Ebike Motor Power Curve Comparison Chart: BOSCH, Yamaha, Shimano, Brose

[Alphbetadog]

Yep, it's not a lie, just an "alternative fact-based" graph...

 

[Sonoboy]

There is clearly something wrong with the graphs in post#1. The Bosch CX motor outputs zero watts at 120 rpm. The graph shows it as 400W. If you extrapolate the graph forward, it would max out at 160 rpm, when in practice, it maxes out at 120 rpm. Somebody got their data seriously wrong. I don't believe that any of those motors make power past 120 rpm. Only the Yamaha one looks approximately correct.

I think what the graph illustrates is the actual electro-mechanical nature of the drive before software limits are imposed by the controller. The limits may vary due to region, local speed limits, etc.

 

[Hugh Jardon]

I think what the graph illustrates is the actual electro-mechanical nature of the drive before software limits are imposed by the controller. The limits may vary due to region, local speed limits, etc.

I don't think it's that. When an electric motor can run much faster than it's working range, it becomes inefficient in it's working range. Motor speed is a very important characteristic. You need it to match the range where you use it for best efficiency. It wouldn't make sense to use a motor capable of 160 rpm at 80 rpm. Have a look at some efficiency curves for motors, and you'll see what I mean. The high efficiency is biased towards the top of the rpm range. see here.
https://evmc2.files.wordpress.com/2014/07/motorcurve.gif

If that curve represented the Bosch motor, it would have an efficiency of 50% at a cadance of 80 and 40% at 65, which is where a lot of casual cyclists work.

 

[Trail Cruiser]

I don't think it's that. When an electric motor can run much faster than it's working range, it becomes inefficient in it's working range. Motor speed is a very important characteristic. You need it to match the range where you use it for best efficiency. It wouldn't make sense to use a motor capable of 160 rpm at 80 rpm. Have a look at some efficiency curves for motors, and you'll see what I mean. The high efficiency is biased towards the top of the rpm range. see here.
https://evmc2.files.wordpress.com/2014/07/motorcurve.gif

If that curve represented the Bosch motor, it would have an efficiency of 50% at a cadance of 80 and 40% at 65, which is where a lot of casual cyclists work.

True, back in the early days of ebikes somewhere in the 2011-2012, Bosch already spent enormous research and development investments. And they already focused on energy efficiency where the motor rpm (using the proper gear reduction) is matched to the human cadence (also at it's most efficient rpm range). This naturally stretches the mileage for each charge of the battery.

 

[Trail Cruiser]

Ebike Motor Power Curve Comparison Chart. This test result was leaked recently and has been a topic of conversation in the ebike world for the past few weeks. It shows the power curves of Bosch Performance, Bosch Percormance CX, Shimano, Yamaha and Brose motors.

I was at a dealer event for Moustache ebikes last month in France and this chart was referenced. Good data. I understand it was a leaked chart from one of the motor manufacturers.

Joe

View attachment 17593

All 3 makers Bosch, Shimano, and Brose (except Yamaha) have their gear reductions matched to efficient human cadence range (60-110 rpm). The plateauing of Brose's power is more of a function of the battery's output modulation (capped at 350 watts) while the other s are allowed to perform at full motor capacity. Less watts fed into the motor equals better mileage for Brose.

Yamaha is over geared and is focused more at the lower half of the human cadence range resulting to higher torque at lower rpm, and capitalizing on the "zero cadence" or full torque from a standstill. Using a smaller motor, it attains comparable torque output but at the expense of losing it's operating range in the higher cadence (running out of steam). Torque, power and efficiency goes down beyond 80 rpm.

 

[Sonoboy]

I don't think it's that. When an electric motor can run much faster than it's working range, it becomes inefficient in it's working range. Motor speed is a very important characteristic. You need it to match the range where you use it for best efficiency. It wouldn't make sense to use a motor capable of 160 rpm at 80 rpm. Have a look at some efficiency curves for motors, and you'll see what I mean. The high efficiency is biased towards the top of the rpm range. see here.
https://evmc2.files.wordpress.com/2014/07/motorcurve.gif

If that curve represented the Bosch motor, it would have an efficiency of 50% at a cadance of 80 and 40% at 65, which is where a lot of casual cyclists work.

The confusion can be traced to the e-bike community, and human nature, wanting to shorten everything in our language, often at the loss of clarity. While the bikes are described as having 'motors', in actuality (with one exception) they employ gear-motors. The exception are direct drive hub motor bikes, like a Stromer. These are great for speed and simplicity, having only two main parts, but they sacrifice hill climbing ability for that speed. All other hub-mounted and mid-drive units run the electrical motor in its most efficient range (which is too fast for our use) and then use a gear reduction system to slow this speed to a useable range. A byproduct of gear reduction is increased torque, which aids hill climbing. So, for example, Bosch geared its speed line to achieve 45 kph, but its torque is 67 Nm. Conversely, the CX line is limited to 25 kph, but has a greater torque output of 75 Nm.

