1500W DD hubmotors with a 35mm wide stator @ 2600W

September 1, 2016
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This is a direct drive (DD) hubmotor that I have been waiting for someone to produce the last two years, and now, someone finally has. This article will explain what’s good about it, and why I like it. We are recommending that it works well at 52V X 50A = 2600W.

If you want to sell electric bike kits in the US, and you want a specific set of features that are not currently available in an existing Chinese factory wholesale catalog, you may have to order a Minimum Order Quantity (MOQ) to get them to produce it. It can be any number from ten to a thousand. Several manufacturers are actually producing these now.

The Crystalyte H35, setting the standard

Let me start by explaining the DD hubmotors that were used a few years ago, and how we got to the DD hubmotors we have today (<- click there). When I started reading about ebikes (back in 2009), there were very few choices available for the builders who wanted “just a little extra” power.

Geared hubmotors are the most common ebike motor, and for good reason. They are light for the amount of wheel torque they provide, and systems that operate well at around 48V X 25A = 1200W remain a very popular combination for street commuters. However, at somewhere around 2000W, the largest available geared hubmotors sometimes experience heat distress, due to a limited heat-shedding path. Therefore, hot rodders embraced the larger direct-drive hubmotors from the beginning.

The king at the time was the Crystalyte H35 (the name refers to a magnet “Height” of 35mm, when the motor is laying on it’s side). The “kV” of a motor refers to how many RPM’s a motor will turn for each volt that is supplied. More volts equals more RPM’s. A popular retailer imported two kV models at the time, which they erroneously named HT and HS for Torque  and Speed. The “S” was a faster kV, and the “T” was a slower kV (with the slower motor being suitable for higher volts, to arrive at the same RPM’s as the fast kV model, when it’s at a lower voltage).

Adding more amps creates a lot more heat  than raising the volts, so…since the actual power limit of a motor is often simply how much heatthat  they can survive, early hot rodders immediately used the maximum amps that the motor would survive, and then began raising the volts (as many volts as they could afford, or…as many as they could fit into the frame). One good example of this is the ventilated motor on Nick’s eTownie from 2014.

“…Lyen’s 12-FET controller is now set for driving the Crystalyte HT3525…The temp gauge in the motor never shows more than 80C [of heat] and that is with bursts of 5500W…Now, I’m hitting 42-MPH [67 km/h] on 24S (24 X 4.10V per cell = 98.4V), and…nothing is getting too hot…”

The nominal power of this system is [3.6V X 24S =] 86V X 60A = 5160 Watts (If you like 5000W, you should really use an 18-FET controller to avoid the controller getting too hot).

One of the reasons a motor with a 35mm wide stator was popular with hot rodders was that…it was the widest that a stator could be, while still leaving enough room for a common 7-speed freewheel, and also allowing the motor to fit into the common bicycle frame drop-outs with a 135mm width (of course, with two torque-arms located on the outsides of the frame drop-outs).

The popular MXUS 3000W hubmotor has a 45mm wide stator (which allows even more power), but…it is commonly used with only a single-speed freewheel.

Leafbike 1500W, and thin laminations

The Crystalyte H35 has worked great  at its rated power (48V X 30A = 1500W), but…those who used a lot more power than that (up to 5000W) would be risking heat damage, or even mechanical damage…such as broken axles from using higher watts coupled with high regen-braking.

Nick ventilated the side-plates of his H35 to let the frequent excess heat out. However…what if he could have higher power with less of the produced-heat in the first place?  One of the sources of the high heat in his hot-rodded motor was the eddy-currents in the steel laminations of the stator (which make up the cores of the motors’ electromagnets). Thinner laminations would result in less eddy current waste-heat, and the Crystalyte has the common 0.50mm thick lams. Also!…thinner lams cost less than ten US dollars per motor.


99 laminations in a 35mm width equals a very thin 0.35mm per lam. “If you got big problems I feel bad for you, son. I got 99 problems but…thick laminations ain’t one”

Last year, a company called Leafbike began selling a hubmotor with the common 205mm diameter laminations (8-inches in diameter), and with a popular 35mm wide lamination stack (commonly called a 205/H35 by manufacturers). Also…the Leafbike hubbie had thicker motor phase wires from the factory (a common garage-upgrade for hot rodders), a stronger axle, and most of all…the thinner 0.35mm laminations.

