INTRODUCTION Government regulations in the United States and other nations effectively demand the production of battery-only electric vehicles (BEVs) whose sole source of propulsion energy is electricity. Today, battery technology is still challenged to supply sufficient energy by itself for vehicles that customers will purchase in the numbers required by the regulations. Although most drivers drive less than 60 km (or 40 miles) on most days, day-to-day variation in driving distance and driving conditions causes drivers to reasonably demand a vehicle that has a much greater nominal range. For an electric vehicle (EV) classification where the extended-range powertrain of the Chevrolet Volt (which operates as an EV until battery energy is low) is excluded, range is subject to the limits of practical battery technology and acceptable battery cost. Today, the most expensive part of a typical BEV is the battery itself. The fundamental cost of the battery, that is the cost of the cells themselves, may exceed the cost of the entire remainder of the propulsion system. Part of the cost of the BEV battery is due to the requirement for output power, but the primary cost driver is from the requirement for enough output energy. The battery must deliver enough energy to provide sufficient range to make customers feel comfortable in everyday driving. For such range, an optimized propulsion system for a BEV must also include an electric motor that is efficient over a wide range of driving conditions and an efficient mechanical connection from the motor to the wheels. This combination makes the best use of power and energy from the battery, so as to minimize the power and energy requirement on the battery while delivering appealing vehicle performance and range. At the same time, this combination of electric motor and mechanical connection to the wheels, known together as the drive unit (DU), must also be lightweight and compact, in keeping with the need for an efficient vehicle. The drive unit must also be exceptionally quiet, as compared with the powertrain of a conventional automobile, to deliver one of the special benefits of the BEV, relatively peaceful driving. Furthermore, this particular drive unit must meet the commercial customer driving demands by being robust to different driving conditions, including hill climbing, merging, freeway driving and hot and cold temperature extremes. GM used experience with the drive unit from GM EV1, the first modern production BEV, in the design of the 1ET35 for the Spark EV. The original concept vehicle for the EV1, the GM Impact, was one of the first vehicle demonstrations of neodymium-iron-boron permanent magnet (PM) motors, but in the early 1990s, the production of high-energy magnets was relatively immature. For production, the EV1 design was a relatively conventional squirrel-cage induction motor. Both Design Optimization, Development and Manufacturing of General Motors New Battery Electric Vehicle Drive Unit (1ET35) Shawn Hawkins, Alan Holmes, David Ames, Khwaja Rahman, and Rodney Malone General Motors Co. ABSTRACT The General Motors (GM) 1ET35 drive unit is designed for an optimum combination of efficiency , performance, reliability, and cost as part of the propulsion system for the 2014 Chevrolet Spark Electric V ehicle (EV) [1]. The 1ET35 drive unit is a coaxial transaxle arrangement which includes a permanent-magnet (PM) electric motor and a low loss single-planetary transmission and is the sole source of propulsion for the battery-only electric vehicle (BEV) Spark. The 1ET35 is designed with experience gained from the first modern production BEV, the 1996 GM EV1. This paper describes the design optimization and development of the 1ET35 and its electric motor that will be made in the United States by GM. The high torque density electric motor design is based on high-energy permanent magnets that were originally developed by GM in connection with the EV1 and GM bar-wound stator tech