Electric Sportbikes - The Silent Future
An introduction to electric sportbikes
November 16, 2010
By Alan Cathcart, Andrew Trevitt
Photography: Kevin Wing
With the growing emphasis on eco-friendly technologies in the automotive sector, it's no surprise that motorcycles are headed in that direction as well. The death of the internal combustion engine is still a long way off, but it appears that an all-electric solution is the replacement of choice, as opposed to the gas/electric hybrids currently offered in the automotive sector. That only makes sense, as it would be difficult to squeeze an electric motor and battery as well as a gasoline engine and fuel into a motorcycle. The electric motor has been around for ages, but it's only recently that battery technology has improved to the point that a reasonable amount of energy can be stored in a small enough package for motorcycle use.
In an electric motor, coils...
In an electric motor, coils generate a magnetic field that moves around the circumference of the stator. The rotor, with a permanent magnet or coils generating its own magnetic field, follows along, much as a compass needle rotates when you move a magnet nearby. This is the DC brushless motor from Honda's CR-Z hybrid automobile, rated for 13 horsepower and 58 ft-lb of torque.
There are three basic components to an electric bike's powertrain: The battery, motor, and a controller that essentially translates throttle position into acceleration and speed. Just as there are many types of internal combustion engines in use, there are many types of electric motors. These can be categorized as AC or DC and brushed, induction or permanent magnet. AC and DC are fairly obvious, but the other aspects require some explanation. An electric motor turns by virtue of opposing magnetic fields in the stator (the outer, "static" part of the motor) and rotor (the inner, "rotating" part). The magnetic field in the stator is generated by passing electric current through windings; in the rotor, however, the magnetic field can be created in three ways. Most DC motors use brushes to pass current into windings in the rotor. Brushed motors are relatively inexpensive, but bring about maintenance and reliability issues - the brushes can fail and need to be replaced regularly. In AC motors, the field can be induced into the rotor without any actual contact, much as a transformer works. An induction motor is typically more reliable than a brushed motor as there are fewer parts to wear or fail, but is more expensive and requires more elaborate speed controls. Finally, a permanent magnet can be utilized; the magnetic field in the rotor is created with a magnet usually made from a rare-earth material. A permanent-magnet AC motor is sometimes referred to as a synchronous motor, because the rotor turns at a specific speed. An induction motor, in which the rotor lags behind the rotation of the magnetic field in the stator, is sometimes called an asynchronous motor.
There are still other types of motors - DC motors do not necessarily have to have brushes, and some AC motors have "slip-rings" in place of brushes. With the introduction of inexpensive electronic controls, the difference between AC and DC motors is not so clear; in fact, a universal motor can run on either power source. Because electric bikes are still in their infancy, companies are still experimenting with the various technologies; many different examples of the various types of motors can be found among the bikes shown here.
The Brammo Empulse ( www.brammo.com...
The Brammo Empulse (www.brammo.com
), expected to be available in mid-2011, has a 40 kW motor offering 59 ft-lb of torque. Three versions offer lithium-ion battery sizes from 6 kWh (60-mile range) to 10 kWh (100-mile range), and the company claims a top speed of more than 100 mph. List price starts at $9995 for the 6 kWh model.
Typically, a motor's output is expressed in kilowatts (kW), a measure of electrical power, and torque. For example, the Brammo Empulse has a sealed permanent AC synchronous motor rated at 40 kW with a maximum torque of 59 ft-lb. It takes 736 watts to make one horsepower, so the Empulse makes about 50 horsepower at the engine's output shaft. Note that an electric motor makes its peak torque at all rpm, from almost zero to its peak. For the Empulse, we can use the torque and power figures to calculate a maximum engine speed of approximately 4500 rpm.
All the bikes shown here use some form of lithium-based battery. Lithium has several advantages over other materials, and gives the best compromise (for now) of cost, size and weight. A typical lithium cell generates 3.6 volts compared with the 2 volts in each of the six cells of your standard motorcycle battery or the 1.2 volts of a nickel-metal hydride cell. This means fewer cells must be joined together to generate the voltage necessary to run the motor, resulting in more reliability as well as less weight and size. A lithium-ion battery is a rechargeable unit similar to what you would find in a laptop computer or cell phone; a lithium-ion polymer battery uses a solid composite electrolyte rather than a more traditional organic solvent, and the individual cells can be packaged into more elaborate shapes.
Roehr Motorcycles ( www.roehrmotorcycles.com...
