Electric power: sketch of battery in car.

Electric power for petrol and diesel engines.

  • 3. January 2017
  • E-Mobility
  • Illustration: Realgestalt
  • Text: Walther Wuttke

The 48-volt on-board power supply makes it possible: on the newly developed engines, Mercedes-Benz combines conventional technology with hybrid powertrains.

“The reports of my death are greatly exaggerated”, quipped a very much alive Mark Twain about the news of his purported passing. The developers of internal combustion engines are having a similar experience these days. While the imminent demise of petrol and diesel engines and their replacement with electric powertrains are being proclaimed almost incessantly, the developers are working on ever cleaner and more efficient petrol and diesel engines, which however rely on a bit of electric pick-me-up.


Because the powertrain development at Mercedes-Benz now combines an electric boost with conventional technology. The company has now presented its latest innovation, newly developed engines that blur the lines between conventional and hybrid powertrains thanks to a 48-volt on-board power supply.

Outstanding fuel economy

For Thomas Weber, responsible on the Daimler Board of Management for Group Research and Development, this combination is a logical step. “The systematic optimisation of our hi-tech engines plays a crucial role in our road map towards sustainable mobility. For the mobility of the future, we are deliberately not committing ourselves to one solitary form of powertrain, but to a coexistence of efficient and clean petrol engines, diesels, plug-in hybrids, battery and hydrogen powertrains. Each of these types of powertrains has its justification and future prospects.”


With the integration of the 48-volt on-board power supply, the modern engines achieve outstanding fuel economy. In addition, the new on-board power supply drives, among other things, the particularly power-hungry components such as the water pump and air conditioner compressor. Furthermore, the powertrain architecture also allows integrating innovative technologies such as the electric booster compressor now presented as a world-first. The compressor provides sufficient boost pressure within a fraction of a second. The results of this partial hybridisation are significantly lower fuel consumption and CO₂ emissions.

' For the mobility of the future, we are deliberately not committing ourselves to one solitary form of powertrain. '

Thomas Weber, Member of the Board of Management of Daimler AG, Group Research & Mercedes-Benz Cars Development

Booster for accelerating

The integrated starter alternator (ISA) combines the starter and the alternator in one electric motor positioned between the engine and the transmission, eliminating the need for a belt to drive the ancillaries. This also benefits the space requirement of the powertrain. Thanks to ISA, the new powertrain fits under the bonnet in six-cylinder in-line configuration. ISA also handles cold starts and speeds up fast engine warm-up during this particularly critical phase for the environment. As in a hybrid powertrain, the electric motor integrated into the ISA also serves as a booster for accelerating, and supplies the lithium-ion battery with additional energy recovered during braking.


In the long-term, the higher costs of this technology should be more than off-set by the significant fuel savings. The savings are between ten and 15 percent, and are thus on a level previously only achieved by hybrid powertrains. This was also made possible by the fact that the engineers are now able to run the engine in an economical map more often.

Significantly lower fuel consumption and CO₂ emissions.

The S-Class takes the lead

The lower emissions are also realised because the technology is able to switch the engine off more often than with today’s start/stop systems. For example, the engine is switched off briefly when the driver releases the accelerator pedal and the vehicle is coasting to a stop at a traffic light. If the engine is needed again, the powertrain quickly spools back up thanks to the 48-volt system. The new technology will be introduced in the model range next year with the S-Class taking the lead. Other models will follow step by step.


The technology of the 48-volt on-board power supply allows increasing the output in boost mode temporarily by ten to 15 kW (14 to 20 hp), and recovering 80 percent of the braking energy. As a result, CO₂ emissions are cut by between seven and 12 grams per kilometre. Many of the advantages of the ISA also apply to the belt-driven starter alternator (BSA), which uses the existing mounting points on the engine.

Higher voltage for more comfort

In addition to the technical advantages such as lower fuel consumption, the 48-volt on-board power supply also impacts the comfort features. Because the climate control system, electric heating elements or fan can in the future be operated at a higher voltage, meaning that at identical capacity, just one fourth of the energy has to flow through significantly thinner and lighter wires. Furthermore, the new on-board power supply allows constructing further elements from the areas of infotainment and assistance systems.


The first engine to use ISA technology is the new six-cylinder M256. The new engine has an output of more than 300 kW (408 hp) and thanks to ISA delivers the road performance of an eight-cylinder engine with considerably lower fuel consumption and emissions. The new M264 four-cylinder petrol engine produces the output of a six-cylinder engine. It is equipped with a belt-driven starter alternator and a 48-volt water pump. It will also début next year as the first four-cylinder engine in the S-Class.


Seven percent less fuel consumption

In addition, the new petrol engines are fitted with a particle filter that further reduces the impact on the environment. Other new developments to be launched are an all-new eight-cylinder engine with cylinder shut-off, and a six-cylinder diesel, which consumes more than seven percent less than its predecessor while producing a higher output (over 230 kW/313 hp).

80 percent of the braking energy can be stored.

On the road to global battery production.

Daimler commits to the future of electric mobility and expands its Kamenz location in Saxony to a global centre of production and competence for lithium-ion batteries. To this end, Daimler will quadruple the production and logistics space to 80,000 square metres. Construction on the new production facilities has now started directly adjacent to the existing manufacturing plant. As a result, Daimler subsidiary Accumotive will in the future produce all batteries for the hybrid and electric vehicles of the Mercedes-Benz and smart brands in Kamenz, about 50 kilometres from Dresden. In addition, the stationary energy storage units and the energy storage units for the 48-volt on-board power supplies are also being built in Kamenz. This technology will be gradually integrated into the various model series in the coming years. “We are evolving into a centre of competence for global battery production”, explains Frank Blome, Managing Director of Deutsche Accumotive and in the future responsible for the battery production worldwide.

All in all, Daimler will invest some 500 million euros at the Kamenz location – more than half of the investments in the global battery production network slated for the coming years. At the end of the expansion phase, Kamenz will be home to one of the world’s largest and at the same time most modern production sites for batteries. It is intended to satisfy the growing demand for innovative energy storage units.

“By 2025, we will have more than ten all-electric vehicles in the range of passenger vehicles alone. At the same time, we are consistently advancing our plug-in hybrid initiative and the introduction of 48-volt systems. High-efficiency batteries are an important component of our strategy and an integral part of the vehicle architecture, and thus not an off-the-shelf product. The development, production and integration of these complex systems are part of our core competences,” declared Daimler Chief Development Officer Thomas Weber at the start of construction. Daimler is the only German manufacturer that produces the batteries for its electric and hybrid vehicles in-house.

The new plant is designed for carbon neutrality to amplify the climate-friendly effect of electric mobility in this way as well. To achieve this, the energy is supplied by a combined heat and power plant, and a photovoltaic system in concert with stationary battery units. Solar panels covering an area the size of two football fields will be installed on the roof of the new factory. They are designed to deliver a capacity of two megawatts. In addition, the new factory is equipped with state-of-the-art machinery and technologies. The production facilities are also supposed to set new standards in the area of Industry 4.0.

Related topics.