Renault is aiming to become the first carmaker to make the switch from 14-volt to 42-volt electrical systems.
The French carmaker says it will introduce a model with a combination of 14- and 42-volt power in 2004. Renault expects to launch full 42-volt application in 2007, when all the components needed for the system will have become cost effective.
'There are increasing demands on electrical systems in modern cars,' said Michel Vimont, Renault's vice president of electric engineering.
'More electrical functions and accessories - such as mobile phones, Internet entertainment and electronics-based safety systems - are being introduced. Therefore, the industry has decided to make the transition to 42 volts.'
Using the Scenic as a prototype, Renault has been developing a 42-volt electrical system since 1998.
On-board voltage was last changed in the late 1950s and early 1960s, when carmakers made the switch from 6-volt systems.
Average demand for electric energy in cars has climbed from 650 watts in 1970 to 950 watts in 2000. It is predicted to rise to 3,500 watts in 2003 - and to 5,000 watts by mid-decade.
'We would need an electric current of up to 357 amps for 5,000 watts,' said Vimont. 'Under the existing 14-volt system that would require much thicker wiring. There would also be the risk of components malfunctioning. With a 42-volt system, electric current can be restricted to a realistic and workable 119 amps.'
The use of higher voltages at lower currents is more power- and weight-efficient, partly because it can reduce the amount of copper cabling in vehicles. The reliability of electric connectors would also increase, said Vimont.
To illustrate how power-hungry modern cars are becoming, Vimont said the next-generation Renault Laguna will have 19 computers performing 62 different electrical functions. The current model has about the same number of on-board computers - but they perform just 25 electrical functions.
Added to this, electric braking systems, electric power steering and even camless electric valve operation are all under development.
'There is a clear trend to replace mechanical functions with electrical functions, in addition to the increasing number of electrical interfaces,' said Vimont.
At present, certain components are not compatible with a 42-volt electrical system. For example, lower voltage is required for a vehicle's lights. Too much power can cause ordinary light bulbs to blow. Bulbs that can handle the higher voltage are too delicate for vehicle use.
To solve the problem, Renault has developed a bi-tension electrical installation system that uses a main 42-volt battery and a smaller battery capable of providing 14-volt power when needed.
'But from 2007 we will be able to offer a complete 42 volt-only model,' said Vimont.
Stephan Kraus, spokesman for Robert Bosch in Stuttgart, agrees that 42 volts will become the future auto industry standard. But he believes Renault's target for full 42-volt application is ambitious.
'We are convinced that the transition will start in four or five years, but it will be a gradual process,' said Kraus. 'Dual voltage, or so-called bi-tension electrical installation, will be used for quite a long period of time. I don't expect full 42-volt systems to be available before 2010 - and then only on luxury models.'
Kraus said dual-voltage systems are attractive because they allow the gradual introduction of 42-volt components, so carmakers don't have to wait for every type of electronic component to become available.
But the drawback is that dual voltage usually requires two battery systems, extra wiring and added complexity, he said. Weight will also increase because 'you need two batteries and two generators,' said Kraus.
He also said that for safety reasons, electric brake-by-wire systems would always require two parallel circuits.
'We need to decide which components are suitable for transition to 42 volt first, and which - such as bulbs - will remain 14 volt for the time being,' he said.
Vimont could not say how much it will cost Renault to make the switch to 42 volts.
'Because the transition will run parallel with the introduction of new electric applications of certain components, it is difficult to assess the financial consequences,' he said.
Vimont also said the application of a static fuel cell as an alternative electric power source to traditional batteries is something the industry is working on. Renault is cooperating with BMW on development of a static fuel cell power source.