What is in that subconscious mind of yours?

[Geebee]

I meant a moped e-bike class, higher speed and power similar to S-class.
To me going up hills in low gears is all part of cycling, if the body is willing I can use the crank drive to fly up hills and if not I ride up like a normal cyclist but using much less energy.

 

[morphix]

I never found a hill I can't climb yet on my 26" 250W 36V10Ah and we have some INSANE hills in my town. Even on the steepest hills (which even have me out of breath just WALKING up) the bike will make an impressive start then crawl up the last bit on throttle-only When I had a 5Ah battery that didn't cut it, the motor would literally cut-out on mega steep hills!

 

[Waspy]

I never found a hill I can't climb yet on my 26" 250W 36V10Ah and we have some INSANE hills in my town. Even on the steepest hills (which even have me out of breath just WALKING up) the bike will make an impressive start then crawl up the last bit on throttle-only When I had a 5Ah battery that didn't cut it, the motor would literally cut-out on mega steep hills!

Forgive me Morphix, but I used to live in Pershore.

What town in Worcestershire has insane hills?

I have seen insane hills in Cornwall, but I don't recall an abundance of them in Worcestershire.

 

[Scimitar]

1000W is easily getting into small motorcycle teritory at which point id rather have the motorcycle with better handling,wheels,tyres,seat and most of all brakes.

1000W is 1.25bhp; hardly find a small motorcycle with such a puny power output these days and not since the Raleigh Wisp.

 

[RobF]

Forgive me Morphix, but I used to live in Pershore.

What town in Worcestershire has insane hills?)

Malvern.

Edit: Message too short to post, but the answer is still Malvern.

 

[GaRRy]

The explanation isn't that easy, but has to do with the fixed relationship between motor rpm (and hence bike speed) and applied voltage. Motor rpm is determined not by power, primarily, but by the applied voltage and a motor constant, Kv. For example, the motor on one of my ebikes has a Kv (measured as wheel rpm) of about 10 rpm per volt. On a 36V nominal battery, no matter how much power I put through the motor, it is still only ever going to turn at 360 rpm maximum. On a 20" wheel this gives a maximum speed (with no real load) of just over 21 mph. I can double the power, by just increasing the current limit by a factor of 2, but the bike still isn't going to go any faster at all as the speed is limited by the maximum rpm that the motor will spin at.

This is a characteristic of permanent magnet electric motors. It means that, in practice, there needs to be a fairly big difference between the maximum power point (which is usually around half maximum motor rpm) and the maximum speed point.

Sorry still makes no sense to me as based on this you seem to be saying if I had a 10KW motor it would not perform any better. Now its obvious more powerful motors exists as S class in Germany proves so i still feel you are arguing from the wrong point of view for OP question which in simple terms is if far more powerful ebikes were allowed would you get one. My answer is still no as I would not feel safe. Unless of course it had the wheels, suspension etc of a moped/small motorcycle but they already exist any way so whats the point as it would then have the same restrictions CBT,License,Insurance,Helmet etc.

 

[GaRRy]

1000W is 1.25bhp; hardly find a small motorcycle with such a puny power output these days and not since the Raleigh Wisp.

Remember thats 1.25 hp constant with a peak of say 5 hp so may not be as quick of the line as a moped but would soon get you up to 30 mph on the flat especially as you are adding extra power as well. Most motorcycle deaths/accidents happen in 30 mph zones when cars pull out of junctions. At least on a motor bike I have the brakes that may allow me to stop in time on a bicycle forget it.

 

[Waspy]

Malvern.

Edit: Message too short to post, but the answer is still Malvern.

Oh yes Malvern, I'd forgotten about Malvern. It's like the Ayers Rock of Worcestershire.

 

[morphix]

Forgive me Morphix, but I used to live in Pershore.

What town in Worcestershire has insane hills?

I have seen insane hills in Cornwall, but I don't recall an abundance of them in Worcestershire.

We're pretty close then, have you been to Redditch? It's a town in a valley basically..where I used to live was Churchill which has one of the steepest hills up to neighbouring Beoley village (hence the name)... going down that hill is crazy and very dangerous as it leads right onto a very busy junction with a blind corner due to big hedges. There is also a hill at Churchill known as Bomford's Hill which is almost Malvern-like which gives a speculator view right across the town and beyond from the top which is completely flat.. that has some off-road tracks on it and I sometimes cycle up there, or just on the grass.

