Leaf / leafmotor / leafbike high efficiency 1500w motor

[cycborg]

How would an 8T be expressed? (8*8T?)
What is the first number -- pole count?

What is the easiest way for people to know what kind of motor they have, if they get the cover off: count the poles? (From what I have read here, counting the turns is not possible without damaging the motor?)

What does "SOC" stand for? I searched it. Many people were using the term, every time acronymized. Couldn't figure it out by context.

Sorry you didn't get a reply to this yet. I know it's frustrating trying to find references to unfamiliar nomenclature.

SOC = state of charge.

The first number in the winding count is the number of parallel strands in the winding. The motor is made with small-gauge wire to facilitate winding, so several strands will be paralleled to get an effective thicker gauge. But there is only so much space beetween the stator teeth, so if you put more turns around the tooth, you have to use proportionally fewer parallel strands. This is why when you multiply the parallel strands by the number of turns, the numbers are approximately equal. In this case, the windings are 60-65 strand-turns.

Counting the turns is difficult if not impossible because x turns of y strands looks pretty much the same as y turns of x strands, or any other combination where the product is close to xy. You can figure it out by measuring the phase resistance, but this isn't trivial for a couple reasons. First, the resistance is very low so you can't just use an ohmmeter - you have to apply a known current (typically in the 1 A range) and measure the voltage at the terminals. Second, someone has to have done this to a known winding so you can back-calculate from this. I don't think anyone has done this for this motor yet.

 

[mchlpeel]

So for more hill climbing ability what matters most.

More total copper fill (5T) or more parallel strands? (4T)

 

[speedmd]

You dont't have to be such a jerk.

Yes, but.. but.. as wifee says many days, it just comes so natural for me. Sorry, paypal / good vendor abuse just pisses me off to no end.

Glad to see the link to the science and math myth thread, and can not but wonder why anyone would want a high turn count 1500 watt motor if they are looking for good speed (above 25mph).

 

[mchlpeel]

Well the myth thread may be full of useful information but it just blew my mind in about 5 seconds.

I was always under the impression that if I have a battery supplying a constant voltage and amperage that when you change the winding from say a 4T to a 5T that top speed decreases but torque increases.

I'm completely lost as to which motor winding is best.

I would assume the 5T is better because it has the most copper fill so can get the work done with less amps. To compensate for less speed I just increase volts

Hopefully someone can dig me out of this knowledge hole

 

[spinningmagnets]

So for more hill climbing ability what matters most

There are many compromises, you must chose the least objectionable for your commute and personal preferences. Best for hill climbing is to keep the magnet speed up in the motor. between copper fill and turn-count, start with the lowest top speed you can be happy with on the fastest part of the commute, and then calculate the rest.

1. You could go to a mid drive like the LR kit, but...if you don't want that, you don't want it (no need to explain).

2. Go to a higher voltage and a lower turn-count to have the same top-speed. More volts, less amps, because amps are where most of the heat comes from.

3. Can you go to a smaller rear tire? A moped rim will allow you to use a one-cross pattern on a 17-inch moped rim (which is the rough equivalent in size to a 20-inch bicycle wheel with a 3-inch tire). If you go to a smaller tire diameter, you can get a faster winding of motor to get the top speed back where you wanted it. Its an "odd look" to some builders, but it works.

4. If you are set on a rear hub, and also a 26-inch bicycle wheel (2.5-inch tire?), my last suggestion is to ventilate the sideplates to let the heat out, add a temp sensor, and throw a ton of amps at it. If the motor begins bogging down and the bike slows on your steepness of hill...there will be a certain point where the heat suddenly goes way up. If you can keep the motor RPMs above that point, it will survive. Ride up your hill at wide-open-throttle (WOT) and pedal along as much as you can (may require a 52T-60T chainring)

 

[Kodin]

Why ventilate when the freewheel version is so perfect for oil cooling? A tube of RTV and some 17mm shaft oil seals are all you need. They even have the bores built for it.

 

[cycborg]

I would assume the 5T is better because it has the most copper fill so can get the work done with less amps. To compensate for less speed I just increase volts

This is correct. If you build a 72 V nominal system as opposed to a 48 V system, the 5T should get you to the speed you want. 48 V systems are more common, so this would give you more choices at lower cost, but there's plenty of 72 V stuff out there. You just have to balance this choice with the 1.5 % more copper in the 5T. That's not a huge performance boost.