Roehr Motorcycles (www.roehrmotorcycles.com
) has announced four new electric models. The $16,965 eSuperSport has an AC induction motor with 48 horsepower powered by a 5.8 kWh lithium iron phosphate battery. The $27,595 eSuperBike (shown) has two motors for a total of 96 horsepower and a larger 7.7 kWh battery, while the $34,495 RR version has up-spec components and will be available for street or track use. A turn-key racer for the TTXGP or e-Power racing series is available and has a higher capacity 10 kWh battery.
Batteries are rated in terms of energy with units of kWh (kilowatt-hours), a measure of how much power the battery can produce and for how long; this would be equivalent to the size of the fuel tank on a conventional motorcycle. Current technology sees batteries weighing approximately 15 pounds per kWh, and several companies claim a range of about 10 miles per kWh. For a range of 100 miles, your electric bike would have to carry approximately 150 pounds of battery. Just as how you ride and the size of the engine determines how far you'll get on a tank of gas, an electric bike's range depends on how it is ridden and the output of the motor.
The energy rating of the battery also determines how long it takes to recharge. The units can get confusing here, but the quickest a standard household electrical outlet could charge a battery is 1.5 kWh per hour; our bike with a 100-mile range would take at least seven hours to charge from empty. This is also referred to as Level 1 in standardized charging station terminology. A high-voltage/high-current AC connection, such as a dryer outlet, is referred to as Level 2 and reduces the recharge time by a factor of four. Level 3 refers to a high-voltage/high-current DC connection that offers very short charging times and will be available at quick-charge stations, the first of which was recently opened in Portland, OR.
In a simple electric-motor application, such as a ceiling fan, a rheostat can be used to vary speed; in a high power application, however, the rheostat itself draws too much power and efficiency suffers. Consider another method to control the fan's speed: If we had a standard switch, you could turn the switch on and off at a certain rate; how long the switch was on compared with how long the switch was off would determine the fan's speed. In an electric motorcycle, the motor is turned on and off using electronic switches - transistors - thousands of times every second, and this controls speed relative to what the rider calls up with the twistgrip. Here is where the AC/DC division becomes blurry. Modulating a DC voltage in this manner essentially turns it into an AC signal, and additional transistors can be used in the controller to run a single-phase or multi-phase AC motor with a battery (that provides DC voltage). Pumping all this power through the required electronics can generate a significant amount of heat, leading to air-cooled and even liquid-cooled controllers.
While MotoCzysz ( www.motoczysz.com...
While MotoCzysz (www.motoczysz.com
) is not yet offering a complete motorcycle for sale, this D1g1tal Dr1ve System is available. The $42,500 setup consists of the company's 100 horsepower, 250 ft-lb liquid-cooled motor, a liquid-cooled controller and a lithium polymer 10 kWh battery pack.
Brammo's Enertia model is...
Brammo's Enertia model is now available at authorized Best Buy dealerships. Its 13 kW permanent magnet AC motor generates almost 30 ft-lb of torque and is powered by a 3 kWh Lithium-ion battery.
KTM plans to release two electric...
KTM plans to release two electric Freeride models at the Tokyo motor show this year. The supermoto version shown here has a 43 ft-lb motor with a 2.5 kWh battery and is expected to weigh less than 220 pounds.
While the major manufacturers...
While the major manufacturers are mostly absent thus far in the electric bike field, Honda plans to lease this EV-neo electric scooter to businesses in Japan later this year. In his mid-year CEO speech, Takanobu Ito said the company "will introduce electric motorcycles to both advanced and emerging nations, further improve product performance and cost competitiveness and strive to become a market leader in this field."
The $9995 Zero S ( www.zeromotorcycles.com...
The $9995 Zero S (www.zeromotorcycles.com
) is currently available and features a 4 kWh lithium-ion battery powering a 30 horsepower brushed DC motor. The company was recently awarded a sizable grant from the California Energy Commission and funds from the City of Santa Cruz to begin development of a "new advanced compact electric powertrain project."
The controller unit can be used for more than just changing the speed of the motor. An electric motor can also be used as a generator, pumping energy back into the battery; under braking, the controller can determine how hard the motor works in that manner, giving a set amount of what we usually call engine braking. It's possible to add in practically any electronic control that we currently have available on gas-powered motorcycles, such as traction control, wheelie control and various power modes.
Most of the motorcycles here utilize a low-revving motor and a direct drive from the motor's output shaft to the rear wheel for a simple and efficient powertrain. Adding a transmission of some form, however, will allow the use of a faster spinning engine, which in turn would make more horsepower from its already strong torque. For example, the 2010 Toyota Prius has a smaller electric motor than the previous model, but the addition of a gearset means it spins twice as fast and generates more horsepower. The Mission One (detailed in the accompanying sidebar) has a single-speed gearbox with a similar effect, and it's likely that we'll see more similarly equipped bikes in the future.
