Determining electric bike range and hill climbing ability

[Ian]

And there was us thinking, expect margin decreases.
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brilliant

 

[coops]

In terms of determining the range and hill-climbing ability of ebikes, the best approach I can see is to look at the relevant contributions of each part (rider, bike & motor) separately & then to add them up.

Given that the basic "bike" part is sound, a motor torque graph, plus bike & rider weight, plus tyre type, and bike gearing are enough information to quite easily get a very good idea of the performance.

It's interesting what you say chazpope, because I was asking a closely-related question recently, regarding hub motor design, torque & speed and your point illustrates how hub motor design can, it appears, affect the usefulness of the torque it produces, and so highlights the trade-off between low-speed torque for efficient hillclimbing or high-speed torque for maintaining a speed on the flat.

I agree with you that, all other things being equal, the bike which maintains a higher speed on the flat for the same power output will have a better range, and is more efficient - on the flat. But... as Ian said it will be less efficient under most conditions: the gain in range on the flat will be quite small, and the loss in hill-climbing ability and range in mixed terrain with moderate to steep hills on the same bike will be much greater, due to it having torque for maintaining speed, not climbing hills, making it a poor choice in general for use on other than gentle slopes & flats. That's just one way that hub motor design can affect the overall capability, efficiency and range of ebikes: there are others:

The steepest slope manageable depends largely on the motor's peak power output, the speed(mph) at which that occurs, weight of bike & rider & gearing/pedal contribution.

The range in hilly terrain depends largely on how much and how fast the motor's efficiency drops as the speed drops from its point of maximum efficiency and revs (also minimum power) on the flat to its point of minimum useful efficiency (and maximum power) at the peak torque point. The lower the efficiency at or near peak power, the more energy is used to do the same amount of work: usage goes up, so less distance can be travelled for the same amount of energy. A bigger battery may take you further, but will not improve your efficiency & will be unnecessary extra weight if a better, more suitable & efficient motor could give the same range as the heavier battery. A bike efficient for hills should also handle headwinds ok.

Range on the flat with no wind, for the same battery capacity varies less than in hills and is easier to calculate, any good motor running close to maximum efficiency at normal cruising speed. Stops & starts may impact efficiency/consumption, & thus range, on some bikes more than others, but those could be picked up on quite easily, and in most cases the style of riding (throttle use etc.) can be modified or learnt to get best range from them.

That covers some of the motor aspects. Put all the pieces together & add the rider & bike contribution elements & you get a good picture of the overall performance for each bike.

Until you get a puncture or crash .

Stuart.

 

[Wisper Bikes]

Tests

Surely amongst all you Pedelec Wizards there must be some consensus of opinion on what would constitute a good unbiased test! We are all agreed that we need one.

As I said in my previous post I am sure all committed Pedelec manufacturers would be delighted to test their vehicles on an even playing field (even if it had a 3% incline ) and pay for the privilege.

How many components should the test have? If we could initially agree on that we would have a starting point.

All tests should have a rider weighing 75kg with weights making up the exact 75kg

They could be. (Suggestions taken from previous posts)

Throttle only

1. A timed 0 to 100m
2. A flying 100m
3. An incline to be decided over a given distance.
4. A range test at 15.5mph on a circuit.

Regarding the pedelec mode, it would be simple to rig up a rolling road with resistance control and apply an 240v A/C electric motor to the crank with torque control, this could be regulated quite easily. And put a weight on the rear rack to stop tyre slippage. Run all the tests three times and take a mean average.

All the Pedelec tests would be based on 0 to 100m.

What do you think? Too simple?

Beast regards David

 

[flecc]

No tests are needed in my opinion David.

All we need are first. the power curve for the motor with consumption and net power plotted against watts on the vertical axis and mph on the horizontal, and second, the bike's weight as sold complete with battery.

That gives us the maximum speed and the hill climb/towing capability. From that, ranking charts can be produced in moments which could include the variable of rider weight, without which any test results are useless.

For example, on bike X, I at eleven stones weight can climb a sample steep hill in bottom gear contributing 100 watts, very easy. A sixteen stone rider on bike X would need to expend 350 watts to do the same, which could well be impossible for very many riders. Thus a good climbing bike for me could be a completely useless one for some, illustrating why provision for rider variations is essential.

