New BMC "High Torque" motor V2-T

[cycle9]

Announcement: New high-powered, higher-torque BMC hub motors

We have worked with BMC to develop a new "high-torque" version of their latest high-powered, internally-geared hub motors. This is very similar to the new V2/Thunderbolt/Puma motor (depending on whom you're speaking to, it may be called any of those things), but the new motor, V2-T, has a higher winding count on the stator poles. What does that mean?

This emphasizes torque over speed. That will have two benefits.
- First, for those who have steep hills and/or heavy loads to carry, this new motor will be more efficient for that purpose
- Second, for those who don't need or want their bike to travel at 30 mph @ 36V, this will reduce the top speed to around 22 mph at 36V, and around 28 mph at 48V. For example, this will make it easier to build a bike that complies with some state laws for on-road usage (many states/territories limit top speed to 20mph, though both the law and its enforcement varies widely).

We only have four of these motors on the way initially (to arrive early next week), and two are spoken for. If results are good, we'll get more in mid to late December. BMC is also making them available to other suppliers, though to my knowledge there are only a total of 8 in existence at the moment (someone else will have the other 4). We are building these up in heavy duty wheels using Sun Rhyno Lite and/or Mammoth rims, with double butted 2.3/2.0 Wheelsmith spokes. We're treating the initial shipment as a beta test, and so are looking for a few capable testers. I haven't listed them on our website yet, but will do so in the next week or so. In the meantime, feel free to contact me about it (morgan at cycle9.com). I've attached a few images of some of the BMC motor internals and externals here.

For the technically savvy:
BMC claims the torque will be 38% higher on this motor. But, that really depends on what controller it is paired with, and at what speed the torque is measured. I've been having a great discussion with Justin over at ebikes.ca about what higher winding counts actually mean in terms of real performance (thanks, Justin!). The upshot is that if winding counts are doubled, that does not result in a doubling of torque, due to the motor's inductance. But, as winding count increases, the resistance of the motor is increased, which leads to a more efficient coupling of motor plus controller for lower speed operation. The most efficient case is to have a controller that can produce exactly the amount of current that the motor can accept, without having to go into current-limiting mode. Once we have the new motors in hand in the next few days, we'll measure the resistance and determine the optimal controller pairing from that.

Morgan
http://www.cycle9.com
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[cycle9]

The new V2-T higher torque BMC motors arrived a few days ago. On the outside, they look identical to all the other BMC motors, they use the same shell. We haven't opened one up yet, but they do weigh about one pound more than the V2-S, which is a sign of more copper windings, as we'd expect. Total weight on the motor is 9.0 lbs.

There are presently only 8 of these in the USA, and we have the four pictured here. Three of those are spoken for, with one available for an additional beta tester. One of the four will be sold as lightly-used, since we will do our testing with it here, first. For the beta tests, we charge a bit less than the normal price, with the understanding that since they are new motors, there could be unforeseen problems. We will of course support users with any issues/warranty in the case of any problems.

We'll have some built into wheels early next week, and will report back with further testing results.

Morgan
http://www.cycle9.com

 

[knoxie]

Hi

Yes I tested the same motors about a year ago. what was odd was the higher RPM motors developed the same torque as the lower RPM higher torque motors? very odd so Mark went with the higher RPM motors as they were faster and still performed the same up the hils, There is a post about the test on here somewhere.

Knoxie

 

[Lowell]

Knoxie: That's the exact same motor you tested? If so, that's disappointing to hear I keep waiting and waiting for something new and better to come along... maybe in 2009?

 

[cycle9]

Hi Knoxie:

BMC claims these are "new," and so I wonder what information you have that indicates these are the same that you tried?

Regardless of whether they are truly new or not, they do have more windings. As I mentioned previously, increased winding count sometimes but doesn't always mean more torque - it entirely depends on your voltage, amperage, and controller resistance, which may have confounded your previous testing results.

The ideal situation for torque, for a given controller, is to have a motor that can exactly consume all the current produced by the controller, without any need for current limiting in the controller (and to have the controller with very low resistance). In very simplified (and not entirely correct) terms, if you have a 35A controller, and a battery at about ~50V, then the ideal situation for low speed torque would be motor windings at ~1.43 ohms (derived from R=E/I). But, most controllers will act to reduce voltage and increase current (through PWM), so reality is not quite as simple - it would actually be lower optimal resistance than this.

In any case, the point is that, if you have a motor whose resistance is very low (due to large gauge windings and/or low winding count), then to produce optimal torque, you need to have a very high current controller to power it (and, a battery capable of producing that high current). On the other hand, if you need to limit the current (usually due to battery capability limitations), then having a motor with more windings will produce more torque. This is particularly true for high voltage, lower current setups. I am pretty sure that testing these at 72V will produce a noticeable difference in torque, and I suspect that this will also be true at ~48V, though less so.