An ES member bought one and began testing it. The results were better than expected. He chose a fast kV so he could have a top speed near 40-MPH without needing extra-high volts, but…that choice usually meant that the motor would run a little hot. The thinner laminations helped to keep the heat low enough that the results were impressive. If you tried hard enough, you could certainly still get this motor too hot, but…it could definitely take more power and still survive.

Electricbike.com recommends that the stator of a hubmotor should stay below 200F / 93C, for reliable operation and acceptable longevity. Your actual resulting top-speed will be the result of motor kV, system voltage, tire diameter, rider weight, and wind resistance. Of course, 140F (60C) as a cap is more ideal for a long life.

The Cro, MXUS, and…aluminum stator supports

A few years ago, the biggest hot rod hubmotor was the venerable Cromotor (with a 50mm wide stator). It’s pretty much an electric motorcycle hubmotor that had its axles machined to fit a bicycle frame, and the spoke holes were drilled small enough to fit 12-ga moped spokes (thinner 14-ga are common on bicycles), as opposed to thick 80-MPH 10-ga motorcycle spokes. To see our article on using moped rims and spokes on an ebike, click here.

The Cromotor had the desirable high-efficiency thin 0.35mm laminations (more of the input watts went to making power, instead of making waste-heat), AND…it also had one other awesome feature. Instead of a thin stamped-steel stator support  to connect the central axle to the stator electromagnets at the rim…it had a thick cast aluminum stator support (the spider).

Why would they add this extra weight? The answer is…HEAT.

On flat land, you might hit the accelerator hard for a few seconds, which would draw the maximum [heat-producing] amps, in order to accelerate. Then, you move into a “cruise phase” where the amps slide down to a level where the ebike (or E-motorcycle) is simply maintaining speed. This cruise phase allows the battery/motor/controller to cool down a bit…at least until you stop, and then you have to jump at the green light again.

By swapping-in a thick aluminum stator support, any “temporary” heat spikes from using max-amps can be absorbed quickly, and then shed over time.


Someday I will make a clock out of one of these…the key feature in this pic is the thick cast “six spoke” aluminum stator support, which can absorb and shed heat spikes.

It’s important to understand this because…swapping-in an aluminum stator-support does not improve the motors’ continuous  heat survivability. By that I mean that, if you are driving up a long and steep uphill at a constant max amps? an aluminum stator support will eventually  still get too hot (however…it can delay the onset of “heat-soaking”).

Where this feature really shines is in a user-profile that runs on fairly flat land (and maybe a few mild hills). You can dramatically increase the temporary “peak” amps that you can shove down a DD hubmotors throat, if you have this aluminum stator-support feature. How much? The real number is actually…how hot is it getting? We believe 200F / 93C is a practical limit, and if you want to use more than 52V X 50A = 2600W…we also recommend you install a temp sensor with a digital read-out.

Nick used over 5000W in a Crystalyte 205/H35 motor, but…he also ventilated the sideplates, and…he had a temp-sensor so that he could “back-off a little” when he had abused the motor a little too much…(of course, he also didn’t have thin laminations and an aluminum stator support at the time….*wink).

The big story two years ago in DD hubmotors was the sudden popularity of the MXUS 3000W DD hubmotor. It had thin lams, and an aluminum stator-support. It was more powerful than the Leafbike 205/H35, and it cost less than the Monster Cromotor 205/H50 (The MXUS has a 45mm wide stator).

Who makes the 1500W?

The Leafbike company was asked several times if they would produce an aluminum-stator support version of their thin-lamination 205/H35 motor, and…the MXUS and QS companies were both asked to make a 35mm wide stator version of their “thin lamination with an aluminum stator-support 205mm OD stator” motor, but…so far nobody has agreed to make these, until now.

A certain distributor might have a product made by two different factories, in case there is a problem with production. That way, you always have at least one source running, and also…if one of them starts making a bad product, you can tell from customer warranty claims which factory was making the crap. I’ve had this motor apart, and I don’t see any distinguishing marks, so the source is probably only one Chinese factory.


