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‘Entering the electric car scene is an absolute necessity. We cannot
afford not to be present if electric vehicles suddenly take off.’ The view
of Jurgen Hubbert, chief of the Mercedes-Benz passenger car division, is
shared by most of the world’s car manufacturers. It also explains why, at
a time when thousands of people in the car industry have been laid off,
annual expenditure on developing electric vehicles (EVs) exceeds £5
billion worldwide.

At the Paris Motor Show earlier this month, Renault’s new EV, the Zoom
caused quite a stir. Other leading European manufacturers, including Volvo,
Peugeot, Citroen and Fiat, showed off their latest electric prototypes –
stylish vehicles that aim to change public perceptions of battery-powered
cars. In Europe, as in the US, there is a scramble to get EVs into the marketplace.
Competition is so fierce that manufacturers will even use underdeveloped
battery technology to produce cars that are less powerful and more expensive
than petrol and diesel cars.

The lead comes from the US. Californian zero-emission legislation alone
will create an annual market for at least 100 000 EVs by 2003. In Europe
there has been little debate on how or when the US lead could be followed,
despite pollution levels that are frequently higher in European capital
cities than in Los Angeles. Schemes in Cambridge, Zurich, Geneva, Stuttgart
and Cologne suggest it is much easier to ban cars and trucks from polluted
city centres than to enforce a switch to electric power. But the French
government is attempting to buck the trend. It has invested £55 million
in a project to trial electric hire fleets, numbering a few hundred cars,
in each of 10 major French cities within the next two years.

ASSAULT ON BATTERIES

In general, however, there is little political pressure in Europe to
support EVs. This will only change if they are produced more cheaply for
other markets, such as the US, prompting greater competition. European cities
could then price out conventional vehicles with road tariffs, or simply
restrict access. Most European manufacturers are developing electric designs
on this possibility, which many see as inevitable within the eight-year
lead time that radical new vehicle technology requires.

The first generation of mass-produced electric cars will cost more than
petrol or diesel powered cars but car makers believe that pioneers will
reap the financial rewards. So certain are some car makers of the financial
advantages, that several have chosen to use existing lead-acid battery technology,
with all its shortcomings. These first-generation EVs, however, will have
less power and be less energy efficient.

Modern engines have an average power density of 400 watts per kilogram
and an average energy density of 200 watt-hours per kilogram, whereas equivalent
figures for conventional lead-acid batteries are, at best, 100 watts per
kilogram and 40 watt-hours per kilogram. Power density affects acceleration
and energy density affects range, so it is not surprising that many manufacturers
are developing new battery technologies to improve the performance of their
second-generation EVs. The main contenders are sodium-sulphur batteries
(used by BMW in its prototype E1), alkaline batteries using nickel-cadmium
or nickel-hydride cells, and zinc-air batteries (being developed by two
groups in the US).

All batteries comprise groups of electrical cells linked to generate
voltage and current. Each cell has two electrodes immersed in a conducting
electrolyte and converts internally stored chemical energy into direct current
when an external circuit is completed between the electrodes. Many different
combinations of elements create this flow of electrons from the cathode
to the anode. Whatever the media used, the negative anode is oxidised to
supply electrons to the electrical circuit and the positive cathode is reduced.

Lead-acid batteries use alternate lead and lead oxide plates suspended
in dilute sulphuric acid. During electrical discharge both electrodes are
converted into lead sulphate. The problem is that it takes just one litre
of petrol or diesel to equal the power generated by 100 kg of lead-acid
batteries. This means that over a tonne of batteries, costing well over
£1500, would be needed for an EV to have a range of between 100 to
160 kilometres.

CHARGING AHEAD

The working life of any battery depends on how often and how completely
it is discharged and recharged. A typical 12-volt lead-acid battery used
for starting a conventional car lasts up to five years before it must be
replaced, at a cost of between £20 and £80. Traction batteries
suitable for a simple electric car cost over twice as much. Up to 20 could
be needed to provide even a modest performance with a minimum range of 50
kilometres.

To overcome some of these problems BMW has spent about £330 million
developing sodium-sulphur batteries to power its E1 prototype. It is the
most powerful EV yet developed but offers a practical range of just 100
to 140 kilometres. The batteries cost £16 000 per car, and the prototype
is at least two years from mass production. The advantage of sodium-sulphur
batteries is their weight – about a third less than lead-acid batteries
but with the same power output. ‘It is the most energy-efficient battery
available today, and one you can completely forget in terms of maintenance,’
says Ing Klaus Faust, head of the engineering team at BMW.