One of the things we will be testing is what is the optimal combination of voltage/current to optimize torque output on these. The reason I suspect that is because the "lowly" V1 BMC motor produces more torque at 36V/20A than the V2-S (high speed) at that power level - enough to be noticeable in hill climbing. I actually prefer the V1 on my Big Dummy sports utility bike to the V2-S because of this. However, the new V2-T will accept substantially more power input without getting fried....

@Lowell: The problem with waiting for something better, is that there are fundamental design limitations to hub motors (hinted at above). Increasing windings only has a moderate effect on torque. The only other ways to improve torque are to:
- Increase magnet size (making motor heavier and more expensive)
- Increase stator pole size (making motor bigger and potentially heavier)
- Change gearing. I think the most promise comes from this third point, it could be explored further.

Regardless, I'm pretty sure we can fine tune the controller + motor combination to produce more torque out of these than the high speed motor. But the proof is in the pudding.

Morgan

 

[Jozzer]

Paul is right, the Puma factory experimented with this last year, and there was little difference to the available torque in real world use. After trying both extensivly I went back the faster motor. Efficiency was down a little on the higher torque version too..

Steve

 

[cycle9]

Paul is right, the Puma factory experimented with this last year, and there was little difference to the available torque in real world use. After trying both extensivly I went back the faster motor. Efficiency was down a little on the higher torque version too..

Steve

Steve,
What controller did you do the tests with? At what voltage? And do you know that the winding configuration is the same as the new motor (i.e. same wiring gauge, same number of turns)? I'd like to know the details, because that information is not forthcoming from BMC themselves.

There is another thread here on the forums about the BMC motors. They too have the new hi-torque motor, they say they have tested it, and they claim it has "a ton of torque", though that assessment is not very quantitative.

Anyway, as I explained, the controller/voltage/current parameters all make a big difference in efficiency and torque numbers - more than most people realize. The ebikes.ca hub motor simulator is a great way to explore this, especially by playing with the advanced settings for controller resistance and current limit. The controller makes a BIG difference in how the motor performs. The greater the controller resistance compared to that of the motor, the bigger difference in torque. So, if you compare two higher-resistance motors with different winding counts (e.g. the Crystalyte 4xx series), there is little difference in torque, unless using a high resistance controller. However, comparing two lower-resistance motors (Crystalyte 5xxx series), the torque difference is greater, because the relative contribution to total system resistance is greater for the controller. If the motors you previously tested had the same gauge windings as the V1 motors, but higher winding count, your result would not surprise me at all. The resistance on the standard V1 is already high. But with the new motors, which have much lower internal resistance than previous BMC models due to the thicker wire gauge, I suspect there will be a difference, unless one has a very low resistance controller and very big battery pack.

Regardless of whether it is or isn't the same as the motor you folks previously tested, or whether you paired it with the appropriate controller, we're taking a scientific approach to testing this firsthand. We also carry the V2-S and the V1, so ultimately, our goal is to figure out which one is best for each job, not to just promote the V2-T for the sake of it (if it proves to be a dud, we'll send them back to BMC). I think it would be great if these do have more torque for certain applications (cargo bikes, high voltage setups, climbing big hills), but if they do not, we will not promote them.

Morgan

 

[cycle9]

We have done some initial testing on the new V2-T motor. I'm not one for over-hyping things, but this has some significant acceleration.

We paired the V2-T with a Crystalyte 35A 36-72V analog controller. We tested it at both 36V and 48V with our LifePo4 batteries (tomorrow we'll test 72V). It definitely feels more torquey than the V2-S motor. It accelerates up a hill at 48V that the V2-S does not, and on which the Crystalyte 400 series, eZee, and BMC V1 all struggle.

Top on-bike speed is ~19 mph at 36V and ~23-34 mph at 48V. This is a great motor for someone looking to run a high-voltage, hill-climbing/cargo setup, without wanting outrageous speeds.

We will be doing more quantitative testing and report with rigorous numbers.

Also, regarding the previous posts claiming that they had already tested this motor last year. Today I spoke to the owner of BMC, and he stated clearly that this motor has not been made available before, and that the one you folks tested must have been someone else's modification, or something different.

We may have one more available from the initial lot, depending on whether one of the people on our waiting list decides to go for it or not. More will be coming in for spring.

