Data I have gathered from hub motor data sheets

[Little-Acorn]

I have asked a number of vendors of hub motors, for data sheets or performance charts on their motors. From those, I have put together a few lists of how much torque a motor produces at full throttle at various speeds, how many amps it consumes, how efficient it is, etc. This list is as accurate as the data sheets they sent. Caveat Emptor. I found this a useful guide in deciding what hub motor to buy.

I have also put together a list of what features each vendor offered with their hub motor (Controller, thumb throttle, battery charger, that cute little twin LED headlight with a power gauge on it, etc.). It's data taken from their ads - I listed the Ebay ad in the cases where I found them on Ebay. In a few cases, they told me in emails that they did or did not offer a certain feature or part. Some Ebay ad numbers are now expired, but will still come up. In that case, the vendor usually has a new ad out with the same products and features - click on "See other items" in the expired ad.

I'm mostly interested in the 48V 1000W motors, so that's what most of these are. There are other motors I haven't listed, of course.

Nearly all the data sheets they sent me, only listed full-throttle performance, and only for the upper-RPM range. So you can't tell directly from this, how a motor will perform during a half-throttle cruise, how efficient it will be then, etc. But you can tell if a motor has the oomph to push you up to 25mph or whatever.

I also did some tests on my own bike (Trek 7500, 700c wheels, 3/4" tall 116psi tires), riding down a long hill (asphalt paved bike path, no wind that day, sweet) and finding what speed the bike kept a steady speed while coasting. Then measured the slope of the hill, and worked out how much push, and how much torque, and how many watts, it would take to keep the bike going at that steady speed on flat ground with my 30# bike and my 265# lard @ss in the saddle. No electrics, of course, the bike isn't converted yet, so I'll have to figure in that weight later. But this gives me an interesting look at roughly what I can expect.

On a 1.71 degree slope, the bike coasted at a steady speed of 23.1 miles per hour, according to a speedometer I calibrated pretty carefully. With an all-up weight of 295 pounds, that means that the forward push from gravity at that speed was 8.806 pounds, and was being exactly balanced by the wind drag, tire rolling resistance, etc. of me and the bike. That much push at that speed works out to 298.3 foot-pounds per second, which is 0.542 horsepower, or 404.5 Watts. Nobody has checked these figures yet except me, and I could easily have made mistakes. Please let me know if you find any!

Bottom line, it would take 404.5 Watts pushing against the ground, to keep me and the bike going at 23.1 mph on flat ground on that kind of surface with no wind. A motor operating at, say, 70% efficiency, would need 577.9 Watts of electricity from the battery to go at that speed with me on that bike. Looks like the 48V motors I have data sheets for, could do that easily without opening the throttle all the way... once we got up to that speed, of course. This looks promising!

Hope you all find them usable. Click on each picture below (there are two) to get the full-size version. Shoot me any questions or comments you may have.
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[dogman dan]

Nice work. It took me a minuite to realise that the first chart is giving a no load speed on the wheel. At first I was like WT Heck? All the speeds seemed really fast! And the amps really low. On the bike on the road, the speeds would be slower and the amps higher, but that still a great way to compare em. In the second chart, the speeds are more like what people of average weight (less than 200 lbs) get in the real world. With more motors represented, this would be a good chart to have in the tech reference section.

 

[Drunkskunk]

great charts!
I'm dubious of many of these new claimed 1000 watt motors showing up on ebay and other places. The pictures look all the world like 500 watt motors. Some of the scematics they post look like they were ripped from Clyte or 9C, fliped mirror image, and had the numbers relabled off by 1 or 2mm. the scetches rarely match the picture of the motors, and while most don't list the weight, the few that do put them in the 6 to 7kg range. just right for 500 watt motors.

 

[Little-Acorn]

Nice work. It took me a minuite to realise that the first chart is giving a no load speed on the wheel.

Yep, took me a minute to realize that too. The charts I've been getting from these companies, don't list Amps, Torque, Efficiency etc. as a function of RPM. Rather, they list Amps, RPM, Efficiency etc. as a function of torque. At first I wondered how the chart had been made, but finally fingered it out.

My guess is, they mount the motor/wheel combo on a device with a brake. Then they apply 48V and let it spin. At first, they don't apply the brake at all, so the motor spins up to its max RPM. Sort of like your taking your E-bike, lifting up the motorized wheel, and opening the throttle all the way - the wheel just spins in midair. Then they apply enough brake to slow the wheel down a little and hold it there, still with full throttle. They measure how fast it's turning, how many amps, how much drag the brake is applying. Then they apply a little more brake to slow the wheel down a little more, and measure those things again. Then a little more brake, measure again etc. That's my guess, anyway.

