Module Level Thermal Propagation Verification under EU Regulation Guidelines
EU battery regulation requires module thermal propagation testing with five-minute occupant warning signals before external flammability occurs.
Thermal Propagation
Meaning
Sequential transfer of thermal runaway from a single failing battery cell to neighboring cells within a pack leads to a large-scale hazardous event. Preventing thermal propagation is the core objective of modern pack-level safety design. By incorporating thermal barriers and gas-deflecting vents, engineers can contain the initial failure to a single cell or a small module.
The boundary of this safety design is reached if the total energy released exceeds the containment capacity of the outer housing.
Heat Transfer
Conduction through the electrical busbars and radiation from the hot cell casing are the primary drivers of cell-to-cell failure. This continuous heat transfer raises the temperature of the adjacent cell above its critical thermal runaway point. Preventing this cascade requires both thermal insulation and active cooling.
Gas Dynamics
Hot gases ejected during the initial vent can ignite and create a flame front inside the enclosure. If this gas flow is not directed quickly out of the pack, it will cause rapid thermal propagation by heating the tops of the other cells. Dynamic venting paths are therefore designed to channel these gases to the exterior safely.
Safety Regulation
Global standards mandate that a battery pack must prevent thermal propagation to allow passenger escape. Under these rules, demonstrating this mitigation is necessary for vehicle type approval. This requirement has transformed pack design by prioritizing structural separation.