The referenced chart you linked concerns a motor alone, without a geared reduction. The first chart in this thread shows data for the various gear-motors.

 

[Hugh Jardon]

Bosch themselves say that the CX motor maxes out at 120 rpm. So there's no way that it produces 400w at that speed. That's the main point. The 120 rpm is the crank speed. it's irrelevant what the actual motor speed is. The shape of the efficiency curve will be the same. The only thing that changes with gearing is the scale at the bottom of the graph.

 

[Trail Cruiser]

Bosch themselves say that the CX motor maxes out at 120 rpm. So there's no way that it produces 400w at that speed. That's the main point. The 120 rpm is the crank speed. it's irrelevant what the actual motor speed is. The shape of the efficiency curve will be the same. The only thing that changes with gearing is the scale at the bottom of the graph.

There is a big difference between claimed figures to comply with regulations and actual "peak" numbers which all the motors are capable of. It seems that Brose is more compliant to regulations. On the plus side, Brose is more likely to have superior mileage per battery charge.

 

[Alphbetadog]

...Brose is more likely to have superior mileage per battery charge.

I have both emtbs with the Bosch CX and Brose motors and this has been exactly my experience. Typically I only get about 18-24 miles on the Bosch, whereas in the same terrain I have gotten over 43 miles and still had a bar of juice left.

 

[E-Wheels]

I have both emtbs with the Bosch CX and Brose motors and this has been exactly my experience. Typically I only get about 18-24 miles on the Bosch, whereas in the same terrain I have gotten over 43 miles and still had a bar of juice left.

Which of the drives do you believe is the most reliable and if you had to choose one which would it be and why

 

[Alphbetadog]

Which of the drives do you believe is the most reliable and if you had to choose one which would it be and why

Both are a lot of fun, and have worked flawlessly so I can't comment on whether one in more reliable than the other. But Bosch seems to have more developed service dealers than Brose. In my state (AZ) there is no Brose servicing dealer. However, despite that, if I could only have one emtb I would chose the Brose powered Bulls. Much better range, silent, and just seems to give a more true mountain bike experience.

 

[Trail Cruiser]

Which of the drives do you believe is the most reliable and if you had to choose one which would it be and why

I think both Bosch and Brose are equally reliable. I recently had a chance to ride both Bosch and Brose powered Bulls ebikes back to back at a newly opened store (Sleek Ebikes) at my area at Westchester County, New York. The store owner mentioned about the "whine" from the Bosch motor. I kind of like it, since I get subtle auditory feedback from the motor, to let me know how hard it's working for me. The Brose seems to be imperceptable, no noise, no vibrations, and no sudden "push" whatsoever. So it all depends on the rider's taste. I would probably choose a Bosch powered ebike on my next purchase.

 

[Larry Ganz]

I took my recently updated Haibike FS CX powered bike and spent most the ride in EMTB mode. I initially really liked it because it made it a little more "intuitive" like my Brose powered Bulls. Was nice just to leave it in "automatic" rather than actively change the power setting depending on the terrain and desired assist. However, like Ravi and maybe others have reported, it does suck the juice much more than my usual changing modes (I previously rode mostly in TOUR, and just occasionally go into TURBO on steep climbs). I found myself 13 miles into the out-and-back ride with only 2 bars left. It was mostly flowy singletrack but with several good serious climbs. Got a little concerned with only having 2 bars left so I put it in ECO for the ride back. Made it with only 1 mile of range left, for a total ride of 22 miles. I have the 400 watt battery. So my takeaway is that emtb is fun, and for casual rides less than 20 miles, or somebody new to emtbs is trying out my bike, but to maximize range I think it is best to manually change modes.

So, will you go back to "riding mostly in TOUR and just occasionally go into TURBO on steep climbs"? And if so, how much range do you expect to get riding the old way vs with the new eMTB mode?

 

[Alphbetadog]

So, will you go back to "riding mostly in TOUR and just occasionally go into TURBO on steep climbs"? And if so, how much range do you expect to get riding the old way vs with the new eMTB mode?

Hi Larry, it turns out I didn't have the new eMTB software update, but rather the previous ver. 1.6! I conjured it up in my head that there was a difference, perhaps because previously I rarely ever used "SPORT" mode. It the past I would just use TOUR, but when I needed some extra assisted would bump it up two clicks to TURBO to get the big hit. SPORT seemed like a waste of time as it I noticed early on that it typically only increase the range over TURBO by one mile. So sorry to say I was "all wet" on my previous report, and I don't in fact have the eMTB mode!

