ElectricMotorcycleForum.com
Makes And Models => Zero Motorcycles Forum | 2013+ => Topic started by: kensiko on October 15, 2014, 02:59:54 AM
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I just saw a graph about the Model S motor efficiency curve, which explain the increased range of the 85D.
What's the efficiency curve of the Zero motor?
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Ask Ryan or Liveforphysics!
Doc
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There's a great thread somewhere where one of the inner circle posted several efficiency curves for (IIRC) the Zero motor, Brammo and even the motor that Mission uses. A little searching should find it. Tons of good information on that thread.
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Ideally for best range you want to be below 4200 RPM as field weakening starts to kick in then. Although it's pretty flat for almost the entire RPM range. If you want slightly more range at a sacrifice of about 30% torque (there's plenty to spare anyway!) you can get a 98 tooth rear sprocket which could help highway range by around 5-10%. It takes a smaller belt and the swing arm needs to come off to install the new belt but I have been running a 98 vs 132 for the last 2 years and love it! Anyone trying to squeeze a little more range for highway trips should try it.
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I'm more interested in efficiency VS torque chart.
Thanks for all your comments, when I have some spare time I will search a bit more. For now many things are going on and I won't have much free time before Christmas.
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No news about this?
I'm really curious also!
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I thought I would resurrect this thread because efficiency came up in the ‘Zero Should Hire a Aerodynamicist’.
So it’s very obvious that the Zero range cuts in half when you drown away at 75 MPH on the freeway. A lot of this is the poor aerodynamics of motorcycles in general, but another factor is electric motor efficiency.
Here are some quotes from the other thread:
How much is energy consumption do to motor inefficiency at high speed and not aerodynamic drag. Gearing could help that.
Almost none; I think the powertrain efficiency is measured about 90%
Electrical efficiency begins to fall away after 3,500 rpm as greater amounts of field weakening are used to extend the rpm range of the motor at the given battery voltage. It will be about 10% less at 5,000 rpm and 20% less at top speed.
Yes, an electric motor is up to 90% efficient, but according to quotes on this forum, efficiency starts dropping at 54 MPH (stock gearing on a S/R).
54 MPH 90%
77 MPH 80%
100 MPH 70%
Another way to put this is, from 54 MPH to 77 MPH wasted heat generation – power that does not even get to the rear wheel- DOUBLES!
It looks like Electric Terry has already figured this out (in post #3) and has went to a smaller sprocket with a practical compromise to torque.
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IYes, an electric motor is up to 90% efficient, but according to quotes on this forum, efficiency starts dropping at 54 MPH (stock gearing on a S/R).
54 MPH 90%
77 MPH 80%
100 MPH 70%
Another way to put this is, from 54 MPH to 77 MPH wasted heat generation – power that does not even get to the rear wheel- DOUBLES!
It looks like Electric Terry has already figured this out (in post #3) and has went to a smaller sprocket with a practical compromise to torque.
Hey Killroy, where are those numbers coming from? I remember seeing a 2D graph of motor efficiency vs. RPM for the Zero motor, and nowhere did it go below 90%; IIRC, it achieved 94% at the sweet spot. I can't find it now, but I'm really skeptical of your numbers. Also, just because the motor is in "field weakening" mode doesn't mean the efficiency is dropping -- in fact, "field weakening" refers to the inductance of the motor coils not allowing peak current to build up as high at higher RPM, so it could very well be more efficient in that mode.
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I quoted Sendler.
I would love to see that graph. Maybe there is some confusion with Torque and Power Curve vs speed.
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A while back, I measured the Range and Power curves for my 2013 DS as a function of speed. As you can see, the data points aren't super tight together, but the method I used to gather them wasn't the most accurate either. Still, it gave me a good idea. More details here: here (http://ptruchon.pagekite.me/wiki/rangevsspped).
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That is a good graph.
Yet motor efficiency is only a small part of that.
What is in the graph is all the motion resistances combined together, motor efficiency and 'hotel loads' like lights, dash, heated grips, which are small.
The main motion resistance are rolling resistance, areo drag including winds, hill climbing and braking.
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I believe the motor efficiency diagram was in a recent presentation video from Zero Motorcycles.
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I believe the motor efficiency diagram was in a recent presentation video from Zero Motorcycles.
In the ZeroCast a couple of months ago, efficiency was mentioned, but no figures.