Several plug-in electric vehicle fire incidents have taken place since the introduction of mass-production plug-in electric vehicles in 2010. Most of them have been thermal runaway incidents related to the lithium-ion batteries and have involved the Zotye M300 EV, Chevrolet Volt, Fisker Karma, Dodge Ram 1500 Plug-in Hybrid, Toyota Prius Plug-in Hybrid, Mitsubishi i-MiEV and Outlander P-HEV. Most hybrid electric vehicles available in the market today use nickel-metal hydride batteries which do not pose the same risk of thermal runaway as lithium-ion batteries.
As of February 2014, four fires after an impact have been reported associated with the batteries of plug-in electric cars. The first crash related fire was reported in China in May 2012, after a high-speed car crashed into a BYD e6 taxi in Shenzhen. Two incidents occurred with the Tesla Model S in October 2013, one when a Model S caught fire after the electric car hit metal debris on a highway in Kent, Washington, and another involving a loss of control and collision with a tree in Merida, Mexico. A Tesla Model S being driven on a highway near Murfreesboro, Tennessee caught fire in November 2013 after it struck a tow hitch on the roadway, causing damage beneath the vehicle.
The U.S. National Highway Traffic Safety Administration (NHTSA) is conducting a study due in 2014 to establish whether lithium-ion batteries in plug-electric vehicles pose a potential fire hazard. The research is looking at whether the high-voltage batteries can cause fires when they are being charged and when the vehicles are involved in an accident. Both General Motors and Nissan have published a guide for firefighters and first responders to properly handle a crashed electric-drive vehicle and safely disable its battery and other high voltage systems.
Background
JMSTar electric vehicle fire.wmv -
Frequency of vehicle fires
Fire incidents in highway capable vehicles occur relatively frequently. A study of U.S. fires from 2003-2007 finds that fire departments respond to an average of 287,000 vehicle fires per year, or 30 vehicle fires per hour, and that vehicles were involved in 17% of all reported U.S. fires. The study also finds that roughly 90 highway vehicle fires and 0.15 highway vehicle fire deaths were reported per billion miles driven.
Thermal runaway
Lithium-ion batteries may suffer thermal runaway and cell rupture if overheated or overcharged, and in extreme cases this can lead to combustion. To reduce these risks, lithium-ion battery packs contain fail-safe circuitry that shuts down the battery when its voltage is outside the safe range. When handled improperly, or if manufactured defectively, some rechargeable batteries can experience thermal runaway resulting in overheating. Sealed cells will sometimes explode violently if safety vents are overwhelmed or nonfunctional. Reports of exploding cellphones have been published in newspapers. In 2006, batteries from Apple, HP, Toshiba, Lenovo, Dell and other notebook manufacturers were recalled because of fire and explosions.
Non-automotive incidents
One incident that caught the attention of U.S. federal regulators was Dell's recall of 4.1 million lithium-ion batteries in laptop computers in 2006. Dell said the Sony-made batteries posed a fire risk under rare conditions, due to a manufacturing defect.
The Pipeline and Hazardous Materials Safety Administration (PHMSA) of the U.S. Department of Transportation has established regulations regarding the carrying of certain types of batteries on airplanes because of their instability in certain situations. This action was partially inspired by a cargo bay fire on a FedEx airplane and the crash of UPS Airlines Flight 6. On 16 May 2012, the United States Postal Service (USPS) banned shipping anything containing a lithium battery to an overseas address due to fires from transport of batteries. The ban was lifted on 15 November 2012.
In the Boeing 787 Dreamliner's first year of service, at least four aircraft suffered from electrical system problems stemming from its lithium-ion batteries, resulting in the whole Dreamliner fleet being voluntarily grounded in January 2013. The Federal Aviation Administration decided on April 19, 2013 to allow US Dreamliners to return to service after changes were made to their battery systems. Japanese authorities announced they were doing the same for their airplanes. The NTSB eventually determined that the cause was a fault within one of the cells, and faulted Boeing for not designing it to withstand a short-circuit, and the FAA for not considering the possibility in their certification process.
Safety guidelines for fire hazard
In the United States, General Motors ran in several cities a training program for firefighters and first responders to demonstrate the sequence of tasks required to safely disable the Chevrolet Volt’s powertrain and its 12 volt electrical system, which controls its high-voltage components, and then proceed to extricate injured occupants. The Volt's high-voltage system is designed to shut down automatically in the event of an airbag deployment, and to detect a loss of communication from an airbag control module. GM also made available an Emergency Response Guide for the 2011 Volt for use by emergency responders. The guide also describes methods of disabling the high voltage system and identifies cut zone information. Nissan also published a guide for first responders that details procedures for handling a damaged 2011 Leaf at the scene of an accident, including a manual high-voltage system shutdown, rather than the automatic process built-in the car's safety systems.
