Battery pack modeling for the analysis of battery management system of a hybrid electric vehicle

Battery forms a critical part of the hybrid electric vehicle (HEV) drivetrain. An important constraint to the effective performance and reliability of the battery is its unpredictable internal resistance variation along the driving cycle. Temperature has a considerable effect on this internal resistance and thus the battery management system monitors cell and battery pack temperature in accordance with the state-of-charge to prevent thermal runaway. Li-ion batteries which offer possible solutions to the HEVs energy and power density demands thus need to have a good thermal management system in order to enhance their performance. This paper aims to develop a battery pack model that would analyze the variation of internal resistance as a function of temperature. The study of the losses would help in designing a cost effective efficient battery management system.

I. Introduction

HYBRID ELECTRIC VEHICLE (HEV) is an optimal combination of two power sources, a conventional internal combustion engine (ICE) and a rechargeable energy storage system (battery). Increasing emission standards across the globe have popularized this alternative form of transportation. Unlike conventional vehicles, vehicular power demand is shared between the two power sources to reduce the fossil fuel consumption in HEVs [1]. Moreover, regenerative braking used to charge the onboard battery system also reduces the loss of brake power in the form of heat. These developments lead to a cheap and low emitting means of transportation. The main challenges in this path of development are battery and battery management system (BMS).