A hybrid battery cell voltage equalizer considering thermal behavior and capacity fade characteristics

Abstract

The thesis focuses on developing a robust, high-fidelity lithium-ion battery model adaptive to changes in operating temperature, aiming for accurate estimation of state of health (SOH). The thesis proposes two novel methods for lithium-ion battery SOH tracking and estimation using the developed battery model. Furthermore, the thesis introduces a hybrid battery cell balancing topology designed to achieve optimum balancing speed and enhance battery health by reducing temperature rise and frequent battery cycling during balancing. The proposed hybrid balancing topology combines active balancing for cell-to-pack balancing and passive balancing for excess energy dissipation, depending on the current battery state of charge and voltage of individual cells. The suggested balancing strategy enhances balancing speed, and the control strategy is easy to implement. Lastly, the thesis conducts a detailed comparative analysis of passive, active, and hybrid cell balancing topologies to demonstrate the most suitable balancing strategy for an industry-ready battery management system.