I've shot some video on my YouTube channel of some hills I've done around town. There's some worse hills in the Redditch town centre than Churchill, the older part of the town...even my 10Ah battery struggles with those as I approach top.



Actually I've been wanting to measure the incline of some of the hills around my town but wasn't sure a reliable way to do it... now I have a smartphone running Android I can use Maverick to measure the altitude below and at the peak of hills and it should be possible to work out from that?

 

[morphix]

Malvern.

Edit: Message too short to post, but the answer is still Malvern.

Yeah Malvern is without doubt the most severe for hills (more like mountains!), Elgar used to cycle them apparently!..Redditch doesn't compare to Malvern.. but for a regular town, Redditch has some pretty bad hills for cyclists still compared to other relative flatter parts of country.

 

[flecc]

1000W is 1.25bhp; hardly find a small motorcycle with such a puny power output these days and not since the Raleigh Wisp.

But the electric motor has it's maximum torque at zero revs so accelerates off the mark far faster initially than any i.c. powered equivalent size. In truth they can't really be directly compared in all circumstances.

 

[Jeremy]

Sorry still makes no sense to me as based on this you seem to be saying if I had a 10KW motor it would not perform any better. Now its obvious more powerful motors exists as S class in Germany proves so i still feel you are arguing from the wrong point of view for OP question which in simple terms is if far more powerful ebikes were allowed would you get one. My answer is still no as I would not feel safe. Unless of course it had the wheels, suspension etc of a moped/small motorcycle but they already exist any way so whats the point as it would then have the same restrictions CBT,License,Insurance,Helmet etc.

Sorry I couldn't make it clearer. Perhaps an example might help:

Let's take one of my crop of ebikes as an example. The ebike in question has a cheap programmable Xiechang controller, so I can easily plug in a laptop and set the current limit, and hence the power, to any value I like within reason, from near-zero to to around 1,140 W as a safe maximum.

The battery voltage is about 38V (it's a 10S LiCoO2 pack, made from RC batteries) most of the time and the Bafang SWXH motor has a Kv (measured at the wheel) of abut 10 rpm/V. The wheels are 20" in diameter, so the maximum wheel rpm is about 38 X 10 = 380 rpm. This means that the maximum theoretical speed is about 22mph or so, but motor losses etc result in a true maximum speed of around 16 to 17 mph.

So, what happens when I vary the power?

If, for example, I set the current limit to 7A, then I get about a legal 200W output from the motor (assuming 75% motor and controller efficiency). This is just about enough to allow the bike to do 16 to 17 mph, although acceleration is certainly sluggish.

So what happens if I now plug in the laptop and turn the current limit up from 7A to 26A, giving a motor input power of about 1000W? Does the bike go any faster?

The answer is no, it doesn't. The reason is that 7A is just about enough to allow the motor to run at its maximum rpm with the bike on the flat. Increasing the power from about 260W input to about 1000W input makes it no faster on the flat, but does significantly improve hill climbing ability and acceleration, from the increased torque.

If I wanted to make this bike go faster, then I'd need to increase the battery voltage, not just increase the power, as it is primarily voltage that determines motor rpm and hence speed.

A good example would be my latest ebike build, where I have a smaller and less powerful motor (a Q100) but have increased the battery voltage to about 60V (15S of LiCoO2 RC battery packs). This has a top speed that is somewhere around 28 to 30mph, despite having a maximum power input of only around 900W, less power than the other bike that will only do about 17 mph with 1000W input power available (but which will also do around 17 mph on about 1/4 that power).

I'm not sure if I've made things clearer or not, but I hope so.

I should point out that I don't run with these high current limits, and hence power settings, most of the time, as both bikes are actually nicer to ride when turned down to lower power levels.

 

[Scimitar]

Remember thats 1.25 hp constant with a peak of say 5 hp so may not be as quick of the line as a moped but would soon get you up to 30 mph on the flat especially as you are adding extra power as well. Most motorcycle deaths/accidents happen in 30 mph zones when cars pull out of junctions. At least on a motor bike I have the brakes that may allow me to stop in time on a bicycle forget it.

Utter rubbish.

 

[GaRRy]

Utter rubbish.

Which bit ?. Im not saying current legal ebikes produce this just that they could if the power limit was removed. As for the motorcycle bit thats fact not rubbish or do your really think a bicycle can stop as quick as a motorbike ?

try reading this

http://www.bikelawyer.co.uk/bike-accident-statistics

couple of quotes

- Right of way violation accidents (38% of cases)

Clarke et al found that road users other than the injured motorcyclists are usually the cause of crashes and therefore road safety initiatives should be targeted at those other road users in addition to bikers.

