Motor/Controller watt ratings, what they mean.

[wesnewell]

Unless otherwise stated, They are the max ratings for continuous 24/7 operation. IOW's a motor/controller rated for 1000W can run forever at 1000W without damage to the motor or controller under normal operational uses. This does not mean that is the maximum power of the motor or controller. Many will operate at 5 times or more of the rated value happily for short periods of time. As an example, I have a 1000W rated motor I've been using over 4 years with ~15K miles on it. I use a 72V 1500W controller with a max amp draw of 40A. I run it on 24s lipo at 100.8V hot off the charger. That's a 4032W rating.

 

[John in CR]

Unless other wise stated, They are the max ratings for continuous 24/7 operation. IOW's a motor/controller rated for 1000W can run forever at 1000W without damage to the motor or controller.

Really? How do you explain that without some kind of thermal shutdown protection I could take almost any 1000W motor/controller combo and cause a failure during the first battery cycle?

 

[wesnewell]

Yep. Anybody can do that, so I added under normal operational uses.

 

[cwah]

Its also about motor peak efficiency. You may saturate motor by overpowering it and running it way below optimal efficiency

 

[DrkAngel]

"Motor watt ratings" are a point of sore contention!

Historically, and ethically, the watt rating is the designed motor output at the specified voltage and amperage.
Example:
"500w" Bafang crank drive motor:
Notice! 48V 20A = 960w (input) = Rated 48V 500w (output)

Globally, to comply with legal limits, motors are rated by watt output capability, at a specified voltage and typically with a matched controller.
Various countries limit "legal" maximum motor output to 200w, 250w, 500w, 750w etc.

Sadly, and most dishonestly, some will rate their motors by watt input.
The same 1500w input could output anywhere between 50w- and 1300w+ usable ...

Well ... some claim that their "system" can run 1500w continuous input without overheating, and that is why they claim 1500w.

What actually happens is that ... on optimal terrain, at a maintainable speed, watt input is 1500w, with no overheat.
So they are likely cruising on level good surface road, near peak efficiency ... possibly 80% efficient.
That would be 1200w usable and 300w damaging heat.
The same 1500w input at slower speed, up a hill?, might output 500w usable power and 1000w damaging heat.
To keep the motor from overheating they would have to reduce heat to ~300w or - by reducing watt input to 1/3rd?

So their "1500w" is now a 500w ... by their same reasoning ... ?

The only way to accurately rate their motor system, using their reasoning, would be to rate the motor by its continuous heat dissipation potential ... 300w?

 

[dogman dan]

Note, system wattage and motor wattage are not the same thing.

Motor wattage, is like Wes said. It's a wattage the motor can run at indefinitely, under lab conditions. Presumably under some load, to get the thing to draw said voltage at all. I'm going to guess the lab test load for 500w is comparable to a fat middle aged man sitting up riding a bike 20mph without pedaling. That's pretty easy to do indefinitely.

My experience is that direct drive motors are fairly comfy running up to 4x the rated wattage. Geared motors, more like 3x. That's assuming fairly hard riding. Rider not a 120 pound teen or woman, and riding in a place where hills can easily be more than a mile long. In other words, some reasonable long duration at close to max system wattage.

Re the legal stuff, I thought the EU watt limits were entirely based on motor rating. So 250w rated motors only. Run them on anything you want, but take a small 250w geared motor and feed it 2000w, well the problem solves itself fairly quickly. :lol: Either the rider never really uses all 2000w, and he's no problem, or he hooligan rides it to death in one ride and is quickly removed from the street or trail.

USA state laws are based on system wattage, which is entirely unenforceable.

 

[DrkAngel]

Motor Watt Output "mapped" by current limiting

"Full" Current - Motor of same rated watts will have better acceleration, climbing ability but lower attainable speed.
With sufficient amps, the typical electric motor outputs maximum watts at about 40% of no load speed.
Nearly universally this corresponds to a 50% efficiency!
So, a 1000w input ... outputting 500w usable energy + 500w wasted-damaging heat.
Efficiency, at full throttle, above this speed increases till top speed but motor watt output declines.
This is effective for varied terrain.
The motor has greater output capability as it begins to slow when engaging a hill.


Current limiting - Motor of same rated watts will be more speed capable.
In order to increase efficiency and to reduce weight and cost, the same motor can use lighter windings and reduced amp controller to limit low speed watt output.
Maximum motor output might occur at 80% of no load speed and 80% efficiency.
This will maintain the same top speed as higher amp input but rather than decreasing efficiency + increasing motor watt output when engaging a hill, efficiency decreases and motor output decreases.
Most common with most RC flight motors.
Low speed and hill climbing performance and durability is poor!
Very susceptible to damage from exceeding rated "watts".
Best applicable to eaBikes, eBikes for level terrain or mid-drives with multispeeds.

