Electric Car Fire Risk Looks Exaggerated, But More Data Required.
“At this time, any comments on the cause are speculative and of course will be subject to investigation”
The fire risk from electric cars appears to be less than for conventional vehicles, although Americans awaiting their new Volkswagen’s to be delivered from Europe could be forgiven for doubting that as their new cars were destroyed, apparently by a spontaneous lithium-ion battery fire on the Felicity Ace.
The ship sank last month.
Any firm conclusions on fire risks are not yet possible because there is not enough data to decide that pure electric cars are more prone to spontaneous fire than internal combustion engine (ICE) ones, or more likely to burst into flames after an accident.
As for the fire on VW’s car transporter from Germany to the U.S. carrying almost 4,000 vehicles, probably including battery-electric Porsche Taycans, Audi e-Trons and VW ID.4s, a report in Britain’s Daily Mail quoted the Felicity Ace’s captain Joao Mendes Cabecas saying lithium-ion batteries in the electric cars on board caught fire.
VW warned against a rush to judgement.
“At this time, any comments on the cause are speculative and of course will be subject to investigation,” VW said.
As the battery electric vehicle (BEV) revolution gathers pace, spontaneous fires, or electric car fires after accidents, have attracted media attention. If you see a picture or video of a pricey Tesla engulfed in a spectacular fire it’s easy to make the lazy assumption that this is somehow a problem with all electric cars. After all, a bog-standard internal combustion engine (ICE) car on fire would probably not be in the headlines.
Recent data whipped up a storm amongst zealots from both sides. Electric car enthusiasts liked the idea that National Transportation Safety Board (NSTB) data, analysed by AutoinsuranceEZ, showed BEVs were far safer than hybrids and ICE cars. AutoinsuranceEZ said the numbers showed electric cars were less prone to fire than other vehicles, with hybrids the most dangerous, followed by gasoline vehicles.
Hang on a minute said the doubters, the data shows no such thing.
Graham Conway, principal engineer at the Southwest Research Institute in San Antonio, Texas, said there’s not enough information to decide if EVs are more prone to spontaneous fire than ICE ones.
“It is still too early to make any conclusions about EVs and spontaneity of fires. I just don’t think we have the sample size of data or the reporting structure for fires to say with any certainty. What is clear is that the fire is more difficult to deal with, the energy release during the exotherm of the electrolyte takes a lot of cooling to extinguish,” Conway said
Conway said the data didn’t allow for solid conclusions.
“The NTSB data said that after 41 fatal collisions involving BEVs, 1 caught on fire (2.44%). The NTSB data said that after 20,315 fatal collisions involving gasoline vehicles, 644 caught on fire (3.17%). The NTSB data said that after 543 fatal collisions involving Gasoline Hybrid vehicles, 12 caught on fire (2.21%),” Conway said.
“But 41 crashes vs 20,315 crashes vs 543 crashes make it statistically irresponsible to compare these numbers. For example, if there was a 42nd crash with an EV and it caught on fire then it would be 4.76% of EVs or double the rate of hybrids. Until the sample size is the same and significant we just can’t say which will be worse or not,” Conway said.
EVs generally appear less likely fire risks, but the data is limited
Richard Billyeald, chief technical officer at Britain’s Thatcham Research, said EVs generally appear less likely fire risks, but the data is limited.
“Our latest research indicates that the risk of a fire for all types of EV remains less likely than for ICE vehicles. It should be noted that the usable data only goes back five years and even now the number of EVs on the roads still represents a very small sample size. This is also reflected in the safety testing we conduct in the U.K. on behalf of Euro NCAP (European auto safety), where despite the robust impacts to the front and particularly the sides of the vehicle where the battery is most vulnerable, there have been no resultant thermal events,” Billyeald said.
As battery technology progresses, fire risks are likely to lessen.
“The likelihood is that the EV fire risk will reduce over time, as the industry moves towards solid-state batteries and technology developments that are less susceptible to ‘thermal runaway’ and other associated catastrophic events. U.K. government statistics on possible thermal runaway events show that fires are holding steady or even reducing slightly, despite the rapid increase of these vehicles on the market,” Billyeald said.
Hard to say
LMC Automotive analyst Oliver Petschenyk said it’s hard to say whether ICE cars or EVs are more or less prone to fires. With ICE vehicles, typical fire causes are brake fluid leaks igniting after exhaust contact, and electrical short circuits, which are usually design failures. Common EV failures include an internal cell short which could lead to thermal runaway.
“I believe the likelihood of a vehicle’s battery failing is becoming ever more less likely. However the number of EVs on the road is increasing possibly at a higher rate so I believe thermal events for the foreseeable future are still likely,” Petschenyk said.
In a frontal crash an EV is unlikely to cause thermal runaway.
“Side impact or underside puncture I believe may pose a greater risk to EVs than ICE, anything that can cause cell damage or to short, but again assuming the battery has adequate fail safes, thermal runaway risk is minimized. There have been situations where EVs can ignite some time after an incident, this is typically due to coolant leaking into the battery and again causing cells to short, but similarly the risk of this happening is ever diminishing as technology and fail safes improve,” Petschenyk said.
“I believe the biggest risk to hybrids and PHEVs (plug-in hybrid electric vehicles) is driven by package. Due to the requirement of fitting two powertrains into one vehicle (ICE powertrain and EV powertrain) all components are much more densely packaged, thermal control and electrical components may need to be packaged quite close to exhausts. In addition, batteries are subjected to a much higher duty cycle than EV batteries, they are discharged to zero and charged to 100% more frequently and typically faster (at the cell level) resulting in faster dendrite formation (another way in which cells can fail via internal short circuit),” Petschenyk said.
Thatcham’s Billyeald said there’s no doubt that EV’s pose a special problem when they do catch fire.
“Of more significance is that once an EV is on fire, it is more challenging to deal with,” he said.
Burn for days then reignite
EV fires can burn for days and often reignite when the fire seems to have been defeated. Fire-fighters are now trained that total immersion in a swimming pool-like structure may be the only way to make sure it’s out. And what might appear to be only slight damage can be terminal.
Batteries, which can stretch to all four corners have more area to be damaged compared with an ICE under the hood. Batteries are also a huge cost component. For instance, the battery in a Jaguar I-Pace costing roughly £70,000 ($100,000) is about half – £35,000. So, insurance costs are likely to be massive and could well price these vehicles away from any but the most high-income buyers. Given that prices are currently at least twice as much as a regular ICE car, this would be a hurdle that dooms electric cars to the margins.