Michael Czysz (shown) won...
Michael Czysz (shown) won the Mazda Raceway Laguna Seca e-Power race aboard the MotoCzysz E1pc, while Mark Miller won the 2010 TT Zero race at the Isle of Man on the same machine, averaging just under 100 mph and posting the fastest top speed of 135 mph.
More interesting advances are in the pipeline. US Highland, currently manufacturing on- and off-road models using four-stroke singles and twins, recently announced a joint venture with Millennial Research Corporation and its innovative magnetronic hub motor. The MotoCzysz E1pc utilizes a battery pack with eight individual batteries that can be quickly and easily swapped, an interesting workaround to the recharge-time issue. Battery technology is continually evolving, with increasing energy density. For now, electric bikes are definitely more expensive than their internal combustion counterparts, but that will certainly change as time goes on. The federal government is supporting the industry with a 10 percent tax credit (up to $2500) on an electric vehicle purchase, while some states are offering further incentives - notably Colorado with an almost $5000 tax credit. At the rate development is moving along, an electric sportbike may be in your garage sooner than you think.
Mission One E-Superbike Road Test
Riding an electric bike is especially underwhelming if you're a sportbike rider, craving the thrill of going fast to the background music of a high performance engine's throaty induction roar and purposeful exhaust note. Trying to convince yourself that the superior sound of speed is utter silence, leavened with muted tire roar and a hint of chain lash while whizzing along flat out at 60 mph, is mission impossible. That's where the Mission One e-Superbike produced by San Francisco, California's Mission Motors (www.ridemission.com) comes in, set to hit the marketplace in May, 2011 at $68,995 for the debut Premier Limited Edition version. So what does that hefty retail price get you, and why is it any better?
What got me interested in finding out was the sight of Mission One rider Jeremy Cleland on the Bonneville Salt Flats last September, rocketing his prototype streetbike to a new AMA electric speed record at 150.059 mph. The very same bike had finished fourth in the Isle of Man's inaugural TTXGP e-bike race in the hands of Tom Montano, averaging more than 74 mph for a single standing-start lap of the 37.75 mile course. Invited by Cleland & Co. to visit Mission Motors in San Francisco to try out the bike myself in a real world road ride, there was only one option. California, here I come...
After heading north from the city over the Golden Gate Bridge into the biking heaven that is Marin County, then hooking up the Mission One for a 90-minute recharge at the Sand Dollar restaurant, we headed back to the city the long way round, carving canyons climbing to the peak of Mount Tam to take in its breathtaking vista over the whole of the Bay Area. 'We' was myself and MM software engineer Seth LaForge aboard his Ducati 916.
The Mission One is in practice a contradiction in terms completely unlike anything I'd ridden before. It's a genuine high performance motorcycle that's fun to ride, and will outperform an R1 or RSV4 or 1198 off the mark, albeit without the agility and nimble handling of its lighter petrol-engined brethren. And unlike other e-bikes, where the sound of silence eventually ends up detracting from the experience, the Mission One utters a muted but decidedly angry rasp when you get it on good. "The noise comes as a combination of the native sound of the motor, the primary gear reduction, and the noise of the chain drive," says Mission's Edward West.
You need to tiptoe to climb aboard the tall single seat and encounter the decidedly sporty riding position, with your body stretched forward to reach out for the clip-ons attached to the race-quality 43mm Öhlins fork. To boot up the bike, access the switch that by way of security instead of a key is hidden behind the lower right fairing flank, press down on the bright red E-STOP cutout button mounted on a plate tacked on to the Attack Performance adjustable upper triple clamp, and flick on the ignition switch to the right of the four mounted at the back of the dash. The others are there to switch on the pumps for the oil cooling the engine and the water chilling the controller, as well as the supplementary fans cooling the separate radiators for each of these. The MM-developed motor controller that's the real trick element in the Mission One's mechanical and electronic makeup takes the voltage and current from the batteries and creates a three-phase waveform that powers the 350V AC induction motor, which is in turn so powerful that its excessive heat must be cooled by oil. And running upwards of 100 kW of power through the controller generates heat that must also be dissipated, in this case by water jacketing.
