we in agreement here that the Wh/mile is the main number we should be focusing on?

I agree. Miles per WH would be fine too, but the small ratio makes for a more unwieldy fractional result.
 
So let me see if my Redneck mind can grasp this:
yesterday I went on a 21 mile ride, starting and ending in my driveway, So all elevation and wind effects are essentualy averaged to Zero.
So my useable numbers are:
21 Miles
15mph average
287Watt hours used.

Thats all I really need to compare, right?
I would have tried to hold to 10mph average, but thats slow and boring.
15mph average happens to be full throttle on the 4012 switch.

So If I follow how things are being done, this means I'm getting 13.67 Watts per mile at 15mph? Does that sound reasonably efficent?
 
jondoh said:
So are we in agreement here that the Wh/mile is the main number we should be focusing on?

I thought of another reason not to divide by weight. If you inverted watt hours per mile, you would get miles per watt hour-- which is similar to miles per gallon in a car. Nobody talks about gallons per mile per pound of vehicle because the weight and general efficiency of the vehicle is already considered in miles per gallon. The same is true of watt hours per mile. The weight and efficiency of the bike is already a part of the Wh/mile number so there's really no reason to divide by weight.

I propose a new unit of measure: Volcanos per coulumb per stone. :lol:
 
Lowell said:
I propose a new unit of measure: Volcanos per coulumb per stone. :lol:
+1

And to make things fair for everyone, units should be variable.
 
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