NHTSA research of fire risk
In August 2012, the National Highway Traffic Safety Administration (NHTSA) decided to begin a US$8.75 million study of whether lithium-ion batteries in plug-electric vehicles pose a potential fire hazard. The research is looking at whether the high-voltage batteries can cause fires when they are being charged and when the vehicles are involved in an accident. The reason for the research is based on the risk posed by 400-volt lithium ion batteries compared with standard 12-volt lead-acid batteries used in gasoline-powered vehicles. General Motors is assisting NHTSA researchers, and the study is expected to continue through 2014.
Electric vehicle incidents
A Future EV
About 6 a.m. on 17 November 2010 a fire broke out on the vehicle deck of the MS Pearl of Scandinavia on its way from Oslo to Copenhagen. The ferry's fire sprinkler system put out the fire before any of the crew or the 490 sleeping passengers were injured and the ship could dock in Copenhagen under its own power. It was determined that the cause of the fire was a short circuit in the plug of an extension cord used to charge a rebuilt Nissan Qashqai, converted into a battery electric vehicle by the Sakskøbing based company A Future EV. The company owner was returning from Norway where the vehicle had started the approval process for general sale there, and had used an extension cord to charge the vehicle from a general purpose power outlet on the ferry. The ferry operator DFDS Seaways consequently prohibited vehicle charging on board its ferries while the investors withdrew their support for the vehicle company forcing it into bankruptcy.
Zotye M300 EV
A Zotye M300 EV operating as a taxicab caught fire in Hangzhou, China, in April 2011. No one was injured as the driver and two passengers evacuated the electric car in time. Due to the incident, the city authorities decided to halt all electric taxis on safety concerns, 15 of which were M300 EVs out of a fleet of 30 electric taxis. The city's official investigation team found the cause of the fire was the car's defective battery pack due to lack of quality control during manufacturing. According to the investigation report, the battery pack problems include: leaking of battery cells; damage of the insulation between battery cells and the walls of the aluminum container in which the cells were stacked; short circuits occurred within certain containers and those involving supporting and connecting parts. One of the stronger short circuits ignited the car’s back seats. The lead investigators said that "...in sealing and packing the battery cells, in loading and unloading the battery stacks, insufficient attention had been paid to several safety factors; monitoring procedures had been inefficient or neglected in the process of manufacturing, battery charging/switching, and vehicle driving, failing to detect anomalies." The report added that the battery cells on the car were made by Zhejiang Wanxiang Group.
Chevrolet Volt
As a result of a crash-tested Chevrolet Volt that caught fire in June 2011 three weeks after the testing, the National Highway Traffic Safety Administration (NHTSA) issued a statement saying that the agency does not believe the Volt or other electric vehicles are at a greater risk of fire than gasoline-powered vehicles. They added: "In fact, all vehicles â€"both electric and gasoline-powered â€" have some risk of fire in the event of a serious crash." The NHTSA announced in November 2011 that it was working with all automakers to develop post-crash procedures to keep occupants of electric vehicles and emergency personnel who respond to crash scenes safe.
In further testing of the Volt's batteries carried out by NHTSA in November 2011, two of the three tests resulted in thermal events, including fire. Therefore, the NHTSA opened a formal safety defect investigation on November 25, 2011, to examine the potential risks involved from intrusion damage to the battery in the Chevrolet Volt.
On January 5, 2012, General Motors announced that it would offer a customer satisfaction program to provide modifications to the Chevrolet Volt to reduce the chance that the battery pack could catch fire days or weeks after a severe accident. General Motors explained the modifications will enhance the vehicle structure that surround the battery and the battery coolant system to improve battery protection after a severe crash. The safety enhancements consist of strengthening an existing portion of the Volt’s vehicle safety structure to further protect the battery pack in a severe side collision; add a sensor in the reservoir of the battery coolant system to monitor coolant levels; and add a tamper-resistant bracket to the top of the battery coolant reservoir to help prevent potential coolant overfill. On January 20, 2012, the NHTSA closed the Volt's safety defect investigation related to post-crash fire risk. The agency concluded that "no discernible defect trend exists" and also found that the modifications recently developed by General Motors are sufficient to reduce the potential for battery intrusion resulting from side impacts. The NHTSA also said that "based on the available data, NHTSA does not believe that Chevy Volts or other electric vehicles pose a greater risk of fire than gasoline-powered vehicles." The agency also announced it has developed interim guidance to increase awareness and identify appropriate safety measures regarding electric vehicles for the emergency response community, law enforcement officers, tow truck operators, storage facilities and consumers.
