Looking for 250W option

Hello ES,

I've been reading here immensely, wrote a few short answers, and planned my first ebike.

I can't find the information I am looking for. Maybe I haven't searched for the right terms.
I am looking for suggestions for a motor for a tow truck. On most of my ways I can sustain a cruising speed of 27kph to 32kph. Not so in my home town: I live in Germany in a rather hilly area. 10% for 5km is an actual road sign on my way home. I can do this. But at 10pm this is really hideous. With my trailer and my two kids this is the exact opposite of fun.

conditions:
rear hub. I rode my wife's mid drive. Don't like it.
250W: typical is 15A @ 36V. You get away with 18A @ 36V. I guess 12A @ 48V is legal, too.
Top speed between 20kph and 30kph.
10sp cassette, Disc brake, 135mm width, 4kg max

So. Now is question time:

1.) Is a hub at this power level on these hills actually a good idea? Should I reconsider a mid drive?

2.) Is there a difference between a 12T MAC @ 48V, 12A and a 10T MAC @ 36V, 15A? I think I'm missing something here.

3.) Are there any Direct Drives to fulfill my ideas? Is this a valid consideration for 250W?

4.) Is there a performance difference between a heavy motor and a light motor (let's say an MAC and a Q100C) if the setup is as identical as possible (same top speed, same voltage, same current)?

Thanks in advance!

Ford

250w in a rear hub, up 5 k of 10%, towing a heavy trailer, stands a very good chance of melting the motor. If you pedal hard enough, it might only get very very hot. But for certain, it will turn at an rpm up that hill that means half of the power, or more, will got straight into heat.

You may hate that mid drive, but it IS DEFINITELY what you need.

Or 2000 w, in a very large DD hub motor.


1000w would do it, in a low rpm dd motor, if you run it in a 20 inch wheel. But still, way less efficient than any mid drive.

Not that that this is any help, but ... this seems to come up so often, I have to wonder if it's really due to some natural law, or if it's the usual consumer market herd behavior - market can't demonstrate demand for a low speed hub, because no one will offer a low speed hub in the absence of a demonstrated demand? Like would it be theoretically possible to develop a half speed gearing for installation in a MAC motor?

Why are you fixated on such low power levels for your needs and requirements?

You need a mid drive setup, like the BBSHD or the Cyclone 3000W. As long as you are a responsible e-bike rider, there is no need to be fixated on 250W, 500W or 750W or whatever power levels you are fixated on from some lame ass law that is put in place.


Some examples of the irrationality of dumb laws....like low watt levels....

Why does an 120lb person have to have the same power levels as a 375lb person?

Why do companies (like Ford or Ferrari) sell vehicles capable of 280km/h in North America, where the maximum speed limit is only 110kph anywhere on the continent?

Why are there speed limit signs, yet the majority of people still break the law by going 5 or 10 over the limit, yet still drive, in a safe manner?

Why are there stop signs and red lights, when people never come to a complete stop, yet they still do not get into an accident because they are looking around to not cause an accident?

Why do I fixate in 250W?
Because we Germans have no sense of humor and always obey the laws, no matter how pointless.
WRONG
Because in case of traffic collision - no matter whose fault - my insurance won't pay if I have been riding an illegal vehicle.
Most get away with 36V and 18A. 350W?

MACmotors build a 16T MAC on order. We even have a seller in Germany who has it in stock. Is this worth a try at 36V and 18A?

I think I should clarify my weight requirements:
Trailer: 16kg
Kids: 30kg
Myself: 94kg
Bike: right now about 13-15kg.
Adds up to 140kg plus vehicle.
My bike is a 28", 29", 700c, whatever you call it.
I didn't know I was pulling an extreme load…

Why I disliked my wife's mid drive:
It is a Bosch motor. 100% proprietary. I distrust proprietary systems.
It is impossible to ride switched off and it is really annoying to go faster than the motor. If the motor stops at 27kph, you will ride no faster than that. It feels like I am suddenly going up a hill although it is a flat section at the river Rhein. Without a motor I ride the same part steadily at 35kph.
I really fear destroying the motor when I stand up or kick too hard. I usually replace my BBs after 1500km.
It felt like it was kicking the bottom of my feet. Weird.

Let's say I go a little illegal at 500W. What are my options?
36V 25A or 48V 18A?
BBS02, TSDZ, extremely slow DD, 16T MAC?

Suddenly this is getting more difficult.

Ford Prefect said:

1.) Is a hub at this power level on these hills actually a good idea? Should I reconsider a mid drive?