The electricbike.com test mule (a vintage GT Chucker DH frame), located in our secret Kansas division test lab. Seen here with a 26 X 2.0 front tire, 19-inch moped rim on the back using 12-ga spokes with a 2.2 inch DOT tire (soon to be replaced with a 3.0 tire after a few burn-outs). Brakes are a dangerous “scrap bin” 160mm front cable disc, and testing is done on long “abandoned airstrip” straights where there is no traffic. Battery is a 70A Luna pack using 30Q cells. The battery case is an organic fiber material made from renewable resources, with the materials “re-purposed” from local bins on trash “pick up” day…because we care about the environment. Handlebars are salvaged from a trash-day BMX.

Here is a pic showing one of electricbike.com’s test-mules. Also, here’s an interesting story about why engineering test-vehicles are called “mules”. A mule  is a cross between a female horse, and a male donkey (assuming it’s a donkey who owns a step-ladder). The offspring that results has some of the benefits of both, but is not intended for production. The joke is that…two mules can’t reproduce (the inter-species mutation doesn’t have the proper equipment). In order to get a mule, you must always use a horse and donkey for parents.


The mid-power 1500W, the awesome MXUS 3000W, the Monster Cromotor, and “beast-mode” QS 205 all look the same from the side. The width of the stator makes all the power difference. The aluminum torque-plates shown here don’t have their end-clamps on (at least, in this picture), and these plates have been hacked to fit onto three different frames so far. Be professional for goodness sakes, don’t do this…water-jet some steel torque plates.


The 1500W DD hubmotor on the right side, with a single-speed freewheel

The pic above shows one of the reasons someone might want to get this motor. “In theory”, this motor (along with the Leafbike 1500W and the Crystalyte H35) has enough room on the right side to use a 7-speed freewheel and derailleur. I recommend a 6-speed Shimano “megarange”, because…let’s be honest…at these power levels you only need 2-speeds. Second gear is “I want to pedal along with the motor at top speed so the cops think I’m a bicycle”…and also, first gear is “something on my system isn’t working, and I need to pedal home on this heavy-ass ebike”.

I am only using a 16T single speed in the pic above because…it’s what I had laying around.


The 1500W on the left side. This is where you would adapt a disc brake onto it…if you were smart. You can see here that IF I had mounted the axle shoulders in the stock 135mm frame frame drop-outs, it would have fit. I recommend using a controller with the regenerative-braking function (regen). However, if you can also fit a disc brake on the back, DO IT!

Lets crack this beotch open, what’s inside?

Some of our new readers are new to bicycles, and even more are completely new to ebikes. If a certain user-profile leads you to buying a hub-motor, it’s only a matter of time before you want to crack it open, and poke around in its guts. Plus, if you use more watts than we recommend, and then you fry a Hall sensor? you will need to “don the gloves” and perform some surgery.


Make alignment dimples. Just a tiny mark, don’t go deep. You can even just scratch the two pieces with a sharp knife, or paint a stripe with red nail polish from the dollar-store…

The hole locations for the bolts that attach the side-plates to the central part of the motor are typically symmetrical. However…take my advice, before you dis-assemble ANYTHING…mark how it was oriented before you pull it apart (don’t ask how I learned that). “A smart man learns from his mistakes. A wise man learns from someone elses…”


The left side of the 1500W axle. The coiled metal spring-looking thing is an “anti-kinking” support for the cable. If you use horizontal drop-outs, the cable would exit straight down as a “drip loop”

One of the top five differences between a cheap ebay kit and the hot rod motors we recommend is that…the power wires from the internal motor exit the motor case from INSIDE the drop-outs (seen in the pic above). Low powered hubs often locate these wires inside a hollow axle. Doing that makes the axle weak, and it also limits how fat the wires to the motor can be. Thin wires are bad, and should be beaten with a stick until they cry for mercy.

In the pic above, I have sliced an axle-nut lengthwise to make a standoff inside the frame drop-out. If you look closely, you can see the axle-shoulder that would normally be pushed up against a bicycle frame drop-out, with a common width of 135mm. I cut the axle-nut with a hacksaw, and smoothed the cut with an angle-grinder (yes, I have scars on my hands).

If I had used a 26-inch wheel, I would have also located the axle in the normal frame location, with the two torque-plates just on the outside. However, my decision to lace the hub to a 19-inch moto rim with a 2.2-inch tire (equaling a 24-inch outer diameter) meant that I needed to locate the axle at least an inch lower than the frame was designed for.

