Videos of battery fires continue to bring the crash safety of EVs into the spotlight, but should you be worried?
Data from the US National Transportation Safety Board and Bureau of Transportation Statistics showed that for 2022, full battery-electric vehicles had significantly fewer fires reported (per 100,000 sales) than combustion engine-only and hybrid vehicles in the country.
Media reports and videos of seemingly spontaneous electric vehicle fires regularly blow a cloud over battery safety.
Unlike light and portable EVs (i.e. e-scooters or e-bikes), electric cars have much bigger batteries and a more advanced, complicated battery management system (BMS) and algorithm designed to ensure safe operation, using comprehensive thermal management methods.
Just like driving with a tank of highly combustible and constantly igniting fuel in a traditional combustion engine, during normal operation, it is safe to drive around with a large high-voltage battery of lithium-ion cells (the most common type in EVs today) under the vehicle floor.
This story was first published in 2019 and has been updated.
Combined with EV owners taking care of their battery – that is, servicing when required, following manufacturer-recommended charging habits (typically charging up to 80 per cent only and not discharging too deep), and mainly AC slow charging (avoiding frequent DC fast charging) – there’s a reduced likelihood of things going awry, not to mention maintaining a healthier battery.
For any vehicle to be sold in Australia, it has to comply with certain Australian Design Rule (ADR) regulations, and a vast majority of these stipulations ensure that a car is safe for occupants and other road users. It’s the reason any vehicle you see in a showroom today will have multiple airbags, ABS, electronic stability control and a whole host of other advanced features once considered the domain of more expensive cars.
EVs are no different: Their batteries and systems must comply with safety rules
There are no special exceptions for new technologies, including electric vehicles. It doesn’t matter whether you’re looking at an entry-level $45,000 MG ZS EV or a hi-po luxury $150,000-plus Porsche Taycan, every EV has to jump through the same compliance hoops as a petrol or diesel car.
In that regard, all vehicles for sale in Australia, including EVs, are regarded as safe at the time of compliance.
Recalls of EVs for concerns over a fire risk – whether while parked, charging, driving, or in the event of a crash – are not common, but they do happen.
- BMW i4 and iX electric vehicles recalled due to fire risk
- Hyundai recalls 2018-2020 Kona EV again over fire risk
Many, many more petrol and diesel cars have been recalled for fire risks – but, of course, there are still many more petrol and diesel cars in the market and on the road.
Are EVs any more dangerous than a regular petrol or diesel-powered car in a crash?
No current data shows that EVs are more likely to catch fire in a crash, but the dangers are clear.
Batteries damaged in a crash or by object impacts can lead to a fire, and a number of incidents around the world have shown that the worst case scenario outcomes are not pretty.
Once the flammable electrolytes in a Li-ion battery are alight, it is incredibly difficult to fully extinguish the fire in a high heating process called thermal runaway.
Batteries are not only full of flammable materials and harmful chemicals, but their massive contained energy is also capable of restarting a fire many times over, even after it appears to be completely out.
But, vehicle and battery manufacturers are continuously developing and improving their products in a quest to ensure maximum safety and durability, regardless of the conditions.
Temperature
Even though most modern vehicles are designed to operate without complaint in temperatures from minus 30 degree Celsius to heat beyond 50 degrees, a lithium-ion battery has a much narrower range of operation – about 15 to 45 degrees.
The efficiency, longevity and safety of the battery relies on its ability to stay within this temperature range. To do that, EVs have more sophisticated BMS software than any type of smartphone or e-scooter, which incorporate heating and cooling.
Clever cooling systems that use liquid coolant pipes and air ducts (on nearly all EV models), along with close monitoring and management of battery load, helps keep the cells within their critical operational range.
Thermal runaway
At temperatures of 60ºC and above, a battery is at risk of so-called ‘thermal runaway’, which is an unstoppable chain reaction causing a fire.
Runaway can also be caused by an internal short circuit, but battery construction is now so reliable that manufacturing defects are virtually unheard of. Though, an external short circuit – caused by a crash – is at some point unavoidable.
It’s worth noting that local car safety body ANCAP assesses the high-voltage battery to check if it automatically cuts out, for any fluid leaks, abnormal heat, or fire after each crash test. It hasn’t reported any battery fires from the 40-plus full battery-electric models assessed since 2011.
