The electrical and
electronic content of a typical car now averages more than 15 per cent of total
content, and with the planned increase in telematics systems – which will see
a far greater level of communication between the car, home, office and central
bureaux – this percentage is bound to increase. That, in turn, means the faithful
12v battery – widely adopted during the 1920s and pretty well universal since
the end of the Second World War – will no longer be able to cope.
But it won’t simply
be a case of changing the battery from a 12v to the new 42v system. It will
force a period of radical change in the way vehicles are constructed. Today’s
power harness is about to be consigned to the history books (with the exception
of a small number of specialist vehicle manufacturers) and in its place will
emerge a multiplex loom with a dramatically-reduced cable count. Within a decade
the space behind the fascia panel of even an average C or B-Class car is likely
to bear a striking resemblance to the inside of a computer central processor
unit, with printed circuits no longer being confined to the back of the instrument
cluster and the inside of the engine control unit box. The whole concept of
the box is likely to disappear, replaced by surface-mounted or embedded integration
of component boards.
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Where the 42v system will
really come into its own is in savings, with reduction in both weight and component
count. The concept makes use of a ‘ring main’ power feed running around
the car, with computer-style ribbon cabling and fibre-optics linking the various
components. These latter connectors will carry switching signals rather than
power, which means that the amount of copper wiring (which is both heavy and
expensive) can be dramatically reduced. These will be arranged into subassemblies,
referred to as LANS, an acronym of Local Area Networks, which integrate with
the main CAN (Car Area Network) to provide actuation for localised functions.
As a guide to the amount of weight which can be saved by such systems, Motorola
reported that replacing the traditional harness with LANs in the four doors
of a BMW gave a nett weight reduction of 15kg.
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The adoption of infotainment features puts excessive strain on existing 12v systems |
A typical car now contains
dozens of microprocessors, not all of which are in constant use – a factor which
has been seized upon by designers who are pursuing ways of sharing microprocessors.
This will lead to a degree of redundancy, not just in the microprocessors themselves,
but also in the circuit boards. One example is the next generation of GPS (Global
Positioning Satellite) data receivers being designed by the Trimble organisation.
Trimble has developed a unit which is able to maintain a data flow even if interrupted
for as long as five seconds. This will allow the unit to share a microchip with
other applications which do not demand constant processing. “It’s
part of a technology ‘road map’ which shows where we will be in several
years’ time,” said Trimble executive David Hall.
The ramifications of 42v
technology for car dealerships will be profound, and will affect several levels
of the typical retail site. Firstly, it will require a completely different
approach within the service bays, as a fundamental characteristic of multiplex
harnesses is a capacity to self-diagnose problems. Secondly, the integration
of on-board telematics will affect the relationship between service reception
staff and customer, due to the ability of a car to automatically inform the
driver and dealer simultaneously of any problems, or the imminence of a service
requirement. Thirdly, there will be a need for reappraisal of stockholdings
of spares and accessories, as the changeover from the existing to the forthcoming
electrical systems will be gradual, rather than happening overnight. Lastly,
a breakdown truck will have to be equipped with a 42v power source for jump-starting
dead cars.
Luxury cars coming off the
production lines in 2005 are expected to feature electronic modules replacing
hydraulic brake and steering systems, electronically-controlled suspension and
traction control systems, complex transmissions which replace the fluid torque
converter with electronic clutches, ever-more-powerful engine management control
system processors, infinitely variable cabin climate control systems, advanced
information, entertainment, location and communications platforms, and the usual
complement of power-adjusted seats, mirrors, windows, and suchlike. This could
lead to an ultimate power consumption of as much as eight kilowatts, whereas
today’s electromechanical cars rarely exceed 1.5 to 1.7kW. Even mid-range
cars are likely to
require a considerably higher power output. One Ford electronics engineer suggests
that future Mondeo-sized cars will need 5kW – three times the consumption of
today’s car.