 

[John in CR]

Okay The Myth talk has gone on too long in this thread. Increasing the turn count does not increase a motor's ability to make torque, period. Adding turns progressively increases the torque per amp, but the copper gets longer and thinner so current handling (current is what makes torque) decreases proportionately, putting you back to the same place. That means that otherwise identical motors with different turn counts will make the same amount of heat for a given torque regardless of the rpm you compare. A slow wind motor can not climb a hill any better or more efficiently. That myth in all its differently worded versions needs to be eradicated on ES, and it should be no different than correcting someone who refers to battery capacity in Amps.

Copper fill does make a difference, and the more total copper on each tooth the better. That makes the 5 turn motor the best choice, because it will make the least heat per unit of torque. With only 1 strand less, a 1.5% difference, the 4t isn't much of a compromise, and the 7t is only double that, but assuming they're all wound with the same size wire I wouldn't touch the 6t with a 10 foot pole.

If you're already locked into a voltage, then turn count could affect your decision. Otherwise it's really only the voltage limits and controller costs as you go to very high voltage that could affect your choice if you're after maximum performance. Voltage is our one real limitation, and since power = rpm X torque and we already know the different winds are capable of the same torque, then the faster wind motor is capable of higher power. Similar limitations apply at the very low speed end of the spectrum, since it may be difficult to find a controller capable of high current at low voltage.

 

[cycborg]

Well the myth thread may be full of useful information but it just blew my mind in about 5 seconds.

I guess any reference to this thread should include a recommendation to skip the initial post, which is very long and completely wrongheaded and will therefore scare off 90% of readers and confuse the rest. Scroll down and scan for posts from liveforphysics and John in CR, who have a good understanding and clear explanations.

 

[mchlpeel]

John in CR really cleared that up.

Really in my situation I am locked into 50.4v nominal.

For the 5T motor we have measured this at 485rpm for 48v

485rpm / 48v = 10.1 rpm per volt

10.1rpm per volt x 50.4v = 509.25rpm at 50.4v


I am using a 26" wheel so.

26" x 3.14(pi) = 81.64 inch circumference

509.25rpm x 60 = 30555 revs per hour x 81.64 inches per Rev = 2,494,510.2 inches per hour


2,494,510.2 Inches per hour = 39.4MPH (unloaded)

39mph - 20% = 31.5mph (estimated loaded speed)

The 20% represents the load I will have on the motor such as body weight and bags etc.
this shows that for over half the pack charge I will be able to travel over 30mph which is plenty of speed for me

HOC would be 58.8v = 36.7mph (estimated loaded)

Unsure what LVC would be but if I use 42v then loaded speed at end of charge would be 26.2mph. I can live with that (it's down hill on the way home)

 

[John in CR]

Well the myth thread may be full of useful information but it just blew my mind in about 5 seconds.

I guess any reference to this thread should include a recommendation to skip the initial post, which is very long and completely wrongheaded and will therefore scare off 90% of readers and confuse the rest. Scroll down and scan for posts from liveforphysics and John in CR, who have a good understanding and clear explanations.

Yeah, it's kinda hard to get to the good stuff in that thread. It took a lot of bullheadedness on my part to get the real experts to step in (Justin, LFP, Miles, etc) to hopefully stamp the myth out once and for all, yet it's so entrenched that it still persists. It's actually quite simple, and the first paragraph in my previous post above summarizes the facts succinctly.

 

[neptronix]

What is misleading about the initial post in this thread?
The 'torque issue' is a forum-wide thing, not specific to here. I don't dispel it myself because i do not fully understand the argument FOR or AGAINST it.

I've ran slow, medium, and fast windings in large and small wheels over the years. In my experience, the tradeoff has more to do with the cost of battery management and charging increasing, the more cells you have.

Early on, everyone thought the 4T would perform worse than a much smaller motor. My 4T lifted the front wheel at 80 amps and i had to tune down the initial torque by adjusting the battery to phase amp ratio in order to get it to stop doing that. Way more powerful than the crystalyte HS3548 i played with in a 20" wheel at 36, 47, and 76 volts nominal.. and this is an even faster winding than the HS3548. It has been dramatically more efficient than the HS3548 as well.

Well the myth thread may be full of useful information but it just blew my mind in about 5 seconds.

I guess any reference to this thread should include a recommendation to skip the initial post, which is very long and completely wrongheaded and will therefore scare off 90% of readers and confuse the rest. Scroll down and scan for posts from liveforphysics and John in CR, who have a good understanding and clear explanations.

 

[Kodin]

One thing people forget about is that the motor is only one part of the equation; switching efficiency and handling in the controller also makes a difference, and if all other items are equal, there are better and worse choices for what voltage to run for a given power level. I'm not at all a definitive source for that information, but it's something to be aware of. I do know that certain types and models of FET will only be good for certain voltage ranges, and they directly affect efficiency and how the motor behaves. For highest efficiency, what would the best FETs be for 48V, 60V, 72V, and 96V configurations? This includes maximum amperage and switching loss at those voltage ranges, as well as switching time, which can either directly or indirectly affect motor timing, and therefore potentially causing interference in a phase-change cycle. To cover all wind configurations, let's say amperage max would be 60A?

