Last Update: August 27, 2015
The small handful of electric car fires have made some worry whether the cars are safe. Actual indications are that electric cars are safer, from fire, than gasoline cars. Especially when you compare the rate of gasoline car fires to electric car fires.
Of course we want safe vehicles and safety on the road. As a result governments around the world have safety regulations, vehicle safety agencies, testing methodologies and more. Just because a car is driven by electricity doesn’t mean it can skip being certified by those agencies. Electric vehicles have to pass the same vehicle safety code requirements as gasoline powered cars. Well, except for the bits concerning gasoline tanks and the like because electric cars don’t have them.
Car safety is a broad area, but what’s gotten the most attention is electric car fires. While we’re going to focus primarily on electric car fire safety, we’ll discuss general crash safety as well.
Electric car fire safety – OVERVIEW
As of this writing there have been a couple electric car fires. The fires were met with worries that electric cars are somehow unsafe because they can catch fire. In some cases the fires were purposely played up for political gain, such as by Mitt Romney and others during the 2012 Presidential campaign. That line of political chicanery went that because the Chevy Volt was Obama’s Baby (FALSE), and that the Volt was explosive (FALSE), that this was somehow proof that President Obama’s green technology jobs strategy was a failure.
Actual indications are that electric cars are safer, from fire, than gasoline cars.
The biggest question here is – if we’re going to be so concerned over car fires, why aren’t we getting so worked up over gasoline car fires? About 200,000 of those occur per year in the U.S. alone, and are so common they go unreported except when there’s a particularly spectacular fire. Oh, and there are plenty of fatalities every year due to these fires. It’s puzzling why an electric car fire immediately gets international attention, where a gasoline car fire barely rates a yawn.
We shouldn’t ignore electric car fires and treat them with the same indifference as gasoline car fires. In fact it would be excellent to increase the attention on gasoline car fires. Is there an appropriate level of attention on the risk of electric car fire without going overboard?
As of this writing there have been a handful of electric car fires, and no injuries (see list of known electric car fires).
That last point is significant because Tesla Motors stresses that their highest priority is occupant safety rather than eliminating the risk of fire. If it’s unlikely for an automaker to design a completely foolproof car that can never at all ever catch fire, then what is the role of the automaker? Maybe, as Tesla Motors claims, it is to mitigate the fire risk as much as possible, and design the car so that if a fire does break out, to reduce the risk to occupants from the fire.
To look objectively the rate of car fires for gasoline and electric vehicles is to measure the number of vehicle miles driven per car fire for each type of car.
Gasoline car fire rate
In early October 2013, after the first Tesla Model S car fire, Tesla Motors claimed “there are 150,000 car fires per year according to the National Fire Protection Association, and Americans drive about 3 trillion miles per year according to the Department of Transportation. That equates to 1 vehicle fire for every 20 million miles driven”.
By the time of the second Model S car fire, in mid-November, Tesla’s management wrote this: “Since the Model S went into production last year, there have been more than a quarter million gasoline car fires in the United States alone, resulting in over 400 deaths and approximately 1,200 serious injuries (extrapolating 2012 NFPA data).”
Another report, dated September 2008 by FEMA, says between 2004-2006 there were 258,000 highway vehicle fires per year. That accounts for 16% of all fires worked by fire departments across the country. Car fires on the highway accounted for 90% of all car fires. These fires accounted for 490 deaths, 1275 injuries, and $1 billion in property loss per year.
An article in the MIT Technology Review, Early Data Suggests Collision-Caused Fires are More Frequent in the Tesla Model S than Conventional Cars, suggests that Tesla’s numbers are an apples-to-oranges comparison. We have to compare the rate of fires from collisions between gasoline and electric cars. Using numbers from FEMA and the Dept of Transportation the article claims the rate of gasoline car fires, from collisions, is one in 32,603 registered vehicles. That’s much lower than the one fire per 6,333 Model S’s, meaning that an apples-apples comparison makes the Model S fire rate worse than for gasoline car fires.
That gives us some data about the rate of gasoline car fires. The data deserves to be torn apart a little more. For instance, it’s likely that a large number of the car fires occur when they’re stationary, rather than on the road. It’d also be useful to know the average age of the cars which catch on fire. Basically, gasoline car fires are pretty common.
Most days on the rush hour traffic report, don’t they tell us about such-and-such highway is a little slow because of a car fire? This is so common that when it happens, the only report about the fire is the traffic reporter.
But what about the rate of electric car fires? Unfortunately we don’t have as many electric cars on the road, and the low number of fires could simply be a result of the small number of cars.
Electric car fire rate
I’ve put together a spreadsheet estimating electric vehicle miles driven based on public data available. In October 2013 it showed 638 million electric miles driven by Chevy Volt, Nissan Leaf, Tesla Model S, and Tesla Roadster owners in the U.S. That’s a subset of EV’s in America, which is in turn a subset of the EV’s worldwide. We have had five known electric car fires, on the road, in 638 million miles of electric driving (two Fisker Karma’s, three Model S’s). This measure is is over the last three years, not per year, and is barely a blip in vehicle miles traveled.
