2018-01-0422 Published 0 3 Apr 2018 © 2018 General Motors LLC.Development of General Motors’ eAssist Gen3 Propulsion System Daniel Cottrell, Michael Andrew Miller, Andrew Oury, Eric Staley, Danny Mui, Dale Osterkamp, and Stephen Poulos General Motors LLC Citation: Cottrell, D., Miller, M.A., Oury, A., Staley, E. et al., “Development of General Motors’ eAssist Gen3 Propulsion System,” SAE Technical Paper 2018-01-0422, 2018, doi:10.4271/2018-01-0422. Abstract General Motors’ 3rd generation eAssist propulsion systems build upon the experience gained from the 2nd generation 115v system and the 1st generation 36v system. Extensive architectural studies were conducted to optimize the new eAssist system to maintain the performance and fuel economy gains of the 2 nd generation 115v system while preserving passenger and cargo space, and reducing cost. Three diverse vehicle applications have been brought to production. They include two similar pickup trucks with 5.3 liter V8 engines and 8 speed transmissions, a 4-door passenger car with 2.5 liter 4 cylinder normally aspirated gasoline engine and a 6-speed automatic transmission, and a crossover SUV with a 2.0-liter turbocharged engine and 9 speed transmission. The key electrification components are a new water cooled induction motor/generator (MG), new water cooled power electronics module, and two major variants of 86v lithium ion battery packs. All three applica - tions share variations of the same components, showing the bandwidth of the 3 rd generation system. The engines include special dual tensioner accessory drive systems to couple the MG to the crankshaft. The transmissions are all modified to support the eAssist system. The torque based control system of the 2 nd generation eAssist system was carried into these applications and integrated with the latest GM corporate common electrical and controls architectures. Introduction eAssist systems continue to have an important role in GM’s electrification strategy that ranges up to full electric and fuel cell vehicles. As a “light electrification” architecture, eAssist is a high value system at the lower power end of the electrification spectrum that is intended to provide significant fuel economy gains in conventional propulsion systems at a relatively low cost. This is particularly useful in vehicles with regulatory limits for CO 2, customer interest in greater fuel economy, and/or applications where the torque assist capability can aid drive quality and performance. In this generation of eAssist, the fundamental architecture of a belt-alternator-starter (BAS) system with a motor generator connected to the crankshaft by a belt was retained, but the architecture was made more flexible to permit application in a greater variety of propulsion systems. In the following infor - mation, there is an explanation of the key requirements, archi - tecture, components of the system, and controls. Note: For clarity, the naming conventions used in this document will be: 36V BAS is the 1 st gen system, 115V eAssist is the 2nd gen system, and 86V eAssist3 is the 3rd gen system. The 115V and 86V names refer to the approximate nominal system operating voltages. The voltages specified in this document for components may vary from the system voltage based on the local conventions used, assumed state of charge, and rounding. System voltages will vary during opera - tion with charging and motoring modes. The 36V BAS system naming is different and was not named for its nominal system operating voltage, which was approximately 42V, but rather was named for the battery component voltage. Key Requirements & Architecture The primary objective of the eAssist3 program was to develop a system that could offer similar benefits to the customer as eAssist at a reduced cost while maintaining the ability to span multiple vehicle platforms. Two important customer benefits included 1) reduced fuel consumption through capture and efficient use of elect