 

[John in CR]

I nominate this thread as worst thread of the year. The title purports that good info is contained, but useful info is buried by so much inaccuracy that it's useless. The mods should simply delete it.

I also nominate wesnewell as ES's most consistent purveyor of bad info. If the incessant recommendation of using RC Lipo while he ran his virtually unprotected weren't enough, and repetitively telling internet posters they needed to put their location wasn't irritating enough, he has what seems like hundreds of times claimed to have run his motor at 4000W when in actuality his motor hasn't seen 4000W for even 1 second, yet he starts a thread called "Motor/Controller watt ratings, what they mean."

 

[wesnewell]

That's real helpful. Now tell me what's wrong with the info. The watt ratings are exactly as I stated as supported by ISO and other standards organisations.

 

[dogman dan]

I'm sure I run a close second for being wrong.

FWIW, my own experience running a similar 28 mm motor actually drawing 4000w 50% of the time, the ride lasted about 20 min, then the flames shot out the vent holes. The motor was read at 450F. I was running on 110 volts, with 40 amps controller.

So my motor was not "able to handle 4000w". 4000w killed it pretty quick. Off the racetrack, running 47 mph continuous, I was able to run much longer, but the draw was much closer to 3000w continuous, riding on straight roads. The motor draws the full 4000w for a few seconds on corner exits, so it takes a ton of corners to even reach 50% of the time pulling 4000w. A setup that cruised faster could draw 4000w continuous.

3000w continuous for the 28mm direct drive motors is more plausible, with big vents to help cool them. Without vents, you can definitely get away with 2000w on "500 watt rated direct drive motors".

 

[DrkAngel]

People really should differentiate between controller input watts and motor output watts!

Motors are typically output watts rated at specified volts and amps.

'Take off the gloves" - remove these rating limits and "jump outside the box" - input watts instead ... and things get really ... ridiculous!
Even a 24V 750w maximum output motor with a 22mph top speed can draw +2600w!

2607w battery output producing 14w motor output!
From a wimpy 24V!
Takes 1.4min to overheat though ...

 

[wesnewell]

I created this to point people to the meaning of the ratings and that they aren't the max the motor or controller can take. The example was just that. Had i known it would be nit picked to death, I would have stated it differently. I've now fixed the example to accurately reflect the data. if that's not good enough for you, I can just delete the example. The actual meanings of the ratings is and was already accurate.

 

[John in CR]

I created this to point people to the meaning of the ratings and that they aren't the max the motor or controller can take. The example was just that. Had i known it would be nit picked to death, I would have stated it differently. I've now fixed the example to accurately reflect the data. if that's not good enough for you, I can just delete the example.

You still don't seem to understand that neither your motor nor your controller ever saw 4000W, not even for 1 second.

The actual meanings of the ratings is and was already accurate.

"Inaccurate" is the correct word. While some motors are rated at their continuous duty output power, those generally aren't the motors we use on our ebikes, no matter how often some ESers claim a motor's rating is it's continuous power rating. At the other end of the spectrum, not even the most optimistic vendors rate motors at the charger cutoff voltage X max battery current. Of course that doesn't stop you, and the only positive thing I can say about that is at least you didn't multiply the top-of-charge voltage by peak phase current like some people erroneously do.

The fact of the matter and what DrkAngel was trying to get at is that motors are rated in several different ways. Other than as a general comparison of ebike motors of similar construction the power ratings aren't very useful, so I won't go into the details.

To complicate things even more, controllers are rated in different manners too.

 

[wesnewell]

My post is totally accurate. if you can't see that, then you're dumber than I thought or you have some other motives. I didn't take into account for component efficiencies because they will vary considerably depending on many factors. But 100.8V times 40A is 4032W. What gets to the motor will be less than that of course, again depending on controller efficiency, wire size, etc., and even the ambient temperature. That's why nit picking my example is just plain stupid.The manufacturer rated wattage on motors and controllers labels should always be the continuous operational wattage under normal use. It should never be anything else unless otherwise stated.

 

[amberwolf]

The watt ratings are exactly as I stated as supported by ISO and other standards organisations.

And if all these ebike and RC motor companies actually followed any of those standards, their specifications might be comparable to each other...but I don't know that they all do (or even that any of them do, consistently).

Most likely there are some that do--but I doubt that the typical hubmotor or middrive or RC-motor manufacturers rate their motors that way, and even if the manufacturer of the motors do, the resellers and rebranders of them don't necessarily even follow what the manufacturer said it could do. (some do, some don't).

I don't know what percentage do and don't, or any particular ones that do or don't, but given how many different ratings seem to have been given for what amounts to the same motor design/construction by different places, they can't all be right.