The numbers in front of us show one electric car fire per 120 million miles or so of electric driving.
We won’t be able to say with certainty what the rate of electric car fires is until there are a lot more of them on the road.
An interesting thing to note is that neither the Nissan Leaf nor Chevy Volt have had car fires, on the road. Yes, there was a famous car fire of a Chevy Volt, but that followed a crash test. There have been several horrendous wrecks of Volt’s and Leafs, but no fires.
Batteries aren’t inherently explosive while gasoline is. Gasoline tanks are essentially fuel bombs waiting to explode, but with top-notch engineering meant to reduce the occurance of that event.
It’s not that lithium-ion batteries cannot burn, they’re simply not inherently explosive. Under the right circumstances batteries can burn – see not only the events listed above, but our page on lithium-ion battery flammability. The risk of battery fires depends on the battery chemistry, as well as how well protected is the battery pack.
The core issue is that any energy storage system – whether it’s gasoline, or a hydroelectric dam, or a pile of uranium, or a battery – has the potential of catastrophic failure. The failure mode depends on the storage technology. Dams can break, nuclear power plants can blow up, etc. Reducing the risks is a matter of engineering work, but we cannot entirely eliminate risk.
Our society has learned how to accommodate the carnage of gasoline car fires. One suspects that over time electric cars will be proved to be far safer than gasoline cars, and that in any case we’ll become collectively acclimated to the occasional electric car fire just as we’re acclimated to the occasional gasoline car fire.
Are electric cars more susceptible to impalements by road debris
Two of the Tesla Model S fires were due to the car becoming impaled by road debris, puncturing the battery pack, causing a short circuit, that leads to a fire.
Are electric cars more vulnerable or less vulnerable? What’s needed TBD is to find actual studies of damage from road debris. What I gather from the following is that road debris routinely causes damage and injury to cars, and that it’s not unknown for metal rods on the road to impale a car coming up through the floorboards.
In electric cars with a battery pack along the bottom of the car, that battery pack serves as an extra layer of protection against road debris. It’s unfortunate that the battery packs have a tendency to catch fire after being impaled.
Driving Hazard: Trash Hurtling Toward Your Car – This report from 1999 looks at Road Debris traffic incidents in 1999. The issue appears to be an epidemic of road debris that results in cars being impaled in various ways.
In 1998, the Florida Department of Highway Safety and Motor Vehicles counted 121 accidents in which cars collided with “movable object on road” along interstates in Miami-Dade, Broward and Palm Beach counties, resulting in 73 injuries.
Named incidents include a rod that poked up through the floorboard skewering the drivers leg, another rod that flew in through a windshield impaling a young woman through her chest, and so on.
A lot of the road debris is thought to accidently fall off the back of trucks when drivers don’t tie the load down securely. When something falls off, authorities call it a ‘leaking load.’
Unknown to driver, her SUV is impaled on metal bar – A 2012 report of a woman whose SUV was impaled by a piece of rebar that pierced all the way to the roof of the car, jamming the car door closed.
German Tourist Dies After Being Impaled By Car Jack – In 1991 a German tourist in Elko, NV, was driving west on Interstate 80 in northeastern Nevada with his wife and two children when they drove over a jack. The tool flipped up and punctured the car’s floorboard, tore through the driver’s seat and impaled the driver through the groin area. He was able to pull off the road and remove the jack, but he collapsed on the highway and died.
Flying debris on I-94 injures two people – In Minnesota, in January 2009, two separate incidents within a few minutes of each other of road debris impalements. In the first incident an object went through a car’s floorboard and hit the driver’s leg, the driver was able to drive himself to the hospital. In the second, an unknown object came through a windshield striking a passenger.
Are lithium battery chemistries inherently explosive or flammable?
The answer to that is – it depends on the battery chemistry. Lithium Iron Phosphate is widely regarded as being “safe” but it’s also lower energy density and lower power density means electric cars with LiFePO4 battery packs won’t go as far or as fast. Tesla’s focus in particular is on fast cars with long electric driving range. It’s fair to ask whether that goal resulted in a car that’s more susceptible to fire. We don’t know, but it’s a TBD fair question.
This report in the MIT Technology Review, “ Are Electric Vehicles a Fire Hazard?” talks about fire hazards in electric car battery packs.
There are inherent risks when you store enough energy to propel a two-ton car at 75 miles an hour for hundreds of miles. After all, thousands of gasoline-powered cars catch fire in collisions each year. In principle, those risks can be managed through structural design and cooling. But could the lithium-ion battery cells themselves be made safer? When batteries are used as intended, there’s only one fire for every 100 million lithium-ion battery cells out there, says Jeff Dahn, professor of physics and chemistry at Dalhousie University. Tesla also guards against thermal runaway events with an extensive liquid cooling system designed to cool the cells so fast that if one cell catches fire, its neighbors won’t. If, however, multiple cells are damaged, the cooling system might not be enough. “If the Tesla pack is abused severely by a large metal object thrust through the pack, it will probably have a fire in most instances,” Dahn says.
That piece closes saying current electrolytes are inherently flammable. Research is ongoing looking for electrolytes that aren’t flammable, and it specifically reports to an earlier report on Solid State Battery research between Toyota and Sakti3.
