Another Tesla caught fire. Are electric cars safe?

In order to cope with the cooling of the entire automobile market, major car manufacturers have now begun to vigorously promote electric vehicles. Among the new cars unveiled at this year's Shanghai Auto Show, a considerable number of them are electric vehicles.

But since its launch, people have never stopped questioning electric vehicles. In addition to concerns about battery life, mileage, and charging methods, battery safety may be a bigger problem.

Tesla, the representative of electric cars, has attracted much attention, and reports of Tesla cars catching fire and spontaneous combustion are common both at home and abroad. Last night, another Tesla car caught fire in Shanghai.

A Model S caught fire in Shanghai, leaving only the frame

On the evening of April 21, a Tesla Model S in an underground garage in a community on Wendi Road in Xuhui District, Shanghai, suddenly caught fire and ignited three cars parked nearby.

According to the surveillance footage, at around 8:15 p.m. on the 21st, a large amount of smoke suddenly came out of the chassis of the white Model S. A few seconds later, flames broke out from the chassis and spread to the surroundings.

The fire department then arrived at the scene in time and quickly put out the fire. From the photos of the scene that netizens later posted, we can see that the Model S that caught fire had been burned to only the frame, and the three cars parked next to it were also damaged to varying degrees.

According to the owner, Mr. Huang, his Tesla model is Model S P85, which he bought three and a half years ago. During this period, the Model S has never had any problems, but he did not expect that the accident would be so serious.

Fortunately, the incident did not cause any casualties.

Tesla posted on Weibo in the morning of the 22nd that after learning of the accident, they rushed to the scene as soon as possible last night, and are actively contacting and cooperating with relevant departments to verify the situation.

Electric vehicle spontaneous combustion accidents occur frequently

Tesla is currently the electric brand with the highest market share and the highest attention, so various accidents involving its electric vehicles have frequently appeared in the news.

The earliest Tesla car spontaneous combustion accident occurred on October 1, 2013. The driver said that his Model S hit something while driving in the HOV lane of Washington State Highway 167. The car then reported a fault and asked the driver to stop. After parking the car on the ramp, he saw the car start to catch fire and then got out of the car.

After investigation, Tesla said that the Model S caught fire because the battery hit a large piece of metal that fell from a semi-trailer. In fact, due to the safety design of its own batteries, the internal firewall of the battery pack prevented the spread of the fire, and the vents also directed the flames from the car to the ground.

Due to several Model S spontaneous combustion accidents, the US National Highway Traffic Safety Administration (NHTSA) announced the start of a preliminary assessment of the safety of the Model S. However, in March of the following year, Tesla announced that it would strengthen the protection of lithium batteries, and NHTSA immediately stopped the investigation.

But until now, Tesla car fires still occur from time to time.

In fact, electric vehicles from many other car brands have also experienced spontaneous combustion accidents, including Zotye M300 (2011), Chevrolet Volt (2011), Mitsubishi i-MiEV and Outlander PHEV (2013), Nissan Leaf (2015), Volkswagen e-Golf (2017) and Porsche Panamera E-Hybrid (2018).

Just one day after the Model S spontaneous combustion incident in Shanghai, another NIO ES8 spontaneously caught fire in Xi'an this afternoon (22nd). Fortunately, there were no casualties or property losses at the scene.

Why do electric cars catch fire?

Tesla battery pack

Digital enthusiasts are naturally familiar with lithium-ion batteries. This type of battery is widely used in various electronic products, including smartphones, tablets, laptops and various wearable devices, and almost all of these types of devices have experienced battery spontaneous combustion or explosion accidents. The "battery door" of Samsung Galaxy Note 7 in 2016 is a typical example.

Lithium-ion battery fires are usually caused by a short circuit in one or more of the battery cells inside - which generates heat. The heat generated by the battery short circuit can ignite the internal chemicals, which then cause the adjacent battery cells to short circuit, causing a chain reaction. The scientific name for this phenomenon is called "thermal runaway."

The Model S in this incident was parked in a garage when it caught fire and was not damaged by any external force. So why did its battery catch fire?

The specific cause of the accident is still unclear, but some people analyzed that this may be because the lithium ions inside the battery cell produced lithium dendrites during multiple charging of the battery - this Model S has been used for three and a half years.

Lithium dendrites will continue to grow like snowflakes, eventually piercing the separator between the positive and negative electrodes, causing an internal short circuit in the battery.

Are electric cars really more likely to catch fire?

That may not be the case. In fact, electric cars may even be safer than gas-powered ones.

According to an in-depth investigation conducted by the National Highway Traffic Safety Administration in 2017, electric vehicles are no more likely to catch fire than gasoline vehicles, and the chances are even lower.

"The propensity and severity of fire and explosion in lithium-ion battery systems may be comparable to or slightly less than gasoline or diesel vehicle fuels," the report reads.

This view is actually supported by data. According to information released by the National Fire Protection Association of the United States, there were about 174,000 car fires in the United States in 2015, and almost all of these cars were gasoline cars.

Tesla also claims that gasoline cars are 11 times more likely to catch fire than their electric cars. They said that 300,000 Tesla cars have traveled a total of 7.5 billion miles on the road, with only 40 fires, which translates to 5 fires per billion miles. In contrast, gasoline cars have as many as 55 fires per billion miles.

Of course, the current data is not enough to prove that electric cars are really safer than gasoline cars.

What is the difference between spontaneous combustion of electric vehicles and gasoline vehicles?

A Model S caught fire at a supercharger station in Norway

The biggest difference between the two is the time it takes to catch fire. Once exposed to sparks or open flames, a gasoline car fire will catch fire almost instantly, and spread very quickly.

There is usually a time lag between a battery short circuit and catching fire because the internal heat needs to reach a certain level before it can cause a flame.

In some cases, this time difference is beneficial because it gives the occupants time to escape. In some accidents, the driver did escape successfully after realizing that something was wrong.

But we can't be careless because of this. If a battery short-circuit occurs in an electric car while it is driving, the time difference between the short-circuit and the fire may prevent the driver from discovering the problem in time.

The safety of electric vehicles is questionable, but we should not demonize them

Electric cars have only been around for 10 years and have yet to become widely popular. We still have many doubts and concerns about this new type of car.

But perhaps it is precisely because of these doubts that reports of electric vehicle accidents have received so much attention.

Are electric cars really less safe than gasoline cars? This is still undecided. We should not jump to conclusions before investigating the cause of the accident.

The emergence of new things always brings risks and opportunities, and this is true for all walks of life. As the future trend in the automotive field, electric vehicles now have high expectations, but behind these expectations, there are still doubts about their safety. It may take time to eliminate these doubts.