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A laboratory in Palo Alto where Tesla Motors was testing lithium-ion batteries was shut down for about three weeks in January after the batteries caused a fire and damaged a water line in the company’s testing chamber, according to Fire Department records obtained by this publication.
The Jan. 11 fire that temporarily closed the lab was the second blaze that occurred at the Tesla facility at 3500 Deer Creek Road in a little over a month. On Dec. 10, Palo Alto and Mountain View firefighters responded to a fire that reportedly took place in a battery cell and spread to a chair outside the fume hood. The December fire caused about $100,000 in damage, according to Fire Department records.
Tesla did not respond to questions about the two fires.
According to Palo Alto inspectors, both fires were caused by thermal runaway, a self-reinforcing process in which an increase in temperature changes the conditions of the environment in such a way as to cause a further increase in temperature, often with explosive results. In both incidents, this was caused by an accidental failure of electrical components, the records show.
Tesla, which was formerly based in Palo Alto and which opened its engineering headquarters at the former HP campus in Stanford Research Park in 2024, has experienced several recent incidents with battery equipment overheating or burning. In November, the company announced that it is recalling 10,500 units of its Powerwall 2 battery power systems for fire and burn hazards after receiving reports of overheating, according to Reuters. And last month, a battery storage system that powered Tesla chargers in a San Marcos mall caught on fire, prompting the closure of several businesses and half of the shopping center’s parking lot, according to the San Diego Union-Tribune.
In Palo Alto, the fire damage in both cases was relatively modest, though each incident required evacuation of the building and a heavy response from the Fire Department.
When firefighters arrived at about 7 p.m. on Dec. 10, they were directed to an area in Building 26 with a hood where small batteries were being tested, according to a report from the incident. Given the high level of smoke, firefighters upgraded the call to a second alarm, though most of the units were relieved shortly thereafter once the fire was knocked down by the sprinkler system.
“The fire appeared to have extended out of the hood and burned the walls and ceiling near the hood,” Fire Capt. Daniel Fortino wrote in the report.
Deputy Fire Chief Kevin McNally told this publication the day after the Dec. 10 incident that the heavy response was prompted by the size of the building and the large amount of smoke.
“There was a lot of smoke coming,” McNally said. “They were able to extinguish it and evacuate the building.”
Palo Alto fire crews remained on scene to remove as much water from the building as possible, according to the incident report. When Fire Inspector Brent White investigated the scene, he found that there was water leaking from the ceiling to additional lab spaces on the floor.
White and Fire Department Investigator James Crain noted in their report that the lab area, which had 2 inches of standing water, was still energized. Tesla personnel tried to de-energize the area but were unable to locate the electrical breakers, according to the inspection reports.
In talking with a Tesla technician, fire inspectors learned that the company was running tests with two cylindrical batteries at a time, which involved adding salt water to simulate a salt-water flood in a vehicle. The company was testing to see how close the cells could be together, according to the report. One of the technicians posited that a cell may have fallen outside the fume hood and onto a chair, which then caught fire.
The inspectors also noted that even after the fire was extinguished, water continued to flow to the site because an incorrect post-indicator valve was shut down.
The two inspectors taped off areas that had fire exposure contamination from flooding and products of combustion, according to the report. Clean Harbors, a company that specializes in cleanup of hazardous materials, came to the scene and made a plan to remove water from affected areas.
White concluded in his report that the cause of the fire was determined to be “accidental failure of electrical components (experimental lithium-battery cells) leading to thermal runaway.”
According to inspection records, the scene was handed over to Tesla representatives at about 2 a.m. on Dec. 11.
A month later, firefighters returned to Deer Creek Road for another structure fire at a Tesla lab. This time, the fire was reported shortly before 8 p.m. on Jan. 11 and caused about $10,000 in damage.
Fire Capt. Ryan Stoddard reported that upon arriving at the scene in Building 24, where the fire occurred, the responding firefighters were escorted by a Tesla security guard to the fire alarm control panel, which uncovered smoke in the basement elevator lobby.
“We walked down to investigate the area and saw light colored smoke/vapor cloud often representative as a lithium-ion battery fire,” Stoddard’s report stated.
Firefighters found that a fire had burned in a cabinet that included electrical equipment. Based on staining on the walls, it appeared as if some lithium-ion batteries had exploded. The fire was extinguished upon the firefighters’ arrival and there was water on the floor that reportedly came from a water line that ruptured during the fire, according to the report.
Mountain View Fire Department responders were released from the scene shortly after they arrived.
White, who responded to this fire as well, learned from a Tesla employee that the area where the fire started had contained testing chambers for lithium-ion batteries, according to his report.
“These batteries are experimental in nature with differing chemical makeups in an effort to produce improved cells,” White wrote.
He noted in the report that part of the process is to run the batteries through cycles of energization and de-energization.
“The test chamber where the incident occurred was performing such a test when a cell or cells went into thermal runaway and ignited causing an explosion which initiated the smoke detector at the elevator directly outside of the laboratory,” the report stated.
When a Tesla employee led the fire inspector to the test chamber, White saw that the chamber door was dislodged and the area had fire and smoke damage. There were also fragments of batteries on the wall about 5 feet from the test chamber and a small amount of water on the ground from a coolant line that had melted, according to the report.
“It was noted that the room itself was not de-energized and there were still experiments occurring in adjacent test chambers,” the report stated.
Fire Department staff and Tesla employees agreed that no experiments were to occur until the company obtained a HazMat closure permit consisting of “environmental remediation from an approved company with wipe sampling to confirm that there was no continued threat to life, property or the environment,” White wrote.
He confirmed with Tesla that “they understood that the laboratory was off limits” until the PAFD confirmed the finalization of the closure permit, the report states.
The city signed off on the closure permit on Feb. 3, according to Meghan Horrigan-Taylor, the city’s chief communications officer.
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