The Different Types of E-motor Layouts in Electric and Electrified Cars

written by Niccolò Ferrari

Nowadays, all automotive companies are transitioning to electric mobility in one way or another. Some of them are developing full electric vehicles, others are taking these changes one step at a time, through the electrification of the models’ range through mild hybrids and full hybrid cars.

Based on the requirements of the project, such as budget, performance and car features, engineers must decide between various layouts of electric motors, differentials, gearboxes, and batteries. 

The most straightforward solution to convert a traditional petrol model to a hybrid car is to develop a mild hybrid variant out of it. This is the easiest solution, because the battery pack is usually 24 or 48 Volts and of reduced dimensions, which can be easily stored below one of the passenger seats. However, the “electric” features of this layout are limited. The e-motor is usually placed between the engine and the clutch, providing a power boost during acceleration, and recovering energy under braking. A 100% electric drive is usually not allowed with this layout. However, these variants are convenient and economic to produce.

The second step in the electrification process is usually the full hybrid layout. These models are based on higher voltage batteries, from 200 to over 700 Volts depending on the models, with the possibility to allow an external recharge (plug-in). Car makers take different and original approaches to this kind of vehicles. The majority have a battery pack placed below the rear passenger seats, in a transversal orientation, with an electric motor connected through an additional clutch to the engine and gearbox. This allows to engage and disengage the e-motor based on the power requirement and use case. A different solution which some car makers developed is the use of smaller motors on one of the axles, usually the one not propelled by the ICE. There can either be 1 single electric motor with a dedicated differential, or two independent ones. This solution can also be combined with a hybrid powertrain on the other axles, creating a 4WD solution (this is cleverly done on the Toyota Prius 4x4). 100% electric mode is allowed. 

Finally, full electric vehicles, also called BEV (Battery Electric Vehicles). These vehicles all benefit from high voltage battery packs, from the 375 Volts of a Tesla Model S, to the 800 of a Porsche Taycan. Usually, since these battery packs are incredibly heavy and bulky, they are placed on the bed of the chassis to reduce to a minimum the impact of the hefty pack on driving dynamics. Having the pack placed in the lowest point of a vehicles, provides very reduced roll and decent handling. 

In conclusion, there is no single and ideal solution, nor does an ideal vehicle, or layout exist. Companies are finding various ways to achieve the same result: independent from the type of application, the aim is always to get the most efficiency out of the car, considering project’s budget and timing.

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