Under the microscope: the technology of the compact hybrids: Transverse is more

Sep 14, 2019

The vehicles belonging to Mercedes-Benz's compact car family feature transversely mounted engines. A compact hybrid traction head has been developed for the 8G-DCT dual clutch transmission which follows the same technical principles as the corresponding component on the vehicles with a longitudinally installed engine. An electric output of 75 kW and a range of up to 77 kilometres are a guarantee of driving pleasure.

It is a permanently excited synchronous motor as an indoor runner. The stator is permanently integrated in the traction head housing, while the low-loss wet clutch is incorporated in the motor's rotor. On-demand stator and rotor cooling allow use of the electric motor's peak and continuous output without any problems. For the first time on a Mercedes-Benz vehicle, the combustion engine is started by the electric motor - the compact hybrids do not have a separate 12-volt starter.

High system output for driving pleasure

The electric machine achieves 75 kW. Together with the 1.33-litre four-cylinder engine this produces a system output of 160 kW (218 hp) and a system torque of 450 Nm. Thanks to the EQ Power of the electric motor, these vehicles respond to the accelerator very rapidly and deliver impressive performance: for example the A 250 e takes 6.6 seconds to accelerate from 0 to 100 km/h, with a top speed of 235 km/h.

A lithium-ion high-voltage battery with a total capacity of approx. 15.6 kWh is used as an electric energy storage unit. It can be charged at an external electric energy source. The A 250 e and B 250 e can be charged with alternating or direct current. A corresponding vehicle socket is located in the right-hand side wall of the vehicles. This means that the compact plug-in hybrids can be charged at a 7.4 kW Wallbox with alternating current (AC) within 1 h 45 min from 10-100 percent SoC (Status of Charge and with For direct-current charging (DC) the battery can be charged from 10 - 80 percent SoC in around 25 minutes.

The batteries are supplied by the wholly-owned Daimler subsidiary Deutsche ACCUMOTIVE. The high-voltage battery is water-cooled and weighs approx. 150 kg.

Clever packaging, innovative exhaust system

An innovative exhaust system makes clever packaging possible: rather than extending to the end of the vehicle, the exhaust ends in a centrally positioned outlet under the vehicle floor, with the rear silencer housed in the transmission tunnel. Integrating the fuel tank into the axle installation space creates room beneath the rear seats for the high-voltage battery. This results in only minimal reduction in boot capacity compared to the sister models without hybrid engines. The aerodynamics likewise benefit from this arrangement, because the underbody is very smooth.

Because the compact models use scaled-down technology from the third plug-in generation, all of its functions are also available. These include in particular the intelligent, route-based operating strategy, taking factors such as navigation data, speed limits and route into account. Pre-entry climate control is an important comfort feature, as the vehicles have an electric air conditioner compressor. The pre-entry climate control can also be activated conveniently by smartphone. The towing capacity of the compact hybrids is also impressive at 1600 kg (braked).