Battery Safety

News from AVL’s Virtual Battery Development

Battery safety and hazard prevention are vital during the development and homologation of electric vehicles that use lithium-ion batteries.

Internal short circuits, electrical overload and mechanical damage can cause an uncontrollable rise in battery temperature. If the cell reaches a critical temperature, self-accelerating exothermic chemical reactions will generate a huge amount of heat in very short time. As a result, this massive heat release can cause the adjacent cells to overheat as well.

In a chain reaction, this can overheat the battery module and, in the worst case, the entire battery pack. This process, also known as thermal runaway, results in severe damage to the battery system or even to the entire vehicle from fire and explosion.

AVL has developed models to show the misuse of battery cells, the thermal runaway and venting of the cells and then the propagation through the entire battery set. The specifically developed flammability Index serves to indicate the ignition probability of the escaping venting gas. It considers the upper and lower flammability limits of the actual species fraction.

Furthermore, our models check the temperature and an autoignition index indicates whether the venting gas will auto-ignite or not. This is evaluated individually for all the major gas components within the venting gas. This helps to define measures to improve the safety and reduce the risk of severe battery hazard.