A multifactorial analysis of thermal management concepts for high-voltage battery systems

Abstract

This research contributes to the goal of the cost reduction of vehicle electrification by addressing the thermal management of Lithium-Ion energy storage systems. Lithium-Ion secondary batteries are currently the state of the art for energy storage for vehicle electrification; however, to operate efficiently over their entire lifetime, these batteries must be held in their optimal temperature range. Concurrently, thermal management system cost must be minimized in order to guarantee the economic viability of vehicle electrification. To do so, novel thermal management concepts must be identified and compared to determine the ideal solution. This research presents a method for efficiently and reproducibly comparing diverse battery thermal management concepts in an early stage of development to assist in battery system design. The basis of this method is a hardware-based simulation model of a prismatic Lithium-Ion battery, called the Smart Battery Cell (SBC). The SBC models the thermal behavior of a prismatic automotive cell without the use of active chemistry. By removing the active chemistry, enhanced reproducibility of the experimental conditions is possible and hardware-in-the-loop integration can be realized, allowing for rapid reconditioning between experimental trials. The elimination of active chemistry reduces the safety risks associated with Lithium-Ion cells, making the use of the SBC possible with thermal management systems in an early state of developed, and without costly safety infrastructure. The integration of thermocouples leaves the thermal contact surface undisturbed, allowing the SBC to be integrated into diverse thermal management systems. Eight SBCs are combined to a reference module, as the cell module consisting of multiple cells is the current state of the art in battery system layout. By analyzing the thermal management concepts at module-level, the effects between cells can be observed (versus the analysis of a single cell), and the results from the module-level analysis can be scaled to different battery system sizes. The multifactorial analysis performed at module-level considers not only the thermal performance of the battery thermal management systems, but also the energy consumption, vehicle suitability, production complexity and economic viability. From the analysis, recommendations are made for the development of optimal thermal management systems to facilitate the cost reduction of vehicle electrification.