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The GM EV1 electric vehicle – on sale
this year in the United States.
Electric Vehi
Where are they now?
During the early 1990s there was great
media publicity concerning electric cars.
They were to be the solution to the world’s
pollution problems, with some of the more
optimistic industry experts predicting that
we would be driving them before the turn of
the century. So where are they now?
By SAMMY ISREB
4 Silicon Chip
icles
Several of the world’s leading car
manufacturers have been developing
electric vehicle technology during the
past few decades, with Ford and General Motors leading the way. Ford’s
latest electric vehicle, the 1998 Ford
Ranger EV, is due for release in the
near future, GM has the EV1 passenger
car and Toyota has an electric version
of the RAV4.
The Ford Ranger EV was designed
using data obtained from the Ford
Ecostar test program, which began
in 1993 and involved 103 Ecostar
two-passenger EV delivery vans, operating throughout the US, Canada
and some of Europe.
Powered by a sodium-sulphur battery, the Ecostar fleet has covered over
1,000,000 kilometres, the greatest of
any EV fleet so far. Much of the new
technology to be incorporated in future electric vehicles has been tested
in the Ecostar. This includes:
(1). Traction Battery: An advanced
sodium sulphur battery operates at a
temperature of over 200°C and features an energy density three times
greater than conventional lead acid
batteries.
(2). PEC (Power Electronics
Centre): The Ford Ecostar
contains an advanced power
control system, incorporating
an inverter to produce AC
power for the motor.
(3). DDLM (Diagnostic
Data Logger Module):
Records every aspect of
the vehicle’s performance,
allowing for later engineering analysis.
(4). Solar Energy: Using
solar panels mounted above
the wind
shield, accessories
such as fans can be powered
from the sun, saving on air-conditioning and thus the battery.
(5). Multiplexing: Because of the
complexity of the different electronics
modules in the Ecostar, conventional
wiring would require 200 separate
circuits. Multiplexing allows the eight
different modules to communicate
over a single pair of wires.
To be released in the United States
next year, the 1998 Ford EV Ranger
shares the body of the petrol-driven
Ranger but that is where the similarities end. This pickup truck features
4-wheel ABS brakes, dual airbags,
climate control, power steering and
regenerative braking. The Ranger uses
a 90 horsepower 3-phase AC induction motor with no gearbox and it is
rear-wheel driven. An inverter works
with the 312V, 23kW sealed lead-acid
battery system to convert the high
voltage DC to 3-phase AC.
Low rolling resistance tyres and
lightweight aluminium wheels, together with the regenerative braking,
give the Ford Ranger a range of about
90 kilometres, with an electronically-governed top speed of 120km/h.
Both the Ecostar and the Ranger
use a conductive charging system.
This system automatically checks
for a proper electrical connection to
the vehicle, checks that the charging
station is ready to charge the battery,
confirms the battery type and charge
station capacity, and ensures that all
safety systems are working before
proceeding to charge the vehicle. A
full charge is achieved in 4-6 hours,
depending on the state of battery dis
charge.
GM’s EV1 electric vehicle
Set to challenge Ford in the EV
market place is General Motors, with
their new electric vehicle, inventively
named the EV1. It has recently gone
on sale in America and sells for about
$US35,000.
The EV1 is a front wheel driven
aluminium-bodied 2-door passenger
coupe. The designers of the EV1 have
tried to boost the range of the vehicle,
not by using special batteries but by
taking other measures, such as lowering body weight and drag.
In fact, the EV1 has a drag coefficient of 0.19, compared to between
0.30 and 0.40 for a standard production car. This was achieved by taking
extraordinary steps such as closing
off the underside of the car, covering
the rear wheels with skirts, using
low rolling resistance tyres, and even
building the radio antenna into the
roof rather than having a standard
extendable antenna.
A 137-horsepower 3-phase AC-motor drives the EV1. This motor is water
cooled and revs from 0 - 13,500 rpm.
This wide rpm range, coupled with
a broad torque curve, eliminates the
need for a transmission.
Acceleration is quite good, with
the motor propelling the EV1 from 0
to 100km/h in around nine seconds.
Powering the EV1 is a 312V battery
pack, made up of 26 maintenance-free,
valve-regulated, lead-acid modules.
Environmentalists will be able to drive
the EV1 knowing that the batteries are
98% recyclable. Because safety is a
crucial factor in any electric vehicle,
the batteries are of sealed construction in which all the liquid acid is
encapsulated in a diaper-like material
between the individual lead plates.
This results in a battery so safe that
a hole could be made in the case and
no liquid would flow out.
Clever electronics
At the heart of the vehicle’s electronics system is the inverter. This
uses six Insulated Gate Bipolar Transistors (IGBTs) which perform the high
power switching needed to convert
the 312V DC from the battery system
to AC for the motor. These IGBTs can
July 1997 5
passes it through the car in order to
heat it. Cooling is achieved through
a CFC-free energy efficient air-conditioning system.
Inductive charging
A 137 horsepower 3-phase AC motor drives the EV1. It is powered by 312V battery pack, made up of 26 maintenance-free lead-acid modules. The motor
is water-cooled and revs from 0 - 13,500 rpm which eliminates the need for a
transmission.
handle up to 600V at 750A, making
them very rugged indeed.
An inventive electronic circuit
controls the drive and braking system.
Known as the Galileo Braking System,
it uses software to constantly monitor
the driving conditions and selects
ABS braking or traction control when
appropriate.
This electronic system also monitors tyre pressure and inflates the
tyres when necessary. In addition, a
regenerative braking system is used
to charge the battery during braking
and this significantly boosts the range
of the vehicle.
Another major design feature of the
EV1 is the inclusion of a heat pump.
This works as a heat exchanger to
move hot or cool air inside and outside
the car. The pump takes coolant from
the motor and inverter electronics and
Toyota plans to release an electric version of its RAV4 to fleet buyers in the
United States in early 1998. The EV RAV4 is basically a reworked petrol RAV4
featuring a nickel metal hydride battery.
6 Silicon Chip
The EV1 features an inductive
charging system that is far superior
to the chargers used by many other
electric vehicles. Instead of using a
conventional electrical connector, it
uses a fairly bulky paddle, encapsulated in an insulating material, that
is plugged into the car. The great
plus of this system is that there are
no exposed conductive parts, as the
electrical energy is transferred inductively; a great safety feature.
The paddle can be immersed in
water, run over by a car and so on,
without any risk. If the cable to the
charging paddle is severed, this will
be detected and the power shut off
within a few microseconds. Whilst
the complexity of this charging system
will boost its price, inductive charging
seems the way of the future.
Toyota’s RAV4
Set to rival both Ford and GM,
Toyota plans to release an electric
version of its RAV4 to fleet buyers in
the United States in early 1998. The
EV RAV4 will basically be a reworked
petrol RAV4 featuring a nickel metal
hydride battery.
With a top speed of 125km/h and
a range of 190km, the RAV4 is competitive. However, the RAV4 will not
become economically viable for the
mass market in the near future, due
to the high price of the nickel metal
hydride batteries and the fact that (unlike the EV1) large scale production is
not envisaged for the moment. Over
the next few years, only 320 EV RAV4s
will be produced for fleet trials.
Although this article has described
the market-leading electric vehicles
that have emerged in the past few
years, there are quite a few others from
smaller car manufacturers that have
not been mentioned. And although
the EV1, Ecostar and Ranger are set
for large-scale production, their sales
are likely to be limited to the US and
parts of Europe.
As yet, no electric vehicle is widely available in Austra
lia and none
is likely to be for some time. It will
probably be the better part of a decade before we see serious EV trials
SC
in Australia.
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