Simulation-Based Optimization of Voltage Architecture for Belt Starter Generator Mild Hybrid Electric Vehicles Using Fuel Economy and Cost–Benefit Analysis

Abstract

The increasing demand for improved fuel economy and reduced greenhouse gas emissions has accelerated the development of mild hybrid electric vehicles (MHEVs) as an economical alternative to full hybrid and battery electric vehicles. Among the available architectures, the Belt Starter Generator (BSG)-based mild hybrid system has emerged as an attractive solution owing to its relatively simple integration with conventional internal combustion engine vehicles while providing significant improvements in fuel efficiency. However, the selection of an appropriate electrical system voltage remains a critical engineering challenge because higher voltage levels improve electrical performance but simultaneously increase system complexity, manufacturing cost, and safety requirements. This study presents a comprehensive simulation-based optimization of voltage architecture for BSG mild hybrid electric vehicles by simultaneously evaluating fuel economy improvement and system cost. A validated vehicle model was developed using the Autonomie simulation platform and calibrated against experimental data obtained from a 48 Vdemonstration vehicle. Six vehicle configurations comprising a conventional internal combustion engine vehicle, a 12 V stop-start system, and BSG mild hybrid systems operating at 24 V, 36 V, 48 V, 84 V, and 120 V were evaluated under the Worldwide Harmonized Light Vehicle Test Cycle (WLTC). The analysis included battery performance, motor operating characteristics, state-of-charge behaviour, regenerative braking capability, and overall fuel economy. A detailed component-level cost analysis was also performed to determine the economic viability of each voltage architecture. The simulation results demonstrated that fuel economy increased progressively from 30.6 mpg for the baseline vehicle to 34.22 mpg for the 120 V system. However, the incremental improvement beyond the 48 V architecture was minimal, whereas component costs increased substantially because of larger electrical machines, higher-capacity batteries, power electronics, and mandatory high-voltage safety equipment. Cost-benefit analysis revealed that the 48 V BSG architecture achieved the optimum balance between fuel economy improvement, electrical efficiency, packaging requirements, and manufacturing cost. The findings indicate that the 48 V mild hybrid architecture represents the most practical and economically sustainable solution for large-scale deployment of next-generation mild hybrid passenger vehicles

Keywords: Mild Hybrid Electric Vehicle; Belt Starter Generator; 48 V Architecture; Vehicle Simulation; Fuel Economy; Cost–Benefit Analysis; Autonomie; Voltage Optimization