Leafbike has been producing a uncontrived momentum hubmotor that has earned a place of respect with electric velocipede enthusiasts, and I decided it’s time to explain why it keeps vibration the competition in this size range. So, lets take a look…

The thing that makes this model special is the extra-thin 0.35mm laminations in the stator-core, and I’ll get to that in just a bit. But first…I’d like to talk a little well-nigh the popularity of uncontrived momentum hubmotors in this size range. The most affordable ebike kits are the so-called 1000W uncontrived momentum hubmotors. They typically have a stator using the worldwide 205mm diameter laminations, and then then hubmotor manufacturers stack them to make the motor wider if you want increasingly power. There are worldwide hubmotors advertised as 1000W, 1500W, and 3000W which all share the same laminations. This commonality of parts makes these laminations increasingly affordable due to mass production.

Once the width of the lamination stack is assembled, the manufacturer wraps copper wires virtually each lamination stack “tooth” to make the electromagnets that are turned on and off to spin the motor. The popularity of the 1500W size is due to the fact it is the widest hubmotor that still allows a worldwide velocipede frame with 135mm wide dropouts to use a worldwide and affordable 7-speed freewheel.

This moreover ways that the 1500W size looks scrutinizingly identical to the worldwide 1000W size externally. The really fat monster QS 205/50H only leaves unbearable room for a single-speed sprocket, which makes it’s powerful width plane increasingly conspicuous.

Years ago, when someone who was new to ebikes bought a unseemly 1,000W uncontrived momentum (DD) hubmotor, they often fell in love with it, but…they wanted increasingly power. Simply subtracting a increasingly powerful controller and shower usually ended up with a fried motor. So…they went when to the internet and bought a larger Crystalyte H35. The “35” in the name is considering the rotor magnets have a “Height” of 35mm, and as a result, the matching lamination stack is moreover 35mm wide. The 1000W hubmotors typically only had a 28mm wide stator.

These 35mm wide stator-motors performed just fine when you limited them to the nominal 1500W, but…their performance was outstanding if you doubled that for a few seconds for a splash of velocity using 3,000W.

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Thin Laminations

The real magic is in the thin laminations. It sounds odd that a slightly thinner lamination could have a big effect, but it does. What’s plane stranger is that it financing less than $10 per motor to switch from the worldwide 0.50mm laminations to the thinner 0.35mm ones, and yet…they are not as worldwide as you might imagine.

This affects a miracle tabbed “eddy currents”. When a magnet passes over a ferrous material (like the iron in the steel laminations), some of the electrons in the iron molecules are pulled and shoved virtually by the magnetic field of the magnets. Without the electromagnets are tuned off and the permanent magnets have passed over, those loose electrons go when to any nearby imbalanced iron molecules. The longer a loftiness that they travel when and forth, the increasingly heat they generate. Using thinner laminations limits how far the eddy currents can travel.

Because of this, the Leafbike hubmotors are listed as having a 90.5% efficiency, which is largest than average. Years ago, I though a few increasingly percentage points of efficiency meant that a given motor might provide a little increasingly range from the same battery, so…I didn’t really superintendency well-nigh that. Then, I found out that those few percentage points of efficiency meant that the less efficient motor was converting increasingly shower watts into waste-heat. As a result, fewer of your shower watts were converted into work. The Leafbike 1500W hubmotor stuff worldly-wise to take upper power while producing less waste-heat is where the magic is.

So, how much power can the Leafbike 1500W really take? Electric velocipede kits from China are commonly found to have wildly inaccurate power ratings. Some are down-rated to make a powerful component seem legal, and others are over-rated to impress buyers with how powerful they are. Based on several years of ebike hot-rodders using this hubmotor, I can confidently say that 50V X 30A is it’s unvarying rating, meaning that…if you load it lanugo unbearable to continuously yank 1500W, it will not shrivel up.

