HUB MOTOR CAPABILITY

[danielrlee]

Most of what was written in that thread is correct, but the content is often misunderstood and mis-quoted. The main conclusion is that if you have two different motor windings, say 36v 201 rpm and 36v 260 rpm and run the 201 rpm one at 36v and 20 amps and the other at 48v and 15 amps, they'll behave exactly the same - torque, power, speed and efficiency (all those numbers are approximate, so don't calculate to the nearest watt and say it's wrong);

however, if you run both motors at 36v and 20 amps, the 201 rpm one will give more power and less heat at low rpm than the higher speed one and the high speed one will give more power at high rpm than the low speed one. The higher speed one will always make more heat and waste more battery than the 201 rpm one when they run at the same rpm. This paragraph is the important difference between the two motors that people seem to struggle to understand, and this is why it's important to choose a motor with the right winding speed and voltage combination. View attachment 18288
In this chart you can see that the higher speed motor always has lower efficiency, lower torque and lower power than the lower-speed one in the range that the lower speed one can run. The battery, controller, throttle, incline etc. are the same for both.

Completely agree. That's why I included the statement "At any given performance point....." when I introduced the discussion to the thread. Running different windings on the same voltage and current will give totally different performance characteristics as you rightly mention.

When you're designing a system from scratch though, there's no requirement to stick to a specific voltage or current.

 

[D8ve]

Most of what was written in that thread is correct, but the content is often misunderstood and mis-quoted. The main conclusion is that if you have two different motor windings, say 36v 201 rpm and 36v 260 rpm and run the 201 rpm one at 36v and 20 amps and the other at 48v and 15 amps, they'll behave exactly the same - torque, power, speed and efficiency (all those numbers are approximate, so don't calculate to the nearest watt and say it's wrong);

however, if you run both motors at 36v and 20 amps, the 201 rpm one will give more power and less heat at low rpm than the higher speed one and the high speed one will give more power at high rpm than the low speed one. The higher speed one will always make more heat and waste more battery than the 201 rpm one when they run at the same rpm. This paragraph is the important difference between the two motors that people seem to struggle to understand, and this is why it's important to choose a motor with the right winding speed and voltage combination. View attachment 18288
In this chart you can see that the higher speed motor always has lower efficiency, lower torque and lower power than the lower-speed one in the range that the lower speed one can run. The battery, controller, throttle, incline etc. are the same for both.

Damm you D8veh
Using facts and diagrams to explain. It wouldn't be allowed in the brexit thread I assure you.

 

[Deleted member 4366]

When you're designing a system from scratch though, there's no requirement to stick to a specific voltage or current.

very good point, but what most people don't seem to grasp is that you need to know the motor's kV (winding speed). Most sellers don't even tell you what it is.

 

[PatH]

Far from it, they are some of the most beautifully designed and built pedelecs in existence. Their quality and that of their sister Koga pedelecs is outstanding.

Not very powerful and best suited to Dutch conditions at introduction, they now claim much higher torque though I think they somewhat exaggerate that.

For a rider in an undemanding area where no hill is over 10%, a good way to spend £2000. But my comments are restricted to the bikes with the Ion rear wheel DD hub motor. They make a few front hub motor bikes with a motor I know nothing about.
.

Erm, yeah, just to say, this is rubbish, ride 1000 miles on another man's bike and come back with an opinion.

A 1 in 10 hill is nothing for my Sparta, a fit cyclist can output 100W continuously so with 250W you are already 2.5 times more powered,

Yes it was £2000 but 4,000 miles in I consider it money well spent, it's bulletproof, it did complain of overheating on a very hot day (before I even got going) but I am glad the software has the sense to stop the system before damage can occur.

After 2 years of hard use I can appreciate the details, the derailleur gears have never needed adjusting, most of the components are high quality stainless steel or aluminium, a good clean and some oil and wd40 and keep the tyres at the right pressure is all it takes.