The batteries are hermetically sealed metal casings containing liquid
sodium and sulphur, which are the electrodes, either side of a porous aluminium
separator plate, which acts as the electrolyte. But sodium and sulphur are
highly corrosive and are dangerous and expensive to make. They must also
be heated beyond the melting point of sodium and sulphur (as high as 300
°C) to reach operating conditions. A further constraint is that, if
not recharged, they lose 25 per cent of their heat every day. After four
days the liquid sulphur and sodium solidify and the batteries cannot be
reused.

Volkswagen and Varta Batterie, of Hanover, hope to solve the EV power
problem with a new alkaline battery. It uses nickel anodes in potassium
hydroxide solution as the electrolyte, with a metal alloy capable of storing
hydrogen as the cathode. They have invested around £300 million developing
an electric hybrid vehicle combining power from solid fuel with the nickel-hydride
cells. ‘Alkaline systems provide impressive acceleration and have the advantage
over other systems of being recharged in only a few minutes,’ says Franz-Josef
Kruger, director of research and development at Varta Batterie. ‘Their energy
density of 60 watt-hours per kilogram is about twice that of a conventional
lead-acid battery,’ he adds. ‘And thanks to modern charging techniques,
they can be restored to over 80 per cent of their charge capacity within
10 to 20 minutes.’

Other key players in Europe’s electric vehicle stakes, Fiat, Renault,
Clean Air Transport (an Anglo-Swedish consortium) and PSA (Peugeot and Citroen)
are already using traditional lead-acid battery technology in EVs for the
mass market. Fiat is producing limited numbers of an electric Panda car
and has shown its future intent with an electric version of the new Cinquecento
minicar, to be launched next year.

Clean Air Transport has invested heavily in new production facilities
at the Worthing base of its British partner International Automotive Design.
It plans to build 1000 vehicles next year, initially for the Californian
market. The main power is provided by a 34 kW electric motor using sealed
156-volt 14 kWh lead-acid batteries in the cheaper model, and 180-volt 23
kWh sodium-sulphur batteries in the more expensive version. The range on
battery power alone is about 40 miles, but a small petrol-powered unit will
extend this.

French government backing for for the installation of 18 recharging
centres has encouraged investment in EV development there. Peugeot and Citroen
have had electric vans in limited production since 1989. These, together
with the 205 electrique and the latest PSA models on display at the Paris
Show, use sealed, lead-acid cells. Nickel-iron and nickel-cadmium, at seven
times the cost, were rejected, reducing performance to a top speed of 85
kilometres per hour (down from 100 kilometres per hour) and the range to
about 60 kilometres (down from nearly 140 kilometres).

THE CLEAN AIR TICKET

In 1990, the Californian zero-emission programme called for the number
of totally non-polluting cars being manufactured to rise from 2 per cent
in 1998 to 10 per cent by 2003. Competition for a share of this market is
great, but there is also cooperation and government money to direct and
expand the technologies available. As in Europe, the EVs closest to the
marketplace are also powered by lead-acid batteries, making long journeys
impractical. Two groups in the US are working on a zinc-air battery that
will recharge instantly. It is being developed by Dreisbach ElectroMotive,
with sponsorship from Southern California Edison, and, independently, by
scientists at the Lawrence Berkeley Laboratory, in cooperation with the
University of California at Berkeley.

The chemistry of a zinc-air battery is similar to that of a conventional
alkaline dry cell, except that the oxidising agent used is oxygen taken
from the atmosphere. This results in a considerable weight saving, and energy
density levels as high as 200 watt-hours per kilogram. ‘Our first cost indications
suggest that zinc-air batteries in high-volume production could become available
for $27 per kilowatt-hour of battery capacity,’ said Mike Cheiky of Dreisbach
ElectroMotive. This is less than half the cost of lead-acid batteries.

Once battery technologies allow EVs to become competitive, in terms
of price and performance, success will depend largely on their clean image.
Marketing people are already preparing to counter allegations that using
electricity to power vehicles merely shifts the pollution problem out of
the city to the power station, or to where its emissions are carried.

Geoffrey Howard is the editor of Automotive Visions magazine.