Ridden tests would be less accurate for comparison due to variables like air conditions, temperature which can affect batteries adversely, road surfaces and unmeasurable small incline variations, tyre pressures, rider bulk and clothing etc. Furthermore, a test on one incline won't easily indicate to a prospect a bike's ability on very different inclines.

I could easily set up a cheating status with any bike and circumstance to put it in a better position on any surface test. The figures I'm asking for cannot be fiddled without subsequent risk of exposure, they are so easily checked.

Technical details on power and weight is what the highly experienced motor industry has supplied for many years, and I think we should learn from their considerable experience and knowledge. As with them, we can leave the road testing to the independent magazines.
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[Ian]

In my view the only valid test would be a scientific measure of the efficiency of the electric drive train over the entire operating range. The only way that could be done would be to put the bike on a dynamometer in a lab, something the better manufacturers can do but is beyond the scope of the average user.
All bikes are designed differently, some for speed, some for range, some to be inexpensive, some to comply with legal requirements in various countries, some bikes are designed for use by experienced cyclists who don't want a lot of help, others are designed to emulate mopeds. They will all perform differently, but to publish a simple comparison of performances would be very misleading, the tests done by experienced independent reviewers who can interpret the results are far more meaningful.

 

[coops]

Hi David,

That's an interesting proposal you made for an ebike "trials" event and I'm sure many here would welcome the chance to try out many different bikes in well-designed "trial" conditions (hopefully we'll come up with some crackers, don't you worry ) if it can be organised.

I don't think there would necessarily be a single winner or loser in such a trial; while some bikes may be better "all-round" performers, others may excel for a particular use and such trials should help to show that.

Flecc and Ian got there first, but I think we're speaking on the same lines:

While I am in favour of trials to test the feel of a bike & its performance, the most important ingredients of a good bike are good design & quality components and build: in my view, any tests or trials, public or private, should be to verify that the design works and the build is durable, and if they are both ok, then good performance should follow . Styling & feel are subjective, but with performance everyone speaks the same language .

It would be advisable for anyone to re-read this entire thread before posting test proposals: as said before, the performance of an ebike, including energy efficiency & range in any terrain, maximum/most efficient speed for climbing any given gradient, top speed, steepest gradient attainable for any given fider, can all be fairly easily and accurately calculated from the design, and so tests would simply be a confirmation of how well the design works & the quality of the parts used, and that has practical benefits: a range test not strictly necessary, for instance, because if the power consumption for different gradients is measured a good estimate of range can be easily calculated for terrains of different levels of hilliness for riders of different age & ability, taking into account the assistance the bike's own gearing gives too.

So again I say, since real-world measurements are rather too messy to give reliable, accurate results which can be used to determine likely performance for a given individual, your test proposals are not too simple, but rather are unnecessarily complicated. It would be far better for manufacturers to give full information relevant to performance, and to have confirmed their designs are working & evaluated these figures beforehand in a controlled way, so that any tests/trials are just that, not measurements (and then they'll be a more relaxed and enjoyable experience too ). I'm sure the side-by-side results of any trials should then be a reflection of the performance figures; they should certainly not be the prime source of them, since that puts the onus to prove performance on the individual, not the manufacturer, and with all due respect that will not do .

I am encouraged that you show keeness to ensure that you are doing your utmost to ensure your bikes are as good as they can be, you are clearly enthusiastic about them and I wish you success .

With best wishes,

Stuart.

 

[chazpope]

almost all bikes will easily reach the UK limit without reaching maximum motor power simply because it requires somewhat less than 200W to overcome friction, drag and rolling resistance at 15.5 mph.

Ian do you mean all this in conditions without pedalling ?

My experience with 4 Cambridges and 2 Salisburys is somwhat different from what you describe. The Cambridge gets up to about 12-13 mph, haven't got a figure for Salisbury, but it is slower by at least 10%.

If you then start pedalling the motor is happy to help you up to about 15 miles and afer that you are on your own. During this transitional period I can see that the motor current drops (battery voltage goes up) - because now the total torque is split between the chain cog and the motor and the motor draws and delivers less power.

