INTRODUCTION Battery electric vehicles (BEVs) have made sporadic inroads into the light-duty vehicle market since the start of the automotive industry over a century ago. Within the last five years, a new generation of BEVs has emerged, offering useful range for most commuters and a smooth and responsive driving character. The Chevrolet Spark EV [1, 2], introduced in the US, Canada and Korea in 2014, is an excellent example of that generation. With an EPA label range of 82 miles, 0-60 mph acceleration under 7.5 seconds, and the ability to charge from a 50 kW DC station, the Spark EV is an affordable and fun-to-drive second car with exceptionally low operating cost and no tailpipe emissions. To bring BEVs to a wider audience of mainstream customers, the Chevrolet Bolt EV must virtually eliminate “range anxiety” by greatly increasing driving range, while building on the strong performance of the previous generation. Key to achieving that goal is a propulsion system that can combine high levels of stored energy, efficiency, power and torque. This paper describes how the propulsion system for the Chevrolet Bolt EV was defined, starting from a challenging set of requirements that included enabling a 200 mile range, comparing design alternatives, and optimizing it through rigorous analysis. KEY REQUIREMENTS The key requirements of the propulsion system for the Chevrolet Bolt EV were to significantly increase driving range and to maintain or exceed the excellent acceleration performance of the Chevrolet Spark EV , when applied to a larger vehicle platform. Table 1 presents some of the main vehicle requirements of the Chevrolet Bolt EV at nominal conditions. As seen in Table 1, the Chevrolet Bolt EV was targeted to be larger than the Chevrolet Spark EV , yet with improved performance, grade launch capability and, most importantly, driving range, exceeding a US Environmental Protection Agency (EPA) rating of 200 miles. The 200 mile target was developed based on the real customer driving data analysis of the Chevrolet Spark EV and the General Motors range-extended electric vehicle, Chevrolet V olt. That data suggested that a BEV with 200 miles of range could almost completely eliminate “range anxiety” for the vast majority of customers in daily driving situations. Table 1. Vehicle Performance Requirements The performance of the vehicle is also dependent on the ambient temperature and the battery energy level. Since the battery is optimized to support a large capacity, it is designed to use a large voltage range. As the remaining battery energy decreases, the battery Design of the Chevrolet Bolt EV Propulsion System Jinming Liu, Mohammad Anwar, Peter Chiang, Shawn Hawkins, Youngsoo Jeong, Faizul Momen, Stephen Poulos, and Seunghan Song General Motors Co. ABSTRACT Building on the experience of the Chevrolet Spark EV battery electric vehicle, General Motors (GM) has developed a propulsion system with increased capability for its next generation Chevrolet Bolt EV . It propels a new lar ger electric vehicle with significantly greater electric driving range. Through extensive analysis the primary propulsion system components, which include the drive unit, traction electric motor, power electronics, energy storage, and on-board charging module, were optimized individually and as an integrated system to deliver improvements in propulsion system ener gy, power, torque and efficiency. The results deliver outstanding EV range and fun-to-drive acceleration performance. CITATION: Liu, J., Anwar, M., Chiang, P., Hawkins, S. et al., "Design of the Chevrolet Bolt EV Propulsion System," SAE Int. J. Alt. Power. 5(1):2016, doi:10.4271/2016-01-1153.2016-01-1153 Published 04/05/2016 Copyright © 2016 SAE International doi:10.4271/2016-01-1153 saealtpow.saejournals.org 79Downloaded from SAE International by Univ of Nottingham - Kings Meadow Campus, Monday, September 17, 2018voltage decreases, which causes the power capabilities of both the battery