Battery Health Management System for Automotive Applications: A retroactivity-based aging propagation study

Advances in lithium-ion battery technology have created new opportunities for this energy storage system to penetrate much deeper into the transportation sector, especially through automotive hybridization. In automotive applications, managing and optimizing the safety and reliability of batteries is of great interest for both users and manufacturers. To this purpose, battery management system (BMS) implements critical tasks such as monitoring battery health status, charge control, and cell balancing together with the evaluation of state of charge, state of health, and state of life. In this paper, we focus on BMS tasks related to the battery health management. We first cover main definitions, terminology and concept of batteries in automotive applications. An electrical-thermal-aging model of the battery cell is proposed, which is written in terms of fast (i.e. state of charge) and slow (i.e. state of health) dynamics. The time-scale separation of the proposed model is characterized quantitatively. A framework to analyze the propagation of aging from cell-to-cell within a battery pack is developed and the properties of an interconnected system from a degradation standpoint are studied. Further, a generalized framework for interconnected cells exhibiting the phenomenon of retroctivity is described. In addition, the effect of retroactivity and the extent of aging propagation are evaluated in a series and parallel topology, first and in a mixed series-parallel battery configuration later.