Published on May 21st, 2022 | by Daniel Sherman Fernandez


Latest C-Class Comes With A Mild Hybrid That Works Better Than A PHEV

How does the Mercedes-Benz mild hybrid technology work?

The mild hybrid technology electrifies combustion engines. As a result, the new models of the C-Class family offer even better driving dynamics while at the same time consuming much less fuel and this comes from the new four-cylinder engines which are available as mild hybrids.

The 2022 model C-Class is offered with the newly developed M 254 four-cylinder petrol engine. For the first time, this petrol engine is equipped with an integrated starter generator (ISG) and a 48-volt vehicle electrical system.

“From the very first rotation on, the ISG provides 15 kW of additional electric power.”

In concrete terms, this means that every Mercedes that is equipped with an ISG and a 48-volt vehicle electrical system is a mild hybrid. Unlike the plug-in hybrid technology, the electric motor in a mild hybrid does not drive the car, but instead assists the combustion engine at low engine speeds, such as when starting or accelerating.

The new four-cylinder engines of the C-Class use integrated starter generators of the second generation. This ISG combines the starter and the generator into a high-performance electric motor that is located between the combustion engine and the transmission.

Mild Hybrid

This electric motor is connected to a 48-volt battery that supplies the vehicle electrical system and the electric machine with electricity. By combining the ISG with a 48-volt vehicle electrical system, it not only optimizes driving dynamics, but also efficiency.

With this M 254 four-cylinder petrol engine (258hp, 400 Nm of maximum torque) there is an additional 15 kW of electric power and 200 newton-metres of torque are temporarily provided.

A positive effect that also applies to fuel savings. Despite improved driving dynamics, mild hybrids can achieve fuel savings and CO₂ reductions that, previously, could only be attained by plug-in hybrid models.

This is made possible by the 48-volt battery, which can store energy and supply it to the electric motor. Thus enabling the system to offer typical hybrid features, such as recuperation, load point shift, coasting, and an almost unnoticeable restart of the engine in the start/stop function.

Mild Hybrid

How does recuperation work in a mild hybrid?

Energy is released during braking or when approaching a vehicle up ahead. The ISG recovers this energy by converting (“recuperating”) it into electricity that is used to recharge the 48-volt battery. The 48-volt battery stores the recovered energy and supplies it to the electric motor. This way, the electric motor can provide the combustion engine with up to 15 kW for a more dynamic acceleration.

What is meant by coasting?

Another feature that helps to actively save fuel is known as coasting. If the driver takes his or her foot off the gas pedal when the ECO drive program is activated, the combustion engine is uncoupled from the drive system and switches off completely. It really makes the driver feel as if the vehicle is coasting smoothly along the road.

The engine restart from the coasting mode is barely noticeable because the starter generator brings the combustion engine to synchronous speed very quickly and evenly. This makes the starting procedure even quieter. The same applies to restarting the engine with the start/stop function, so that the driver hardly notices the restart procedure.

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