So why do you think that is ? Both look like commuter bikes - designed to cruise on the flat - no point to put the peak power at the low revs point.

Because the top throttle speed I am getting is less than the legal limit I assume at that point (where the motor is running out of steam) it delivers its maximum continuous power, also I would think the bike would be designed (geared) to do that ? Even if this is not the 'peak' power - it is the 'kind of power' that I think most cyclists are interested in.

I am also considering that on the flat the power required is greatly and non linearly affected by the speed. As an example - according to some math models that claim to be reasonably true - to get from 12.5 mph to 15.5 mph you would need 50% more power, that is an awful lot. So my interpretation of this is that the max throttle-only speed is defined by the motor power rather than its top rpm spec ?

In my earlier post I suggested only 2 tests. I am not at all sure to what extent if you can derive the range from these, I am simply trying to have a discussion about it, far from trying to promote it with pseudo science as some test-sceptics would suggest.

However I think that the 0-100 and flying 100m tests would (to a potential buyer) be very indicative of the bikes overall performance. The 0-100 test would put the bike through its torque curve, peak power will be reached at some point during accelleration. The second test - whether or not related to 'power' - would be also in my opinion a very important buying point - after all you don't want to be overtaken by people with 'normal' bikes on your way back from work. Right now if I have to choose between Cambridge and Salisbury (both rated 200W) on the blind - what have got to go on ? Having these figures will make my decision much easier.

Also I 'promote' these tests because I believe they could be at this stage easily done by bike owners rather that manufacturers and hopefully manufacturers will get the message and start quoting some meaningfull figures.

Looking at bike models you find that 5 kg +/- in cyclist weight adds or takes only 2-3 Watts, so no big issue with varying weight there. Speed on the other hand - especially above 12 or so mph has a much greater effect on power.

Publishing torque curves would of course be nice but what good would it be to the general buyer - also consider the fact that the controller has a play in it as well doing voltage or pulse modulation. I am not sure how the motors are driven but 'constant voltage' theory may not always exactly apply.

At this stage I think it would help the discussion if we had some figures from interested participants.

 

[flecc]

Figures.

In a typical case of an eZee Quando, the motor power rises as speed increases to a maximum of about 470 watts net at 8.6 mph. From then the power gradually declines, down to about the 170 watts at 15.5 mph that Ian mentioned in a post earlier.

The 470 watts point is also the maximum torque point at which it's climb limit exists.

The point of maximum efficiency is just short of the 15.5 mph, that not referring in any way to maximum power but to the lowest use of current relative to power. In other words, green efficiency, not the Top Gear variety.

The above is broadly true for all our bikes that are geared to attain roughly the legal limit. I'm sorry that you just don't seem to want to accept that relationship of speed and power, but I can only post the facts.

A to B magazine agree with you in their test on the Windsor, the step through version of the Salisbury, in that they said 13 mph was about it, though it would run on to 15 in favourable conditions. The basic problem is that it's one of the lowest powered bikes around at about 270 watts maximum, so is geared accordingly. As said before, the only difference that Carl of Powacycle observed on the Cambridge was a gearing difference. Since any of these motors have an optimum gearing, I assume the poorer performing one is that one that differs from that optimum.
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[Ian]

Flecc has illustrated above the fact that maximum power does not (and the laws of physics say it cannot) occur at maximum rpm in the case of a permanent magnet motor such as used on bikes.

I do see your point wishing to see comparative testing but due to fact that most machines are designed to pedalled testing them without pedalling is meaningless and will give very misleading results. For example I own two bikes, both have the same meaningless nominal power rating.

Bike number 1 can be ridden like a moped easily reaching 16mph on the flat. Most of the time the pedals serve merely as footrests, only needing to be used on the very steepest hills. This bike would perform very well in your proposed tests and has received excellent reviews although has no outstanding achievements to it's credit

Bike number 2 is reluctant to pull off without assistance, accelerating slowly to 10 mph above which it performs well until a hill is reached. This bike would perform badly in your tests and yet an identical example has won the tour de Presteigne on both occasions, has successfully completed the Royal British Legions annual London to Paris ride and has numerous other accolades to its credit. The reason being that it is designed to pedalled, and when ridden as intended will wipe the floor with most of the opposition, but it will not perform without being pedalled which shows how pointless such testing would be without an experienced and unbiased reviewer to qualify the results.