Those three quantities (Amps at 48V, RPM, brake drag) will let you figure out torque, Watts of power taken in by the motor, Watts of (mechanical) power the motor puts out, efficiency, and power wasted as heat/noise/whatever. They put all that info on their chart, with torque along the bottom of the chart, and the other things along the vertical axis. In a few cases I've found lists of the data instead of a pretty chart. But sometimes the list is more useful than the chart.

Yes, all the measurements are at fairly high RPM, which translates to a pretty high bike speed, where most people frankly won't ride. I have a hunch this is because they used a standard controller to apply power to the motor. These being brushless motors that run on three-phase AC, you can't just hook the battery directly to the motor, you have to use a controller that changes the battery's DC into AC.

Most standard controller have a current limit, they can't put out more than 30 amps (or whatever their limit is). When these guys were testing, they found that as they applied more and more brake, the motor drew more and more current (and produced more torque). When they got it down to 200-something RPM, still with the throttle wide open, the motor was demanding more current than the controller could supply. And the controller automatically started supplying LESS than the full 48V, to keep the current below 30A, even though the throttle was being held wide open by the testing guy. This probably happens a lot when you ride your E-bike. But the people doing the tests detected this, and stopped the test at that point, so they could present accurate data where the motor really was getting the full 48V. So we only get data at the higher RPMs, that is, where current draw was low enough that the controller's current-limiting function hadn't kicked in yet. Remember, the controller limits current by reducing the voltage to the motor, even if you're holding the throttle wide open and demanding full power.

In real life (i.e. not on a test stand), this probably happens a lot, as I said. If you're riding slowly, maybe 5 mph, and you want to speed up, you open the throttle all the way. Your batteries are supplying 48V to the controller as they always do, and that doesn't change. But the controller can only supply 30 amps to the motor, so it automatically reduces the voltage it gives to the motor, and you're only accelerating with 35 volts or so at the motor itself. As you speed up (still with throttle wide open), the motor isn't demanding so much current, so the controller automatically adjusts the voltage it's giving so that the current stays at 30amps. Eventually you get up to 30mph or so, and at that speed the motor is only demanding 25 amps at 48 V. So by then, the controller is giving the motor full voltage again.

This brings up an interesting experiment. Suppose you had a BIG controller that could supply, say, 100 Amps? And batteries that could do the same? And you pedaled the bike to 5mph and then opened the throttle all the way, as before?

Two things would happen:

1.) The bike would accelerate like a bat out of h*ll, and
2.) The motor would start heating up pretty fast. Maybe along with the wires.

If you're VERY careful with that full-throttle business (and had that big 100-Amp controller), you might get away with this, briefly. Most people don't treat E-bikes like dragsters, or push them hard up long hills where the motor is forced to produce maximum torque at a full 48V with no current limiting. If you had your 100-Amp controller, and went up a long hill with the throttle wide open, your motor might draw 50 or 60 Amps or more. At 48V, that's 2000 or 3000 Watts or more - far more than your motor was designed to handle. Some motors would keep going and put out the huge torque you could expect from that kind of power... but as I said, they would start heating up pretty fast. If you kept the throttle wide open, soon your motor would get so hot, you'd fry it.

There's a reason these vendors supply a controller with current limiting, and it's not just because they're cheap. It's so you won't set your motor on fire going up a long hill.

If you never ride ANYWHERE except on perfectly flat ground, you might get away with using a super controller like that 100-amp one. If you opened the throttle at low speed, it would rocket you up to 30mph pretty quickly, with the motor heating up rapidly. But then at 30 mph, you'd back off on the throttle to maintain speed at 30, and feed a lot less current to the motor. And with the air flowing over the motor at that speed, it would have a chance to cool back down, before reaching the point where you fry it.

When a manufacturer says its motor is a 1000-Watt motor, they mean that's the most power the motor can take in, pushing your bike at decent speed for a LONG time, without getting so hot that it damages itself. If you have a super 100-Amp controller, you can easily feed it more power than that - but it will start heating up a LOT, and you will destroy it pretty quickly.