If you’ve read many of the wares we’ve written in the past, you’ll know that a hubmotor’s temporary peak rating is usually twice the continuous power level. This ways I’m rating this motor as stuff capable of 3,000W for quite a bit of time surpassing you have to let off the power and let it tomfool lanugo some. That’s pretty nuts for a hubmotor that’s not very large or heavy. It gets plane crazier if you read the next section unelevated on heat shedding mods…

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Getting Rid of the Heat

Somewhere virtually 3,000W @ 60A, this motor reaches saturation. This ways that if you add increasingly amps whilom that, you will get a little increasingly power, but no where as much as when you are using a lower power level. The value of copper mass in a 35mm wide stator can take 30A all day, but somewhere virtually 60A the heat really starts to increase a lot per spare amp. If you occasionally hit this motor with 60A, you might not want to do that for very long. It will phlebotomize your shower fast, and it will “heat soak” the stator windings, considering you are moreover exceeding this motors worthiness to shed heat.

A few years ago there were a lot of experiments well-nigh how to help these hubmotors shed increasingly heat. The most simple and obvious method was to cut large holes in the side-plates. If you widow a temp sensor to the stator (highly recommended for all hot-rodded hubmotors), That would tell you when you were unescapable a danger zone where the heat might forfeiture the stator. This kind of modification unliable you to use 60A increasingly frequently, and for longer amounts of time for each time that you hit it.

However, wearing large holes in the side-plates allows dirt to get into the inside of the motor, which can forfeiture the trestle bearings, among other things. Doing this still works for a short-term race, but it’s not a solution I recommend for long-term commuting. If you want to alimony the hubmotor shell sealed-up, the remaining options are…adding ATF, upgrading to a tint aluminum stator core, or subtracting ferro-fluid (FF).

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ATF, Tint Aluminum Core, or Ferro-Fluid?

Although the sideplates of a DD hubmotor are aluminum (which is known to swizzle and shed heat well), there is an air-gap between the hot electromagnets in the stationary stator and the spinning permanent-magnet rotor. If you add well-nigh a small coffee-cups worth of synthetic Automatic Transmission Fluid (ATF) to the inside of the hubmotor, this fluid spreads out as soon as the motor starts spinning, and it fills that air-gap. This provides a path to speed up the heat in the stator reaching the aluminum side-plates, so the heat can be shed to the outside air.

This is good for high-amp performance, but it comes at a price. No matter how well you try to seal up the side-plates, the ATF will occasionally leak out and drip, or worse it will be flung onto the rear brakes. Testing has plane verified that when the cadre of the motor is heating up and cooling off it causes the motor to “breathe” through tiny air-gaps in the copper wire strands in the motor phase wires, so…you must moreover add a small vent to a side-plate to prevent pressure differences. Subtracting ATF is like the ventilation-holes we talked well-nigh before…good for a race, but not worth it for a long-term street-fighter.

And this brings us to the option of using a tint aluminum stator cadre instead of a thin steel stamped plate. Of undertow the cores of the individual stator electromagnets are still stacks of this laminated steel sheets, but between the trestle and the electromagnets there needs to be some support structure. I bought a hubmotor once with a tint aluminum core, and it worked as advertised. The thick aluminum mass undivided heat-spikes from temporary upper amps, and then shed that heat over time when I was cruising withal at my top speed. Nonflexible velocity draws upper amps, but maintaining speed unquestionably draws very few amps by comparison.

So, why isn’t that what I’m recommending? It works and there’s nothing wrong with it. The tint aluminum cadre was first seen on the large motorcycle hubmotors, like the QS 205/50H. Due to popular demand, plane the mid-sized hubmotors have had this option widow to their catalog. The MXUS 3000W can be purchased either way, with a cadre of stamped steel or tint aluminum. The marrow line is that the tint aluminum stator cadre is increasingly expensive, and heavier.

When an electric motorcycle is using 8,000W or more, a few uneaten pounds or kilos of weight in the motor isn’t that noticeable, but…the Leafbike 1500W really shines when its used in a fairly light downhill bicycle frame due to its reasonable weight, and unrenowned power.

And this brings us to the final option, which is the one I recommend. Subtracting Ferro-Fluid (FF) ways that you have dramatically improved this motors heat-shedding ability, and that ways you can use 3,000W or 60A very frequently, and for surprisingly long stretches.

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Ferro-Fluid and the Leafbike hubmotor

FF was ripened to help the magnets in high-performance music speakers to shed heat, which unliable smaller speakers to be driven to a louder sound level. It doesn’t run out through tiny gaps in hubmotors considering it sticks to magnets, like the permanent magnets in the rotor of an ebike hubmotor.

