When there's a discussion about electric cars of home battery solutions, you often hear or read comments about the (un)safety of li-ion battery packs in case of accidents or fire. The US-based National Fire Protection Association (NFPA) teamed up with Tesla to see what would happen if a Powerpack catches fire.
The Tesla Powerpack is quite a bit bigger than the Powerwall solutions for consumers, this business solution features 16 individual storage pods, versus the one power pod used by the residential version. Each pod has around 900 battery cells, for a total of around 14,400 battery cells, capable of storing 100kWh of energy. That covers about ten days of electric power use for the average West-European family.
NFPA simulated various scenarios, including what would happen if one or more cells within a single pod went into thermal runaway, and how an external fire impacts a Powerpack. A full overview of the tests can be read at Electrek, the conclusion is the Powerpacks are well-designed and do not pose a fire spread hazard. When a fire starts inside a pod the safety features prevent the fire from propagating to the rest of the Powerpack, and when there's an external fire the consequences are confined to the pack:
“However, no violent projectiles, explosions, or bursts (other than a overpressure release of the thermal door refrigerant) were observed during the test while the Powerpack was exposed to the burners, while it was in a free burn state, or after flames were no longer visible. Flames remained mostly confined to the Powerpack itself. Weaker flames emanated from the exhaust vent of the Powerpack, the front thermal door grill, and around the front thermal door seal at varying times throughout the test.”
Quite impressive to see how little happens when there's a propane burner installed to simulate a constant fire right on the side of the Powerpack. It takes over 35 minutes until some white smoke starts coming out of a vent, and flames don't start coming out of the Powerpack's back panel until after the 1 hour mark.