Reducing automobile fuel consumption and CO2 emission are global priorities, due to the environmental concerns and emissions regulations. Among many technologies of improving fuel economy of engine, the “Engine Idle-Stop” with BAS (Belt Alternator Starter), also called ISG (Integrated Starter Generator) is the one, which has been in production by various carmakers for more than a decade. The “Idle-Stop” system can turn off the combustion engine when the vehicle is stationary, such as, at red lights, or, in traffic jam. This technology significantly reduces fuel consumption and CO₂ emissions, especially in city driving.

Comparing to conventional alternator, which was only driven by belt to generate electricity, BAS in FEAD (Front-End Accessory Drive) of Mild Hybrid vehicle can be used as an electric assist motor to drive belt system for “belt start” and “boost”, and, can also be used as a generator driven by the belt during engine operation and vehicle braking to generate electricity. The challenge for BAS belt drive system is the BAS torque reversing in different modes.  To ensure the BAS functionalities, a traditional approach is to increase the static belt tension to very high level. Disadvantages of belt drive with high tension are short belt fatigue life, and high system friction loss which will reduce the fuel economy.

This presentation will give an overview of functions and merits of current BAS Mild Hybrid System. In this presentation, the basic requirements for the BAS system design will be discussed. Litens new technologies for BAS system will be introduced with testing and simulation results. These new technologies are devoted to lowering belt tension, lowering system friction loss, lowering system NVH, and, increasing system durability and life. Validation test with a GM BAS Mild Hybrid vehicle will be shown in this presentation, as well.