Transmission specialist Antonov reports that exhaustive testing of an electric vehicle equipped with the firm's multi-speed transmission over eight different drive cycles has proven that its multi-speed unit delivers approximately a 10-percent improvement in electric motor efficiency compared to a single-speed solution.

Antonov's business development manager, David Paul, says the transmission firm's analysis, shows that with a single speed gearbox, there is significant variation in drive-cycle efficiency, whereas a multi-speed unit tends to be more consistent. Additionally, Paul claims:
Inevitably, there is a compromise with a single speed gearbox particularly in terms of low speed acceleration, hill climbing and high speed cruising. The 10 percent step change improvement in efficiency can be achieved with just two ratios, but technical compromises remain in other areas. Three or more ratios are better, delivering additional improvements in performance and refinement as well as efficiency, with each additional ratio providing small incremental gains in cycle efficiency.
The UK's Technology Strategy Board asked Antonov to present detailed findings at the Cenex Low Carbon Vehicle Event 2011 at the Rockingham Motor Speedway in the UK, so keep your eyes peeled for more info on this potential plug-in breakthrough.


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  • 36 Comments
      2 Wheeled Menace
      • 3 Years Ago
      Do a search on google for 'electric motor efficiency curve' and you will notice that most electric motors have an efficiency bump, followed by a decline to 0% efficiency all around.. The trick for peak efficiency is to keep the motor at it's optimal speed, and that doesn't occur on a single speed all too often, unless you find the sweet spot MPH and travel at that speed indefinitely. The other factor is torque. The faster you go, the less torque you have. This is where a gearbox can come in handy, big time. You can downsize the motor using a transmission, even if said transmission only has 2 or 3 speeds.
      nbsr
      • 1 Month Ago
      Going from 2 to 3 gears has a major impact on usability. With 2 gears you might be OK switching them a couple of times a day - entering or leaving a motorway. Which would happen to produce some noticeable boost in both performance and efficiency. With 3 or more gears you're supposed to shuffle between them all the time much like you'd do it driving an ICE car. Unless the transmission was fully automatic I don't see this happening - most people would simply settle for using at most two gears in daily driving. What IMO makes most sense is integrating a simple 2 speed transmission with a differential to reduce the number of gears (and thus reduce losses and noise). Most EVs need one pair of gears anyway, why not make their ratio switchable?
      krisztiant
      • 3 Years Ago
      At long last. Thanks for Antonov, now the hardcore manual transmission fans can order their EVs with a driver-operated clutch and gear stick. Yay! /s
        skierpage
        • 3 Years Ago
        @krisztiant
        (Are you failing to apply the sarcasm tag? /s means end strike-out text.) I don't see any clutch fork, clutch plate, or mechanical connection in Antonov's diagrams, so I doubt there will be a mechanical clutch. Paddle shifter maybe. I wonder how Antonov compares with Fisker's transmission.
        EJ
        • 3 Years Ago
        @krisztiant
        If you talk to anybody who has converted a manual to EV, they wind up leaving it in second because shifting may keep your heel-toe skills in-tact, but it does zero for performance gains. Much like a DCT, shifting actually lowers your overall performance.
      krisztiant
      • 3 Years Ago
      It seems EV transmission is the new "magic spell" on EVs. Vocis technical director, Richard Taylor claims this also: "Electric motor efficiency drops off at low load levels and towards the extremes of speed. Multiple gear ratios with electronic control allow the motor to be kept in the region of greatest efficiency for a much higher proportion of the time, allowing significant range extension." "An EV will typically have a transmission ratio that is higher than the ideal, simply to give it enough top speed. “With multiple ratios, we can provide much better laden pull-away as well as improved top speed without increasing the powertrain size." http://www.hybridcars.com/news/vocis-road-testing-multi-speed-ev-transmission-30934.html So, either there is something in it or they're trying to keep their product alive in the upcoming EV era. At the moment it's hard to decide without satisfactory "damning" evidence. I'd rather like to see something like e.g. a Variable Torque Motor to succeed, which eliminates any need for any transmission. http://variabletorquemotors.com/about/
      • 3 Years Ago
      If you've got something worth saying, say it clearly. If you don't have something worth saying, use obfuscating jargon. "10 percent step change improvement in efficiency" is opaque. First, let's observe that a quality motor, such as the one in my Leaf, is probably around 91% efficient, and therefore, if as the article text states, there is a "10-percent improvement in electric motor efficiency," then that would be something as we've now effectively got a 100% efficient motor. Not happening. 10% faster, perhaps? If so, easy to prove: put it in an otherwise identical car and show is that 0-60 went from say 10 seconds to 9 seconds. Maybe 10% more efficient? Fine, same thing: put it in a control car and go 110 miles instead of 100. But all we have is, 10% "step change improvement": if by that it means that it can put 10% more torque to the ground, well congratulations, you've got yourself gear reduction. Take a bow for that otherwise mysterious achievement. Look, one of the things I really like about my Leaf is that there is one major moving part, and it should be riding nearly frictionlessly on a couple of life-time bearings. Please don't complicate matters for little effective benefit. Keep the costly, weighty, complex, shifty, maintenance-requiring, breakage-inducing transmission out of my nice simple EV.