Of course, it's also true that most batteries can't supply that much current either, even if you have a super controller that can. Lead-acid batteries can, for a brief time (that's why they are used to start car engines), but if you do it for a long time, then their voltage will start falling off in less than a minute, and if you discharge them too fast too far that way, you can damage them.

Applying more than 1000 Watts to your 1000-Watt motor, can be done for a BRIEF time without damaging the motor, if you back off pretty quickly afterward and let the motor cool down. Even 30-amp controllers can do this, at 48V. Accelerating your E-bike up to speed, can briefly draw more than 1000 Watts, and the motor will start heating up. But if you back off as soon as you reach that speed, you will be OK.

Pushing it up a long hill at full throttle, where you NEVER back off, is a different matter, and you can fry your motor if you just open the throttle all the way and keep it there forever, while the hill prevents the bike from getting up to full speed and you never back off the throttle. Even checking the motor temperature by feeling the outside of the motor shell, isn't real accurate, since the heat is produced in the internal parts of the motor, which will get hotter more quickly than the outside shell.

 

[dogman dan]

My opinion on these motor ratings is that they are all "500 watt" motors too. So put a 48v 30 amp controller on it and it's a "1000" watt motor. What they don't tell you is that the 1000 watt is likely to get hot faster. No big deal with lame sla's that stop you from riding after 20 minuites, but with lifepo4 in the 20 ah size you can ride a motor to death in some conditions. Anyway putting 1000 watts into a motor designed for 500 is not the same as designing a motor for 1000 watts. These ebay "1000 watt" motors are not comparable to a clyte 5304.

Motor heating is tricky though, 750 watts at 48 v won't heat the motor the same as 750 watts at 36v. Each motor winding and the controller it's run on is going to have different characteristics that are not going to be easily generalized or simplified. About all you can say is that riding a certain speed and then pedaling to go faster takes some load off the motor and makes the ride more efficient.

 

[Little-Acorn]

Well, the definition of a "1000 Watt motor" SHOULD be that 1,000 Watts is the highest power it can run CONTINUOUSLY under normal conditions, without getting hot enough to damage itself.

Whether any of these manufacturers are building motors that actually meet that definition, is anybody's guess. Maybe they are. Or......?

Testing can find out... if you don't mind taking the risk of frying something you just paid $300 to buy and ship from China.

Remember that with a hefty enough battery and controller, it's possible to shove MORE than 1,000 Watts through one of these motors, without realizing you're doing it. Particularly if you go up a long hill without pedaling and don't back off on the throttle, or something like that.

 

[amberwolf]

I have yet to see motors *or controllers* in general labelled with their *continuous* power ratings, because those are usually so much lower than their peak power that the marketing departments would much rather advertise the peak, and then just not say anywhere which one it is, and never publish the continous rating. Or else, if pressed, say that it is peak and for how long, so they don't get too many attempts to warranty-return units burned up by trying to use them at that peak for continous duty.


That said, there *are* some motors that actually get labelled "continous duty", on their nameplate. Just not usually outside of industrial motors of various types.

There is also "treadmill duty" which is usually better than "peak" power rating for it's accuracy as a judging method, but it is still not a continuous rating *and* it means different thngs according to different manufacturers, apparently.

If it doesn't say "continous duty", meaning that you can essentially run it at that power output for the expected lifetime of the motor, as long as you keep it's temperature down to the max spec'd one for that power level, then I would always *assume* they are listing *peak* power for some generally unknown period of time (specifically, until the motor gets beyond it's max temperature rating, if it has one, or until it's hot enough to damage components in it, if it doesn't).

You'll be safer with such an assumption, even if it is not entirely accurate.

 

[dogman dan]

The variables always left out are time, and ambient temperature. I find most of the moderate wattage motors I've tested can handle full power for about 45 minuites when its warm, say 90F. After that, having a temp sensor is a good idea. When really pushing a motor, like a 13% grade hill, then time to get pretty hot might be just a few minuites.

In less hot conditions, say 80F and under, then the motor will get hot but not overheat. It will reach an equilibrium where it doesn't get hotter unless climbing a steep hill.

These observations were made on brushless motors, a 750 watt atoema, and a 350 watt fusin gearmotor. My 5304 clyte takes a lot longer to get hot. Brushed motors seem to get hot a lot faster.

A real good thing to know would be the difference in time to get hot for a given motor kit when using 36v, and a higher wattage at 48v. So far though, I don't have a big enough 48v battery to test this, and now it's getting too cool to do much heat testing. I should get a bit more scientific with my motor testing. So far I've just tried to kill them and reported if they last under normal use in hot weather, at 36v.