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Mid drive works much better on hills. There is a 2 speed (2 gear ratio) hub drive out there you might want to look at; the Xiongda. I believe it is sold as a 250 watt motor so that would work well for you.

2.) Is there a difference between a 12T MAC @ 48V, 12A and a 10T MAC @ 36V, 15A? I think I'm missing something here.

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12T means 12 turn. Increasing the number of turns lowers the motor constant (= slower) and running at a higher voltage speeds up the motor, so increasing voltage while reducing the number of turns keeps you at about the same speed.

3.) Are there any Direct Drives to fulfill my ideas? Is this a valid consideration for 250W?

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1) Consider the Xiongda.
2) Most motors can take ferrofluid to improve cooling. Consider that.
3) Consider going up in motor size but using the same controller/battery; if the motor constant is about the same then the performance will be about the same but you will have more heat dissipation available. For example the Crystalyte NSM or SAW hubs might work. They are good to about 500 watts and are still relatively small.

4.) Is there a performance difference between a heavy motor and a light motor (let's say an MAC and a Q100C) if the setup is as identical as possible (same top speed, same voltage, same current)?

Click to expand...

If the motors have the same motor constant, the same gearing (i.e. none for a direct drive) and are on the same size rim, then performace between a heavy and light motor will be very similar - except the larger motor will run cooler.

Ford Prefect said:

MACmotors build a 16T MAC on order. We even have a seller in Germany who has it in stock. Is this worth a try at 36V and 18A?

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I think so. I consulted the Motor Simulator - https://www.ebikes.ca/tools/simulator.html. It has no 16T, so I chose 8T and a 14 inch wheel. Looks OK. 260Kg total load and 10% grade, 100W human power, 14 kph for 52 Wh/km.

So you aren't going far at that rate, with an ordinary battery, and efficiency is not great at 79%, but it doesn't overheat. If you can go down a wheel size, that's helpful.

IMHO going a bit illegal is the same as going 5000W illegal, but you are on the right track, you'd be much more happy with 500W then the lame 250W route.

https://www.ebikes.ca/learn/power-ratings.html

The reason we don't have a simple power level for each motor or kit is that there is no standard or even consistent way to provde a numeric 'watts rating' for a motor system. You can see the exact same motor listed as 250 watts, 500 watts, and 1000 watts by different vendors, and there is a valid justification for all those number. That makes a vendor or manufactuer's watts rating in isolation a fairly pointless figure for choosing or comparing setups, and we're not keen to particiate in that kind of arbitrary numbers game.

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There is NO SUCH THING as a "rated watt" or any standarized method for rating ebike motor power.

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The actual power output of a motor depends entirely on how heavily it is loaded in a given situation and the maximum electrical power that the controller lets flow into the motor, it has little to nothing to do with a rating anywhere.

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Yeah, and I should add - I don't remember what the wattage was, for that MAC 8T 14 inch wheel simulation, but it was certainly way over 250W. (Actually there would have been several numbers to choose from, including power delivered (?) by the motor, and power consumed from the battery, which are of course not nearly the same at 79% efficiency.) The inputs were a 36V battery and 20A controller, which nominally would be pretty close to 750W, but that's the bottom of the scale for the simulator. It's my vague impression that all this may be more or less OK - the rated power isn't necessarily an absolute limit - but I really have no idea. You'd have to verify that the system can actually deliver enough watts to get your hub up to a reasonably efficient speed.

Ford Prefect said:

I am looking for suggestions for a motor for a tow truck. On most of my ways I can sustain a cruising speed of 27kph to 32kph. Not so in my home town: I live in Germany in a rather hilly area. 10% for 5km is an actual road sign on my way home. I can do this. But at 10pm this is really hideous. With my trailer and my two kids this is the exact opposite of fun.

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I think you should look at middrives; you will get a lot better performance out of it because you can shift gears to get low RPM / high torque when you need it, and high RPM / low torque when you need that.

The hills are the big catch with a low power system, with the load you need to pull.

mid drive for this job

No, its not difficult. Its just you want to avoid a mid drive, even though a mid drive is the ONLY solution that has any chance at all of hauling you, and two kids in a trailer, up hills using only 250w.


So how do you do this on pedal power only anyway? You do it by killing yourself putting out 500w for as long as you can, and putting that through the low gears of the bike. You need to do the exact same thing with your motor, put that 250w through the low gear of the bike, and then you will still put out that 500w, but for a shorter, easier to handle time period.


ONLY with 2000w, are you going to fly up that hill at good speed, and medium effort.

RE motor ratings. There are motor watts ratings, but no particular standard for how that is done. Or rather perhaps, no standard at all for what the marketing boys will call stuff.

