After mechanical, thermal or electrical abuse, a battery can undergo thermal runaway, a chain of exothermic side reactions that cause an uncontrolled rise in temperature, often resulting in fire hazard or even explosion. For that reason, the global safety standard “GTR 20” requires a thermal propagation test for battery packs in electrical vehicles to ensure that at least five minutes remain after the thermal runaway of a cell in a battery pack before fire occurs.
The goal of this Master thesis is to improve the thermal runaway simulation, more specifically, the approach how the function for the released heat inside a battery cell during thermal runaway is generated. A new developed script automatically detects characteristic points of the thermal runaway phenomena from measurement data and uses it as boundary for a generalized function split in three segments, the Polyfit.
To validate the model, the generated heat release function is then used for a 3D thermal runaway simulation for three pouch cells and three prismatic cells from the measurement series. The simulation results are analyzed and compared with the measurement data. The temperature profiles of the calculation match the associated sensor signals. Especially in the time span of the fast-thermal runaway, where the focus of the master thesis was set, the results are promising.
The new model offers a fast way of deriving a generalized heat rate function for a given cell. With the script an automatized and objectified workflow for any cell type was developed. It can assist and support setting up a 3D thermal runaway simulation for any cell type and allows adjusting the shape of heat rate function if needed.