This bike originally came with a 9-speed derailleur, and since I already knew I was going to use a single-speed, I also took this opportunity to locate the axle about two inches farther back, so I didn’t need to break the chain and re-attach it at a different length.


The 1500W axle. I had to touch-up one side of the axle-flats with a file to get it into my 10mm wide drop-outs. The flats are 10mm, the threaded portion is 14mm diameter, and the center of the axle is 16.4mm. Thicker would be better, but…this isn’t bad.


Removing the side-plate retaining bolts with a 4mm allen hex wrench, on the cable side. If you do this, buy some 4mm stainless steel washers to put under the bolt-heads for when you re-assemble..


Set it on the ground, and push down on two opposing sides of the rim. The center should pop out fairly easy. If you put a finger in-between a steel stator and 46 strong neodymium rim-magnets, they will occasionally slam together and cut your finger-tips off. Lift the center section by the axle. This is no joke…I still have all ten of my finger-tips, so follow my example. Try it with a hot dog, and see if it’s funny when it gets cut in half.


The metal part of the lamination stack of the stator is what makes up the electro-magnets that are turned on and off rapidly. If you like using 2600W, 35mm is a good width. These measuring calipers are plastic, so they don’t conduct electricity around a 1000-WH high-current battery.


It was marked 4/6 inside, and I’m guessing that it means its a 4-turn model, using 6 strands per turn = 24 strands around each stator-tooth. Notice there are slots to add a second set of hall sensors on the opposite side, if desired…Three motor phases equals three Hall sensors. Of course, you could also use a sensorless controller if you want, or…because you fried your last hubmotor’s Hall sensors with too much heat (*sips some whiskey and cries myself to sleep in shame)


The 1500W cable connector on this generic model. The three fatter motor phase wire connectors are obvious. If you look closely you can see the small 5V contacts around the perimeter, there are six of those.

This motor came with a cable that had a proprietary connector that was located about one foot away from the motor. I have read statements from builders where they like being able to break the electrical cable near the wheel, to make removing the wheel (to fix a flat tire?) a little easier. This connector accomplishes that, but…my personal preference is to run long and continuously-unbroken wires up into the battery box, for water-proofing, in order to prevent shorts in case I get caught in an unexpected sprinkle of rain.

The wires between the battery and controller should always be short and fat, but…the three phase wires from the controller to the motor can be as long as you like, with no adverse effects resulting from the added length. I cut this connector set off (to see our article on how to do this, click here), and soldered 12-ga wire from the motor up into the battery case, using 3:1 water-proof marine-grade heat-shrink insulation. The stock phase wires are 13-ga. The Hall sensor extension wires I added were 24-ga. Since Hall wires only carry a 5V signal, they can be very thin, perhaps even down to 36-ga? However, I have found that 24-ga is easier to manipulate for soldering.

Inside the battery bag I will eventually use, the phase connectors will be 4.5mm bullets that I acquired by slicing open some of my XT90 connectors with a dremel using a thin abrasive disc (I have a pile of male/female XT90’s), which are rated at 90A (much more amps than I would use for this motor).


The stock motor has common ring-connectors for the three fat motor phase wires. I cut them off and swapped-in 4.5mm male bullets that I had cut out of XT90 connectors. The heat-shrink on the 4.5mm bullets shown here is 6mm from Hobby-King. I did  not change the stock 6-pin hall sensor Molex connector.

The copper in the stock motor phase wires are 13-ga. My wire extensions from the motor to controller are made from the slightly thicker 12-ga. For the Hall wires, I used 24-ga.

Here’s what you get

Someday soon, many retailers will sell these (or something similar) already affordably laced to a rim, but…this is what I received this month, since I was in a hurry.


The generic 1500W hubmotor arrives. The electricbike.com “banana for scale” is calibrated in four inches and also 10 centimeters.


The first step is lacing the hub onto a rim.

The first step is to choose a rim, calculate what spoke will work, and lace that rim up. One bead of the tire (in the pic above) is mounted on the rim, the opposite side has the bead off of the rim so I can reach inside (you don’t actually need the tire to lace the rim onto the hub).

