Lightweight Electric/Hybrid Vehicle Design

Introduction xxix
conventional bicycles. Electric motorcycles are less common than electric scooters, the BMW
C1 being an example. Recent electric cars have divided between conversions of standard
production models and a small number of purpose built vehicles. Japan’s flourishing microcar
market of smaller and lighter cars is an important target group for electric conversion, for which
acceleration and efficient stop-start driving is more important than range. Such city cars are
distinct from longer-range inter-urban cars and the latter market currently attracts hybrid drive
cars of either gasoline or diesel auxiliary engines, with series or parallel drive configurations.
Fuel-cell cars for the inter-urban market are still mostly in the development stage of value
engineering for volume production.
Commercial and passenger service vehicle applications, that section of the market where
downtime has to be kept to a minimum, and where low maintenance costs are at a premium, are
particularly attractive to EVs. Municipal vehicles operating in environmentally sensitive zones
are other prime targets. In passenger service applications battery-electric minibuses are a common
application in city centres and IC-electric hybrids are increasingly used for urban and suburban
duties. Gas-turbine/electric hybrids have also been used in buses and fuel-cell powered drives.
Guided buses include kerb-guided and bus/tram hybrids, the former having the possibility for
dual-mode operation as conventionally steered vehicles. Guided buses have been used in Essen
since 1980. Trolleybus and tramway systems are also enjoying a comeback.
At this relatively early stage in development of new generation EVs tabular classification is
difficult with probably the only major variant being traction battery technology. A useful comparison
was provided in a Financial Times report 6 on ‘The future of the electric vehicle’ as follows:
Battery Advantages Disadvantages Comments
Lead–acid Established Low energy and Horizon and other high
technology; low cost power density. performance batteries
and fairly long life greatly improve the
(1000 cycles). suitability for EVs but
must be made cheaper.
Nickel– Higher energy density Cadmium very Being used for second
cadmium and cycle life than toxic. generation, purposelead–acid.
built EVs.
Lithium High energy and Expensive. Research into scaling
power densities. up to EV size will
Safety concerns probably provide a
overcome. mid-term battery.
Sodium– High efficiency and Thermal enclosure Several technical issues
sulphur energy density. and thermal management to be resolved before
is expensive. this could become an
Corrosive components. option.
Sodium– High energy and Thermal enclosure Promising mid-term
nickel power densities. and thermal option but currently
chloride Long life (over 1000 management are over twice the cost of
cycles). expensive. the USABC target.
Nickel–metal High power density, Expensive. Promising mid-term
hydride Long cycle life (over option but currently
2000 cycles). over twice the cost of
Twice the energy the USABC target.
storage of lead–acid.