MAC/BMC maximum continuous watts?

Considering these motors are fairly similar, what's the maximum safe continuous wattage these can be run at fairly reliably?
I realise that the harder you run them close to their max, plus road conditions, all play a part in their demise, but maybe 15,000 miles sound ok?
I would expect the gear mechanism to need replacing, but would the main motor survive?
Also, would the maximum rated power vary between different motor winds?

alfantastic said:

Considering these motors are fairly similar, what's the maximum safe continuous wattage these can be run at fairly reliably?
I realise that the harder you run them close to their max, plus road conditions, all play a part in their demise, but maybe 15,000 miles sound ok?
I would expect the gear mechanism to need replacing, but would the main motor survive?
Also, would the maximum rated power vary between different motor winds?

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Wattage level for reliable operation has come up before as here between knoxie and nonlineartom:
Re: Mac10t verses HS3540 on 1600 watts
http://endless-sphere.com/forums/viewtopic.php?f=3&t=40958&p=598979#p598977

I think I have read Cell_man write approximately the same watts before.

The motor rating.

Or, till the motor reaches an equilibrium temperature for the continuous wattage you are pulling that particular day, in that particular days weather.

That's about as cut and dried as you can say it. However, quite a few more watts can be run untill the motor temperature reaches whatever you are calling the stopping point. It may not be continuous at all, but it works out that way if your battery runs out before the motor overheats. I don't know about gearmotors, but 1500w will almost never damage a dd motor that is run at 15 mph or more.

I wouldn't hesitate to run 48v 30 amps on a Mac, if I ever get one.

Really, it's not a how many watts question in the least bit. It's a how hot can your run continuous question. That is more cut and dried for sure. Keep a motor below 200F and you are really unlilkely to see any damage, not even browed windings.

How many amps the MAC/BMC motors can take continuously will vary based on wheel size, winding, and voltage.. no easy answer to that question

I've had no problem running 35-39mph on 15S with an 8T in a 26" wheel for 30 minutes at a time, with pedaling on mildly hilly terrain.
2600w peaks, 1000w-1700w constant is fine.

The MAC/BMC motors are hard to melt, but you can do it climbing very steep grades for long periods of time with >1500W constant.

Keep an eye on the motor heat and you'll figure it out. I'd say this motor is good for 30-35mph reliably, going off my experience.

Deleted..........

I like my MACS!

8t 15s lipo 26" wheel and I can't tell what the controller is set at but it's less than 50a as I have done in 2 clutches when the power is too high. Heat hasn't been the problem as I ride mostly under 1000wats which is faster than I should. 2500w on WOT and it tapers off quick when it hits 20 to less than 500w, 1200 or so for 30+.

i have had a hard time getting a smooth controller setting since we can't read what is in the controller after it's been flashed. One MAC is smmoth from 0 to 40 and the other I can't get the same way, YET. I am writing down my # as I try them, the list is getting a little long.
So stay under 45a controller and the Mac/BMC should live a long time.

I still love my MAC!
2 MACS, 1 BMC V1, 2 BAFANG's, 1 CUTE and 5 DD's in the stable.
Boy am I glad I can't count.

Dan

I run 42a battery x 95 phase amps ( 2.25-ish battery phase amp ratio ) on a cell_man EB3 controller. Very smooth start! have not gone through a clutch yet, but blew through the original white gears after a year of use immediately after i tried running the MAC on 4kW.

It's been a great motor, i think i've had good luck because i've ran it juust below the breaking point.. :lol:

In the past 3.5 years I've owned 5 BMC motors (2 BMC V3, 2 BMC V2-speed, and 1 BMC V2-torque) and have racked over 28,000 commute miles with them. My favorites are the V2-speeds. I've never had a gear or clutch blow out on me, with any of my motors. I think I'm able to get good long, reliable use out of these motors because I use them primarily for commuting and I don't abuse them nor pump too much power thru them.

While riding on my long commutes I mostly cruising and only putting 700-1100watts thru the motor. When I hit steep hills I can crank the power up to 2000watts for for up to half a minute or so but then back it down to below 1300watts for fear of overheating the motor. I've always wanted to put a thermo sensor in these motors so I know for sure when I'm in danger of overheating but I never did.

Worst failure I ever had with these motors was a bearing on the side cover failed, scrubbed and seized. That was on one of my V3 motors that had about 8,000 miles on it when it failed.

Ilia of ebikessf has a lot of experience with the BMC. He recommended a max of 1500W for the one he sold me.

It boils down to efficiency and dissipation. At low speeds with high torque loads the efficiency drops and they can only dissipate a few hundred watts, so as efficiency drops the max safe power also drops.