Fisker Karma
In December 2011, Fisker Automotive recalled the first 239 Karmas delivered to the U.S. due to a risk of battery fire caused by coolant leak. Of the 239 cars, less than fifty have been delivered to customers, the rest were in dealerships. In the report filed by Fisker Automotive with the NHTSA, the carmaker said some hose clamps were not properly positioned, which could allow a coolant leak and an electrical short could possibly occur if coolant enters the battery compartment, causing a thermal event within the battery, including a possible fire. In May 2012 a Fisker Karma was involved in a home fire that also burnt two other cars in Fort Bend County, Texas. The chief fire investigator said the Karma was the origin of the fire that spread to the house, but the exact cause is still unknown. The plug-in hybrid electric car was not plugged in at the time the fire started and it was reported that the Karma's battery was intact. The carmaker release a public statement saying that "...there are conflicting reports and uncertainty surrounding this particular incident. The cause of the fire is not yet known and is being investigated." Fisker Automotive also stated that the battery pack "does not appear to have been a contributing factor in this incident." The NHTSA is conducting a field inquiry of the incident, and is working with insurance adjusters and Fisker to determine the fire’s cause.
A second fire incident took place in August 2012 when a Karma caught fire while stopped at a parking lot in Woodside, California. According to Fisker engineers, the area of origin for the fire was determined to be outside the engine compartment, as the fire was located at the driver’s side front corner of the car. The evidence suggested that the ignition source was not the lithium-ion battery pack, new technology components or unique exhaust routing. The investigation conducted by Fisker engineers and an independent fire expert concluded that the cause of the fire was a low temperature cooling fan located at the left front of the Karma, forward of the wheel. An internal fault caused the fan to fail, overheat and started a slow-burning fire. Fisker announced a voluntary recall on all Karmas sold to replace the faulty fan and install an additional fuse.
BYD e6
In May 2012, after a Nissan GTR crashed into a BYD e6 taxi in Shenzhen, China, the electric car caught fire after hitting a tree killing all three occupants. The Chinese investigative team concluded that the cause of the fire was that "electric arcs caused by the short-circuiting of high voltage lines of the high voltage distribution box ignited combustible material in the vehicle including the interior materials and part of the power batteries." The team also noted that the battery pack did not explode; 75% of the single cell batteries did not catch fire; and no flaws in the safety design of the vehicle were identified.
Dodge Ram 1500 Plug-in Hybrid
In September 2012 Chrysler temporarily suspended a demonstration program that was conducting with 109 Dodge Ram 1500 Plug-in Hybrids and 23 Chrysler Town & Country plug-in hybrids. All units deployed in the program were recalled due to damage sustained by three separate pickup trucks when their 12.9 kWh battery packs overheated. The carmaker plans to upgrade the battery packs with cells that use a different lithium-ion chemistry before the vehicles go back on service. Chrysler explained that no one was injured from any of the incidents, and the vehicles were not occupied at the time, nor any of the minivans were involved in any incident, but they were withdrawn as a precaution. The carmaker reported that the demonstration fleet had collectively accumulated 1.3 million miles (2.1 million km) before the vehicles were recalled. The demonstration is a program jointly funded by Chrysler and the U.S. Department of Energy that includes the first-ever factory-produced vehicles capable of reverse power flow. The experimental system would allow fleet operators to use their plug-in hybrids to supply electricity for a building during a power outage, reduce power usage when electric rates are high or even sell electricity back to their utility company.
In separate incidents during the storm and flooding caused by Hurricane Sandy on the night of October 29, 2012, one Toyota Prius Plug-in Hybrid and 16 Fisker Karmas caught fire while being parked at Port Newark-Elizabeth Marine Terminal. The vehicles were partially submerged by flash floods caused by the hurricane. In the case of the Toyota's incident, a Prius PHV burned and two other Priuses, a conventional hybrid and a plug-in, just smoldered. A Toyota spokeswoman said the fire “likely started because saltwater got into the electrical system.†She also clarified that the incident affected only three cars out of the 4,000 Toyotas that were at the terminal during the storm, including more than 2,128 plug-in or hybrid models. Fisker Automotive spokesman said that the Karmas were not charging at the time of the fire and there were no injuries. After an investigation by Fisker engineers, witnessed by NHTSA representatives, the company said that the origin of the fire was "residual salt damage inside a Vehicle Control Unit submerged in seawater for several hours. Corrosion from the salt caused a short circuit in the unit, which led to a fire when the Karma's 12-Volt battery fed power into the circuit." The company explained that Sandy's heavy winds spread that fire to other Karmas parked nearby, and also ruled out the vehicles' lithium-ion battery packs as a cause of, or a contributing factor to, the fire.
