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Understanding electric vehicle fires: A comprehensive guide

Written by Bridie Schmidt

 

What's in here

Uptake of electric vehicles (EVs) is on the increase in Australia, offering a sustainable alternative to internal combustion engine vehicles. As with any technology, EVs come with their own set of challenges.

How often do EV batteries catch fire?

EV battery fires are far less common than internal combustion engine (ICE) vehicle fires.

But, as it is a new technology, media reports tend to report incidents more often, serving to heighten concerns. For example, a September 2023 incident at Sydney airport saw an MG ZS EV battery from a damaged EV catch fire and set light to four other vehicles.

Electric vehicle fire consultancy EV FireSafe notes in the video below that only 40% of EV fires involve the lithium-ion battery.

Just seven of these EV fires were caused by batteries in Australia including the above incident. That's out of the 120,000 battery electric and plug-in hybrid electric vehicles on the road. In all cases, the battery fires were caused by damage to the battery pack: by arson, home fires, road collision or impact from road debris.

Some other figures to note include:

  • A study conducted by Western Sydney University in July 2023 titled "Fire Incidents, Trends, and Risk Mitigation Framework of Electrical Vehicle Cars in Australia" suggests EV fires are even less frequent: according to the researcher's methodology, Australia experiences approximately six EV fires per million EVs, comparable to the global average. This research suggests that if EV uptake follows the projected trend of reaching 1.7 million by 2030, there will be just 9-10 EV fire incidents in Australia that year.
  • Of 114 lithium-ion battery fires attended by Fire and Rescue NSW between January and July 2023, the bulk of these were not in electric cars, but were related to portable batteries, e-scooters, and e-bicycles. Note, this article refers to electric passenger and light commercial vehicles (LCVs) only. It does not refer to Light Electric Vehicles (LEVs) like e-bikes and e-scooters which present a vastly different fire risk profile.
  • A 2022 analysis by insurance company AutoinsuranceEZ showed that based on US-based National Transport and Safety Board data, ICE vehicles are 60 times more likely to catch fire than electric vehicles and hybrid vehicles are 138 times more likely to catch fire (it is not clear how the analysis defines plug-in hybrids.)

Nevertheless, electric vehicle batteries pose particular safety risks. But, there are strict regulations to address risk factors of EV batteries and the high-voltage cables that connect them to a car's powertrain.

Addressing risk factors of EV batteries and high-voltage cables

The traction battery is the beating heart of an EV, storing the electrical energy that powers the motor. The lithium-ion batteries in EVs are designed to provide high amounts of energy and can pose a fire risk if damaged or improperly managed - even if they have been removed from the vehicle.

For example, in the Sydney airport incident, the MG ZS EV battery in questions came from a damaged EV. Even though it was disconnected from the vehicle, the damaged cells caused thermal runaway (see section below) which eventually sparked the fire.

Additionally, the high-voltage (HV) cables that connect the traction battery and the electric motor as well as other systems, put EVs at risk of short circuit if cables are damaged or defective, creating a potential fire risk.

To reduce fire and other safety risks, all vehicles including EVs that are sold in Australia must adhere to strict ADR regulations. Nine out of ten of EVs on sale in Australia carry ANCAP five-star ratings. Protective measures in electric vehicles include the use of a cooling shroud filled with coolant liquid to prevent external damage or short circuit.

Batteries are also installed in a way that avoids widespread damage, employing thick metal casings to reduce chances of damage and locating batteries centrally in vehicles away from impact zones to minimise risk of damage. Vehicle and battery manufacturers are continuously working to enhance the safety of EV batteries. For example, the cost-effective lithium-iron-phosphate (LFP) battery technology used by carmakers such as Tesla, BYD, MG, GWM, Volvo, Ford, and Volkswagen, offer broader temperature tolerance, thereby reducing the risk of fires.

Thermal runaway and other characteristics of electric vehicle fires

Electric vehicle fires are very different to internal combustion engine vehicle fires. They often display unique behaviours such as large clouds of dark and light vapour, popping noises, and jet-like directional flames at temperatures up to 1000 degrees Celsius. Recognising these signs can help to establish an early emergency response.

Thermal runaway is a self-sustaining chemical reaction within the battery that can spark a fire. It occurs when a cell in the battery gets overheated and can't cool down, causing a chain reaction that heats up neighbouring cells. The state of charge (SoC) plays a prominent role; a battery below 50% SoC is less liable to experience thermal runaway.

Thermal runaway can also happen in an EV that has been in a flood or saltwater. In the event of water ingress, salty water can create a path for electricity to spark thermal runaway.

How are EV fires put out?

Water remains the most effective method for suppressing EV fires, requiring large volumes sustained over an extended period. However, emergency responders are also exploring other encapsulating agents. Even after an EV fire has been suppressed, there's a risk of secondary ignition due to stranded energy in unburnt cells.

Once an EV fire is extinguished, the focus shifts to the safe removal of the vehicle. This involves cleaning up battery cells and debris, and monitoring for signs of thermal runaway. The vehicle is generally considered safe to tow once the traction battery has remained at an ambient temperature for 15-30 minutes.

If you hear popping, hissing or whistling noises or see vapour (which could look like smoke) coming from your EV battery, it is crucial to call emergency services (000) immediately and follow their instructions. If your EV has been in a flood or saltwater, call your manufacturer and have it towed to their nearest premises on a flatbed.

Reducing risks of EV battery fires
  • For electric vehicle (EV) owners, safety starts with proper identification. A blue triangle "EV" sticker or badge on the number plate alerts emergency responders to the presence of a high-voltage battery. EV triangles are required for all EVs manufactured after 1 January 2019.

    EV Tag Placement
  • Installation of charging equipment must adhere to AS/NZS 3000 Electrical Installations "Wiring Rules," ensuring that the charging unit and cable are electrically compliant.
  • Fire and Rescue NSW recommends installing a smoke or heat alarm in garages where EVs are regularly parked or charged.
  • When charging, use extension leads and power sockets specifically designed for EVs and exercise caution in wet weather or during electrical storms.
  • Use only the chargers supplied with the device or certified third-party chargers compatible with the battery specifications. Ensure these chargers bear the Regulatory Compliance Mark.

In the event of an incident, engage the parking brake, switch off the vehicle, evacuate all passengers, and call emergency services, specifying that the involved vehicle is an EV.

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