Multi-Speed Gearboxes for Battery Electric Vehicles

Electric Vehicles (EVs) have started to become a significant part of transportation. Battery Electric Vehicles (BEVs) are one type of EV to draw attention towards. Despite their numerous benefits over gas-powered vehicles, they still have the potential for improvement. The performance and energy efficiency aspects of their powertrains are often not optimized, affecting their real-world capabilities. Multi-speed gearboxes could have the potential to improve the powertrains of BEVs. To investigate this hypothesis, an experiment was conducted where a three-speed gearbox was implemented into the powertrain of a Nissan Leaf, an existing battery electric car. The car’s powertrain specifications and its electric motor performance curve were used to generate the initial graphs. By applying the gear ratios from the gearbox on the motor’s initial values, new data plots were generated. The experimental data consisted of torque-speed relationship, energy efficiency, and loss in power graphs. The results of the experiment were then analyzed to evaluate the effects of the gearbox on the car’s powertrain data. The gearbox showed overall improved combinations of performance and energy efficiency figures. Enhanced performance figures meant that the output speeds and accelerations of the car increased. High energy efficiency outputs at various speeds occurred, which was not obtainable by the electric motor. The significance of the experiment’s results was then applied to helpful uses in real-world driving scenarios. Further evaluation was made, speculating on future helpful uses of gearboxes in BEVs.