A further factor which no amount of theoretical testing will reveal is how "ridable" the bike is, in the case of my bikes number 2 is the most ridable and fun by a very large margin.

 

[coops]

Ian do you mean all this in conditions without pedalling ?

Yes, he does! (correct me otherwise Ian) on the flat at least . Almost all bikes that can reach the legal limit of 15mph, more or less, should consume less than 200W gross at that speed for the reasons given, unless they are rather inefficient.

Your bikes are most likely either lower geared or lower powered or both.

So why do you think that is ? Both look like commuter bikes - designed to cruise on the flat - no point to put the peak power at the low revs point.

Yes there is, unless you never need to go uphill! (but you are lucky in that respect!) Peak power/torque for a hub motor is usually around mid revs anyway, and any gradient requires power roughly proportional to the speed you climb at, so any bike will climb better the lower the speed its peak torque occurs at.

Even if this is not the 'peak' power - it is the 'kind of power' that I think most cyclists are interested in.

Only if you never need to go uphill! (ask flecc, he'll tell you about hills!) - I see a pattern developing here if you've ever had to cycle uphill, you'll know it takes much more power than on the flat. Most hill-capable bikes have peak power of ~5-600W.

I am also considering that on the flat the power required is greatly and non linearly affected by the speed. As an example - according to some math models that claim to be reasonably true - to get from 12.5 mph to 15.5 mph you would need 50% more power, that is an awful lot. So my interpretation of this is that the max throttle-only speed is defined by the motor power rather than its top rpm spec ?

Yes, thats pretty much it: the 50% increase sounds a bit high, but from 15mph to 20mph power consumption on the Torq doubles . The max throttle-only speed, as you pretty much explained yesterday, occurs when the forward driving force of the motor (through the tyres) is equal to the retarding forces opposing forward motion, mostly air & road friction. The motor's driving force depends on numerous factors including power output (voltage x current), gearing and efficiency, not totally unlike a cyclist except an electric one with a fixed riding style . Essentially the motor's design dictates what speeds it runs at with what torque & efficiency.

You're right that we have no definite criteria by which do judge one bike from another, because we are not given the performance information to do so; we aren't even given enough information to calculate performance ourselves! But I could tell you that those bikes are low powered and which would have more power, from information on those and many other bikes in this forum, and none of it based on a useless 200W rating. It would be better if suppliers and manufacturers gave us real performance figures rather than leave us largely to guesstimate like we have to.

The absolute minimum information we need has been specified earlier in this thread, several times.If I had just that much information for any given bike I could tell you, quite accurately, how fast it can go on any gradient, how far it can go in any terrain, for any battery type & capacity, for any rider of any age and ability and for any tyre!

Is that enough?!

Looking at bike models you find that 5 kg +/- in cyclist weight adds or takes only 2-3 Watts, so no big issue with varying weight there. Speed on the other hand - especially above 12 or so mph has a much greater effect on power.

I don't understand what you mean, chazpope, do you mean on the flat? On hills weight increase adds proportionally to the power needed, so if you're twice the weight, twice the power needed.

Publishing torque curves would of course be nice but what good would it be to the general buyer - also consider the fact that the controller has a play in it as well doing voltage or pulse modulation. I am not sure how the motors are driven but 'constant voltage' theory may not always exactly apply.

Yes, I accept that, which is why I've tried now to lay it out as a "worst-case" scenario: preferably we should be given both performance figures and raw data, but the raw data is more useful since we can derive the results from them, whereas we all know where "up to 30 miles range" gets us voltage variations and the like can be accounted for quite easily, unlike the large number of unaccountable variations from trying to measure performance from the bike itself.

Stuart.

 

[chazpope]

Yes, coops, I mean on the flat - this whole discussion is about tests on the flat. You say 'your bikes must be lower geared or lower powered' - yes they must be - and the effect of that is a lower top speed - exactly what the proposed test is about! So if I have these test results I will have a clue about that - otherwise I won't.

