We've previously looked at electric car fires & provided an overview of our initial research findings that show they occur very rarely.
We're increasingly asked about the risk of an electric vehicle (EV) exploding, particularly in underground parking or roadways, such as tunnels. Our research identified & verified fourteen (14) EV explosion incidents since 2010 - that's from a global market of 10 million EVs in operation at the end of 2020.
While it's difficult to know exactly why explosion risk has become a hot topic, I believe the current prominence of EV fires in the media - a US insurance company releasing a comparison study & Elon Musk tweeting about EV battery fires - have understandably led to a fresh wave of uncertainty. In short, a kind of media-drive unconscious bias towards electrified transport.
An electric vehicle explosion, leading to a battery fire, is very rare. Let's have a look at what we mean by 'EV explosion', what the risk is & some of the circumstances in which they've occurred.
What is an electric car explosion?
While the terminology 'electric car explosion' is great for search engine clicks, the correct term we prefer to use is vapour cloud explosion (VCE).
When an EV battery pack goes into thermal runaway, toxic & flammable gases are vented from the lithium ion battery cells. In some cases, primarily in enclosed spaces, the gases form a large vapour cloud.
Around 700L of gases are released for every 1kWh of battery capacity*; to put that in perspective, a Tesla Model 3 can have up to a 75kWh battery, & some newer EV models coming to market may have around 100kWh.
When there is a point of ignition, such as an overheating battery cell, the vapour cloud does one of two things;
around 90% of the time, the gases ignite quickly but not explosively, sucking back the vapours as they burn;
or the gases explode, instantly propagating combustion at subsonic speeds, driven by heat transfer.
Both pose significant risks to emergency responders, as they may happen rapidly &, if you don't know the signs of thermal runaway, without much warning.
What does EV vapour cloud explosion look like?
Of the 14 incidents we've been able to verify, there are several with images or footage that clearly show the force of such an event, including the one above.
2019, Montreal, Canada - Hyundai Kona EV parked in a residential garage, not charging. Possible battery fault, blew garage door & roof away. Scrolling images, credit: CBC.
2019, Moscow, Russia - Tesla Model 3, collision with a parked tow truck while driving on freeway. Minor injuries to driver & his children. Footage credit: @gagorun.
2020, Fujian Province, China - BAIC EX360, Parked in open sided carport, connected to DC charging. Cause unknown. Blew doors, bonnet & debris through carport roof. Footage credit: unknown.
2021, Zhongshan, China - Chery Arrizo E, located in underground residential carpark & connected to charging. Driver sitting in back seat just prior to explosion. Unknown cause. Footage credit: click on image to view on Weibo.
What is the risk of electric car explosion?
As a reminder, EV fires overall are very rare, but EV vapour cloud explosions (VCE) are even less likely, involved in just 10.77% of all EV battery fire incidents since 2010.
When do EV explosions happen?
Of those 10.77% of incidents, we found:
Obviously, underground & enclosed spaces present the greatest cause for concern, primarily due to escape & evacuation, confinement of toxic gases near members of the public & access for emergency appliances & people. Additionally, some early testing that indicates battery fires may have the potential to cause issues with building structural integrity.
A complete overview of EV vapour cloud explosions since 2010 can be downloaded as a PDF or by clicking on the image.
What do we still need to learn about EV vapour cloud explosions?
A lot. The EV FireSafe team will be working with a global network of fire & battery experts to better understand VCE behaviour & risk throughout 2022, & will share these findings as they become available.
As always, thanks for supporting our website & research!
*Stat courtesy of Professor Paul Christensen, University of Newcastle