Decreasing charging time of Lithium-Ion Battery by controlling temperature during the process

Abstract: In this report, which is written for Halmstad University and on behalf of Semcon, a mechanical design process was implemented to evaluate the possibility of executing a low-cost cooling system for one of the battery company’s products. The report started from the background of former studies to clarify the problem and finding existing solutions in the first step and following up with developing concepts based on gathered information from the literature study. The battery company provides a high-performance battery based on customer requirements because of the flexible lithium battery technology. There are two similar conditions in the operating period of the battery. One in the high performance usage of the battery and two in the charging period by adding power to the battery cells. Both of these actions generate heat which is the result of resistance of the material in the cells and the chemical reaction of the cells. The battery company wants to decrease the time of charging period in order to reach the operative condition as fast as possible by enabling fast charging. According to the battery management system (BMS), at high temperatures the efficiency of charging rate decreases and also it has a negative influence on the battery cells performance and lifetime. A cooling system is required in order to fulfil the requirement of having high performance and making fast charging possible for the battery. The goal of this thesis is to develop a cooling system based on literature study with consideration of applying to the lithium battery in order to reduce charging time by decreasing temperature in the modules during the operating period. This report contains the whole developing conceptual design process of the cooling system by starting a wide range of information gathering in the purpose of determining the main variables which have an influence on different cooling techniques. In specific, after deciding about the type of cooling method for the product, the study has been focused on the fluid dynamics and heat transfer by forced convection with airflow. The concept generation executed on the information which was gathered through the information retrieval. The final developed concept has been introduced in this thesis work which has the potential of fulfilling the requirement of designing a cooling system to decrease the temperature of the battery’s modules without making any serious changes in the product. The final concept has been developed by various changes in its components and evaluating those changes by executing simulation for each change. The final concept contains twelve similar heat sinks which have been installed over connectors to provide more surface in the purpose of exchanging heat through the airflow provided by three high-speed fans. In order to force the airflow over the heat sinks, a cover has been designed.