Now I can't see how flecs 'figures' can be relevant on the flat - the higher power figure must be for going uphill ? Obviously a bike that goes at 15mph will use loads more power than the same bike at 8mph.

Ian I see your point but your bike 1 must be a quite different from bike 2 - probably without gears, with a heavy battery etc ? Naturally you would compare the figures of similar bikes - that both have big wheels and gears and are both designed for efficient pedalling. I wonder if the torq was de-restricted when it won these competitions or not. It will be interesting to see what actually this Torq does on the flat - if it has a high peak power then as it is accelerating this power will be employed at whatever lower revs it happens and it should have a great effect on the 0-100 test don't you think?

I am proposing tests on the flat because they are easily repeatble otherwise everybody would have to live next to the same hill. And using the bike on the flat can have simlar demands to hill climbing - when you have high head wind, so the more powerful bike will give you higher speed.

 

[Ian]

Bike 1 is an Ezee Sprint, 26" wheels, identical battery to the Torq.
Bike 2 as you've guessed is an Ezee Torq

The Torq delivers it's peak power at the unusually high speed of about 12 mph, and has virtually no torque under 9 mph hence its poor unassisted performance from a standing start and the need for substantial rider input on steepish hills. Unrestricted speed in still air is 22mph on an absolutely level surface, less on the slightest gradient. Restricted unassisted speed is 16 mph which it will easily maintain over gently undulating terrain due to the fact that the overgeared motor is still in it's peak torque band at this speed.

 

[flecc]

Now I can't see how flecs 'figures' can be relevant on the flat - the higher power figure must be for going uphill ? Obviously a bike that goes at 15mph will use loads more power than the same bike at 8mph.

Of course, the 8 mph maximum power and torque point is an optimum for hill climbing, but it will also use that 470 watts on full acceleration in your test as it passes through that point. The same for all e-bikes, they'll all hit their maximum as they pass their respective points under full acceleration.

The figures were just to illustrate that the maximum power wasn't at 15.5 mph or whatever top speed is on a bike.

Certainly less power will be used cruising at 8 mph than at 15 mph, but the differences are very small on the flat in fact, and academic anyway, since no-one is normally going to cruise at 8 mph.

Believe me, I am not trying to be awkward, but you still haven't resolved the issue of what is flat. No-one can judge a 2% variation from flat and even 3% is very difficult to discern, but they make a very large difference in bike performance as I've shown, much larger than the difference between mainstream bikes,

In fact hardly anywhere is truly plane flat, and that's just one of the reasons why I can't see how the tests can help, since returns would be so suspect, as others have observed too.

I treat your suggestion seriously and accordingly I tried four times to time the acceleration on one of my bikes today. Frankly it wasn't possible to accurately time and ensure an exact speed termination point. As an e-bike nears it's maximum the acceleration rate slows, and at takes at laast 1 to 2 seconds to be sure that it's ended. That makes the time cut off point very indeterminate. Add to that the extreme difficulty of operating a stopwatch while riding or watching a digital readout of seconds and I can't see how the results could be in any way reliable. One rider will anticipate the maximum point from prior knowledge of their bike, while another will be a stickler for the test and go by the actual readout on the speedo, a difference of one or two seconds.

And of course that brings us to speedos. In my experience well under half of riders ever calibrate theirs, just using them as received with a standard and inaccurate wheel size setting.

Sorry Chazpope, but I just can't see it working reliably enough.
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[coops]

Yes, coops, I mean on the flat - this whole discussion is about tests on the flat.

There seems to have been some misunderstanding then chazpope, this thread became "Determining electric bike range and hill climbing ability" when it split off from the original Powacycle Salisbury v Powacycle Cambridge? thread after the discussion drifted from the original topic . A little confusing, I know; it seems we've been talking at slightly cross-purposes for much of this thread .

As flecc said though, even on the flat the acceleration of a bike is a result of torque so would be some indicator of hill-climb strength anyway.

It has already been said many times in this thread that tests will not produce useful results, and the reasons given.