        SealtestDark
        • 1 Month Ago
        They probably mean 10% more efficient than a single speed transmission. So if the motor is 90% efficient and the transmission is 80% efficient then this new version will have transmission efficiency up to 88%. Of course once you actually graph it all out the 10% bonus to transmission efficiency would likely be a peak, and not a universal rule across all speeds. Net result might be that only 2-3% more energy makes it to the road on average. It certainly wouldn't result in a net 10% range improvement across a full range of speeds, because we are only talking about increasing the efficiency of one component by 10% (and that is likely only a peak on the graph). I really don't like the wording of the article. It says a 10% improvement in motor efficiency, but like you I don't think connecting something different to the motor makes it inherently more efficient.
      JP
      • 3 Years Ago
      Unless this is cheaper than another 10% more batteries it doesn't' make much sense for most vehicles. Especially since normal driving speeds between 30-60 mph are probably right in the efficiency range for most single speed EV's.
      Peter
      • 3 Years Ago
      better low end acceleration and better top speed OR 10% in range with no change in driving cycle behaviour
      s1093
      • 3 Years Ago
      What I don't understand is, why they can't just add a cvt to a electric motor and call it a day? yeah, CVTs have a lower torque capacity, but Nissan has CVTs in vehicles with 240+ lb-ft. Honestly, this is what I would do. I have an EV with 4 motors, one to each wheel. Then in between each motor and wheel is a CVT. That way, an EV would have a much higher range because the CVTs would keep electric motors at their optimal speed at ALL TIMES plus there would be an efficiency boost due to the lack of differential. In my mind, there would also be a performance and handling boost as well. AWD and torque vectoring would help big time with traction, acceleration, and handling. This could be applied anywhere from economy cars to supercars. I, personally would like to see AWD electric sports car with 240+ lb-ft to each wheel with CVTs. With that torque and all those gear ratios, acceleration and top speed would crazy and the handling would be incredible as well. Anyone who ACTUALLY knows about this stuff, PLEASE feel free to reply to this, I want opinions about this. Would this work the way I like it will? If not, please explain. If it would work, why aren't automakers working on this? I have yet to see anything exactly like my concept.
        Gordon Chen
        • 1 Month Ago
        @s1093
        CVTs are the least tried and tested transmission. And if a conventional gearbox transmission isn't strong enough to handle a torque of an EV, the CVT certainly isn't strong enough.
        Dan Frederiksen
        • 1 Month Ago
        @s1093
        since CVTs aren't used much in cars either I'm guessing it's either inefficiency or durability or both. with electric motors it is probably just more elegant to use fixed gearing because it can be efficient and potent over a wide rpm range. the elegance is hard to beat
      Gordon Chen
      • 1 Month Ago
      That's what i'm saying. going from 1 to 2 gears should be the most drastic improvement. 2 to 3 is a little less, 3 to 4 is even less, etc. Let's hope the performance is more drastic. The Fiskar Karma guy says with a 3 speed, the FK would reach Veyron speeds.
      throwback
      • 3 Years Ago
      I am curios as to how they are measuring efficiency. To me, range is what matters with an EV. 10% is nice, but how much more range will I get?
        Gordon Chen
        • 3 Years Ago
        @throwback
        10% more. If it's 100 miles, then your new range will be 110.
      Spec
      • 3 Years Ago
      Yeah, I don't know if the 10% improvement is worth the cost of the transmission and the fact that you are adding a mechanical component that will eventually break.
        fly by wireless
        • 1 Month Ago
        @Spec
        It's only 2 speeds so it's a good trade off on efficiency, weight, and complexity. Depending on the setup, it shouldn't yield much in the way of more losses than a single gear reduction. The gain in efficiency makes sense because you have to work as much as you can in the most efficient RPM band of the motor. This set up should allow you to work with a smaller motor in the same application.
      Gordon Chen
      • 3 Years Ago
      That's it? 10%?!
        BipDBo
        • 1 Month Ago
        @Gordon Chen
        I'd say that's pretty significant, especially because that's the improvemnt with just 2 speeds. With 3, there would be more improvement, but it would be smaller. Don't forget, that it would also give much better low end acceleration
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