Most Efficent Motor at 20mph with capability to hit 40mph+

[mvly]

I am planning a ebike touring trip (>300 miles) soon. I just don't know when and where yet.

I want to know what is the most efficient motor for the trip.

I want to max out my distance travel ability per Wh.

So far this is what I know from having 2 motors (BMC V3 and HS3548).

According the CA, the BMC is able to get higher speed and do it more efficiently compared to the HS3548 at any given speed even though the BMC V3 bike.

Is there any other bike out there that can allow me to go up to 40mph while still the most efficent at 20mph?

I am assuming that the BMC V3 would be the best candidate? Is there another other more efficient motor out there?

Thanks,

 

[Kingfish]

I have used the 9C 2806 hub motor to reach close to 40 mph in the past. This year I switched over to the Ebike-Kit Disc hub (supposed to be 2806 equivalent but it might be closer to a 2807) and I was able to hit 42 mph on a flat with my 2WD at 63V/24A-Batt/60A-Phase @ 120%. On my road trip, the 2WD version ran extremely well in the 23-28 mph range, lending impressive torque for hill climbing. Figure that I was hauling 100 lbs. of LiPo, the bike, trailer, and I weighed close to 450 lbs. if you can believe the figure provided by an Oregon Weigh Station.

The problem with hitting 40 mph is that you probably won’t be able to pedal fast enough; I had a pretty steep ratio of 53-11 and even so I was flogging myself above 34 mpg. Also power consumption between 26 mph, 33 mpg, and 40 mph nearly doubles at each increment. Factor in headwind; when you get above 33 mph you will create your own and this is where you’re aerodynamics will come into play; try to minimize drag as best as you can with body coverings. My small front faring allowed me to pick up 2 mph to my top-end. :wink:

Cheers, KF

 

[dogman dan]

By the time you slow to 20 mph, on flat ground all motors will be pretty efficient. I've never seen any difference at slower speeds worth worrying much about, unless it was for an efficiency competition.

But a fast winding motor able to go 40 mph on less volts will be horribly inefficent on steep hills. So if you want real efficiency on hills, you need to screw the 40 mph idea and build a bike dedicated to climbing hills efficiently and going at most 25 mph on 48v.

An 8x8 9c would be a good choice, and if the rocky mountains are involved, even better to use a 6x10 on 48v.

Two motors would do the trick. One slow winding gearmotor in front, and a fast winding gearmotor in back.

 

[Hillhater]

... or you could think outside the "hub motor" box .. ! :wink:

 

[John in CR]

No motor is its most efficient at partial speed for a given voltage. That doesn't mean the system as a whole can't be its most efficient at 20, because the aero drag increases geometrically with speed. If you want the best efficiency at both, then you need a motor with multiple gears. Our controllers do a pretty good job of imitating lower voltage with partial throttle, so you don't give up a lot by slowing down.

For a road trip I think it's better to make sure you're properly set up to be able to make the steepest climbs at the load you'll carry, and still be able to attain the top speed you want on the flats. Partial throttle can give you the economy you want for the long stretches of flat road.

 

[Pure]

... or you could think outside the "hub motor" box .. ! :wink:

+1 If you are looking to get the max distance traveled per Wh then RC motors are the best bet.

 

[SamTexas]

+1 If you are looking to get the max distance traveled per Wh then RC motors are the best bet.

Why is that? What makes RC motors more efficient?

 

[Pure]

I'm not sure of all the technical reasons as to why they are more efficient, just they are. Then there is the added benefit of being able to use them with the gears on the bike.

 

[Toorbough ULL-Zeveigh]

Then there is the added benefit of being able to use them with the gears on the bike.

plus don't forget to include the benefit of added losses that come free of charge with gearing to help reduce the efficiency.

the world record for efficiency is a hub-motor, full stop.
thus far, none of the cognoscenti will dispute this.

otoh the most efficient motor one can actually afford, well, that's where the shadow falls.

 

[amberwolf]

I would actually say "it depends", because if you use a hub motor and ride in stop-and-go traffic with few stretches where you can actually get up to any appreciable speed, but still must have it setup so that WOT gives you high torque for quick startups, as well as high speeds for the few stretches you do get to speed, it may not be as efficient overall as using a motor that runs thru the gears to be able to keep the motor closer to it's higher RPMs where it's not using as much current to produce the power output needed at various speeds.