So far I've run 1,000 watts max and the motor has not warmed up much at all.

It takes time for the heat to propagate out of these motors, so judging the temperature from the outside is not very accurate.

I have ran my BMC v3 at 1600W. But I made sure I was always above 25mph. Anything slower, I drop it to 1000W and pedal assist. This only happens when I am going up a hill. So far 2K miles and no problems other than broken clutch due to the potholes and going over them at 35mph. I say keep it around 1.5KW max and keep your speed above 25mph and you should be fine if you have a V3 or V4S or V4C BMC or the 8T or the 6T MAC. If you have the V2T or the V4T BMC and 10T MAC, then maybe you can have it a bit higher, but I would keep it below 1.8KW for sure.

If you want high power go direct drive. I also have a HS3548 and I put 3.7KW into it and it is fine. I even run it 2KW continuous and no problem. Same rule about keeping the motor moving applies here. If I go slower than 25mph, I drop the power to 1.3KW and pedal assist.

Yes, I know this is an old thread.

Wanted to add a little info from the Grin Tech web site that indicates the answer is 1,000 watts.

The MAC and GMAC are identical as far as how hot they'll get when riding along under steady state conditions.

Here is a link to where I got the info: https://www.ebikes.ca/product-info/gmac.html

8 years later, we can add this info as well.

Mostly, with the 500w rated geared hub motor class, it depends on the load. In general, you can feed them 22 amps of 48v, or about 1200w, provided the grades are under 10%, and the weight of the entire system including the rider is under 300 pounds. This results in about 1000w continuous, when going up longer hills. They tend to pull more like 800w, if its flat, at max speeds.

This is the number E bikekit came up with, after I did testing to destruction with 400 pound loads.

It boils down to this,, not how many watts you are feeding it, but how many watts are you wasting into heat, after you overload it. Don't overload it beyond 300 pounds, and 1200w limited by controller amps is no problem. If the terrain is pretty flat, it can even have 400 pounds and get away with it,,, or,,,, 1500w.

But yeah, if you pull trailers,,, limit to 1000w makes a lot of sense. 48v 20 amps controllers, or 36v 30 amps. And then find a way around that hill.

I can add that I'm 310lbs, and the bike is 65lbs. I have the controller (KT w/35a max) set to limit my max wattage to about 1200-1300w at WOT.

I spend a lot of time in a coastal area with some pretty big hills, big enough where a 1500w direct drive would be totally out of steam at the top while pedaling as hard as I can in 2nd or 3rd gear. With a swap to the MAC 12T and NO other changes made, the MAC 12T powers right through this same scenario, and not only that, battery life has gone from 25 miles or so reliably, to 35 miles. Yes, the MAC is working great.....

That shows that my test conditions, were as bad as it gets, while your environment allows a bit more weight.

I was doing my motor tests to destruction in 5% humidity, which greatly hampers motor cooling, and 110f weather. And my hill was 3 miles long, at 5% to 8% grades. In my test, 400 pound load melted the motor quite quickly, running 1000w continuous. It was lugging down to 5 mph pedaling hard, too slow for a 10T motor.

It easily made the top of the hill at 300 pounds though. So EBK set a 300 pound limit on warranty for their 500w geared motor, similar to a MAC 10t.

Good thought! My normal conditions:
Coastal area I'm in is north central Florida Gulf Coast, and I darn sure won't ride in 110 degree temps! Anything much over 90 will have my bike parked. MUCH higher humidity levels though. Hills aren't 3 miles either. Maybe a bit steeper, but never more than a mile long, generally much less, like a half mile. Think of an area that may have been sand dunes at one time, now covered with grass, pine and oak with a few palm for good measure (to remind you that you are in Fl.). -Al

Yeah, I darn sure don't ride in 110 either. But I did for the testing. I live in a good place to kill motors. hot desert, and a mountain pass starts 3 miles from my driveway. So I could explore the absolute upper limits for EBK, giving them conditions far worse than most. Steepness matters though, most of the warranty claims on kits came from west virginia, where ever hill is 10% or more.

Rode a few days ago with my 12T MAC (52v)...I weigh 210 lbs and my bike weighs 70 lbs. Some moderate hills in the NW corner of FL. Perfect day for testing but not for comfort...ambient temp was 95F.

With a 29x2.6" (752mm OD) Maxxis Ikon on the wheel with the 12T MAC, I was running 140-145 degrees F for a motor temp. Changed to a Vee Chicane 26x3.50" (723mm OD) and my temps dropped about 10 degrees...130-135 degrees F.

My only point is the diameter of your rear tire can make a big difference as well as the voltage (48 vs 52) and the winding of your motor.