For example, in the simple tests you describe, your attempts to achieve consistency do not work:

About 'judging the flat road' - I did propose a solution - do it in both directions and this would cancel the effect of any inperceptible incline and to a certain extent wind, don't you think?

flecc had previously said why the non-flat road makes the measurements worthless. Doing the test in both directions does not cancel error from a non-level surface, it increases it: you would be measuring acceleration and hill climb one way, and speed and downhill freewheel ability the other, in both tests. "Charge the battery to full" does not eliminate large likely variation in charge level and capacity depending on battery age & other factors. Errors in measurement of distance and timing are also inevitable.

The intended measurements themselves provide little useful information for most people, since they give no quantitative measure of hill-climbing ability, or efficiency of acceleration/speed and hence range; the first test sets out to give an assessment of acceleration, the second top speed.

To attempt to control the variables & errors for more useful tests like actual hill-climbing etc. will be even harder, and is largely why this approach has been the subject of much discussion here: I hope this thread settles the matter and prevents much wasted time and effort for no benefit: tests are not a productive way forward.

In my earlier post I suggested only 2 tests. I am not at all sure to what extent if you can derive the range from these, I am simply trying to have a discussion about it, far from trying to promote it with pseudo science as some test-sceptics would suggest.

I can't see any way straightforward way to derive the range from those tests, and certainly not accurately. Even if you were to try to idealise a "range" test and drive constant speed on the flat non-stop, no pedals, it suffers the same problem of too many variables to give accurate results, but it also fails to measure meaningful range (these are the sorts of unrealistic range figures we tend to get from bike makers anyway) since it does nothing to indicate how it is affected by the level and efficiency of the motor's higher power output for gradients and acceleration.

The facts have been given and you simply can't discuss facts; I don't recall anyone mentioning pseudo-science, and myself, flecc and Ian have all tried to make clear to you that tests can only produce misleading results at best: its not a matter of us questioning the test approach to getting data, and the results on one bike in one set of conditions are quite possibly useful to the owner - all of us who ride ebikes and gauge their performance do that in our own way - the problem arises when you try to compare apples and oranges i.e. results obtained under different conditions which cannot be fairly compared side-by-side due to inequalities.

I hope you can see that even tests which are designed to be so simple that they don't measure anything of much use to the majority of ebikers will not produce accurate results, let alone useful results, and that you save yourself the time & effort of doing a task which can only be misleading to others.

At this stage I think it would help the discussion if we had some figures from interested participants.

What would achieve the goal of determining electric bike range and hill climbing ability has been said repeatedly in this thread; figures will only serve to mislead and confuse more than many are already.

Stuart.

 

[flecc]

In fairness to Chazpope, Stuart, I said pseudo science in response to him saying that top speed was at 200 watts, and was the maximum power of the bike. Clearly both are very far from the truth, though judging from his further postings, I think that wasn't quite what he meant. It seems it might have just been badly expressed and that he meant the maximum power to maintain a bike at a given speed would be at it's highest speed, true of course.

I've hit on another problem though Chazpope, which I think would finally kill the acceleration test as a gauge of hill climbing.

Here are two bikes from one manufacturer which would invert the results.

The eZee Quando would easily win the acceleration test to 15.5 mph when matched against the eZee Chopper, the latter only going to it's maximum which is short of 15 mph, and taking longer to do that.

According to your test that makes the Quando the better climber, but it's not. The Chopper outclasses the Quando on steep hills, anything over 12%.

How can this happen? Quite simply, the Chopper motor is geared down to lose some speed in favour of hill climbing, making it better in that department. But because of that, so much of it's acceleration band is in the higher motor rev range where the net power available is very rapidly reducing, the more suitably geared Quando motor is the better, the top of it's power curve falling neatly in the middle of the zone of interest and therefore most effectively able to accelerate. To make matters worse, the Quando which your test would indicate was the better climber, only has a single 70" rider gear so cannot cope with the steepest hills, the Chopper has a full 7 speed hub, adding still more to it's hill climb capability. Only a reviewer or experienced commentator can tell someone that sort of thing.

Looking back on all the comments, everyone agrees with the theory, but no-one agrees that the tests could reliably tell us anything, carrying them out being riddled with such a gamut of problems and variables.
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[chazpope]

coops yes this discussion is off topic now and really it needs to go under a different name so that other people who would be interested can take part - I started this as a comparison between 2 bikes on the flat, proceeded to propose tests and then someone decided this is a discussion about 'determining range' and changed it. To me this was never about range - it is about choosing a bike based on its pereformance on the flat - which I believe can be measured to an accurate enough degree by an interested cyclist. The heading does not reflect the discussion at all and it should be changed - don't know how.