The motor ratings are based on applying a medium load to the motor, and seeing how fast it gets all hot. So a Mac, or the typical direct drive bike hub motors, they are rated 500w. Ooops, yer illegal already. AND, your load is way way beyond medium. So your watts in a hub motor will only melt the motor. (too low rpm under too much load, 15 min and meltdown)

The smaller geared motors are often rated 300w,, oops, illegal. However, these smaller motors can be paired with a controller putting out 250w, and then close enough, legal. But your load, will melt one down. For sure!

Furthermore, are you sure 250w is your limit? I thought most if not all in the EU, had a "speed ebike" class that could have more watts. Still need a mid drive though. Why? Because your load is nowhere near medium when you pull that trailer. You'll just melt a 750w motor/controller setup, such as the Mac on 36v. Too much load with those kids.

Get a 350w mid drive, and claim its 250w if you get into court. It will get you up the hill if your rear sprocket is big enough. Better still, get a 750w mid drive, and run the speed ebike class, if you can.

dogman dan said:

The motor ratings are based on applying a medium load to the motor, and seeing how fast it gets all hot. So a Mac, or the typical direct drive bike hub motors, they are rated 500w. Ooops, yer illegal already. AND, your load is way way beyond medium. So your watts in a hub motor will only melt the motor. (too low rpm under too much load, 15 min and meltdown)

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Sure - at the low RPM you'd get with the usual options, it's bad. Am I wrong about the MAC 16T he says he can get?

I'm assuming that the number is a linear gear ratio scale, such that the 8T turns twice for every one turn of the 16T, so I did the simulation on the 8T with a 14 inch wheel, which would be say 1055mm vs a 700C wheel at 2173mm circumference, so about half. At 20A x 36.6V, this setup is supposed to cruise along at a fair enough clip at just under 600W motor power, 79% efficient, never overheating.

If that adds up, wouldn't this be an option for boatloads of riders like him who have no apparent interest in cruising the flats under motor power, but just want help on the hills? 9 mph up a 10% grade, geared motor with no internal resistance, relatively light weight compared to the 3000W setup that's popular here?

OK. I get it. A hub isn't for me. Just reading knowledge (pun not intended) about mid drives now.

Power Levels in the EU:
There are several options to get a powerful ebike in the EU. EU Vehicle Class L1e. Sorry, only German words. No idea how they are called internationally.
S-Pedelec: 45kph, 500W, PAS mandatory.
L-Mofa: 20kph, 500W, PAS not mandatory
Mofa: 25kph, 2kW, PAS not mandatory
Scooter: 45kph, 4kW

The standard Pedelec (25kph, 250W, PAS) is actually not a class of motorized vehicles but a bicycle. Which means you can do with it whatever you could do with your bicycle. Like changing tires, changing handle bar, changing pedals, upgrade your cassette…

Building your own S-Pedelec is ill adviced. You need a Einzelabnahme which at least doubles the costs. L-Mofas and Mofas are theoretically easy to get legalized. But you are not allowed to pull trailers with passengers. Which is because these classes only exist in twostroke combustion mode. You don't want your kids to breathe whatever your engine produces.

Back to middrives. Is the Bafang BBS02 still state of the art?
Is it possible to change the bearings of the crank's axle when they are worn out?

I would go the "350W" route. Should I order 36V18A or should I order custom programming 48V15A?

I don't need flying uphill. Just a little help from a little friend.

There is a legal 25a bafang bbs02.Bafang made it special from this man in Norway.The nice thing aout the bbs is that you can get any parts you need for repairs.
This is the only man selling them now i belive.I have bough 4 from him.Its powerful and have a throttle that only works if you pedal.
You can contact him on fb

https://www.facebook.com/strommenelsykkel/?hc_ref=ARTFieGi53CdaxXUgaBpFpfO8v0hdM5JC9Xbp_UHva9XQE8XkG5qATqt3PzbUkF4sfA&fref=nf&__xts__[0]=68.ARAlrOHPgnwiTNF52YYfD9EPMb9ANEplyOTgLeBUD5JhI8cTh_AE1OF25IN9eQlUiZ_rKzrzkISbEPP5AXz0blYkXAOsCKE0cxLpxGRyGxxFn0pAQ_Rt8BXd2kv2GVttmFdxVQOKnqBUytLq0sHZrqlq_QUxuCbtt0ng3jTOnvc0KPGk3LaX83h75iTg5RO_FCaeYzoQrNvwknY_U0cn-K-WHJrOycYB3jCXKAj7tW82_1g1Pcnx5WewE9J0b6yXLQQS0bu54nse5C7jXW7BjQKeCg0TyiOA4GL1P3YDIzS_5-9DXrzVhkf1-5dEWmoWfm7rA-9i7iRxDivCmUq4o39G9g&__tn__=kC-R

This should help you a ton!
https://endless-sphere.com/forums/viewtopic.php?f=31&t=35048&hilit=holographic#p510365
:wink:

Has to be bike class to tow the kids.. That does make sense. You'll be fine with a bafang 36v, 350w and some fibbing. Cops won't hassle you unless you are flying with those kids I expect. Or call it S pedelec, if towing the kids is ok with one.