 

[DrkAngel]

I'm sure I run a close second for being wrong.

FWIW, my own experience running a similar 28 mm motor actually drawing 4000w 50% of the time, the ride lasted about 20 min, then the flames shot out the vent holes. The motor was read at 450F. I was running on 110 volts, with 40 amps controller.

So my motor was not "able to handle 4000w". 4000w killed it pretty quick. Off the racetrack, running 47 mph continuous, I was able to run much longer, but the draw was much closer to 3000w continuous, riding on straight roads. The motor draws the full 4000w for a few seconds on corner exits, so it takes a ton of corners to even reach 50% of the time pulling 4000w. A setup that cruised faster could draw 4000w continuous.

3000w continuous for the 28mm direct drive motors is more plausible, with big vents to help cool them. Without vents, you can definitely get away with 2000w on "500 watt rated direct drive motors".

Varied efficiency at differing speeds necessitates that any input watt rating must be meticulously qualified by volt, amp, speed, rpm, terrain, grade, duration etc. - etc. - etc.
4000w input @ 47mph might output 3000w of motor power and 1000w of damaging heat (75% efficient)
4000w input @ 15mph might output 1000w of motor power and 3000w of damaging heat (25% efficient)
and
100V 40A (4000w) likely produces much less damaging heat than
50V 80A (4000w) from same motor ...
etc.
So, simply rating by input watts seems meaningless >> inaccurate >> useless >> ridiculous >> etc. >> etc. >> etc. ... IMO!

 

[999zip999]

What matters is my motors melting ? My new 28mm melted at 3,200watts after 20 minutes. Here wear I need the science of John's hand to check for motor temp. I need to go down and cut that hand off and wire it up for motor temp. Shit might as well get both hands as I need a battery temp monitor. LOL

 

[John in CR]

My post is totally accurate. if you can't see that, then you're dumber than I thought or you have some other motives. I didn't take into account for component efficiencies because they will vary considerably depending on many factors. But 100.8V times 40A is 4032W. What gets to the motor will be less than that of course, again depending on controller efficiency, wire size, etc., and even the ambient temperature. That's why nit picking my example is just plain stupid.The manufacturer rated wattage on motors and controllers labels should always be the continuous operational wattage under normal use. It should never be anything else unless otherwise stated.

The only motive is to expose that you are not the authority that your thread title purports, so hopefully not a single member follows your bad advice. Yet you still you total accuracy when there isn't any. Well, you did get the multiplication correct, but that was probably aided by a calculator, and the numbers are wrong anyway. Wrong numbers aren't the issue since anyone can make a mistake, but the inability to understand they are wrong is an issue, which is highlighted by the fact that you are still sticking with the erroneous 4000W+ claim. I'm even giving you the benefit of the doubt regarding current, though it is suspect, as is anything you post.

That leaves only voltage, and until you understand why multiplying the cutoff voltage of your charger by your controller's current limit produces an invalid result there's really nothing to discuss, and it's not nitpicking. You have to at least get to a reasonably correct input power, before introducing output power to the discussion, and your lack of distinction between input power and power output is a glaring omission. First however, you have to walk before you can run, though this is a case of learning to crawl before walking. Please demonstrate your understanding by explaining why I can say with certainty that no part of your ebike system has run at 4000W, not even if talking about input power, not even for one second.

Hopefully the mods will let you off the hook and view deleting the thread as a mercy killing. Motor and controller ratings is a difficult enough subject to turn into a discussion useful for new people, because even manufacturers and vendors often can't get it right, much less be consistent. Having the blind guy start it gets off on the wrong foot...I'm sorry if "the blind leading the blind" isn't PC anymore.

 

[John in CR]

What matters is my motors melting ? My new 28mm melted at 3,200watts after 20 minutes. Here wear I need the science of John's hand to check for motor temp. I need to go down and cut that hand off and wire it up for motor temp. Shit might as well get both hands as I need a battery temp monitor. LOL

It wasn't the hand itself, but the comparative measurements the hand took regardless of their lack of fine accuracy that lead gave me enough general understanding of my system that I could avoid a thermal failure. That cargo bike is still running, and the motor still factory sealed with no temp sensor installed, though it's probably been years since I felt the motor for heat. :lol:

It turns out that the single biggest factor in running the power that motor sees without heat failure has been the 20" OD wheel, but like most you don't want to hear that.

 

[999zip999]

It's funny how going up a grassy hill or wet sand will heat up a motor. Just that type of motor stall.

 

[John in CR]

It's funny how going up a grassy hill or wet sand will heat up a motor. Just that type of motor stall.

What's even funnier is that for about the same price I can have greater acceleration and greater top speed pushing a much heavier load up the same hill or across the same sand using a stock motor, and have no heat worries at all.

