Electric cars have experienced significant growth in recent years. However, in Vietnam, they are still relatively new, with only a few models available such as the VinFast VF e34 and VF8, Porsche Taycan, Audi E-tron, Hyundai Ioniq 5, and some new Chinese electric car models like the Wuling Hongguang Mini EV.
In addition to concerns about range, charging time, and other factors, fire risk is also a topic of discussion when it comes to electric cars. Especially in the current context, where fire incidents in narrow alleys with high population density are common, fire trucks face difficulties accessing these areas, resulting in severe consequences in terms of human lives and property damage. The question arises whether electric cars are more prone to catching fire compared to gasoline cars. Which type of vehicle poses a greater safety hazard in terms of fire and explosion?
Are electric cars more prone to catching fire than gasoline cars?
The main cause of fire in electric cars is the battery. On the other hand, gasoline cars have multiple causes such as electrical component faults, fuel or liquid leaks, overloaded exhaust systems, overheated engines, and more. Therefore, compared to traditional gasoline cars, electric cars have a significantly lower risk of catching fire. In reality, there are not many cases of electric cars catching fire.
The low fire risk of electric cars compared to gasoline cars is well-documented.
According to data from the National Transportation Safety Board (NTSB) of the United States, there were a total of 16,051 hybrid cars that caught fire in accidents. In comparison, gasoline cars had 199,533 cases of fires. Meanwhile, there were only 52 cases of electric cars catching fire.
Tesla states that gasoline cars have an 11 times higher fire rate compared to their electric cars. The company claims that the best comparison ratio is the fire rate per 1.6 billion kilometers traveled. Tesla, with a fleet of 300,000 cars on the road that have traveled a total of 12 billion kilometers, reported about 40 fire incidents. This number is equivalent to 5 fires per 1.6 billion kilometers traveled. On the other hand, gasoline cars have a rate of 55 fires per 1.6 billion kilometers traveled.
How does a Li-ion battery in an electric car catch fire?
Lithium-ion (Li-ion) batteries in electric cars are highly flammable due to their composition. However, car manufacturers have implemented methods to prevent the fire and explosion of Li-ion batteries. A Li-ion battery consists of four main components: the cathode, anode, electrolyte solution, and separator.
The combustion of a Li-ion battery is usually caused by a short circuit in one or more battery cells, resulting in high heat generation. If the battery of an electric car is damaged due to a collision, fire, or water ingress, a short circuit may occur. This can cause the battery cells to release energy and heat, leading to a “thermal runaway” condition. This chain reaction can cause the battery to fail or explode, resulting in a fire.
Illustration of the burning process of an electric car battery, from short circuit, thermal runaway, combustion, and spreading
Even in the case of an electric car being submerged in water (flooded), contaminants or salt can cause the battery to short-circuit, especially after the water recedes. Movements of the electric car or a damaged battery, for example, when the car is being towed, also pose a risk of a short circuit.
The heat generated by combustion, thermal runaway, or short circuit can melt the foam separator between the cathode and anode of a battery cell. This causes the battery cell to continue discharging heat and producing flammable gas. As a result, the entire battery pack can catch fire. “Heat can transfer to neighboring battery cells and trigger a chain reaction,” explained Mr. Barth.
The most significant difference compared to gasoline cars is the time it takes for an electric car to catch fire. Gasoline fires occur almost instantly when gasoline ignites with a spark or flame, spreading rapidly. In contrast, a battery fire usually requires some time to accumulate enough heat before igniting. In some cases, this delay can be beneficial as occupants of the car accident can escape before the fire occurs. In other cases, even after the battery cells have been extinguished, there is still a risk of re-ignition after several hours or even days, making rescue and repair work difficult.
Illustrative image of a Lithium-ion battery pack in a Tesla car
Electric car fires are more intense and difficult to extinguish than gasoline fires
As mentioned earlier, electric cars have fewer fire incidents compared to traditional gasoline cars. However, once a fire occurs, lithium-ion batteries in electric cars are much more challenging to extinguish. Currently, there are no effective and fast firefighting methods for electric car fires.
The most significant difference compared to gasoline and diesel cars is that electric cars cannot be extinguished with common fire foam. Instead, firefighters need to cool down the battery of the electric car to prevent fire and thermal runaway.
“Lithium-ion batteries produce their own heat and oxygen,” said Mr. Andrew Klock, the Director of Products and Development at the American Firefighter Association. Therefore, cutting off the external oxygen supply is also insufficient to stop the fire, and spraying foam has no effect. To extinguish an electric car fire, firefighters will have to spray a significant amount of water onto the battery pack to cool it down.
Firefighters attending to a fire caused by a Tesla electric car
The majority of electric car batteries are located under the car’s body. Therefore, spraying water onto the body or engine compartment has no effect. “You need to spray water under the car’s body,” added Mr. Knock.
According to the National Fire Protection Association, extinguishing an electric car fire requires more than 110,000 liters of water, about 20-25 times more than a gasoline car, and it takes longer.
Above is the basic knowledge about electric car batteries, the causes of fire, and firefighting methods. It can be seen that both electric and gasoline cars carry inherent fire and explosion risks. Users should pay attention to ensure their safety, as well as the safety of their families and society.
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