I'm curious what you guys have to say, as the motor is not the only variable when deciding on a given voltage.

 

[John in CR]

mchlpeel,

One thing not discussed is the simple fact that all direct drive hubmotors benefit from using a smaller wheel, because they are simply geared too steeply. That even includes my HubMonster motor that I run at 27kw peak input in only a 19.25" OD wheel. You will benefit from running the smallest wheel you can live with, and even just stepping down to a 24" wheel will more than offset the slight edge the 5t has over the 4t motor. Quite often people even find that a small reduction in wheel size doesn't lower the top speed at all using the same motor.

Also, if you're hanging bags off side of your bike in a way that hurts aerodynamics, you're likely to end up disappointed in range and speed. Even at only 30mph the load of wind resistance has a major impact. I measured a few hundred watts difference at 30mph simply my changing from a relaxed upright riding position to a comfortable tuck. If I had a daily commute that used significant portions of my battery capacity, then improvements in aerodynamics would be very high on my list of priorities.

 

[cycborg]

What is misleading about the initial post in this thread?

Sorry, "this thread" was ambiguous; I probably should have said "that thread", meaning the Science blah blah blah thread. Your initial post on "this" thread inspires no objection and much admiration.

 

[neptronix]

Okay got it :lol:

What is misleading about the initial post in this thread?

Sorry, "this thread" was ambiguous; I probably should have said "that thread", meaning the Science blah blah blah thread. Your initial post on "this" thread inspires no objection and much admiration.

 

[mchlpeel]

Page 5 and 6 of this thread talk about the pros and cons of the 24" wheel

Conclusion was that a 24" wheel didn't make a significant difference to performance.

I do get the feeling that I'm being recommended to get the 4t so as not to be disappointed

My only worry is powering up a 13% grade hill, although only less than a mile long I want to know I can do it at a good pace.

 

[neptronix]

I can power up a 11% grade at ~25mph on my 4T, weighing at 185lbs.

If this grade is very long, you're gonna build up a lotta heat. Maybe you want a bigger motor like the MXUS 3kW.

 

[John in CR]

Neptronix,

You've developed the right answer regarding windings not making any difference, so you're probably just missing something small in your knowledge base to really bring it into focus. I didn't have my light bulb moment until last fall. Torque may be your missing part like it was for me. Did you know that torque per amp has a fixed relationship with Kv? ie The torque constant Kt in Nm/amp is equal to 9.549/Kv in rpm/volt. Any motor with the same Kv will have the same torque per amp. That's true even comparing a tiny motor with a big monster. The difference lies in how much current they can handle and how much heat they make in the form of resistance.

Then if you understand that copper losses are current squared times phase-to-phase resistance, a simple example helps prove how 2 differently wound motors are actually the same. If you take a given motor and want to cut its rpm/volt in half, that requires double the turns on each tooth, but only half the copper will fit on each turn, so the wire is twice as long and half as thick. ie Resistance has increased by 4X. The torque per amp has doubled.

To climb a hill at a given speed requires a fixed amount of torque regardless of how the motor is wound, and if you apply the info in the preceding paragraph it's easy to see how the 2 very differently wound motors will make the same amount of heat climbing the same hill at the same speed. Myth Busted!

Even if it's just for one winding we need a reliable measurement of Kv and phase-to-phase resistance for Miles' spreadsheet. That covers copper heat and torque. Then for that same motor we need a no load current at 2 different rpms. This should be of special interest for the Leaf hubbie, because with that data the speadsheet will compute the 2 portions that make up the iron losses of the motor. Then we can see numerically the benefit of the thinner stator laminations and the impact of any improvements their design has in the magnetic circuit of the motor.

We don't have to know or understand the calculations, but the results are interesting, and for the big picture there's even efficiency. Since he's added torque and rpm input, you can even look at efficiency at different voltages and current levels.

Regarding the wheel size difference, relatively small differences in torque are hard to feel without having identical motors and controller setting in different size wheels to run side by side.

John

What is misleading about the initial post in this thread?
The 'torque issue' is a forum-wide thing, not specific to here. I don't dispel it myself because i do not fully understand the argument FOR or AGAINST it.

I've ran slow, medium, and fast windings in large and small wheels over the years. In my experience, the tradeoff has more to do with the cost of battery management and charging increasing, the more cells you have.