Recent European research reveals that nearly 70% of motorcycle accidents involved a car, lorry or bus and that approximately 55% of accidents occur at junctions. It is unlikely that in all these cases the motorist failed to look but rather failed to see the motorcyclist.

Still want to travel as fast as a motorcycle but with out the same braking performance. Cant see how a cyclist is more visible than a motorcycle

 

[GaRRy]

Sorry I couldn't make it clearer. Perhaps an example might help:

Let's take one of my crop of ebikes as an example. The ebike in question has a cheap programmable Xiechang controller, so I can easily plug in a laptop and set the current limit, and hence the power, to any value I like within reason, from near-zero to to around 1,140 W as a safe maximum.

The battery voltage is about 38V (it's a 10S LiCoO2 pack, made from RC batteries) most of the time and the Bafang SWXH motor has a Kv (measured at the wheel) of abut 10 rpm/V. The wheels are 20" in diameter, so the maximum wheel rpm is about 38 X 10 = 380 rpm. This means that the maximum theoretical speed is about 22mph or so, but motor losses etc result in a true maximum speed of around 16 to 17 mph.

So, what happens when I vary the power?

If, for example, I set the current limit to 7A, then I get about a legal 200W output from the motor (assuming 75% motor and controller efficiency). This is just about enough to allow the bike to do 16 to 17 mph, although acceleration is certainly sluggish.

So what happens if I now plug in the laptop and turn the current limit up from 7A to 26A, giving a motor input power of about 1000W? Does the bike go any faster?

The answer is no, it doesn't. The reason is that 7A is just about enough to allow the motor to run at its maximum rpm with the bike on the flat. Increasing the power from about 260W input to about 1000W input makes it no faster on the flat, but does significantly improve hill climbing ability and acceleration, from the increased torque.

If I wanted to make this bike go faster, then I'd need to increase the battery voltage, not just increase the power, as it is primarily voltage that determines motor rpm and hence speed.

A good example would be my latest ebike build, where I have a smaller and less powerful motor (a Q100) but have increased the battery voltage to about 60V (15S of LiCoO2 RC battery packs). This has a top speed that is somewhere around 28 to 30mph, despite having a maximum power input of only around 900W, less power than the other bike that will only do about 17 mph with 1000W input power available (but which will also do around 17 mph on about 1/4 that power).

I'm not sure if I've made things clearer or not, but I hope so.

I should point out that I don't run with these high current limits, and hence power settings, most of the time, as both bikes are actually nicer to ride when turned down to lower power levels.

As I said your not doing what OP says your are giving more amps to the same motor. But what if you used a more powerful motor in the first place ? which is what he seems to be asking.

 

[Jeremy]

As I said your not doing what OP says your are giving more amps to the same motor. But what if you used a more powerful motor in the first place ? which is what he seems to be asking.

Oh dear, I'm not doing a good job of making this clear, am I?

I am doing exactly what the OP did, I'm increasing the motor power, from around 260 watts input power to around 1000 watts input power.

Motor power is determined by the controller, rather than the motor. The reason is that even a small motor will be capable of delivering much more power than its notional rated power. This is because the motor will happily use all the power you can let it have, irrespective of its rating; permanent magnet motors are greedy power hogs, they will carry on drawing current until they overheat and burn out, so this means that it is the controller that determines delivered power.

Using a motor with a higher power rating only allows the continuous motor current to be increased, or the operable ambient temperature to be increased. This is one reason why I can run a 250W rated motor at over 1000W for a few minutes (enough to establish the performance figures above) quite safely. If I wanted to run at this power level continuously then it would be sensible to increase the motor nominal power rating for reliability. Doing this wouldn't make the ebike faster, unless I either increased the battery voltage, or changed the motor velocity constant (Kv) or changed the motor to wheel gear ratio. Of course, I could equally well change these factors for a different speed with a lower powered motor if I wished, up to the lower power limit imposed by the power required to overcome aerodynamic drag and rolling resistance at any given speed.

 

[RobF]

Actually I've been wanting to measure the incline of some of the hills around my town but wasn't sure a reliable way to do it... now I have a smartphone running Android I can use Maverick to measure the altitude below and at the peak of hills and it should be possible to work out from that?

To get the precentage - like on a road sign - the formula iis 100 times the rise, divided by the run.

