Thermal Runaway Explains Why Waymo Vehicles Burned So Utterly within the Current Los Angeles Protests
Throughout current protests in Los Angeles, fires triggered “thermal runaway” in a number of Waymo robotaxis’ lithium-ion battery packs. The phenomenon despatched temperatures previous 1,000 levels Celsius, vaporized a lot of the automobiles and spewed lung-searing hydrogen fluoride
A Waymo car burns in the course of an intersection throughout protests in Los Angeles, California, on June 8, 2025.
David Pashaee/Center East Pictures through AFP
Think about watching a automotive burn till it appears to vaporize and the road itself begins to sag. That occurred on Sunday in Los Angeles, when protesters torched at the least 5 Waymo-branded Jaguar I-Tempo robotaxis. When the smoke cleared, just about the whole shell of every automotive—its roof, doorways, hood, trunk and physique panels—was gone, leaving solely wheel rims and traces of aluminum lacing.
Why did the fires trigger such obliteration? The reply begins with the battery. Every I-Tempo can carry roughly 90 kilowatt-hours of saved chemical power, corresponding to about 170 kilos (77 kilograms) of TNT. That power is distributed throughout lots of of lithium-ion pouch cells, that are sealed in flammable electrolyte and separated by polymer movies as skinny as snack-bag plastic. When anybody cell is punctured or overheated—or set aflame with an incendiary gadget—chemical reactions generate extra warmth than the cell can shed, and neighboring cells comply with in a sequence response. This positive-feedback loop known as “thermal runaway.” In accordance with a 2024 examine within the Journal of Energy Sources, because the battery burns, its temperature can soar previous 1,000 levels Celsius.
At that time, the pack turns into its personal furnace. Aluminum sections of the automotive’s flooring give up, liquefying at about 660 levels C and taking the underbody with them. Magnesium elements—seat-base frames, the bracket that holds the steering column and the cross-car beam that’s situated behind the dashboard—flare brilliant white. Patches of magnesium can catch fireplace and burn fiercely. Plastics disappear as vapor, wheels lose their tire, and even the lidar mast on the roof rapidly resembles an overcooked marshmallow. A 2025 examine in Hearth Expertise and a 2023 examine in Utilized Vitality famous that the position of the battery on the ground—typically known as a “skateboard structure”—makes the ground the most popular zone. Thus, flames radiate upward and outward, cooking every part above.
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All of the whereas, the battery cells vent hydrogen fluoride, a poisonous, lung-searing fuel documented in laboratory check burns of business lithium packs. Among the many disturbing scenes from the current Los Angeles protests, which erupted over federal immigration raids, are these during which protestors stood across the flaming Waymos. Traditionally, first responders with out supplied-air safety have developed throat burns and respiration difficulties upon arriving at scenes with burning lithium-ion batteries. Relying on the hydrogen fluoride ranges, an uncovered individual can start coughing up blood inside minutes. Whereas inhaling concentrations above roughly 30 elements per million (ppm) is straight away harmful to well being, 50 ppm could also be deadly when inhaled for a half-hour to an hour, in response to the U.S. Facilities for Illness Management and Prevention. The Environmental Safety Company estimates that publicity to 170 ppm for 10 minutes could be lethal. Measurements taken close to electric-vehicle (EV) fires present peaks of 150 to 450 ppm, with ranges throughout a lot of the hearth hovering round 50 ppm.
Firefighters name such blazes “battery field fires,” and so they hate them. Flame-retardant foams do little, and fireplace departments now favor high-pressure water lances or immersion pits. Dousing a runaway battery normally means reducing temperatures beneath the runaway threshold for each final battery cell—a process that, in response to a 2021 interview with Thayer Smith of the Austin Hearth Division, can swallow 30,000 to 40,000 gallons (about 114,000 to 151,000 liters) of water. That’s at the least 40 instances the quantity of water required to extinguish a gasoline-car fireplace. In the event you hit the flames too calmly, stranded power reignites hours later—a quirk the Nationwide Transportation Security Board flagged in its 2020 report on EV firefighting hazards.
Automotive designers have tried to handle the hazard. Software program screens cell temperatures and slows the speed at which batteries cost to stop overheating. And it robotically cuts present if something seems to be amiss. But even the very best code can’t rewrite chemistry: in 2023 Jaguar recalled greater than 6,400 I-Tempo automobiles after at the least a dozen of them caught fireplace from overheated batteries—which had seemingly shorted from manufacturing defects of their pouch cells. Six of the fires occurred whereas the automotive was both plugged in or inside a couple of minutes of being unplugged. Waymo’s fleet received the replace to higher regulate the batteries, however software program can’t assist when somebody smashes one of many automotive’s home windows and lights up its inside with a “makeshift flamethrower,” as reported by the Los Angeles Instances.
Might a Waymo van have burned simply as totally? Solely with nice effort. The corporate’s earlier Chrysler Pacifica hybrids, which have been phased out in 2023, saved a tenth of their battery power in a steel-framed shell. Metal retains its form past 1,300 levels C, so after a typical blaze, you’d nonetheless acknowledge the carcass. To stop thermal runaway, Teslas have batteries that use 1000’s of small cylindrical cells locked inside an aluminum tray with titanium undershields and built-in firebreaks. And most manufacturers of electric-car batteries now sit in equally inflexible aluminum or metal bins—and are shifting towards much less unstable chemistries.
Importantly, nonetheless, the scene in Los Angeles on no account signifies that electrical automobiles are tinderboxes. A 2023 examine in Finland confirmed that, mile for mile, they caught fireplace much less typically than gasoline automobiles. However when an EV does burn, the physics shift. You’re now not preventing a puddle of gasoline on asphalt; you’re battling an energy-dense, metal-oxide battery that’s decided to complete what it began—and in such instances, a single Molotov cocktail can flip a smooth robotaxi right into a pool of molten alloy.