 

[999zip999]

I must look like a bicycle as I live in So.Cal next to the beach going 38mph is crossing the line. Plus I run it with homeless motif so not to get stolen. I can't go with the franken cycle look John.
I was talking about the 28mm I'm have a 3,000 5t as does wesnell 4t. I would like a lighter 30mm DD . I can only go so fast as they would end my fun.

 

[dogman dan]

Yeah, deep sand can really strain and heat a hub motor. The quickest I ever melted motors, it was riding with the rim underground. Not enough power to handle the resistance of that buried wheel.

No coincidence the edgerunner, ODK, and others that look exactly like a bike run a 20" wheel hubmotor. Well, those that aren't already moving on to a mid drive anyway.

Also no coincidence that my latest street bike build takes advantage of the 20" hub motor. Thanks John, I knew you were right all along. I nearly went 20" on the last bike, but pure laziness made me keep it 26". Mostly because of not wanting to bother with re lacing my 5000 series motors. And, I needed to do a few thousand miles of test riding the EBK stuff last summer. I'm still sold on 26" wheels for off road, riding around on rock staircases.

Next, on to road testing the same motor kit, on a 20" rear wheel cargo bike. Already obvious it runs better, but won't be doing the over heat test up the mountain till next spring, when it gets warm again.



Back on topic, its a 500w rated motor. But with 22 amps controller and 48v (56.4v top of charge) it runs about 1000w peak briefly. Because of the slow wind, it only runs more like 400- 600w on full speed flat ground cruise of 20 mph. So not much risk of overheat with this combo.

But really, this frame deserves a 50 mph motor.

Backing up to Dark Angels post about my "4000w" race experience. I was exiting those corners above 25 mph. But with no way to measure it, I'm still pretty sure that I was making 1000-2000w of heat for that brief moment exiting the corners. Then by 45 mph on the straights, the motor was running much more efficient, and likely only making 1000w of heat. Ever put your hand on a space heater? Imagine one inside your hub. This 500w rated motor stood somewhere between 3000-4000w of input to the controller for more than one second. But it was not lasting long being used at that level. I don't know what my one mile lap time was, but 11 laps did er in.

I have melted down a 500w geared motor, 10t ,on 1200w potential. (26" wheel) But it took a steep hill 3 miles long, and a trailer full of water to make that happen. 450 pounds of total weight. The motor was stalled down to 6 mph when she blew. So that test obviously had too much weight for the motor, and power level. it's possible the motor could have done it with more power, but more likely what was needed was a 20" wheel.

The exact same test, using identical controller, but a 28mm dd motor passed with flying colors. Oh, it was plenty hot at the top of the mountain, but opening the motor later revealed shiny golden windings. The geared motor had black cooked windings, and the halls had actually melted to the point of grinding to tiny pieces in the can.

 

[999zip999]

The magic hand simple as it sounds, just have to pull over for the magic hand test. But it's a lot hotter inside.

 

[John in CR]

I only did that way back when I was using motors from the factory that holds the Chinese patent for the design copied and used for the generic parts motors you guys so commonly use, 9C, Xlyte H25xx and H35xx, MXUS, Cromotor, etc. Instead of using the magic hand I use magic motors now, whose much higher efficiency (both overall efficiency and peak) means they don't make enough heat to cause concern unless you push them up to extreme power. eg At 100A the motor on my daily rider only makes heat in the copper of 160W. Do the same on your precious 5t motor and you get literally 10 times the heat created in the copper, 1600W. That's with the motor at ambient, so add 20-25% to mine to reflect copper losses at operating temps, but add 30-40% for yours since yours runs much hotter. That's why with my simple cooling mods I can run my motor at 27,000W peak input with no heat concerns whatsoever, or at 15kw in stock form.

To bring things back around to topic, I also have high efficiency hubbies with 3kw and 2kw factory power ratings, and because they're smaller you can cut back their power potential compared to HubMonster by about 1/3 and 1/2 respectively. Of course, following my guidance is needed to achieve similar results, but since it's easy to have a lesser load than this ebiking beached whale, solid performance without heat issues is far easier.

For some reason you guys prefer to follow the Pied Piper and pay more for what I view as Chinese junk in comparison, and then use weak or outright invalid excuses to continue the same pattern instead of exploring outside the box. eg It's not that my motors need a smaller wheel than common ebike motors. Mine will run the bigger wheels far better. An accurate view is that the lesser DD hubbies need a smaller wheels than I'm able to run given the same load and terrain. As far as weight goes, MidMonster weighs the same as a Cromotor and has the same power rating, but MidMonster has some easily trimmed excess weight and has higher power potential due to lower copper losses and lower iron losses, which are what give it greater efficiency. Why bother with facts though since anecdotes seem to be preferred?