Morgan
http://www.cycle9.com

 

[Tom]

One of the things we will be testing is what is the optimal combination of voltage/current to optimize torque output on these. The reason I suspect that is because the "lowly" V1 BMC motor produces more torque at 36V/20A than the V2-S (high speed) at that power level - enough to be noticeable in hill climbing. I actually prefer the V1 on my Big Dummy sports utility bike to the V2-S because of this. However, the new V2-T will accept substantially more power input without getting fried....

I have a V2-S and just wondering what your thoughts are re. an optimal combination for that motor. Is running it at 36V going to be sub-optimal from a torque standpoint?

 

[cycle9]

I have a V2-S and just wondering what your thoughts are re. an optimal combination for that motor. Is running it at 36V going to be sub-optimal from a torque standpoint?

The resistance is so low on that motor, that it can easily soak up 35A+ until it gets up to fairly high speed. So, for more low-speed torque on this motor, the best solution might be to get a higher amperage controller/battery combination (maybe as much as 50A, though whether the motor internals can handle that much power over the long term is unknown). Higher voltage would make a difference in climbing speed (power) and top speed, but won't make much difference at the very low speed torque. So, not knowing the details of your situation, I would guestimate:
- If you have some very steep hills to climb, so steep that the motor is near stalling out at low speeds, then go for higher current
- If the motor is doing ok at low speeds, but you want to climb hills faster, you could go for higher voltage. If you go for higher voltage, you may also want to increase the total current capabilities, otherwise it might feel like a step backwards.

Also, another thing to look at is the internal resistance (and hence voltage sag) of your battery pack. This can make a huge difference in low end torque, in particular. Increasing pack size, or putting another in parallel, etc, can help a lot.

If you want to contact me offline, I may be able to help based on the particulars of your situation.

Best regards,
Morgan

 

[Tom]

Thanks, I really am just looking for low speed torque so perhaps the V2-S isn't such a bad solution for me. I am still putting the bike together so I haven't had a chance to test. I have a 36V/20ah ping that I'm going to try first so probably limited to pulling 35-40 amps.

 

[cycle9]

Thanks, I really am just looking for low speed torque so perhaps the V2-S isn't such a bad solution for me. I am still putting the bike together so I haven't had a chance to test. I have a 36V/20ah ping that I'm going to try first so probably limited to pulling 35-40 amps.

I think you'll like it. The V2-S is a torquey motor, just not as much so as the V2-T. Feed it plenty of current and it will be happy. Hopefully your ping pack can do 2C, because at 35-40A, this motor will fly.

 

[cycle9]

We did a face-off of the new V2 motors (the V2-T versus the V2-S) on a steep local hill. I finally got the video edited to a reasonable length, here it is:

[youtube]YuPOj2SkgDc[/youtube]

Based on those tests, the V2-T is definitely better for climbing, by about 20% at 36V, with the margin growing wider at higher voltages. At 72V, this motor was insane in its acceleration. It was like riding a motorcycle, up to its top speed (about 40 mph at 72V). I hit 2500 watts at one point.

Morgan

 

[Ypedal]

Hey ... great work !!!! THANKS !!!!!!!

I may have to put up a few of my X5's for sale.... :?

 

[pwbset]

Great video. Thanks for sharing and comparing.

 

[Doctorbass]

Hey ... great work !!!! THANKS !!!!!!!

I may have to put up a few of my X5's for sale.... :?

I would really love to see that:

-a REAL comparative video about a X5 5305 and a new BMC-Torque motor in the same exact conditions on a hill!

-a REAL comparative video about a X5 5303 and a new BMC-Speed motor in the same exact conditions on a flat road !

I have the 5305... but not the bmc.. :lol:

Doc

 

[cycle9]

Yes, a real comparison would be great. We plan to keep doing tests like this, and will probably get one of the 53xx series Crystalytes in the Spring to do the testing - unless someone wants to loan us one in the meantime for a similar test. (Next time we do it, we will balance the weight of the bikes to be within a few pounds).

I am also (slowly) developing another, easier test method that can be used on a single bike, but provide exact quantitative results.

Morgan

 

[Doctorbass]

Great!

Me, i'll work on a comparaison between a normal X5 motor and a mooded one for this summer.

Doc

 

[dirtdad]

We also just got in the V2-T. I have built mine up with a full suspension mountain bike with the intention of making it off road worthy where high speeds are not very important. All of my impressions are subjective right now. Even with just 36V it handles steep dirt roads very nicely. It is a little noisy at very low speeds, but when it gets up to a cruise on the road it is very quiet. It has a nice pull off the line. On the road it settles in around 18-22mph, nothing too exciting, but great if you want to hover around legal unassisted speeds, climb hills, carry loads or travel off road.

 

[Ypedal]

If it's anything like my eZee motor, going from 36 to 48v puts some pep into it's step !! :wink: ( true of all hub motors i suppose.. )