Manufacturers are reinforcing battery casings with thick metal to reduce the chances of battery damage – and this is part of why EVs are so much heavier than equivalent petrol and diesel cars.
Along with those protection methods, a vehicle’s design usually locates the battery in central positions away from the most likely impact zones to further reduce the risk of puncturing or damaging the battery casing.
The growing emergence of the more affordable, less energy-dense lithium-ferrous-phosphate or lithium-iron phosphate (LFP) battery technology is also reducing the risk of runaway, with the chemistry having a wider temperature range.
Chinese automaker Build Your Dreams (BYD) adopts LFP in its in-house developed ‘Blade Battery’ cells, which claims to have stronger safety credentials than typical packs – including surviving nail penetration, crushing, bending, extreme high temperature and over-charging tests without causing smoke, fire or an explosion reaction.
Likewise, Tesla is using LFP in its standard RWD models, as is MG and GWM in certain models. Volvo is adopting the type as well, along with Ford, Volkswagen, and others. (A story listing each vehicle with each battery type is in the works.)
Accessibility
Batteries are heavy, large and require little or no maintenance, which means they can be tucked away deep in a vehicle’s structure and often as low as possible to benefit the centre of gravity. But that also means they can be very difficult to access if they are on fire.
Like a petrol or diesel fuel pump that automatically shuts off, modern battery management systems instantly disconnect the battery at multiple points when airbags are deployed in a collision, preventing the high voltage from starting external fires or endangering emergency service workers.
In Australia, most states require hybrid, plug-in hybrid, full battery-electric, and hydrogen vehicles to wear a sticker on the licence plate to indicate to emergency responders to be cautious around high-voltage components.
But, these tiny triangular stickers may not be visible in a crash situation, which is why education needs to improve for first responders to identify an EV and know how to manually isolate the battery (mainly via the 12-volt battery, cut loop or pull fuse), according to EV FireSafe.
ANCAP also has a dedicated smartphone app with manufacturer-supplied documentation for rescuers to understand each EV model’s structure and potential hazards to safely free an occupant, while Hyundai Australia fits its EVs with multiple QR codes showing how to disconnect the battery pack manually (to make sure the battery is isolated).
Fire services have also recognised the hazard of EV fires and are adapting to the unique challenge with best-response techniques or even special equipment.
In 2019, a Dutch fire department’s specially-built truck was given its maiden voyage, dispatched to put out a BMW i8 fire. Instead of dousing the smoking car in water and foam, the $300,000-plus plug-in hybrid sports car was lowered into a bath of water for 24 hours. The firefighters simply couldn’t get to the battery with their hoses or apply enough water to be satisfied that the danger was gone.
Vehicle design is also addressing the problem, and new EVs will allow batteries to be accessed more quickly.
Electrolyte
Under certain circumstances, the electrolyte in lithium-ion batteries can catch fire, but manufacturers are tackling this problem by dividing the battery into smaller cells with separating fire-walls. If one cell catches fire, it is prevented or at least delayed from spreading to neighbouring parts of the battery.
Some manufacturers are also developing less hazardous electrolytes that are less flammable and produce fewer harmful chemicals, which already applies to LFP packs and future battery types including sodium-ion and solid-state.
Given that there are still many more ICE vehicles in the world, there haven’t been enough serious EV crashes to determine if the risk of fire is statistically higher or lower than an equivalent petrol or diesel-powered car.
For a conventional combustion engine, liquid fuel can leak and flow away from the vehicle, spreading the engulfed area. Petrol and diesel also require special foam and chemicals to adequately attack when on fire.
According to analysis by American car insurer Auto Insurance EZ – which used official data from the US National Transportation Safety Board and Bureau of Transportation Statistics – data for 2022 showed full battery-electric vehicles had significantly fewer fires reported (per 100,000 sales) than combustion engine-only and hybrid vehicles in the country.
The good news is that all the mainstream manufacturers regard electric vehicle safety, including reducing the risk of battery damage and fire, as a high priority.
With ongoing research and development, vehicle fires caused by crashes are becoming less likely, thanks to increasingly advanced safety systems in both combustion engines and electric drivetrains.
Ultimately, EVs are less likely to start a fire than combustion engines, but when they do, they are harder to extinguish.
Article courtesy of WhichCar.