I believe there is a considerable body of ebike buyers who like me will be using the bike for commuting, shopping and other general city use (i.e. not hill climbing) All I care about performance-wise is how fast the bike accelerates and how fast it goes - so these tests would be enough for me to decide where to go. In fact I don't care about range at all - every night I recharge my bike anyway - simply because when the battery is full it goes faster, but that is me.

Hill climbing ability is of course important - so there is the valid question - would tests on the flat be indicative of the bikes hill climbing ability ? I believe they would be - because they reflect the bike 'power'. How well that will work is what we are discussing here - and hopefully we will get to the bottom of it, but not without experimentation I think.

flecc I feel you are doing 'not the propper version' of test - where you measure the time it takes to get to 100m (not the time it takes to get to top speed) - the second version - where there are 2 tests only is the 'official one' Clicking a stop watch considering you don't even have to pedal at a fixed mark should not be that difficult, also getting some one else to do it can work.

re what you say of these 2 bikes - perhaps it would be so - but think of cars - does the 0-60 test reflect the car's handling and genaral ability to go round curves and uphill ? No, but still these tests are very popular. Hill climbing ability on a e-bike will always be a slightly fuzzy subject (because is is always to do with pedalling will always be affected by gears, the exact value of the incline etc.) and I am not saying that the overall enjoyability of a bike as a hill climber can be judged from these tests. However I don't think the tests would be 'misleading' as generallty they will reflect the bikes power which also drives the bike uphill. There may always be exceptions - if some special bike is designed to go up a 10% hill all the time its test would be off but I think not wildly off if you see what I mean.

I don't understand what evrybodys issue with non-flat is - if you do the test in both directions as instructed (and obviously take an average of the 2 measurements) the effect of incline would be cancelled wouldn't it?

Ian the ez sprint is rated as 350W nominal on non UK sites - this explains its great performance - and this will show in the test. If the Torq really gets to 100m slower than the Sprint then maybe it is less suitable for city use and at traffic lights when you expect not to be pedalling it hard - this will also come out in the tests.

 

[flecc]

I did look at the test in both senses Chazpope, a specified distance and the run to maximum just to see the difference, and it wasn't on an entirely flat surface either, but I wasn't trying to be specific since I was riding a non standard bike and the measurement wouldn't have value.

I just wanted to see what it was like trying to get a figure for your tests.

The problem on having ground not level isn't solved by two way runs if the person conducting the test doesn't know it's not level.

The fact is that no-one, you included, can judge if a road has a 2% incline, and very few can even detect 3% reliably. Therefore many people will do the test one way unaware of an incline, invalidating their result.

Honestly though, do you really believe that a number of people are going to measure out an exact 100 metre stretch, ensure they have a fully charged battery, own a stopwatch, and carry out such tests, reporting accurately. I honestly doubt there's the slightest chance of that happening. And that's without considering all the variables that others have mentioned, battery age and type alone making a very large difference to performance in a given bike.

I deliberately didn't say the above paragraph before because I wanted to see if anyone wanted to give results and didn't want to prejudge whether anyone would respond. But as you see and as I suspected, there hasn't been one posting indicating willingness to do the test.

The theory is good, but the realisation is too user dependent on co-operation and accuracy. I think you might be surprised how close the mainstream bikes would be in such a test, most of the differences being from tester error.
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[coops]

chazpope,

coops yes this discussion is off topic now and really it needs to go under a different name so that other people who would be interested can take part - I started this as a comparison between 2 bikes on the flat, proceeded to propose tests and then someone decided this is a discussion about 'determining range' and changed it.

Your discussion is off-topic in this thread and should be continued in the correct place & under its correct name: to do so, go to your original Powacycle Salisbury v Powacycle Cambridge thread and post there. The subject of this thread is "Determining electric bike range and hill climbing ability" and always has been clearly labelled as that since it started, when it was moved here so that your original topic & proposal could be fully discussed in the Powacycle Salisbury v Powacycle Cambridge thread, after the subject of discussion diverged from what you intended (it often happens) and that thread is the appropriate place for your discussion .