If you do not need to worry about those stop-and-go conditions, and only compare them over long stretches at higher speeds, it is quite possible a hubmotor would be more efficient than a thru-the-gears setup.

But under stop-and-go conditions, it'll probably depend greatly on how long you can sustain higher speeds, and how often you must stop-and-go with startups of high-torque and power usage, for whether the hub would be more efficient or not.


I hope to be able to test this on my new bike build, by running my 9C 2807 first as a front hub on my commuter route for a while, and then running it as the frame-mounted motor driving a NuVinci hub that automatically adjusts ratios for best motor efficiency based on current usage and speed, on the same route for the same number of trips.

 

[dogman dan]

Efficiency for a hubmotor is all in the winding. My best Wh/Mi numbers have come with a very slow winding, then run at 72v to be able to reach 25 mph. Why? All my hubmotors use just about the same 600w when going 25 mph. But the motor optomized for climbing steep hills spends the least time in the winding up to speed part of the ride. So as it speeds up, it gets to top speed for a given throttle position quicker, and makes heat less. Less heat= less wasted wh.

If you do decide a hubmotor, the best compromize may be a 2810 9c or similar speed in another brand. Then run it at 72v 20 amps. It's a very efficeint winding, but likely you'd only see about 30 mph.

Gearing would be the best way to combine being able to controll the throttle at 20 mph, and getting up to 40 when you want to. A 40 mph hubmotor is usually hard to ride slow because of the lowest throttle position being a lot of watts.

 

[Pure]

Then there is the added benefit of being able to use them with the gears on the bike.

plus don't forget to include the benefit of added losses that come free of charge with gearing to help reduce the efficiency.

the world record for efficiency is a hub-motor, full stop.
thus far, none of the cognoscenti will dispute this.

otoh the most efficient motor one can actually afford, well, that's where the shadow falls.

Sorry I fell asleep at the wheel on this one.

I'm actually referring to several posts I've read on here, (Don't ask me to find them, but I know I wasn't hallucinating) where people with RC dives have reported massive distance per Wh compared to what most see one hub motors. I always assumed it has to do with the fact that the motor being able to use the gears of the bike, has the advantages of being able to stay in it's sweet spot for efficiency where with hubbies we are stuck to constantly having to rev up to that spot.

 

[itchynackers]

FYI-
My rear 9c 8x8 motor on a 4115 fet averages 14.7wh/mile no pedaling, upright riding, flat terrain, 200 watts.

My front 9c 9x7 motor on a 4110 fet averages 12.1wh/mile no pedaling, upright riding, flat terrain 200 watts.

My front 9c 9x7 motor on a 4110 fet averages 10.7wh/mile no pedaling, tucked riding, flat terrain 200 watts.

 

[LI-ghtcycle]

Lots of motors can be made to meet these requirements, however, in real world use, only the better designed set-ups will be able to be efficient at all at 40MPH, and just as big a concern as what motor, type of motor, or battery technology, is drag.

As soon as you are going 15 mph+ drag accounts for more watts than you would ever believe with out seeing the numbers. You could take a very slippery aerodynamic bike and run less than half the watts needed to achieve 40 MPH as a typical bike.

However, it also really depends on when and where you are going 40MPH, and how long? If you're only going to use that in emergency, then just make your goal to do 20 MPH as efficient as possible, and IMHO, unless you're on a closed course race track or other nearly non-stop use with little or no hills, anything lacking more than one gear is going to suffer tremendously in efficiency.

Granted if you're going to be full throttle 90% of the time, gears make little difference, but since you are going on a trip, and presumably it's not one of the flattest areas in the world with little or no hills, and you will not be stopping often for traffic, the motor isn't going to be as important as the battery and controller supplying it.

Most of us will never be able to take a trip where hills & traffic aren't involved, so gears win efficiency, but if you get a drive train with multiple failure points opposed to something as simple and elegant in design as a well designed hub motor, who cares how efficient you are if you're broke on the side of the road while the less efficient hub motor rider waves as he rides by.

Here is a good list of people with E-Bikes listing their respective bikes and the efficiency of their set-ups:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=6615

 

[mylittlepony]

Hey mvly, I made this thread to try and answer such questions. You can't see the motor type directly but if you look a the spreadsheet data you can see more info.

Cheers

 

[999zip999]

30 mph is a more reasonably number and when riding you can see the landscape without tears coming from your eyes. 26mph is a real number.

 

[Grizzlybear]

no brainer - twin Pumas on 48 volts