Re the 16 turn mac. I don't know what it can do, I have only tested to destruction a ten turn. and ridden a 7 turn. But its not like gear ratios when you change the motor wind. Very hard to understand, and I am still not really educated about motor theory.


But I do know this, changing the turn does not really change the max loads the motor can pull by much. In fact, one of the reasons it will get to the top of the hill cooler with same weights involved, is that the motor actually runs on less power, because of the higher relative to the winding rpm. Hard to explain without getting it all wrong and having guys jump me on my explanation.


But I will stand by this for sure. A 16 t mac will climb better, if less overheating is what you call better, AND the total weight at 300 pounds, or close to it.

Its not going to climb 8% grades with 500 pounds all of a sudden, in 26" wheels. That requires actual lower gearing, hence the many mentions of mid drive for him. If this guy had one kid, we could recommend some other options. But him, bike with motor, trailer, and two kids is going to be over 400 pounds I think.


But change the actual gearing with a hub motor,, meaning 20" wheel, and then you would get away with 400 pounds. On the 16t, or on the 10t. Because a smaller wheel is the only way to change the gearing of a particular hub motor. There are some different planetary geared motors, but again, not for 500 pounds.


So why would you want the 16 t mac anyway.. Simply because you want a slower vehicle. Sometimes this is what you really want.. It might be a trike that gets dangerous above 15 mph, It might be you want to have a slower max speed so that you go farther. It might be that you want to climb longer hills, still with that 300 pound limit, and get to the top with less heating. But it WONT have more torque, or carry more weight up the hill because of the slow wind. Only a smaller wheel will increase the torque, with the same watts going in. You can of course, increase watts till the motor fries. That's easy to do with gear motors.

This forum is mostly frequented by people who like very high power setups, and you can see that in the responses.

A 250W motor can provide a big relief on hills and make things easier going in general. The Bafang MG311 hubs that Grin (ebikes.ca) is selling now are great, I've been commuting on one for 3 years and just got a second one for my cargo bike. If you get the right hub you'll have a good mix of power and speed. I normally run mine at 8A maximum, so I'm derating it by quite a bit, and I still feel like it's a great setup.

A nice advantage of using a smaller hub is that you can also run a smaller battery. I commute with 2 LiGo batteries (~100wh each) and this gives me about 40km range, which is more than enough for my needs. It's a lot nicer to ride with a 1kg battery that lives in my handlebar bag than a 3kg battery strapped to the frame.

The total system that I like:
* Bafang MG311 or MG310 hub. I use the MG311 because both of my e-bikes have internal hub gears.
* Cycle Analyst V3
* Sempu or Thun torque sensing bottom bracket (the Sempu is more responsive, the Thun seems to be more reliable)
* 2-4x LiGo batteries or similar, depending on riding style and desired range
* Controller of your choice (I've used Infineon 15A controllers and the new Grin Baserunner, the Baserunner is worth the extra money)

This provides a setup with great and intuitive riding characteristics, isn't that expensive, will help you on hills, and is easy to retrofit to most bikes. I run with a power assist ratio of 0.8x most of the time, and sometimes turn it up to 1.2x when climbing hills, or 1.6x if I'm trying to get somewhere without sweating (like riding to a wedding in August while wearing a suit).

What this setup will be missing is tons of torque to allow you to use it as an e-motorcycle with a throttle. The German laws seem to be designed to prevent building e-bikes as e-motorcycles anyway, so that isn't a big deal. Riding characteristics end up pretty similar to a mid-line Bosch system, though it is hub drive and not bottom bracket.

dogman dan said:

So why would you want the 16 t mac anyway.. Simply because you want a slower vehicle.
...
But it WONT have more torque, or carry more weight up the hill because of the slow wind. Only a smaller wheel will increase the torque, with the same watts going in.

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OK, thanks for taking a whack at that, this is very interesting to me because I seem to have thoroughly misunderstood the MAC motor grading, both as to what it means and as to the purpose of faster/slower winding.

