ELECTRlC LOTUS ELISE
Prototype zero emissions supercar to be unveiled in
Market Engineering Ltd.
Christopher A. Sawyer
Lotus Cars USA Communications
For Immediate Release
A prototype 200-hp Lotus Electre, powered by two Zytek electric motors, will
be unveiled at the Society of Automotive Engineers (SAE) International
Congress & Exposition in Detroit, February 24-27, 1997. The vehicle
will have a power-to-weight ratio equivalent to many supercars and could
enter low volume production if there is sufficient demand.
"This is a really exciting project," says Zytek director Bill
Gibson. "No one has ever built a fully road-ready electric supercar
before, so at this stage we can only speculate on how it will feel. The
driving experience will be quite astonishing."
The Zytek electric Elise is powered by two internal, oil-cooled, brushless
DC motors, individually mounted on light-weight (aluminum) single ratio
Zytek gearboxes. Drive is transmitted to the wheels by equal length drive
shafts. The two motors combined weigh just 57.3 pounds (26 kg) and produce
a total of 200 hp (150 kW).
With instant access to maximum torque anywhere in the rev range and a
total weight of just 1930 pounds (875 kg), performance is expected to be
exceptional. Computer simulation predicts a 30-70 mph time of just 5
seconds -- the equal of many conventionally powered supercars.
Power will come from a 300V Nickel Cadmium battery pack, split between the
previous fuel tank location and ahead of the vehicle scuttle to optimize
weight distribution. The choice of Nickel Cadmium ensures that performance
and "throttle" response are consistent as a steady voltage is
available through the majority of the discharge cycle.
Zytek's electronic control system coordinates all power-related functions
and provides regenerative braking and traction control. The company
believes that the high-efficiency motor and control system together help
to overcome many of the limitations currently imposed by electric vehicle
Zytek has engineered the entire conversion, including the motors,
gearboxes, control electronics and cooling system. Lotus is supporting the
project and will ensure that the car has the best possible ride and
The running gear, bodywork and the extruded and bonded aluminum chassis
are retained from the standard Elise, which is sufficiently light not to
need power steering or power brakes -- both areas where additional
conversion work would have been required. A future phase of development
will see the addition of passenger compartment heating using heat from the
motor cooling oil, which is cooled by the standard Elise radiator.
If the Zytek electric Elise does enter production, the cost of the vehicle
without batteries could be similar to that of the standard car. Owners may
then lease batteries at a penny- per-mile cost equivalent to buying
"Our aim is to make Electric Vehicles desirable, not just necessary
through government mandate." concludes Bill Gibson. "The Lotus
Elise forms an ideal test bed for high- performance EV technology."
Other electric vehicles with powertrains engineered by Zytek include the
Chrysler Intrepid ESX hybrid electric concept vehicle and a zero emissions
kart for indoor circuits. In the Chrysler Intrepid ESX application, the
motors are hub-mounted using a Zytek- designed integrated hub, gearbox and
ZYTEK ELECTRIC LOTUS ELISE SPECIFICATIONS
Maximum Power: 200 hp
Maximum Torque: 100 Nm
Weight: 1930 pounds (875 kg)
Acceleration: 30-70 mph in 5 seconds
Maximum Speed: 90 mph (electronically limited)
Driving Range: 120 miles (using the industry-standard Bosch cycle)
Recharge Time: 60 minutes to 95%
Electre, Supercar Uses Closed-loop Cooling
Hethel, Norfolk, England
A prototype all-electric Lotus Elise, powered by two internal, oil-cooled,
brushless dc motors, weighs just 875 kg. Simulations predict a 30-70 mph
time of five seconds for the vehicle and a range of 120 miles.
Made by Zytek Automotive Ltd., the motors are mounted on lightweight
aluminum single-ratio Zytek gearboxes. Each weighs 13 kg. and the two
together produce a total of 200 bhp (brake horsepower), or 150 kW. A
closed-loop, presurized cooling system for the motors employs a
comventional transformer oil that flows through slots in the stator
laminations, and over the windings. This approach removes heat produced in
the stator winding by FR losses. Zytek claims the motor is the first
production EV motor to use this technique to cool critical components.
Power for the motors comes from a 300 V nickel cadmium
battery pack. Engineers selected nickel cadmium technology to ensure
steady voltage throughout most of the discharge cycle. Recharge to 95%
capacity will require 60 minutes. An electroic control system made by
Zytek coordinates all power-related functions and provides both
regenerative braking and traction control.
Vehicle running gear, bodywork, and the extruded and
bonded aluninum chassis are retained from the starndard Elise. In the
future, passenger compartment heating will be provided using heat from the
motor cooling oil, which is cooled by the starndard Elise radiator.