 

[EddieJ]

There is a big difference between claimed figures to comply with regulations and actual "peak" numbers which all the motors are capable of. It seems that Brose is more compliant to regulations. On the plus side, Brose is more likely to have superior mileage per battery charge.

This a work in progress, and ignoring the extreme peak, you can get a general idea of peak output from a recent ride that completed using a Bosch CX motor with 50wh battery pack.




Watts V altitude.



Watts V speed of climb.

 

[Sonoboy]

Hi Larry, it turns out I didn't have the new eMTB software update, but rather the previous ver. 1.6! I conjured it up in my head that there was a difference, perhaps because previously I rarely ever used "SPORT" mode. It the past I would just use TOUR, but when I needed some extra assisted would bump it up two clicks to TURBO to get the big hit. SPORT seemed like a waste of time as it I noticed early on that it typically only increase the range over TURBO by one mile. So sorry to say I was "all wet" on my previous report, and I don't in fact have the eMTB mode!

To quote an old Seinfeld episode: "Well, it's not like spottin' a toupe". Bosch makes it kinda hard to get the version number to display, and when it does, what is the latest version number? They need to better inform the end user about firmware updates.

 

[Bicyclista]

This a work in progress, and ignoring the extreme peak, you can get a general idea of peak output from a recent ride that completed using a Bosch CX motor with 50wh battery pack.

View attachment 17834


Watts V altitude.

View attachment 17832

Watts V speed of climb.

View attachment 17833

Very cool graphs, @EddieJ ! It shows that an electric motor can produce many times its nominal rating. Now, can your software show a smoothed average?

And, why should we ignore the extreme peaks? If sometimes they are needed, and the motor can deliver them without overheating, I welcome them!

 

[Larry Ganz]

Hi Larry, it turns out I didn't have the new eMTB software update, but rather the previous ver. 1.6! I conjured it up in my head that there was a difference, perhaps because previously I rarely ever used "SPORT" mode. It the past I would just use TOUR, but when I needed some extra assisted would bump it up two clicks to TURBO to get the big hit. SPORT seemed like a waste of time as it I noticed early on that it typically only increase the range over TURBO by one mile. So sorry to say I was "all wet" on my previous report, and I don't in fact have the eMTB mode!

No problem. I usually just leave it in SPORT when off road (don't have eMTB update), because I see very small gains going up to TURBO mode from SPORT, and yet it's still quite powerful when I need it so I usually don't get stuck on easy and intermediate trails.

I can see where eMTB allowing up to 300% assist can come in handy at times if I was riding more difficult trails, while allowing the bike to throttle down the pedal assist when the rider isn't leaning hard on the pedals. When some people are riding difficult trails and leave it in TURBO the entire time, I can see where eMTB can save them some battery life when full power isn't needed.

On tarmac I'm usually okay with ECO and TOUR, unless I have a long steep climb ahead - then I bump it up for a short period until I can get my cadence up enough to maintain speed in TOUR if possible. If I had eMTB mode then I couldn't limit power assist to only 200% when 120% in TOUR isn't enough, so I'd worry about either losing range (vs SPORT) or about getting less of a workout because of the higher assist level.

 

[Trail Cruiser]

I've been using a Bosch loaner bike for the past 2 weeks. I can go much further in a touring configuration with the Bosch Peformance than with the Yamaha PW, despite a smaller battery size (400Wh for the Bosch versus 500Wh for the Yamaha) . In the higher assist levels I find the difference between the drives to be somewhat subtle, but when you switch into ECO or Tour the Bosch is much less tiring than the Yamaha drive in ECO and ECO+. Because of the higher and more supple cadence on the Bosch you can drop into ECO mode much more frequently. I'm getting 15% more range whilst touring with the Bosch despite have 100Wh less battery. You have to be fairly strong to ride the Yamaha in ECO mode (won't even speak about ECO+), whereas the Bosch is much more manageable.

If you have fast legs and like to keep your cadence above 80 rpm, then Yamaha is not for you. Above 80 rpm, the torque, power, and efficiency in Yamaha all goes down.

I learned that the hard way on my TranzX mid drive that also has similar operating range. Now I use a cadence meter so I can optimize the integration between the motor and my own pedal effort.

 

[Trail Cruiser]

Actually the Yamaha works great for me aroound 100 RPMs. But just not in the lower assist levels...

Same as my TanzX, good assist at 100 rpm but in the PAS 4 only (PAS 1 up to 80 rpm, PAS 2 = 83-84 rpm, PAS 3 = 88-90 rpm, PAS 4 = 100 rpm) I rarely use PAS 4 since I want longer mileage on my battery.