Now, flick off the kill switch on the right clip-on and you're ready. Just gently turn the ride-by-wire digital throttle and you'll roll forward, en route to a clean takeoff on your maiden voyage as an e-Superbiker. But get too eager or downright ham-fisted and you'll lay down a darkie from the rear tire once it's hot or, in the case of the slow-to-warm dual-compound rear Michelin fitted, if you're just getting under way for the first time you'll execute the beginnings of a rolling burnout instead.
What we would normally consider...
What we would normally consider the engine bay and fuel tank area is filled with batteries on the Mission One, while the electric motor is placed behind and under the batteries. Running gear is top-shelf, with Ohlins suspension, forged wheels and Brembo discs with PVM calipers.
Out in the real world of no-compromises sportbiking, there is nothing on the street with a sparkplug to light the fire that will out-accelerate the Mission One off the mark. This literally awesome and definitely addictive performance off the line comes in spite of the bike's pretty hefty all-up weight of 525 pounds with oil and water, split 53/47 percent along the quite rangy 1455mm wheelbase. The dynamics of the bike feel good on the move; you do note the weight at rest, but on the go the Mission One feels well balanced. That is no doubt thanks to input from MM's chassis consultant James Parker, best known for the hub-center RADD front end on the Yamaha GTS. The considerable weight by sportbike standards is correctly positioned in the tubular steel trellis frame, with the result that turn-in is good, though I didn't have the confidence on this one-of-a-kind prototype encapsulating the entire MM development cycle to put undue trust in the front wheel to try to keep up turn speeds.
The digital speedo is easy to read, ditto the dash panel next to it telling you the single most vital fact you need to know - how many more miles of charge you have left in the drive battery. There's also a secondary readout showing the remaining charge in the separate 12-volt batteries that drive the oil and water pumps, fans, lights and dashboard display. This small secondary pack is supposed to be kept charged via a link from the main batteries, and it was actually that which cut short our day trip after a 130 mile loop, when the link packed up. We still had 30 miles left on the main batteries after that 90 minute recharge at the Sand Dollar, so I'd go along with MM's claim of a 70-90 mile range for the bike in spirited use - two hours would have been needed to fully recharge the batteries at lunch.
The four toggle switches turn...
The four toggle switches turn on the pumps and fans for the motor and controller cooling systems, while the display panel shows range for both the main battery and the 12 volt battery that is needed to power the lights, pumps and accessories. The lever on the left clip-on is not for a clutch, but rather the rear brake.
The Mission One's 136 horsepower delivered at the output shaft at 6500 rpm is quite useful, though only by 600 supersport standards and this bike weighs 50 percent more than a 600. Still, the awesome blast of drive available from the moment you open the throttle thanks to that massive 115 ft-lb dose of torque available throughout the rev range completely eclipses anything else with a license plate. The motor is connected to the primary gear reduction via a small single-speed planetary gearbox, so with no need to worry about selecting the right gear for a given turn, you can focus on braking where you should, picking a good line, and feeding in the drive again just right on the way out.
To start with, though, we had a problem with the regenerative braking, which is used to recapture some of the kinetic energy expended while stopping the bike and using it to add up to 14 percent extra range by recharging the batteries. MM had the regen set up much too intrusive to start with, introducing what was in effect a severe dose of engine braking every time I backed off the throttle for a turn. Seth Laforge duly supplied a fix over lunch, pulling a laptop out of his backpack to reprogram the regen so it was much less intrusive. That may have lessened the amount by which it recharged the batteries, but now the Mission One was ready to carve corners and go with the flow, gliding through turns on part throttle with a total lack of vibration. Now, it more closely resembled a conventional gasoline bike, but one still endowed with that serious performance at just the roll of the wrist. MM's men say they already have sophisticated closed-loop vector-controlled engine software installed in the ECU, with rider-adjustable throttle maps, regenerative braking maps, traction control features and data collection all capable of being transmitted wirelessly to a server. But because this is still work in progress, they opted not to let me access it at this stage. That will all be part of the customer bike and will form a key element in MM's R&D over the next nine months.
The creation of the Mission One is a key step in the evolution of the sportbike, in redefining the way we think about how we can go fast and have fun on two wheels in the uncertain future. "The principle behind the Mission One sportbike is actually similar to a company like Tesla's," says MM's CEO Jit Bhattacharya. "For so long we have associated electric drive with sacrifice, with having to give something up by switching to electricity, so you get a heavier, slower, less performing vehicle whose primary value proposition to the customer is that it's green. So the public needs to have its perceptions about electric drive changed, and the best way to do this is to build something electric that blows their mind, that performs in a way they don't think is possible, and that they can buy. That's the Mission One, and in building it we want to demonstrate that no compromises need be made to bring about a change, and start a revolution."