04.4 Risks  EV traction battery fire

There are a mix of familiar & new risks to emergency responders

To highlight the mix of old & new risks, we have compared EV traction batteries against traditionally fuelled vehicle fires, to best highlight how where risks are the same, & where they differ.

Risks listed are based on research & discussions with Australian & international subject matter experts. We are not offering fireground management or suppression recommendations, only sharing information & best practice methods.

Internal combustion vehicle fire

Electric vehicle traction battery fire

Vehicle immobilisation

As EVs don't emit engine noise, immobilising an identified EV is a priority to ensure there is no risk to on scene personnel from accidental movement on accerator pedal 

Listen for engine, switch off. Apply park brake. Chock wheels.

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No engine noise, find proximity key & remove. Apply park brake. Chock wheels.

Exposure to toxic gas

Traction battery fires emit a mix of highly flammable toxic gases, including hydrogen fluoride & hydrogen chloride. Breathing apparatus should be worn.

Toxic gases from burnt fuel & metal, plastics

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Toxic gases from burnt lithium ion cells*, metal, plastics

Risk of explosion

As battery cells enter thermal runaway & emit a cloud of flammable gases (vapour), there is a risk of it exploding without warning.

Possible deflagration from fuel

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Possible vapour cloud explosion

Flame intensity

As flammable gases are vented from battery cells, they create intense 'shooting' flames.

Intense flames, easing in a short time

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Jet like, highly directional flames, intense burn for extended period

Flame temperature

The high flammability of battery cell gases results in a hotter burn.

Flames at 815-1000 degrees celcius

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Flames at up to 2760 degrees celcius*

Debris projectiles

Similarly, the venting of gases from battery cells causes debris projection

Chance of debris release

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Battery cell debris projectiles likely as they enter thermal runaway 

Suppress flames + cool battery

Water used to cool the battery pack & knock down flames. Burning cells within the traction battery casing are difficult to reach.
Best practice; let the battery burn out (if possible) to minimise reignition risk.

Application of water to suppress flames

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Water application to suppress flames + cool battery pack. May need to jack up the car. 

Establish water supply

A greater volume of water may be required to suppress a traction battery fire, compared to an internal combustion vehicle.

Up to 4000L (one tanker) of water used

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At least 4000L. Some EV fires have used up to 100,000L. Establish hydrant.

Suppression + cooling can take hours

Several hours may be needed to knock down flames & cool the traction battery.

Fast knock down of flames with water 

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Longer knock down due to thermal runaway in battery pack

More resources may be required

For the reasons outlined above, more firefighters & appliances than usual may be needed.

Eg. One breathing apparatus operator

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Eg. Breathing apparatus operators x 2 due to longer suppression time

Electrocution risk from high voltage (HV) - suppression

Studies found little to no risk of electrocution from EV HV when using unbroken stream of water.
Wear appropriate PPE.
DO NOT contact orange HV with hose or body.

Identify vehicle & refer to manufacturer emergency response guide.

Very low risk of electrocution from 12V battery

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Potential risk of electrocution from high voltage battery, cables & components

Electrocution risk from high voltage (HV) - extrication

Studies found a lower than expected risk of electrocution from EV HV during extrication.
Wear appropriate PPE.
DO NOT cut orange HV.
DO NOT contact traction battery with tools.

Identify vehicle & refer to manufacturer emergency response guide.

No risk

EV Fire RISK graphics-6.png

Potential risk of electrocution from high voltage battery, cables & components. 

Electrocution risk from high voltage (HV) - submersion

Studies found lower than expected risk of electrocution from  EV HV when submerged in water.
Wear appropriate PPE.
DO NOT contact EV HV or traction battery.

Identify vehicle & refer to manufacturer emergency response guide.

No risk

EV Fire RISK graphics-9.png

Potential risk of electrocution from high voltage battery, cables & components.

 Electrocution risk from high voltage - stranded energy

Following fire, a partially intact traction battery or loose, scattered battery cells pose a risk of electrocution from the stranded energy. There is no way to measure or remove stranded energy.
Wear appropriate PPE.
Identify vehicle & refer to manufacturer emergency response guide.

No risk

EV Fire RISK graphics-10.png

Potential risk of electrocution from high voltage battery, cables & components. 

Reignition of traction battery on scene

Medium risk of fire reigniting following initial suppression, with some vehicles reigniting hours, days or weeks later. A burnt EV should be monitored using a TIC.

Once suppressed, low risk of flame reignition

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Once suppressed, monitor for reignition > 60 mins. Listen for hissing or popping noises, dark vapour cloud.

Toxic particulate matter

The toxicity of a traction battery fire poses a higher risk of poor air quality & water run off contamination. Enclosed spaces may need heavy duty cleaning.

Once vehicle is removed, wash area to remove debris

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Monitor water run off & air quality. 

Reignition while tow loading & transporting

Wheel turn while transporting an EV with a partially burned traction battery may engage regenerative braking, supply power to battery & cause reignition. Tow on flatbed only.

Remove burnt vehicle

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Monitor for reignition during removal & transport

15m

15m

Reignition in storage

Store & wreck vehicle

Burnt vehicle should be stored away from structures, other cars. Monitored for reignition.

Monitor for heat, vapour & flames for an extended period.

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All*

  • Lithium ion battery cells expel hydrogen, carbon monoxide, carbon dioxide, hydrogen fluoride, hydrogen chloride, hydrogen cyanide, organic solvents, ethane, methane, hydrocarbons, sulphur dioxide, nitrogen oxides, among others. Source: Prof Paul Christensen, University of Newcastle.

  • Flame temperatures courtesy of the NFPA (US)