Of course now that you mention it, I see the "T" stands for "Turns" and not "Teeth". In principle, once you have gears in there, though the gearing may be fixed, it can be whatever ratio they choose, and they could in principle make various motors with gearing for (say) different wheel sizes, etc. And in that case, of course the effect would be very much like a different wheel size. Apparently this principle has nothing to do with reality, however.

On the other hand, simulations do seem to show slightly better efficiency on hills, for higher turn/ slower speed windings. Though looking harder at that, I see it's rarely enough to manage another 1/2 percent grade or another 10 kg load.

Alex W said:

What this setup will be missing is tons of torque to allow you to use it as an e-motorcycle with a throttle.

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Or the tons of torque required to do what he wants, to haul 260Kg up a long 10% grade. The choice between throttle or the more elaborate pedal sensor control is irrelevant.

donn said:

Or the tons of torque required to do what he wants, to haul 260Kg up a long 10% grade. The choice between throttle or the more elaborate pedal sensor control is irrelevant.

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I had missed the weight comment part of his request, so I went back and looked. He has 140kg plus the weight of the bike, so that is in the 160kg range. Remember that he's comfortable in the 90-100kg range on his own, so it's really not a ton of torque requirements. This isn't about having the motor do all of the work on it's own, just being an assist.

Assuming the bike has a 26" to 28" drive wheel I would pick the lowest speed MG31x hub (remember, this is about the max legal for him). I don't think this is the version sold by Grin, most of their hubs have custom windings for a bit more speed. That'll make a big difference when climbing. The hub will stop providing a speed boost pretty early (around 27-28kph), but that is plenty when hauling kids around.

Getting good torque is one place where mid-drive systems make more sense, because they get the benefit of variable gearing. So that would also be a good system to consider. Ultimately I think the best mid-drive systems are made by Bosch or Shimano and it might make more sense to buy a complete bike rather than a DIY conversion.

Alex W said:

Assuming the bike has a 26" to 28" drive wheel I would pick the lowest speed MG31x hub (remember, this is about the max legal for him). I don't think this is the version sold by Grin, most of their hubs have custom windings for a bit more speed. That'll make a big difference when climbing.

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Will it? As noted above, that's what I thought, too (and it's why I chose a slower winding myself on my direct drive hub), but when challenged on that, I went back and looked harder at the simulations, and while I can see slight improvements in efficiency, the big differences weren't there, for hubs with simulation data and different windings. In some cases the faster winding even appears to get farther before it dies.

My cargo bike weighs about 30kg with all of the kid stuff and I ride with a 15kg kid on it. This is lighter than the OPs setup, but closer than a road bike conversion. I live in Seattle and ride up a fairly steep 3km long hill to get to my in-laws house, so this is a regular ride for us. We also have a lot of >10% grade hills (but not 5km long) that I ride up frequently.

I have a 20" drive wheel with the 10.5 RPM/V MG311 front hub and it makes a huge difference in climbing that hill. I used to have a G01 Fast winding (a very low torque hub, 12.5 RPM/V) and it still made a huge difference, but I do prefer the extra torque of the slower MG311. If I were in his situation I would use the 8.5 RPM/V MG311 to get more torque and less top end speed.

The simulation defaults to very low human assist, make sure that you are putting in 200W of human output to have something pretty realistic for an in shape but not strong cyclist. If the OP is already doing these rides with no assist then he's probably got >200W sustained output.

You are right that these hubs don't have enough torque to do it on their own.

Whatever the human input. I wasn't looking for a successful outcome in his scenario, because that's out of the question. I was comparing hub A vs. hub B, at more nearly successful loads. I didn't find a hub that offers more than one winding, where the difference between windings would account for a half percent more grade, or 20 kg more weight; it wasn't entirely clear that one winding was even better than the other at big loads, let alone significantly better.

Myth?

If you look at the G310 hubs with multiple windings you can see a real difference. Here is a screenshot with 100W of human input:


It is silly to look at zero human input for motors in this range, they are only designed for assist applications. 200W is a more realistic number to use for a cyclist in reasonable condition. These motors are pretty low torque and can barely get the bike moving on their own on a grade like that.

I haven't analyzed it, but I think that there is a limit for these applications where putting more power into the hub doesn't help. I could easily see this on my cycletruck where I'd be riding along with the torque sensing system running the hub at 150-200W. I'd floor the throttle (going up to 500W, the limit that I had set) and the bike wouldn't really get any faster and my work wouldn't get any easier. At low wheel speeds there seems to be a limit to how much power you can get out of the system.