Fire Investigation Based on Time-Sequential Analysis of Lithium-Ion Battery Thermal Runaway

Lithium-ion batteries (LIBs) are widely used in the electric bicycle/vehicle sector, but fire accidents frequently caused by thermal runaway of LIBs have become a severe public concern. From a reverse perspective of safety engineering, investigation of fire accidents based on the historical data recorded by the Battery Management System (BMS) and exploration of the causes of thermal runaway can enhance the safety of LIBs and electric bicycles/vehicles. This study aims to provide support for fire investigation through the analysis of the BMS. By conducting electrical, thermal and mechanical abuse experiments, the variations of the electrothermal parameters involving voltage, current and temperature are examined. The results reveal that these electrothermal parameters exhibit unique time-sequential inter-relationships under each specific abuse mode. A secured relationship can be solidified between the variation features of the electrothermal parameters and the specific cause of thermal runaway, i.e., whether the abuse mode is electrical, thermal or mechanical abuse. Such peculiar time-series variations or inter-relationships can be used for post hoc fire investigation to trace the fire reasons. Based on the findings of this study, a real fire case was analyzed to validate the feasibility of the proposed tracing method by means of BMS analysis. The resultant fire reason confirmed the one given by the authority, thus validating the effectiveness of the fire investigation method.