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15-03-2024 | Drivetrain | Interview | Article

"We Should not Focus Solely on BEVs"

Author: Marc Ziegler

2:30 min reading time

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Thomas Müller, Executive Vice President Powertrain Systems at IAV, talks in an interview about developments in the areas of batteries and electric drives. However, the combustion engine and open-technology development are also of great importance. 

MTZ: Does it make sense to combine different engine and motor technologies in one powertrain?

Müller: Yes, definitely. We know that battery electric powertrains are highly efficient, but renewable electricity is not always readily available. As a result, it is possible that a combination of different technologies in one hybrid powertrain will have a lower CO2 footprint than a BEV under current conditions. Therefore, to achieve the maximum reduction in CO2 emissions, we should not focus solely on BEVs. A technology-neutral approach is needed with other combinations of systems being taken into consideration. One example of this is a highly efficient combustion engine combined with an electric motor to create a serial hybrid powertrain. Given the availability of low carbon fuels, this is a very promising solution. 

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In addition, from a global perspective, it is clear that there are other useful options alongside BEVs. New regulations in China specifically highlight the requirement for combustion engines to be highly efficient and deliberately include PHEVs. E-fuels are also on the Chinese agenda in the context of alternative fuels and combustion engines. The tax on BEVs has been significantly reduced in the USA, but combustion engines are still of strategic importance there. For example, GM has recently announced the development of a new generation of engines. And in Japan, with its well-to-wheel legislation, combustion engines and PHEVs are doing much better than in Europe. The Japanese market remains extremely interesting with regard to both PHEVs and highly efficient combustion engines.

Are there differences between the electric motors used in BEVs and in hybrid powertrains?

This depends heavily on the type of hybrid powertrain. In serial hybrids, the electric motor takes over sole responsibility for the traction and, for this reason, it is no different from the motor in a BEV. In mild hybrids, which can travel in full electric mode up to a maximum speed of 50 km/h, much less torque is needed. In addition, support is provided for only a few operating points, such as boost mode when overtaking or reduced regenerative braking. Because of the lower performance requirements for this application, a high voltage at the level normally found in BEVs is not needed. This results in an electric motor design that is quite different from a BEV motor. The key difference between fuel cell vehicles and BEVs is the battery, but the traction requirements are similar. Therefore, the electric motors are identical in both types of vehicle. In the case of a hybrid powertrain with an internal combustion engine, it depends where the electric motor is located. If it is only on the rear axle and the combustion engine is on the front axle, a BEV axle or a BEV motor can be used. As a result, the electric motors are the same, although they are generally smaller and produce less torque and less power than those in pure BEVs in the same vehicle category. In most hybrids with combustion engines, the electric motor is close to the engine and is directly or indirectly linked to the speed of the engine. At the same time, the space available for installing a motor on the axle is highly limited. As a result, hybrid electric motors may differ significantly from those in BEVs, depending on the type of hybrid system.

You can read more about the interview with Thomas Müller in MTZworldwide 4/2024.


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