Old wine in new skins - what is special about the concept of the 48 Volt-vehicle electric system?02/03/2012
The expert conference of the VDI about “Electrics and Electronics in the Vehicle” in November 2011 left the participants at least with one big surprise: A representative of a vehicle manufacturer introduced the basic concept of a 48 volt-electric system in a passenger car. Preceding this presentation was an appeal of five vehicle manufacturers in July last year in Ludwigsburg, when automotive suppliers were requested to actively develop components for 48 volt-vehicle electric systems. Participants being familiar with the matter have seen a parallel to the discussion about a 42 volt-vehicle electric system at the end of the last decade, which went lost because of the high prices of the components.
Ottmar Sirch from BMW explained why the new concept of a 48 volt-vehicle electric system is different and probably more successful than the 42 volt-vehicle electric system from 2000. Ten years before, it was all about the availability of electric energy for comfort functions. Today, the base is much wider and the need for a new vehicle electric system is a much more pressing issue.Although comfort functions in the new concept are still considered, the core of the concept is about energy savings. And there is a lesson learned from the shortcomings of the old concept: The aim is now to create an inexpensive alternative to expensive hybrids, which is based on the foundation of the well-known and proven start-stop technics to enable a high market penetration with further clearly reduced CO2-emissions at a justifiable additional price. However, not all components have to be converted to 48 volt. But some are fundamental for the implementation of the concept. For instance, with higher voltage generators the 48 volt system can absorb more electric energy than it is possible with a 12 volt system. This electric machine could be used also as an accelerator booster and could keep the combustion engine within an efficient operating range. A 48 volt lithium-ion battery would be able to store more braking energy, which is also necessary for the bigger generator. For the control and for the voltage conversion there is the need for a DC-DCconverter, which can handle the higher voltage and power. Today's frequently applied electric power assisted steering is reaching its physical limits in the upper middle-sized class, which prevents the complete substitution of hydraulic power steering assist by now. Through a 48 volt electric system, a real breakthrough could be achieved. To prevent the fast heating up of the interior more efficient PTC-heating modules and more powerful electric fans could be used. This would raise the exhaust-gas quality as well as the comfort of the passengers. Furthermore, an electric driven air-conditioner compressor may generate convenient air condition inside a car even if the engine is shut down due to a vehicle standstill, which can only be achieved by a significantly raised operating voltage. A number of further applications exist which may operate at 48 volt with operational advantages. These applications may be introduced if a broader penetration of 48 volt has been achieved. If the five vehicle manufacturers should be successful with their proclamation, the initiation of 48 volt vehicle platforms is expected in 2016/2017. Decisive for the success of the approach will be, if the suppliers have the ability to develop such components without or with low additional costs and if they will be launched in sufficient series sizes from the beginning. This will only work if every supplier can get an adequate share of the businesses.