 

[Drunkskunk]

Well, the definition of a "1000 Watt motor" SHOULD be that 1,000 Watts is the highest power it can run CONTINUOUSLY under normal conditions, without getting hot enough to damage itself.

Whether any of these manufacturers are building motors that actually meet that definition, is anybody's guess. Maybe they are. Or......?

Testing can find out... if you don't mind taking the risk of frying something you just paid $300 to buy and ship from China.

Remember that with a hefty enough battery and controller, it's possible to shove MORE than 1,000 Watts through one of these motors, without realizing you're doing it. Particularly if you go up a long hill without pedaling and don't back off on the throttle, or something like that.

That would be interesting to have as a rating, but maybe not The primary rating. Here's why I say that.
I have 2 500w motors. A 9c and a Clyte. both pull around 450watts at 36 volts and full speed on flat ground, both go around 21, 22 mph at full speed. Now If I up volt, running higher than rated voltage, the Clyte will handle 1400watts for 30 minutes in 105' weather and have a case temp cool enough to put you hand on and leave it there.
The 9c can't handle more than 800 to 1000 watts for the same time period.
The Clyte gets pushed to 3000 watts often, can stay at that level for several minutes, and doesn't change temp much more than a couple degrees a minute. The 9C starts to get hot very fast at 1500 watts.

Essentially, they are competitive motors, at reasonable and sain power levels. Their ratings make sense because there performance is similar. But rated by their peaks, they are going to be wildly different motors.


I think there needs to be a better way to rate motors for sure.
Perhaps something like spinning a 26" bike wheel with a 10lbs continuous torque load to max speed, then giving it's running wattage?

 

[Little-Acorn]

Don't make the error of mistaking "Full throttle at full speed" for "Full Power". The two are seldom the same.

The data I put up at the beginning of the thread, is for motors run at full throttle at their rated voltage (48V or 36V). But notice that the amps they draw, is pretty small at the highest speeds, and gets bigger as the motor SLOWS DOWN at full throttle. That is, as the tester applies the brake more and more while holding the throttle wide open.

If you get on your ebike, pedal it up to a decent speed, and then open the throttle and hold it all the way open, the bike will accelerate to its top speed on level ground with you on it. But at that top speed, it might not be using its maximum power. If you start dragging your foot while still holding the throttle open at that speed, the bike will slow down, of course... and the amps will probably go UP. Since you're still holding the throttle wide open, you are putting the full 48V to the motor, whether going full speed or dragging your foot and going less than full speed.

But "power" is volts times amps. You are giving it full throttle all the time here, so the volts is always 48V, assuming your batteries are healthy. But at full speed, you may be drawing (say) 15 amps from the batteries. And if you drag your foot while still holding the throttle wide open, you will probably find you are now drawing (say) 25 amps.

So, with no foot-dragging the motor is using 48x15 or 720 Watts. But with foot-dragging, it is going slower but pushing harder, and using 48x25 or 1200 Watts.

Drunkskunk, how did you get your Clyte to use 1400W for 30 minutes continuously? 1400W is about two horsepower. Were you measuring your voltage and current as you did it?

Amberwolf, you're right that it's sexier to list peak power for a motor, than continuous power rating. But note that some of the motors I got manufacturer's data for, show on their data sheet that they will take as much as 38 amps at 48V, which is nearly 2,000W,. But they are listed as only 1,000W motors. No doubt the motor was heating up mighty fast when it was doing that, but as I said earlier, that's Ok if you do it only briefly, like accelerating up to your favorite speed and then backing off the throttle to cruise at that speed. That motor could easily be called a ***2,000W*** motor, from what's on its data sheet. I wonder why they only call it a 1,000W motor?

Watch out for mistaking "Full throttle" or "top speed" for "full power", they aren't the same, by a long shot.

 

[dogman dan]

One way to get full power for 30 minuites would be to ride straight into a lot of wind, or up a steep hill. But to test a motor right would take a device to add resistance on a test stand, along with all the instruments for measuring watts and motor heat.

Also we'd need to define full power. Truly full power would be at motor stalling, a place I like to avoid. But maybe you could define it as, with resistance device added, motor speed is reduced to 5 mph at full throttle? For me, once you hit 10 mph or less, I want to reduce throttle, and pedal more for the sake of my motor and battery. Too much of that kind of full power needs motors and batteries you don't mind ruining.