Early on, everyone thought the 4T would perform worse than a much smaller motor. My 4T lifted the front wheel at 80 amps and i had to tune down the initial torque by adjusting the battery to phase amp ratio in order to get it to stop doing that. Way more powerful than the crystalyte HS3548 i played with in a 20" wheel at 36, 47, and 76 volts nominal.. and this is an even faster winding than the HS3548. It has been dramatically more efficient than the HS3548 as well.

Well the myth thread may be full of useful information but it just blew my mind in about 5 seconds.

I guess any reference to this thread should include a recommendation to skip the initial post, which is very long and completely wrongheaded and will therefore scare off 90% of readers and confuse the rest. Scroll down and scan for posts from liveforphysics and John in CR, who have a good understanding and clear explanations.

 

[mchlpeel]

So what is the point in having a high turn motor if it adds no benefits?

 

[John in CR]

The conclusion was incorrect then. While "significant" is different for each of us, there is a difference, and almost everyone who rides at 30mph or more with a sealed hubbie is likely to bump up against it's limits on occasion. That's where little nibbles here and there can put you over the hill instead of stopped on the side waiting for it to cool off...or worse. If your routes are easy enough that you don't ever the limits, on a hot day small differences can make a significant difference in the temperature inside. A 10°C increase in copper temperature makes a 4% increase in resistance, so the effect compounds, and the performance difference in a hot motor is something you can easily feel. The less heat you make the less battery capacity is used to make that heat.

Also note that simulations only take a picture at a specific moment or at fixed conditions. The smaller wheel means you can either use less current for the same acceleration or accelerate to speed in a shorter time. This benefit will happen on every acceleration and the benefits accumulate. With a fairly light ebike and rider the difference between just a 24" and 26" wheel is like shedding 20lbs from your total load.

My standing recommendations are:
- With DD hubbies always run the smallest wheel you can live with.
- Use a fast enough winding that you'll never need to use a 24s battery.
- Unless you really have no throttle self control (which means you just
don't have a powerful enough ebike anyway), then set up for at least
a 5 mph higher top speed than the top speed desired on the flats. Then
you don't have to suffer from every puff of wind or slightest incline.
Plus you can still cruise at your desired speed at difference battery SOCs.

I understand that many guys can't live with a smaller wheel because their bike won't pedal or fit right or their routes are too bumpy, but I really cringe every time I see someone wanting to put any DD motor in a 700c or 29er wheel. Unless our rig really has excess power and torque along with excess battery capacity, we live every ride under serious restrictions of power:weight and torque:weight ratios, and no one wants to throw away battery capacity and make extra motor heat doing it.

John

Page 5 and 6 of this thread talk about the pros and cons of the 24" wheel

Conclusion was that a 24" wheel didn't make a significant difference to performance.

I do get the feeling that I'm being recommended to get the 4t so as not to be disappointed

My only worry is powering up a 13% grade hill, although only less than a mile long I want to know I can do it at a good pace.

 

[speedmd]

Is there any room in the slot for a 17th strand of wire. Hard to tell from the photo. 4 turn x 17 strand would be something to check out.

 

[parabellum]

So what is the point in having a high turn motor if it adds no benefits?

Happy controller.

 

[mchlpeel]

Well your arguments are pretty convincing John.

I am strongly leaning toward the 4T in a 24" wheel.

Mostly because it is extremely obvious that your knowledge and experience eclipses mine.

 

[neptronix]

So what is the point in having a high turn motor if it adds no benefits?

You can run low voltage and high amps to get the same speed as a motor
But the motor is still limited in what it can do, whether you run a super high volt, low amp turn.
Go on ebikes.ca and play with the motor simulator for a while. You'll see that electric motors produce more torque from a stall than they do mid or high-rpm.

If your motor cannot produce enough power to keep up with what you're tasking it to do, efficiency drops and heat builds.

Let me make a combustion engine analogy. You can make more torque three ways:

1) increase the RPM it operates at and gear it down - the Honda rice rocket way. ( which is basically what we're doing when we run a motor in a smaller wheel and increase the voltage )
2) Increase the displacement - the oldschool American hot rod way ( same thing we do when we upgrade to a larger motor ).
3) Increase the efficiency of the motor - the high end German car way. ( this is what the leafmotor does vs a Crystalyte H35 series motor. )

Changing the winding and giving it more/less amps/volts does not really qualify as a #4 option. The characteristics of the motor don't change significantly enough. You can only hope that you get more copper fill that is doing useful work when you do this. If the additional copper fill hangs off the stator teeth, is sloppy, etc then you could even lose efficiency in that situation. I would estimate that this is a total crapshoot where you could win or lose ~1% extra power or efficiency. It totally depends on how the manufacturer winds the stator.