Mitsubishi i-MiEV and Outlander P-HEV
In March 2013 Mitsubishi Motors reported two separate incidents with lithium-ion batteries used in its plug-in electric cars, one with a Mitsubishi i-MiEV electric car and the other with an Outlander P-HEV plug-in hybrid. The battery packs are produced by GS Yuasa, the same company that supplies the batteries for the Boeing 787 Dreamliner, whose entire fleet was grounded in January 2013 for battery problems. The lithium-ion battery of an i-MiEV caught fire at the Mizushima battery pack assembly plant on March 18 while connected to a charge-discharge test equipment. Three days later, the battery pack of an Outlander P-HEV at a dealership in Yokohama overheated and melted some of the battery cells, after the vehicle had been fully charged and stood for one day. Nobody was injured in either incident.
Mitsubishi did not issue a recall but halted production and sales of the two models until it determines the causes of the battery problems. The carmaker advised owners of the Outlander plug-in hybrid to drive only on gasoline mode for the time being. In the case of the i-MiEV, the problem is related with a change in GS Yuasa manufacturing process, and Mitsubishi called fleet-vehicle operators with i-MiEVs whose batteries were made under the same process as those that overheated and is working on a possible fix. In August 2013, and after changing a production process to avoid damaging any batteries, Mitsubishi restarted production of the Outlander plug-in hybrid.
Tesla Model S
A Tesla Model S caught fire after the vehicle hit debris on a highway in Kent, Washington, on October 1, 2013. According to the driver, he hit something while traveling in the HOV lane of Washington State Route 167, and exited because the car reported a problem and told him to stop. Flames began coming out of the front of the car at the end of the off-ramp, so the driver left the car. The fire was caught on video by a witness and posted on several websites. According to the Kent Fire Department incident report, initial attempts to extinguish the fire with water were unsuccessful, as the fire reignited underneath the vehicle after appearing to be extinguished. Then, the firefighters cut a hole to apply water directly to the burning battery. According to Tesla, the car owner was alerted by onboard systems to stop the car and exit the vehicle, which he did without injury.
The carmaker confirmed the fire began in the battery pack and it was caused by an impact to one of the battery pack modules by a large piece of metal from a semi-trailer and that the design of the battery pack had isolated the fire the front section's internal firewalls.
The company also said that conventional gasoline-powered cars were much more vulnerable to such a situation, because they have less underbody protection. It also noted that the battery pack holds only about 10% of the energy contained in a gasoline tank and is spread across 16 firewalled modules, meaning that the combustion potential is only about 1% as much. Elon Musk posted on his blog that, based on U.S. automobile miles-per-fire statistics from the National Fire Protection Association, a driver is "5 times more likely to experience a fire in a conventional gasoline car than a Tesla." After news of the accident, Tesla stock fell 6.24% in NASDAQ trading the next day, and an additional 4% the following day, closing at US$173.31. The stock recovered by 4.4% at the closing of the week.
Tesla's CEO, Elon Musk, issued an official statement on October 4, 2013. The statement said that a curved piece of metal from a semi-trailer that had fallen on the roadway appeared to have impaled the one-quarter-inch (0.64 cm) plate on the base of the vehicle. According to the statement, in order for the object to have made a 3-inch (7.6 cm) diameter hole in the plate, the object must have had enough leverage to produce approximately 25 short tons-force (220 kN). After the driver exited the car, the statement continued, the frontmost of the car's 16 battery modules caught fire due to the initial damage, but the battery pack's internal firewalls kept the fire from spreading and vents directed the flames away from the car down towards the pavement. The statement also noted that the fire never entered the passenger compartment. According to Tesla, the firefighters observed standard procedure, and gained access to the source of the fire by puncturing holes in the top of the battery’s protective metal plate and applying water. However, the company noted that although the water and dry-chemical fire extinguisher quickly put out the fire, the firefighters should not have punctured the firewall since the new holes allowed flames to enter the front trunk of the vehicle. Musk closed the official statement explaining that the result of this accident could have been "far worse" had a conventional gasoline-powered car encountered the same object on the highway, because most gasoline cars do not have an armored underbody, leaving the fuel lines and tank vulnerable. He also noted that Tesla's battery pack only contains about 10% as much energy as a standard tank of gasoline and it is divided into 16 sections means that the combustion potential is about 1% of a comparable gasoline-powered car. Based on U.S. statistics from the National Fire Protection Association, Musk's statement claimed that a fire was five times more likely in a gasoline car than in a Tesla car.
