When working as a motor, the ISG supplies electric power directly to the engine, boosting output without burning more fuel. But when working as a generator, the ISG’s role is reversed and it generates electricity that is then stored in the 48-volt battery. As a mild hybrid drive model accelerates, electricity moves from the battery to the ISG, delivering a boost in performance. Then, as the vehicle decelerates, the spinning action of the engine drives the ISG, generating power and charging the battery.

This process happens seamlessly and continuously while driving so that the driver is barely aware of the technology at play. The most tell-tale sign that vehicle is in action is the instant surge of electric-like acceleration it provides.

In the Mercedes-Benz C 300 Sedan, mild hybrid drive delivers an additional 15kW and 200Nm of electric power and torque for a brief period when the vehicle starts and accelerates. This reduces the need for the ICE to use fuel to boost its performance, resulting in strong acceleration, potential fuel savings and reduced emissions over a comparably sized and powered conventional ICE vehicle.

Plug-in hybrid at play

The other innovative hybrid technology in the Mercedes-Benz passenger car range is the plug-in hybrid. This technology effectively bridges the gap between hybrids and fully electric models and gives customers the best of two worlds: in town they can run in all-electric mode, with next to no tailpipe emissions, while on longer journeys this hybrid model utilises the range of the combustion engine.

Unlike mild hybrid drive models that recharge their battery exclusively while driving, plug-in hybrid models can be recharged by plugging in to an electrical power source, just as you do with a battery electric vehicle. This model also captures otherwise wasted braking energy to optimise the battery in a process known as regenerative braking.

The Mercedes-Benz A 250 e Hatchback and Sedan are examples of popular PHEV models that can travel up to 73km in all-electric mode. In this mode, the A 250 e solely uses its 75kW/300Nm electric motor and its 15.6kWh on-board battery. Meanwhile, the highly efficient 1.3-litre, four-cylinder combustion engine (118kW/250Nm) comes into its own on longer road trips.

The combined output of the A 250 e powertrain is a healthy 160kW and 450Nm, with the system switching seamlessly between EV and ICE modes to create exceptional fuel economy in the order of 1.6L/100km (ADR combined cycle), and tailpipe emissions measured at a low 34 grams/km of CO2. Performance is also exceptional, with acceleration to 100km/h from rest taking just 6.6 seconds in the hatchback.