## 3 Main Components of EV Powertrains  
EV powertrains mainly consist of batteries, an electric motor and transmission and their performance can be defined in terms of efficiency and practicality. A highly efficient EV powertrain means that its power consumption (kWh) per distance (km) can be kept as low as possible, thus allowing the vehicle to increase its driving mileage. For practicality, the target is to ensure that the powertrain components are cost effective; the cost for production  
Figure 1: Summary of potentials and challenges of EV regarding environmental and other issues based on literatures in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. and operation (i.e., maintenance) can be kept as low as possible, and sustainable, i.e., with a low carbon footprint from production until application. The purpose of the battery, the first component of an EV powertrain, is to store electricity for the electric motor's operation. To ensure that the powertrain is highly efficient and practical, the battery needs to have high energy density so that it can store high amounts of electric power without affecting its weight. Achieving this involves implementation of new cathode, anode and electrolyte materials. One of the options, suggested by [11], is to increase the nickel content in the cathode. However, this method inevitably leads to the reduction of the cathode's thermal stability, hence risking thermal runaway or damage to the battery [12]. However, according to [13], a high battery temperature, if properly managed, also presents an opportunity to enhance its performance in delivering the electricity to the motor. Because of this, many researchers have proposed either active cooling methods so that the battery's temperature can be optimized to suit various driving conditions, or emerging materials for the anode surface [14; 15; 16; 17]. Nonetheless, such cooling methods require extra management complexity and additional power consumption for operation, while the usage of emerging materials, though promising, usually involves a significant investment for new mining and manufacturing process [18]. This is consistent with the findings by [19], which estimated that new investment of 100 Euros is required to increase the battery capacity by 1 kWh. In short, increasing the battery energy capacity, even though can avoid the increase of weight, has its own challenges in terms of safety, complexity and cost. The next major component of an EV powertrain is the electric motor which is responsible for converting the electricity from the battery into mechanical power to move the vehicle using the electromagnetic induction principle. The motor is controlled by an inverter that regulates the required current flow from the battery to suit the driving conditions. There are two typical types of motor used in EVs: permanent magnet synchronous motors (PMSMs) and induction motors (IMs). In PMSMs, the magnetic field required to rotate the rotor is generated using permanent magnetic materials in either the stator or the rotor. On the contrary, in IMs, the electromagnetic field is produced using a current flow in the rotor conductor. Compared to ICEs, the volume of both types is relatively more compact, and, they also have a higher power to weight ratio. Even so, there are still continuous studies carried out to explore the implementation of advanced materials, like ultraconductive copper for motor windings, and grain boundary diffusion processed magnets, with the intention to increase the motors' power density even further [20]. The compactness and high-power density contribute positively to the power consumption of an EV. Not only that, but these motors also offer high torque capability at low motor speed (RPM) which eliminates the requirement of high gear ratios for vehicle start-stop. This explains the typical omission of multispeed transmissions in the existing EVs.