The U.S. National Highway Traffic Safety Administration (NHTSA) was not able to send investigators to the scene of the incident due to the U.S federal government shutdown. After the agency reopened, the NHTSA began gathering data of the incident. On 24 October 2013, the agency announced it will not open a formal investigation into the Model S fire incident, saying that they had not found evidence that the fire was caused by a vehicle defect or noncompliance.
A second reported fire occurred on October 18, 2013 in Merida, Mexico. In this case the vehicle was being driven at high speed through a roundabout and crashed through a wall and into a tree. The NHTSA did not investigate this incident because it occurred outside the U.S.
A Tesla Model S being driven on Interstate 24 near Murfreesboro, Tennessee caught fire on November 6, 2013 after it struck a tow hitch on the roadway, causing damage beneath the vehicle. Tesla Motors stated that it would conduct its own investigation, and as a result of these incidents, the company announced its decision to extend its current vehicle warranty to cover fire damage and to apply a software update on Model S cars to increase the ground clearance of the Model S when driving at highway speed.
On November 19, 2013, based on the two fire incidents occurring on U.S. public highways, the NHTSA opened a preliminary evaluation to determine if undercarriage strikes presented an undue fire risk on the 2013 Tesla Model S. An estimated population of 13,108 Model S cars were part of this initial investigation.
On November 15, 2013, a fire broke out in an Irvine, California garage where a Tesla Model S was plugged in and charging. The fire appears to have originated at the wall connection where the Tesla charging equipment was plugged in. Shortly afterwards, Tesla updated the Model S firmware to reduce charging current when power fluctuations were detected and replaced wall adapters with a new unit containing a thermal fuse.
On November 18, 2013, Tesla released a software update to the air suspension system to increase the ground clearance at highway speeds and requested that the NHTSA conduct an investigation into the fire incidents. Another fire incident took place in Toronto, Canada, in early February 2014. The Model S was parked in a garage and it was not plugged in or charging when the fire started. As of February 14, 2014, the origin of the fire was still unknown. According to Tesla
"In this particular case, we don't yet know the precise cause, but have definitively determined that it did not originate in the battery, the charging system, the adapter or the electrical receptacle, as these components were untouched by the fire."
On March 28, 2014, the NHTSA announced that it had closed the investigation into whether the Model S design was making the electric car prone to catch fire, after the automaker said it would provide more protection to its lithium-ion batteries. According to the NHTSA, the titanium underbody shield and aluminum deflector plates, along with increased ground clearance, reduce the severity, frequency, and fire risk of underbody strikes. All Model S cars manufactured after March 6 have the .25-inch (6.4Â mm) aluminum shield over the battery pack replaced with a new three-layer shield designed to protect the battery and charging circuitry from being punctured even in very high speed impacts. The new shielding features a hollow aluminum tube to deflect impacting objects, a titanium shield to protect sensitive components from puncture damage, and an aluminum extrusion to absorb impact energy. The new shields, which decrease vehicle range by 0.1%, will be installed free-of-charge in existing Model S vehicles by request or during the next scheduled maintenance. According to the NHTSA, the titanium underbody shield and aluminum deflector plates, along with increased ground clearance, "should reduce both the frequency of underbody strikes and the resultant fire risk."
A fire occurred in a Tesla Model S charging at a Tesla Supercharger in Norway on January 1, 2016. The fire was slow, and the owner had time to unplug the car and retrieve possessions. An investigation by the Norwegian Accident Investigation Board (AIBN) indicated that the fire originated in the car, but was otherwise inconclusive. In March 2016, Tesla stated that their own investigation into the incident concluded that the fire was caused by a short circuit in the vehicle's distribution box, but that the amount of damage prevented them from determining the exact cause. Tesla stated that the Supercharger detected the short circuit and deactivated, and a future Model S software update would stop the vehicle from charging if a short circuit is detected.
See also
- Boeing 787 Dreamliner battery problems (related to lithium-ion batteries)
- Lithium-ion batteries and safety
- UPS Airlines Flight 6, a crash caused by the thermal runaway of its lithium-ion battery cargo
- Vehicle fire
References
External links
- NHTSA Interim Safety Guidance for Vehicle Owner/General Public
- NHTSA Interim Safety Guidance for Law Enforcement/Emergency Medical Services/Fire Department
- NFPA Chevrolet Volt Emergency Response Guide
- Should Battery Fires Drive Electric Cars Off the Road?, Scientific American, 12 November 2013.
- Videos
- Tesla Model S EV Safety Training for Emergency Responders, YouTube. Production: Ron Moore and Brock Archer, with collaboration of Tesla Motors, October 2013.
