Despite my last post regarding the miniscule number of actual electric cars on the road, and admonition that we are firmly at the BEGINNING of the tinkerer/innovator market stage, the wider press frenzy and flurry of OEM press releases has had an effect of urgency. Although remaining largely unobtanium, the blizzard has certainly spurred the aspirations of the more inventive among us. And it solidifies my feeling that there is a lot of electric car to be yet built. Basically, we don’t know what the future vehicle looks like.
This is a bit startling when you think about it. Not only do we have new batteries finally, but innovation in this area continues predictably enough. But on things like the Electric Motor, what can really be done that hasn’t been done in the past 150 years?
Actually, a lot. Several viewers have pointed me to some startling innovations, largely coming out of the United Kingdom.
Electric drive trains share the basic problem ICE drivetrains for automobiles exhibit. A typical 15 inch wheel and tire rotates about 750 rpm at 70 mph and correspondingly less at lower speeds of course. Electric motors do not operate well at 750 rpm and are really unwell at 50 rpm. We say they develop full torque at 0 rpm, but that is a little misleading. What they mostly develop is heat at those levels.
The “sweet spot” of course is much wider at perhaps 2000-3500 rpm for most motors of AC or DC. And so in direct drive applications, you will often see a gear ratio of 8.25:1 in a single speed gearbox.
Converting existing cars, the single speed 8.25:1 gearbox is largely unavailable. So it is usually easier to just retain the existing manual transmission.
A couple of problems there, none insurmountable. First, many desirable vehicles don’t have a manual transmission. Would you believe the most popular vehicle of ANY make is still the Ford F150 pickup truck? ANd would you believe they just don’t make them with manual transmissions any longer? Unobtainium.
There is weight and efficiency loss through the transmission, and one of the most popular questions we receive at EVTV is the continuous suggestion that we bail on the transmission and go direct drive.
Direct drive poses some all around problems, but by far the largest is this matter of RPM matching.
Basically, this would involve a drive train somewhat like the Tesla Model S with a motor IN an axle with gear reduction linearly between the motor and the wheel. All doable. All expensive. All custom.
There is actually an alternative – magnetic gearing.
Magnetic gearing does an rpm reduction and a torque multiplication based on magnetic coupling using rare earth permanent magnets. Magnegear is a good example. They do a rotary magnetic gear reduction for the oil and gas industry drilling operations.
These are frictionless, very low maintenance and very volumetrically attractive notions. But aren’t electric motors mostly about magnets and magnetic fields. Yes, Johnny, they are.
The video above describes a company with a technology for magnetic gear reduction, but their Pseudo Direct Drive takes this a step further – putting the gear reduction IN the motor. By combining magnetic field windings with a series of rare earth magnet rotors, they do both the motor thing and the gear reduction in one package.
In this way, you can have a motor spinning at 2500 rpm and the shaft of the motor spinning at 500 rpm in a very small package.
Yasa Motors carries this a step further. Robert Lewellyn does a take on this I found engaging.
They are cloyingly careful not to include any details in their description, but it appears to use a three phase Sevcon controller to spin an outer rotor of a few neodymium magnets that then induce current in a series of wound armature coils – effectively doing the gear reduction with an output of 750 NM of torque in an incredibly small package. Better it appears you can STACK these pancakes to get whatever power level you want.
Forget wheel motors. By putting these inboard with a short shaft, you can get all the advantages without the unsprung weight and durability issues.
So electric motors for electric vehicles really do have some peculiar needs and requirements. And there is indeed room for innovation in such a mature technology as electric motors. I find both of these technologies utterly fascinating. But they share a common theme – a 3 phase space vector inverter.
We don’t really have one.
I have gone on about bottom balancing since late 2009 in a world of top balancing BMS gurus who insist I’m a whacko. Now WHAT OEM has MORE experience with Lithium Cells than ANY other?
The answer will NOT surprise you. DeWalt. They’ve been using these cells in power tools for years now. And as it turns out, their BOTTOM BALANCING PATENT rather predates anything I might have ever said about this.
I also said that Akio Toyoda, Chairman of Toyota Motors might have FELT the Winds of the Future but he could not BE the Winds of the Future. Apparently he does not agree. The company announced at their Las Vegas Dealer meeting that there would be 35 Tesla/Toyota RAV-4s built in 2011 with a product introduction in 2012.
Purported to equal performance of the gasoline version, the vehicle should have a 100 mile range and drive much like the ICE version.
The company also announced the 2012 launch of the Scion IQ EV – a 65 mile per charge city roadster about the size of the ill fated Daimler Smart ForTWo. Again, no pricing or planned production numbers.
They do also plan a plug-in version of the Prius with an electric range of 14 miles. So Toyota seems to have gotten electric religion, at least at the press release level. Next year in Jerusalem. Always next year…
I must say I find both these pure electrics from Toyota attractive.