The pencil shown is inserted into the air-fill stem hole, and the first four 12-gauge butted spokes are shown in a one-cross pattern (bought from Dans Comp). Start like this so the air-fill stem will be “boxed”, and easier to reach when you are done. Repeat the pattern clockwise, then “tension and true” them properly, or…have a bike shop do that. This rim is a Holmes MMP 1.6-inch wide aluminum single-wall moped rim, capable of properly seating a 2.2-inch up to a 3.0-inch wide tire…

By the time you read this, sellers will have lacing available for this hub, so email them for a quote. I suspect the majority of riders will spec either a 24-inch bicycle rim, or a 19-inch moto rim (both very similar in size), and capable of mounting 2.2-3.0 inch tires. Off-roaders have been moving towards mid-drives, and also the largest possible hubmotors (MXUS, Cromotor, and QS), but I expect this motor to do quite well with street ebikes.

How much do I like it? I usually sell the parts I test once an article is done, but….I’m keeping this one.

A customised 3000W electric Nirve Switchblade from Lee in Vancouver Canada

A customised 3000W electric Nirve Switchblade from Lee in Vancouver Canada. This type of street ebike is the perfect candidate for this new hubmotor.


16.8 lbs, or…7.6 kg. Toes included for size comparison (The motor isn’t huge, I am just a small hairy deformed mutant). This scale is calibrated for measuring the weight of my dumps after I’ve eaten a huge bowl of high-fiber chili with beans, so this weight is accurate.


Enough! I appreciate the response, but…this hub looks just like any other hubmotor…”from the outside”. I tried to make it as interesting as possible, but…I’m only human.

What Controller?

If you are happy with 52V X 45A = 2300W, then you could get-by with a 12-FET controller if it is using the cool-running and efficient 3077 FETs inside.

I don’t know of anyone who is making a 15-FET controller, or an 18-FET with 3077’s, so…the next bump up is a common 18-FET controller using 4110 FETs, capable of any voltage up to 96V. The bad news is that…such a controller is more expensive, and also physically larger. The good news is that a controller like this won’t get hot at anything “up to” 72V X 65A = 4600W, so you will have a lot of room to play with it.

I recently bought an 18-FET controller from two separate vendors, and I haven’t been able to get either one of them to run…tests on this motor were performed with a 12-FET at 45A. I am looking forward to 40% more wheel torque once I can access 65A…


The discussion over whether to get a hubmotor over a mid drive will continue as long as I can foresee. The answer between those two will simply depend on what your preferences are, and what you are going to do with the kit. Some builders are already using this hub at over 5000W (only occasional power peaks, not continuous). I will be writing soon about Ferro Fluid and motor-shell fins (to read that article, click here), so…any mods that improve heat-shedding will broaden the range of applications for motors that are a little lighter, like this one.

There is nothing wrong with running this motor at 60V or even 72V, but I think the majority of builders that choose this motor will likely run it at 44V, 48V, and 52V (12S, 13S, and 14S, respectively), with the main benefit being that a s lower-voltage battery pack might be more affordable, and maybe slightly more “fit-able”?

From ES member Trailblazer: “…I’m on a 26” x 2.5 (Hookworms). And with the 25R triangle battery I got from Luna, I’m going 36-mph at 4.2KW. This thing is a beast…”

If you use this hubmotor, and it is getting hot under your particular loads, you might want to move up to the slightly heavier MXUS 3000W, which can be found at Kinaye Motorsports. (They are now called “WCEC” / West Coast Electric Cycles) I have had good luck with them. It has a 45mm wide stator, compared to the Edge’s 35mm, so it can produce about 30% more power with less heat.

If you like DD hubs, but your 1500W is never even getting warm, you could likely get by with a lighter DD hub, like the TDCM from ebikes.ca

However, I am often asked about which kit would “make me happy”, and…for most of the type of people I ride with (with street ebikes), this is it. I’d spec a steel frame (perhaps a Felt Bixby?), because using an aluminum frame isn’t going to change the fact that this is a heavy motor. And having a 6-speed megarange freewheel on this may make it look like it’s a bicycle (more than a single-speed) but that is a stealthy smoke-screen. So…this makes the Edge 1500W a “sleeper”…

…a wolf in sheeps’ clothing.

Written by Ron/spinningmagnets, September 2016

Grew up in Los Angeles California, US Navy submarine mechanic from 1977-81/SanDiego. Hydraulic mechanic in the 1980's/Los Angeles. Heavy equipment operator in the 1990's/traveled to various locations. Dump truck driver in the 2000's/SW Utah. Currently a water plant operator since 2010/NW Kansas

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