Driveline Efficiency in Electric Vehicles: A Review of Architectures and Gearbox Power Losses

Optimizing transmission efficiency is critical for advancing electric vehicle (EV) technology. This review paper covers advanced driveline schemes for electric cars and electric heavy vehicles through a selection and analysis of articles published over the past decade, focusing on passenger and commercial electric vehicle drivetrains, transmission efficiency modeling, gear optimization, and tribological and NVH outcomes. The selected sources are grouped into analytical themes to map current academic and industrial developments in transmission topologies, specifically comparing single-speed reduction units with two-speed and multi-speed configurations. A comparative summary is discussed to consolidate the characteristics, complexity, efficiency impact, and typical applications of the various gearbox types. The review article is complemented by an examination of loss mechanisms through the lens of international tribological research. Key focal points include mechanical power losses, gear and bearing friction, and the trade-offs associated with low-viscosity fluids for electric vehicles to provide a comprehensive support resource for researchers and designers in the field of transmissions for EVs. Future development trajectories are delivered regarding the increase in efficiency and specific challenges of EV gearboxes.