The rise is easy - how far you've risen.

The run is a bit more complicated, it is the horizontal distance travelled from start to finish, which will be shorter than the length of the hill as you've cycled it.

To calculate the run, you need to think of the hill as a triangle in plan view, and use dear old Pythagoras.

For triangles, he worked out the square of the hypotenuse (length you've cycled) is equal to the sum of the square of the other two sides - the height you've gained and the run.

You have two of the values, so working out the third is simply a matter of playing with the equation.

All this assumes the gradient rises at a constant angle and in a straight line.

I don't know if it works for a long, twisty hill.

 

[shemozzle999]

The only effect of a legally regulated 15.5mph 1000w motor would be that you would not need any effort to turn the peddles in any type of terrain whether delivered through a PAS or throttle, albeit would require a larger, heavier and more expensive battery to maintain the range requirement.

The powers that be are right to not allow this, but not to restrict the method of delivery i.e. ban the throttle.

If they knew anything about bikes they should have concentrated on solving the problem by insisting the controller was encapsulated so that it couldn't be modified and fit it with a internal fuse to stop the dabblers from overvolting. Then you would not need bike type approval only approval for the controller and home builders could produce legal bikes without being subjected to climbing through all the hoops to get the bike type approved.

 

[Jeremy]

The only effect of a legally regulated 15.5mph 1000w motor would be that you would not need any effort to turn the peddles in any type of terrain whether delivered through a PAS or throttle, albeit would require a larger, heavier and more expensive battery to maintain the range requirement.

The powers that be are right to not allow this, but not to restrict the method of delivery i.e. ban the throttle.

If they knew anything about bikes they should have concentrated on solving the problem by insisting the controller was encapsulated so that it couldn't be modified and fit it with a internal fuse to stop the dabblers from overvolting. Then you would not need bike type approval only approval for the controller and home builders could produce legal bikes without being subjected to climbing through all the hoops to get the bike type approved.

Pretty true.

Not allowing a throttle has always seemed silly, particularly from my perspective of having moved from a recumbent back to an upright. As anyone who's ridden one knows, you can't start off by pedalling on a recumbent very easily, as they don't balance as readily at low speed as an upright. This makes pulling of on a hill tricky, if not impossible at times. Adding a small motor (I used a Tongxin) and a throttle fixed this, by giving just enough assist to pull away and retain balance. Without a throttle it would have been fairly pointless to fit a motor, as the recumbent was a lot more efficient to pedal than an upright much of the time.

Personally I've always felt the power limit was a fairly pointless thing to stipulate. It's hard to measure, meaning you can get a wide spread of apparent power ratings for exactly the same motor, depending on how you choose to measure it (which is why the UK SI 1168 regulations stipulate a specific test method defined in an old British Standard). It also has little or no bearing on third party damage or injury risk, as that is almost purely a function of speed and mass.

Far better would have been to have a simple, easily tested, set of regulatory requirements that only specified the maximum speed under power and the maximum weight of the bicycle, less rider. The weight limit would effectively set the maximum power/range trade off, as high power could only be available for a short range, due to the battery energy density and motor weight limitations. Setting the maximum speed under power to 15 mph or so would ensure that the potential to cause injury or damage would be no worse than for an ordinary pedal cycle.

Best of all, both of these parameters could very easily be verified by the police if need be, with no need for engineers or specialist equipment. A simple ride down the road with a GPS to establish the maximum assisted speed and a hand held weighing balance to check the weight would be all that was needed. At a stroke it would remove all of the daft debates about power, legality etc that frequent this forum at times and make it clear to all exactly what is, or is not, legal.

What's even better is that it is a form of regulation that is a perfect match to the governments drive for "better regulation", in that it is entirely risk-based, as all regulation of this type should be.

 

[jackhandy]

Actually I've been wanting to measure the incline of some of the hills around my town but wasn't sure a reliable way to do it... now I have a smartphone running Android I can use Maverick to measure the altitude below and at the peak of hills and it should be possible to work out from that?

Gps height measurement is notoriously inaccurate, morphix - far less accurate than position, which is, of course, excellent.

The best ways to get a fairly true height is to visit the location several times until you get a consistent figure; or read the contours & spot heights on an ordinance survey map.

If you're sufficiently interested, try the Viewranger app. It lets you download 2 O/S map tiles free to tryout the program. 2 tiles of your area in 1:50000 (1" to a mile) should give you something to play with.