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By GlobalData |
|
Tomorrow’s
vehicles with 42v multiplex harnesses |
There was some talk of a
gradual transition to the new high power systems, with a number of cars running
dual batteries and sub-looms, but this was soon discounted. As BMW designer
Peter Thoma explained: “Running a dual system would exact an unacceptable
weight penalty.” His argument was that if higher voltage is to happen then
it should happen in one bite. The replacement for the current 7-Series is likely
to be BMW’s first model with a 42v system, with other models following
suit as they move on a generation. This pattern is likely to be mirrored by
the other major manufacturers. Audi is expected to equip the new A8 with 42v
systems within three years, the next E- Class Mercedes-Benz will probably have
this electrical system, and so forth.
Car manufacturers are not,
however, skipping lightly into step with each other on the matter of 42v technology.
While all major car companies agree that adoption is a matter of when, rather
than if, there is a minefield of potential problems. For example, there is not
yet a confirmed global standard, so sub-assembly and component suppliers are
waiting to see what everybody else does before committing to a complete new
product range. Nobody wants to be wrong-footed into a choice which will force
them to make further changes in five or ten years’ time. Transition costs
are frighteningly high – which is likely to force mergers and alliances which
would otherwise not happen – and there is the medium term compounding problem
of dealing with the enormous pool of vehicles which are a legacy of threequarters
of a century of 12v operation.
There is also the sheer
cost of all this re-engineering, not least the price of accelerating or completely
restructuring the testing and manufacturing processes. Recalls – or worse still
litigation – as a result of component failure is a major headache to vehicle
makers. This has led to an unprecedented degree of collaboration as manufacturers
abandon the old culture of entire self-containment in favour of shared experiences.
The major suppliers of components and sub-assemblies – Delphi, Visteon, Motorola,
STMicroprocessors, NEC, to name but a few – are working more closely than ever
before with car manufacturers, and are sharing resources and experiences.
 |
|
Headlamps
are expected to use central lighting sources and fibre optic distribution |
One surprise name which
has popped into the arena is Continental, the tyre maker. A subsidiary of this
company has been designing and prototyping a device called the ISAD (Integrated
Starter-Altemator-Damper) to replace the starter motor, generator, flywheel
and clutch or torque converter. Mounted between the engine and gearbox, the
unit allows a considerable weight saving and although it can be made to work
on a 12v electrical platform, it is at its most efficient at 42 volts. As well
as saving weight, the device also provides scope for engines to be far more
compact – especially when those engines are running with electrically operated
coolant pumps, and with individual solenoid-type valve actuators in place of
the usual camshaft-rocker arrangement. Again the provision of a high-amperage
42v power system as the enabler of this technology makes for a compelling argument
in its favour.
The truck market is likewise
bound to be affected by the development of higher voltages. For many years heavy
commercial vehicles have dealt with the increased electrical demand by using
a 24v battery-based wiring loom, but this is forecast to ultimately disappear,
to be replaced by a common system which will enable component manufacturers
– and of course the makers of telematics technology which is being snapped up
with a fervour by fleet operators – to commonalise on 42v battery platform.
 |
|
Volvo was an early adopter of multiplex harnesses -albeit with 12v battery power |
Opposition to 42v technology
is coming from two main areas. Producers of auto bulbs, besides having invested
heavily in 12v and 24v bulb manufacturing plants, have a second, more furtive,
reason for opposition; the car of tomorrow is likely to make widespread use
of fibre optics from a central light source, which will naturally reduce the
bulb count. And, of course, makers of traditional lead-acid batteries see their
market disappearing, too, as the new power units make use of lithium-polymer,
nickel-metal hydride, or suchlike.
Finally, for those who may
be wondering why 42 volts have been chosen rather than any other power level,
it’s because that voltage provides sufficient scope to run all anticipated
electrical and electronic systems without overstepping the potentially lethal
50 volt threshold.
