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The majority of studies in automotive electrification technology focus on the performance of high voltage HEV and EV powertrains. With the introduction of microhybrid systems as a near term technology trend, this work focuses on an analysis of low voltage (<60V) systems across multiple vehicle segments and region-specific regulatory drive cycles. Vehicle simulation results are presented for 12V and 48V vehicle systems equipped with start-stop and regenerative braking, features commonly associated with microhybrid vehicles. Simulation results show that fuel economy benefits from start-stop vary significantly between drive cycles. In contrast, total energy recuperation is similar across all vehicle classes for 12V microhybrid systems. For 48V systems, total recuperated energy increases with vehicle mass while the percent fuel economy benefit is highest for lighter vehicles.

The microhybrid electric vehicle (MHEV) has increasingly received attention since it holds promise for significant increases in fuel economy vs. traditional gasoline vehicles at a lower price point than hybrid vehicles. Passive parallel connection of the traditional 12V lead acid battery and a high power lithium ion battery has been identified as a potential architecture that will facilitate fuel economy improvements with minimal changes to the electrical network. Enabling a passive dual-battery connection requires a design match between the two batteries, including characteristics such as battery size and resistance, so that the performance can be optimized. In this work we have developed a hybrid model that couples electrochemical model of lithium ion battery (NMC-Graphite as an example) and an equivalent circuit model of lead acid battery in order to study the behavior of 12V dual-battery microhybrid architectures.