What if an electric car gets wet?
The fear is that a wet electrical system will short circuit and burst into flames. The fact is that electric car owners drive in the rain all the time without electrocution or rain. How? Automotive engineers know a thing or two about waterproofing the innards of an automobile, right? It’s just a matter of engineering to make things waterproof.
Charging an electric car in the rain?
The J1772 protocol used in charging connectors was carefully designed for safety, including use in the rain.
Over on the Wikipedia they have this to say: “The J1772 standard includes several levels of shock protection, ensuring the safety of charging even in wet conditions. Physically, the connection pins are isolated on the interior of the connector when mated, ensuring no physical access to those pins. When not mated, J1772 connectors have no voltage at the pins, and charging power does not flow until commanded by the vehicle. The pins are of the first-make, last-break variety. If the plug is in the charging port of the vehicle and charging, and it is removed, the control pilot and proximity detection pins will break first so that the Power Pin relay in the charging station will be shut off and no current will flow.”
That’s pretty technical, but what it basically means is there are multiple safety interlocks built into the J1772 interface. The power pins don’t even have power until the car and the charging station have agreed to start charging. There are some tricks in the physical interface to ensure the power will be turned off before the connector is all the way removed.
What about the fires in flooded Fisker Karma’s?
Good point, because there were some Karma’s that caught fire when flooded. It was a special circumstance, that occurred during Hurricane Sandy (a massive mega storm in October 2012 that devastated the New York City area). A vehicle import processing/storage area in Port Newark, New Jersey, was flooded by the storm surge. The initial report was that 16 Fisker Karma’s caught fire and then exploded due to being flooded. But, that initial report came from Jalopnik, a news source that leans towards the lurid.
In later reporting we learned that the situation was not quite as Jalopnik had reported. Sixteen Fisker Karma’s did catch fire, but did not explode, as did several other cars in that lot. Several Toyota Prius’s and a Prius Plug-in either started smouldering or caught fire. The pictures published by Jalopnik showed the fire was contained to the front of the car, and on the Karma that means the engine compartment and not the EV battery pack. The Karma is a plug-in hybrid and has a gasoline engine up front.
It became clear that after being submerged in five feet of salt water, that a short circuit formed in the “low voltage circuit” (12 volt system). The short circuit caused a fire, and it’s believed the fire started in one car spreading to the others.
Lithium battery fires on airplanes?
In 2013 the Boeing 787 Dreamliner, which had just gone into service, had to be grounded because of fires in lithium battery packs. I don’t know enough about these fires and TBD TODO need to explore it some more.
There have been a couple cases where lithium battery shipments on cargo airplanes have caused fires and crashes. As a result air shipment of lithium batteries is highly regulated by UN authorities.
Chevy Volt’s in garages that caught fire, and the NHTSA crash test Volt
In early 2011 a couple cases occurred where Chevy Volts were in garages that caught fire. Some controversy erupted at the time that maybe it was proof electric cars were unsafe. The flame of controversy was fanned by revelation later that year of the Chevy Volt that caught fire following a crash test.
In each case (see links on the Chevy Volt fire page) the Volt was cleared from culpability in the fire.
Garage fires happen routinely, and it’s not unknown for people to store flammable stuff in a garage that then catches fire.
There is at least one way an electric car sitting in a garage could catch fire. EIther design flaws in charging stations, or a botched installation job, could result in a fire. The whole purpose behind the standardised electrical wiring code is minimizing overheating in inadequate wiring that causes a fire. But, wiring isn’t always “up to code” and there are occasional fires due to any kind of bad wiring. Yes, the electrician is supposed to ensure charging stations are properly installed with wiring which will handle the 6 kilowatt charge rate. But electricians are human and may make a mistake.
Electric car crash safety
Now that tens of thousands of electric cars are on the road, we have some data with which to gauge whether they’re safe in car crashes. Other parts of this page have focused on how likely electric cars are to catch fire, but how do they fare in crashes generally speaking?
The answer of course depends on how well the manufacturer did with the car, hence the crash worthiness rating earned by the car. With NHTSA that’s the 5 star, 4 star, etc rating.
Hi Mr. Hughes, I got your name from my Volt Dealer here in Orange County, CA. I bought a 2013 Volt in November 2012 for my 20 year old daughter Caroline and we all loved it. I have a Porsche 911s and a BMW 740il. The Volt was our favorite car to drive. On August 3rd, a drunk driver hit Caroline from the right rear traveling in the same direction. The drunk driver hit our Volt so hard it knocked the Volt off the road down a 15 foot embankment. Caroline in the Volt rolled several times down the embankment before hitting a tree. Caroline was taken by ambulance to a local hospital where she suffered only a black eye, arm lacerations and stitches to her left foot. Our Farmers insurance adjuster said he never saw a car that mangled without a fatality. We are grateful to you and GM for making the Volt so safe. The fact that Caroline survived that crash was a miracle from God and the 10 Volt airbags. I am in the middle of buying another Volt right now and thought you would like to share this story with anyone else at GM or with any potential Volt buyers. Dr. Kerry Johnson