A method of mitigating propagation of a thermal event in an energy storage system having a plurality of cells is disclosed. The method includes the steps of identifying the heat sources within the energy storage system and plurality of cells. The method then controls a temperature of the energy storage system and plurality of cells and also detects predetermined conditions within the energy storage system. The method then performs a predetermined action based on when one of the predetermined conditions is detected. A plurality of sensors and switches along with associated hardware or software will be used to control the temperature of the energy storage system upon detection of predetermined conditions involving overheating, over current, over voltage of the like.