I'd like to try a 10T MAC with a 26x3 Duro Beach Bum (703mm OD) if I can ever find a 10T Freewheel Rear MAC motor...EM3ev just stopped selling them and I am having troulbe finding one anywhere besides Alibaba. I'd like to stick with the Freewheel version of the MAC because I have several rims already laced to MAC freewheel hubs.

I wouldn't hesitate to run 48V / 30 amps on a MAC

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I agree with dogman, this is the data that has been accumulated by dozens of posters. The true max depends on the application. If you are on flat land, then the motor will draw max amps for a couple of seconds, and as soon as you attain top cruise speed, the amps drop down and simply maintain speed. You could probably go to 1500W often if you give the internal parts time to cool off between accelerations.

If you do all of the bad things, you must lower the max amps.

A. Tall wheel like a 29'r
B. Use max amps on a long uphill
C. heavy rider + cargo
D. A, B, C at the same time.

I recommend a 24-inch wheel, and a 2.4-inch tire to make the tire the same outer diameter as a common 26-inch (if mounting the hubwheel on a 26 frame). Doing this may require a frame with a rear disc brake.

MAC is a geared hubmotor, and it has a poor heat-shedding path. Ferro-Fluid does not help geared motors shed heat, only DD hubs. For a geared motor, you have the option of adding a coffee-cups volume of ATF, or drilling ventilation holes in the sideplates (which causes its own problems).

The plastic gears act as a mechanical fuse. If you get the motor hot, the max torque before damaging the gear-teeth goes down, so....max performance is attained when the gears are cold at the beginning of a ride. If you want to use more than 48V X 30A = 1500W on mild hills (or flatter terrain), then buy a spare set of gears when you buy the MAC. Your hills/body-weight/wheel-diameter are not like mine, so my max power on a MAC is not the same as your max power. Get an internal temp sensor, so when you fry the gears, you will know what your true max power is.

Been running my 12T mac at 140-145C = 293F. Ambient temp was 95 "F". My mistake on the temp units above. I lubed the MAC gears with Mobil SHC 100 many miles ago.

Never had a problem with the gears or the clutch. My temps may be a little higher than others because I ride standing up at all times due to arthritis...so my frontal area is a little bigger. When I model my set up with the Grin Tech Motor Simulator...I use 264 lbs, "Fatbike Upright" for drag, and a 2% incline...that matches the steady state motor temps pretty close to my actual riding conditions and the steady state temps I see.

Justin says the MAC can handle 1,000 watts steady state: https://www.ebikes.ca/product-info/gmac.html. I think that is a little conservative plus it is the amperage you need to worry about as opposed to the wattage. Since heating is proportional to Amperage squared X R. But if we use 50v as an average for 48v and 52v batteries, you can say 20A max continuous for a MAC for the most part...and it gives you a little bit of a safety factor IMO. But like Spinningmagnets posted...there are a lot of variables that can influence temperature A.-D. above :thumb: .

For short periods of time, I have run 50A Battery and 130A Phase current through my 12T MAC using a 14s/52v battery with no adverse effects (the clutch never slipped and the gears held up just fine). Based on that experience, I'd expect the motor windings to be the first thing to go so a temp sensor is very important for any MAC IMO. I have my Cycle Analyst programmed to roll the power back starting at 140C and to shut the motor down completely if it reaches 150C. I'd recommend lower than that for most until you know how your temperature rise behaves.

Liquid cooling will drop the motor temps about 30C steady state and works great as long as you can keep the liquid in the motor and not get anything slippery on your brake rotor :lol: . I gave up on liquid cooling due to leakage and no back brakes...now I just go to a smaller diameter wheel/tire if my temps start to run too high and a mid drive (BBSHD) for off road .

There are a lot of variables that affect the temperature of a MAC so my experience above may not be the same as what others will experience...proceed with caution would be my advice :wink: .

Iv'e got a 10T on 52V. I throw 60 Amps at it and so far havent had eny issues with that. Been ridning with theese settings for well over 600 miles. Bying a new controller to put eaven more on it.
Im 264lbs and bike is about 60lbs.
29" inch wheels.

I've heard from others that MAC can take 2kw continuously if the weight is below 275lbs but since the previous poster is 260 + additional weight of 60 at 52V 60A is 3100W with 600 miles on it, but is that 2500W+ very rarely or all the time?

Krohnk said:

Iv'e got a 10T on 52V. I throw 60 Amps at it and so far havent had eny issues with that. Been ridning with theese settings for well over 600 miles. Bying a new controller to put eaven more on it.
Im 264lbs and bike is about 60lbs.
29" inch wheels.