We wrote well-nigh FF in 2017 (to see that article, click here), and without several years of hot-rodders using it, no downsides have been discovered. This stuff works. It was so popular, we moreover wrote an installation guide in 2018 (to see that article, click here). Using FF ways you can have the lighter version of a hubmotor, while still having the upper peak power potential.

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Why not 72V?

Running the Leafbike motor at 72V can be washed-up (20 cells in Series / 20S), and that does provide increasingly power with no spare heat. However I am a big fan of 48V or 52V for ebikes. This is a much safer voltage range to work with, the batteries are cheaper, and there is a largest selection of batteries.

On a side-note, if you overly have a power outage, the inverters that are labeled as 48V-input will winnow both 13S and 14S shower packs for the input (48V and 52V). This ways that these large electric velocipede batteries can power an inverter to provide 120V AC in an emergency.

If you read our vendible on understanding motor terms (to read that article, click here), this size of motor can have the option of several variegated windings, tabbed a motors “Kv”. This affects how many RPM’s you will get per volt that you wield to the motor.

Since all these variegated Kv options use the same stators, they all have the same value of airspace virtually each stator-tooth. This ways that the coils can be made from many wraps of thinner wire, or fewer wraps of thicker wire. Since the faster Kv motors (lower turn-count) use fatter wire, they have less resistance, plane if you only use half of their higher speed potential. Listed unelevated are the turn-counts misogynist from Leafbike. I recommend the 4-Turn, plane if you don’t unquestionably travel at that upper of a top-speed. The top road-speeds listed unelevated are for a 26-inch wheel and a 2-inch tire.

4T / 13.1 Kv = 631rpm @ 48V = 39mph
5T /10.1 Kv = 485rpm @ 48V = 30mph
6T / 7.0 Kv = 336rpm @ 48V = 21mph

Leafbike calls the 4T model their “45 MPH” Kv winding, but that speed is with the motor unloaded and spinning in the air.

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A Cargobike Proposal

I occasionally get asked what well-nigh what type of system is the most reliable. My favorite ebike is a mid-drive, but I have to shoehorn that the simplicity of a DD hubmotor is nonflexible to beat. And one increasingly way that you could make it climb hills largest with less heat is to lace it to a smaller rim, like a strong 20-inch BMX rim. This lowers the top-speed, and increases the wheel torque, without any other changes.

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What Controller?

If you are a longtime hot-rodder, you don’t need any translating from me well-nigh controllers. However, if you are fairly new to the ebike game, I would definitely recommend that you stick with the factory controller and throttle for your first time virtually (also, get a spare throttle for troubleshooting, they are cheap). This guarantees that the components are all plug and play. A sine-wave controller would forfeit slightly more, but would run nearly silent. The affordable stock controllers use a “trapezoidal wave” which is sometimes tabbed a square-wave, and they have a slight buzzing noise when accelerating.

I have found the Leafbike website to be a bit worrisome to navigate, but the standard controller for the Leafbike 1500W kit is a 40A unit using 12-FETs, but…they do stock an 18-FET controller that is rated for 55A. If you want the larger controller, search for:

“48V / 52V 2000W fat snow velocipede motor controller“

In the pic below, we can see the Leafbike uses the worldwide size and shape of lamination with 51 stator teeth. It’s 3-phase, so 17 electromagnets per phase. The rotor has 46 neodymium permanent-magnets, so when programming a custom controller you would input 23 “pole pairs” (they unorganized the north and south facing the stator). A radial outrunner with three Hall sensors so the controller knows the position of the rotor as it spins. A well-padded thick axle.

The woebegone plate in the part-way is the thin stamped-steel stator support. The phase wires are a thick 3mm-squared in cross-section area. It unquestionably “looks like” dozens of other hubmotor models, but this pic doesn’t show that the laminations are 0.35mm thick, instead of the worldwide thicker 0.50mm. That is where the efficiency and low heat come from.

For a link to just the yellowish motor, click here.

For a link to the full Leafbike 1500W kit, click here

As far as the battery, if you don’t have a preference, I recommend the 52V Luna Cycles Wolf pack. If you like this option, specify the power version that can put out 50A.

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Written by Ron/spinningmagnets, March 2022