Experimental Validation of a Module-Level Battery Safety System for Thermal Runaway Containment

Abstract

A test to validate a module-level battery safety system for high-capacity aviation batteries was developed and performed. The test assessed the safety system’s effectiveness in containing fragments, smoke and other emissions resulting from battery fire, known as thermal runaway, as well as its ability to prevent propagation of thermal runaway to adjacent battery modules. This was done to enable flight-testing of a hybrid-electric aircraft which used this battery safety system. The battery in this study was built from lithium-ion cells and was sized specifically for the National Research Council of Canada’s (NRC) Hybrid Electric Aircraft Testbed (HEAT). The battery safety system was evaluated destructively by forcing a fully-representative battery module into thermal runaway. Modules were installed in a test cell at the NRC’s battery performance and safety evaluation research facility. The target module was deliberately forced into thermal runaway by applying heat externally to a single cell. Adjacent ‘observer’ modules were used to evaluate heat transfer and temperature rise at the next nearest modules. The battery and its safety system were instrumented with thermocouples and pressure sensors at critical locations, monitored by optical and infrared cameras, and evaluated in an environment representative of the aircraft installation. Fourier Transform Infrared (FTIR) Spectroscopy was utilized to measure concentration of any leaked gaseous compounds resulting from thermal runaway. A test procedure for evaluating thermal runaway containment and non-propagation, including pass criteria was developed. The first design iteration and test resulted in a loss of containment. The battery safety system was redesigned based on the knowledge gained by testing the first iteration and ultimately resulted in full containment of a thermal runaway. It was determined that by using and validating a module-level battery safety system, the risk posed by a thermal runaway event could be significantly reduced, providing time to safely land and complete an emergency evacuation of the aircraft following a battery fire.