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Weight only matter when going up hills. Would need a weight/grade ratio.

markz said:

I've heard from others that MAC can take 2kw continuously if the weight is below 275lbs but since the previous poster is 260 + additional weight of 60 at 52V 60A is 3100W with 600 miles on it, but is that 2500W+ very rarely or all the time?

Krohnk said:

Iv'e got a 10T on 52V. I throw 60 Amps at it and so far havent had eny issues with that. Been ridning with theese settings for well over 600 miles. Bying a new controller to put eaven more on it.
Im 264lbs and bike is about 60lbs.
29" inch wheels.

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It only pulls full amps til i hit ~30 kmh, then it tapers off. Like first 2-3 second. When im at top speed, about 55 kmh (on the flats) it pulls ~25 Amps.

And that should not fry your motor. It could if you stopped every few feet and started up again, or were in a race on a go kart track, where you would slow from top speed to corner about 15 times per one mile lap.

But change that to you are towing a trailer up 5% grade, and the total weight load is 400 pounds, and your motor will fry in about 20 min. Or a bit longer, if your hill is not 20 min long in length.

Less than 300 pounds, the motor will be easily able to maintain 15 mph or so up a 5% grade, and run efficient enough to avoid an overheat. But you are already over 300 pounds total load.

If you start putting 500w of waste heat into that shell, it will quickly melt inside. I've melted motors while the outer case was cool enough to put your hand on it.

Get a 500w halogen light sometime. Plug it in and put your hand on the glass. See how quick it gets too hot to touch. You get into a full throttle but the speed is less than 10 mph situation, and you may be putting 1000w of your power into heat.

Its not usually the wattage that melts a motor, its the load on it. But that said, you can still overkill a winding to the point where optimal conditions like you describe still waste a lot of power. In general, much more than 1500 watts into a geared motor is flirting with disaster. And what do you get for it? If not in an actual race, why put your motor into potential for a melt down?

You want that bike to take off faster, or pull more load up a mountain, put 30 amps each into two motors. Otherwise, the smart thing to do is limit your amps to 30 through that motor, or get a big DD motor designed for more.

Those geared motors are rated at 500w. 3x that works fine if the load is not excessive. 6x that is not wise. Fast wind or slow, its a 500w rated motor. And you want to run more into it? The motor will however briefly, be making a lot of its watts straight into heat now, with 3000w. Pointless to force more into it. Too much power for the wire resistance gets you an oven heating element, but being copper with varnish on it, it don't run very long as an oven.

Choose a slower winding ONLY for designing a bike to run slower. 10 t is about optimal for a 26" wheel, giving you sub 30 mph top speeds on 48v. If you design for 15 mph, then a slower wind could be chosen, but only if above 15 mph is dangerous for that type bike. for example, tadpole adult trikes should never go much faster than 15 mph.

But after all that, go ahead and put 120 amps into it. Its fun as hell melting motors. I just got to do it a lot with free motors. I was melting them on purpose, to get limitations for warranty on motors for E-Bikekit.

Krohnk said:

markz said:

I've heard from others that MAC can take 2kw continuously if the weight is below 275lbs but since the previous poster is 260 + additional weight of 60 at 52V 60A is 3100W with 600 miles on it, but is that 2500W+ very rarely or all the time?

Krohnk said:

Iv'e got a 10T on 52V. I throw 60 Amps at it and so far havent had eny issues with that. Been ridning with theese settings for well over 600 miles. Bying a new controller to put eaven more on it.
Im 264lbs and bike is about 60lbs.
29" inch wheels.

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It only pulls full amps til i hit ~30 kmh, then it tapers off. Like first 2-3 second. When im at top speed, about 55 kmh (on the flats) it pulls ~25 Amps.

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Krohnk...IMO you are pushing it with 25A continuously. Steady state, that will exceed 150C. If you never exceed 25A it will take about an hour to get the motor to 150C but it will eventually get there and with some starting/stopping/hills you may get to 150C quicker than an hour.

23A continuously will get you to about 135C...stead state.

Justin at Grin Tech has run a MAC at 150C on his dyno and I have run mine at 150C for about 30 minutes while out riding so that is why I use that figure. You may be able to go hotter but once you exceed about 140C, things start to get away from you quickly as far as temperatures if you hit a hill and/or stop and start a lot.

If you are running a Cycle Analyst, you can program it to roll the power back at 140C or so and to shut the motor down if you exceed 150C...those are the settings I use.

You can exceed 150C for a very short period of time without doing any damage but that is the highest temp I can safely say will not do any damage.

You can also go way over 25A when the motor is cooler for short periods of time...I am running a 12T MAC and I have my controller set for 60A Battery and 140A phase current and have never had any issues with my gears/clutch/motor BUT I also don't exceed 150C for motor temps.