Volkswagen first upgraded German domestic models of the Beetle to 12 volts, but waited until 1967 to follow suit with its export Love Bugs.
In the early days of motoring, most car features were mechanical, with electricity playing only a minor role, if any.
These days, however, standard features such as heated seats, power windows or driver assistance systems consume a great deal of electricity, requiring ever-increasing current to flow through the now standard 12-volt wiring systems.
As a result, some manufacturers have started installing a second, 48-volt network in their cars.
In general, higher voltage allows for more powerful functions in a vehicle.
"The 48-volt technology can be easily integrated into the architecture of conventionally engined vehicles and offers functions that until now have only been found in high-voltage hybrid systems with 300 to 400 volts," explains Bernhard Klein, head of development and electric vehicles at automotive supplier Continental.
The SQ7 TDI.
These functions include running the power braking, steering and lights while a car coasts with its engine switched off to save fuel, instant engine starting and efficient recuperation of braking energy.
"A 48-volt hybrid system is the best way to reduce fuel consumption and CO2 emissions at a reasonable cost," argues Klein.
Fuel economy could be increased by about 13 per cent at standard consumption, and around 21 per cent in urban traffic if coasting, engine shutdowns at traffic lights and recuperation were all standard thanks to a 48-volt system.
In addition, higher voltage can more easily meet the rising electrical demands of modern cars.
Audi, for example, has installed a 48-volt sub-network in its SQ7 TDI SUV, which powers both the electrically driven compressor - a kind of turbocharger - as well as the electromechanical active roll stabilization system.
Mercedes is also adding more voltage to its newly developed vehicles and engines, notes Michael Weber, head of the on-board power and electromagnetic compatibility department at Mercedes.
In a new six-cylinder petrol engine model, an integrated 48-volt starter-generator is used to electrify the whole car, supplying power to features such as the electric coolant compressor, an additional compressor for the turbocharger, the water pump and a voltage converter.
The main advantage? The generator does not need a belt drive and no longer has to be positioned directly in front of the engine. This, in turn, reduces the overall length of the motor and reduces the car’s weight.
"In principle, all high-performance vehicles are predestined for a 48-volt electrical system," says Weber.
The advantage lies not only in the higher voltage, but also in the cabling. A basic electrician's principle is that low-voltage systems require fat copper cables because of resistance.
Raise the volts to 48 and thinner wires with reduced cross-sections become possible. Less heat is generated in the wires, less power is lost and less space is required in the car for the cables.
With a 48-volt system, four times the current could be transported in a cable with the same thickness as a 12-volt cable, which helps decrease the vehicle weight.
BMW is also set to rely on 48-volt technology, with electric-controlled turbochargers, air conditioning, start-up aids and traction control all likely to be draw the higher voltage.
Over the years, there have been calls for cars to run 110 volts, but there have always been fears of electrocution during accidents.
"48 volts represents a good compromise between a sufficient energy supply and reasonable effort and risk," says a spokesman for the German automaker. These networks can offer increased performance in top-of-the-range cars and increased savings in the compact car segment.
Even so, not all vehicles will be upgraded to higher voltage systems in the future.
The main reason for this, explains Weber, is the availability of the required components, which are either exclusively designed for 12-volt systems or are far more expensive in 48-volt versions. In addition, many vehicles require relatively little power and can thus function just fine with a 12-volt electrical system in place.
