Safety management for electric vehicle batteries in a tropic environment

Abstract

To ensure the safety of a battery system certain measures can be employed. Monitoring the actual battery temperature is crucial to guarantee a safe use of the system while an optimized cooling system for the battery pack helps to improve the liability, prevent safety shut-offs and extend the battery's lifetime. Additionally, possibilities to monitor the state of health of the battery on a longer time scale are necessary to avoid over-stretching the battery's capability of storing energy on the one hand and to reduce investment costs on the other hand. This paper deals with different approaches to handle the battery temperature, especially under challenging tropical outside conditions. A temperature distribution model is developed and evaluated using combined data from a sensor matrix and an infrared camera. This method is used for real-time temperature measurements to investigate and monitor the temperature distribution on pouch cells. The simulation of different cooling systems is presented to show the need of a steady temperature distribution within a battery pack. The goal is to avoid excessive load on certain cells, which has a high impact on a safe use of the pack and reduces lifetime significantly. Finally, an approach to characterize the battery thermodynamically is presented. This is expected to be a useful tool to measure and monitor the state of health of a battery and first investigations are shown for different cell chemistries, performed on commercially available full cells.