You get what you pay for, all the engineering and reliability is in the motor, there's a video on youtube showing an ION drive being dismantled and fixed, the connectors had perished, but the motor itself, like that 20 year old Black and Decker drill your old man had, still worked perfectly.

Can't go wrong with tried and tested technology, just because it's from Holland doesn't mean anything.

 

[flecc]

Erm, yeah, just to say, this is rubbish, ride 1000 miles on another man's bike and come back with an opinion.

A 1 in 10 hill is nothing for my Sparta, a fit cyclist can output 100W continuously so with 250W you are already 2.5 times more powered,

Yes it was £2000 but 4,000 miles in I consider it money well spent, it's bulletproof, it did complain of overheating on a very hot day (before I even got going) but I am glad the software has the sense to stop the system before damage can occur.

After 2 years of hard use I can appreciate the details, the derailleur gears have never needed adjusting, most of the components are high quality stainless steel or aluminium, a good clean and some oil and wd40 and keep the tyres at the right pressure is all it takes.

You get what you pay for, all the engineering and reliability is in the motor, there's a video on youtube showing an ION drive being dismantled and fixed, the connectors had perished, but the motor itself, like that 20 year old Black and Decker drill your old man had, still worked perfectly.

Can't go wrong with tried and tested technology, just because it's from Holland doesn't mean anything.

What a strange response, considering I praised the Sparta's superb quality!

I merely commented on it's limited ability when it was introduced, something you clearly know nothing about, since it's obvious that you have the modified model. That is however still one of the lower powered pedelecs on the market, fact, and your mention of overheating on hot days and the software shutting it down is confirmation of that. Of all the e-bikes I've ridden over the last 36 years, no others have ever done that on even the toughest of climb conditions.

I stand by my comments and would not recommend the rear wheel DD motored Sparta or Koga to anyone who regularly has to tackle hills over 10%, since there are so many pedelecs that are far more capable performers.

However, you don't only have to take my knowledge based opinion. The most experienced of all published pedelec reviewers is David Henshaw of A to B cycling magazine. Here is his precis on your Sparta model:

Quiet, well-equipped, but a little weak for hillier areas. Bigger batteries (up to 600Wh) cost quite a bit more

Finally for your information, no pedelecs are limited to 250 watts power, that is merely their legal rating. In practice they all have maximum power greatly exceeding that, differing as widely as two to one. Your Sparta motor is in the bottom band.
.

 

[PatH]

Well, when it displayed the overheat message I hadn't even started to ride, it was a rare baking hot day and the bike had been in direct sunshine for hours.

Of course there are more powerful motors, but you miss a trick, old school derailleur layout is the most efficient power train by a margin, the pedal power is direct to the wheel, you aren't driving through a gearbox motor.

Where I live is a popular circuit for club riders, these guys can ride pretty hard for 50 miles, they smash me on the flats, but if I meet one on a hill, any hill, they are working at peak power and I'm keeping up, easily.

The Shimano Dynasys group set helps here, its indexing is bang on and has never needed adjusting, it just works.

Let's talk tyres, 700c running at 85 PSI, low rolling resistance right there.

It all adds up, the reviews are just by journos who tried it for a couple of hours and felt that the other people might be right and that it would not do for hills.

It's a proper well engineered bike, and I need to talk about the rock solid handling too, 35mph downhill and I bottle it, the bike doesn't.

Cornering ability is something you come to trust, I can throw it about like I stole it, or tackle fast racy curves, and it's safe and assured.

As a package, it's hard to deny there's much wrong with it.

Apart from the slight fear about things going wrong costing £££ but I've had so much from it already it's worth the price of admission.

You pays your money innit?

