The National Transportation Safety Board (NTSB) investigation revealed that almost 50,000 gallons (190,000 liters) of water were used to extinguish the fire on a Tesla Semi.
The truck caught fire after a crash in the early hours of August 19 on Interstate 80 in California. A Tesla employee was driving the vehicle to the company’s facility in Nevada when he tried to make a turn while going uphill. The vehicle veered off the road and collided with several trees before catching fire.
The authorities had to close a busy freeway due to security concerns, since ignited EV batteries emit dangerous fumes and pose the risk of a potential explosion that can endanger nearby lives.
The report further indicated that firefighters had to resort to emergency measures, usually employed in extinguishing wildfires, as they used an aircraft to drop fire retardant to contain the fire around the truck.
Previous reports suggested that the battery’s temperature climbed up to 1,000 degrees Fahrenheit during the firefighting operation.
The lithium-ion batteries in electric vehicles can undergo thermal runaway after catching fire. The heat generated within the battery triggers a series of chemical reactions that release even more heat, leading to temperatures well beyond 1,000 degrees Fahrenheit. Once thermal runaway starts, stopping is difficult, and the battery may continue to reignite even after the initial suppression attempts. This is one of the reasons why EV batteries require so much water to extinguish fires.
According to the report’s findings, the truck was equipped with the Advanced Driver Assistance Systems (ADAS), but it was not engaged at the time of the accident.
The NTSB is investigating the crash further and will issue a safety recommendation report later. The agency does not have enforcement powers and can only provide recommendations to the car manufacturers. It urged EV manufacturing companies to introduce new safety protocols to limit the thermal runaway of the batteries while also developing vehicle-specific responses to fire hazards. Similarly, the agency advised EV companies to issue guidelines that clearly outline the process of storing vehicles whose lithium-ion batteries are damaged.
The Tesla truck was later taken to an open-air facility for observation, but the battery did not reignite.
In December last year, another Tesla car consumed more than 36,000 gallons of water after catching fire in Alabama. On the other hand, a conventional vehicle normally requires around 1,000 gallons of water after catching fire.
In 2021, the NTSB found that EV battery fires are also dangerous for fire responders who have to work closely with them and that manufacturers do not take necessary steps to include fire extinguishing guidelines.