Hill climbing ability is of course important - so there is the valid question - would tests on the flat be indicative of the bikes hill climbing ability ? I believe they would be - because they reflect the bike 'power'. How well that will work is what we are discussing here - and hopefully we will get to the bottom of it, but not without experimentation I think.

No, as I said in my last post, your acceleration test would give some indication of torque, but gives no quantitative measure of ability on gradients, which is what most people will want to know i.e. can I get up my local hills?

I don't understand what evrybodys issue with non-flat is - if you do the test in both directions as instructed (and obviously take an average of the 2 measurements) the effect of incline would be cancelled wouldn't it?

No, as I explained in my last post, and flecc explained in the link contained therein. Please read them, and our other posts in this thread, to answer your questions about why tests are unreliable.

Ian the ez sprint is rated as 350W nominal on non UK sites - this explains its great performance - and this will show in the test.

No it doesn't. The U.K. version is not 350W and as has been said many times in this thread, the "nominal" power rating of a motor, on its own, gives no indication of performance, whatsoever. The U.S. 350W version of the ezee sprint has a different motor from the UK version in line with their generally different ebike laws (e.g. 20mph limit, not 15mph) and is illegal for road use in the U.K.

If the Torq really gets to 100m slower than the Sprint then maybe it is less suitable for city use and at traffic lights when you expect not to be pedalling it hard - this will also come out in the tests.

No it won't: because your test parameters are subjective so will your conclusions be. First, you don't have to pedal hard to get results on a Torq; second, a derestricted Torq with only gentle pedalling, or perhaps none, would probably wipe the floor with almost any other production ebike, even over 100m! What is suitable for one person does not suit another. The only clear way to evaluate bikes is to give performance & usage limits, then let people choose according to what fits their needs, usage & riding style.

Your approach is very misleading and posting incorrect speculation as facts is misleading for others. Please don't do it!

To avoid further confusion about what is the topic of this thread, please continue your discussion of your original topic i.e. your test proposals on the flat, if you want to, in your original thread.

Thank you .

Stuart.

 

[chazpope]

re the incline business - wrong perceptions are already taken care of in the test - it directs you to do it always both ways; i feel the wind may be more of a problem. stop watch - every old digital watch is one, and if you don't have one lying around - it is a quid on the market

I don't know what if any the response would be, certainly the wrong heading does not help that. I for one would not be interested in the topic as it is now, I guess I will re-post it. Otoh if one dealer or manuf does the tests - others will follow and one day, who knows - non b/s figures may be published. Thers is no data yet to judge if these tests would be worth it or not - we can only make a guess about it for now, wheather permitting I will have a go on the weekend, but I have to dig out my computer first.

 

[flecc]

Thanks Chazpope.

With respect though, you are operating from an extremely poor knowledge of electric assist bikes and just making wrong assumptions all the time. You've posted mistake after mistake in speaking of them, the latest being yet again on the understanding of motor ratings.

The Sprint 350 watts you spoke of is the US nominal rating on that overseas motor, the same thing as the UK 200 watt and European 250 watt nominal ratings. and has nothing whatsoever to do with either the motor output or it's performance.

In fact that US market Sprint 350 watt motor has a maximum power of 700 watts. As it's geared to achieve roughly 20 mph for that market, that 700 watt maximum occurs at about 12 mph. The UK and Europe 200/250 watt Sprint motors have maximum power of 500 watts, occurring at about 8.6 mph.

These mistakes make it difficult for the very knowledgeable members of the forum to give credence to what you're saying, and I think it best if you follow the general postings for a while and also read back on past entries to improve your knowledge of the bikes and motors.

These nominal ratings are a notional legal requirement for the power put down onto the road as an average over time. As such they are virtually impossible to assess or measure, and amount to a guide to manufacturers. For example, a five minute climb at 400 watts power at the wheel interface with the road, followed by a five minute glide down the other side on no power will meet a legal requirement of 200 watts, this being the average over the ten minutes of the trip. You can see that this doesn't in any way relate to a bike's actual outputs.
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