 

[John_S]

It is a fact that the direct-drive Sparta and Koga do have poor hill climbing ability and are only a good choice of bike for someone who lives in a relatively flat area. It is probably true that for the large majority of people, the most important aspect of an e-bike is its hill climbing ability. This is definitely true for me. I own a BPM-powered Woosh bike that has exceptional climbing ability, even with 19 stone of weight to transport when I ride with my six-year old on board. It can easily tackle all the hills where I live. If I were to ride a direct-drive Sparta or Koga with the weight of myself and my child on board, I doubt that it would be much fun at all coming to any sort of a hill.

 

[Deleted member 4366]

It's a proper well engineered bike, and I need to talk about the rock solid handling too, 35mph downhill and I bottle it, the bike doesn't.

Didn't you have problems with spokes and the display?

Though it's generally a good quality bike, I wouldn't call it well-engineered with that massive motor and the battery at the back. It would probably be a lot better if the battery was nearer the middle, but instead of engineering that, they took the easy option.

 

[PatH]

Yeh but that's just wearing it in.

You don't buy a nice electric bike without knowing how to look after it.

 

[PatH]

It is a fact that the direct-drive Sparta and Koga

It's not a fact at all I am proof positive.

 

[PatH]

Come back to me when you have done 4,000 miles.

Rubbish about the battery on the back.

It's been nothing but a great thing to have.

 

[Charliefox]

When people burn out their motors and controllers, in most cases it's because they went too slow , which can be because they didn't give their motor enough power. Different motors are wound for different speeds. you can have 500w DD motors that climb like a goat with minimal power. Look at those electric scooters. They don't even have pedals to help them on the hills There's no exact answer to the question, You have to consider many things at the same time. Winding speed is fundamental, then there's torque. bike speed, output power, weight, incline, volts and current all affect it.

Never buy a motor unless you know it's winding speed. Once you know that, you can estimate everything else.

If you're thinking of a new bike, Mountainsport, tell us what you're trying to achieve. Maybe we can recommend something.

Interesting. I have a 36v 500W DD front hub motor kicking about and was wondering if it was worth it to buy a 48v bottle battery and a suitable sinewave controller to improve the torque. Would it work or should I just use it with the original controller?

 

[Deleted member 4366]

It depends on the winding speed. Some go way over 40 mph at 48v, so you need very high current to keep them out of their inefficient zone. Others (not very common), do 15 mph flat out, so would be fine at 48v. It's best to test the no-load maximum speed first, then you know what you're dealing with. for that, you can use any battery/controller combination that are compatible with each other. The motor will run at any voltage. Your need the rpm/volt (know as kV), then can calculate the max speed at any other voltage by multiplying it by the voltage because maximum no-load speed is directly proportional to the voltage.

 

[Woosh]

If you have big hills to climb, how about a Bafang SWX02 code 16 48V?
Slower winding means bigger torque.
I run it with a Lishui 1260 48V 17A controller, 48V 12AH HL downtube battery, maximum power is about 750W.
This motor is fitted with Hall sensors.

http://wooshbikes.co.uk/cart/#/product/uid-188-swx02-48v12ah/bafang-swx02-48v-250w-26in-rear-hub-kit-with-48v-12ah-battery

 

[topographer]

maximum power is about 750w.

Not 816?

 

[Woosh]

Not 816?

some is lost along the way.
It still climbs better than the 36V SWX02.

 

[Deleted member 4366]

Have you tested the no-load unrestricted speed?

 

[Woosh]

Have you tested the no-load unrestricted speed?

No, I haven't.
I am on holiday at the moment, will ask Jim to check this out.
The winding code is 16, that's 192 RPM at 36V, so it should be around 250 RPM at 48V, same as the current SWX02 code 12 at 36V that we sell, the 48V offers a wider range of power.

 

[Deleted member 4366]

That's what I would have thought, but a couple of years back 48v code 16 BMS were reported as 15 mph max, so I'm not sure if the code is related to kV or actual RPM.

 

[Woosh]

I tested it briefly, it goes well over 20mph.
I'll ask Jim to give it a good run. It's still early days, may use it later on production bikes if I can get the 48V certification issue clarified.