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04.10 EV battery fire suppression

How do firefighters put out an EV battery fire?

Due to the self-sustaining nature of thermal runaway, ​we've moved away from using the word 'extinguish' in relation to lithium-ion battery fires and instead prefer to discuss how we suppress & contain them.

We're going to break this page down into three parts:

  • Best practice methods

  • Challenges of EV battery pack designs for firefighting

  • Products coming to market

This page is best viewed on a computer screen; if using a mobile or tablet you may have to turn sideways to see scroll options for two tables.

What are the best practice methods for putting out an EV battery fire?

There is no one method to manage an EV battery fire, rather three methods used globally that have emerged as best practice; Cool, Burn, Submerge.

Each of these EV fire incident management methods are valid options for suppressing & containing an EV in thermal runaway. The Cool or Burn options do not require fire agencies to purchase or use additional tools, which may be cost prohibitive or difficult to carry.

EV battery fire suppression - cool
Use fog nozzles to knock down flames & provide cooling jets onto battery pack exterior to cool down the exothermic reaction of thermal runaway.

Pros:

  • Recommended by all EV manufacturers

  • Firefighters are 'seen' to be doing something by public

Cons:

  • Doesn't get water where it needs to be

  • Like 'putting out a kitchen fire by spraying water on the roof of a house'

  • Water usage may be in excess of 10,000 litres

  • Run off will need to be monitored & captured, particularly near waterways

Case study:

A plug-in hybrid EV was accidentally submerged in salt water at a boat ramp, with thermal runaway following removal, which was knocked down by firefighters, & secondary ignition occurring while being towed. Crews used two hose lines to cool the battery pack for an extended period. 15th May 2020, Port Moody, Canada

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What are the challenges of suppression using the Cool method?

There are two main challenges with firefighting an EV battery fire: position & access.

The position of the EV battery pack makes firefighting difficult:

We previously looked at how a traction battery is constructed, & how (in most EVs) it is positioned along the floor pan of an electric vehicle, between chassis rails.

 

If the battery pack goes into thermal runaway, the position means:

  • It's difficult to locate the area in the pack thermal runaway is occurring, either visually or with a thermal imaging camera (TIC)

  • Spraying water onto the outside of the pack to cool it often means firefighters have to be close to the vehicle & risk exposure to jet like flames

Lithium-ion battery pack underneath an electric vehicle

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It's usually impossible to get cooling water onto the battery cells:

The construction of an EV battery pack where individual lithium-ion battery cells are contained within a module, & modules within the pack, means getting water where it needs to go to cool the cells is almost impossible.

However; we are aware of some cases where an EV has been involved in a collision, & firefighters were able to direct water into the pack where it had torn open, to directly cool the battery cells. This is safe to do & does not carry the risk of electrocution (unless the EV is connected to energised EV charging).

Cells & modules are contained within a pack, which is IP rated & essentially waterproof

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What about extinguishment or suppression products?

As with all emerging industries, a range of products claiming to 'extinguish' EV battery fires are being aggressively marketed to both fire agencies & the private sector as the answer to EV battery fires. 

We are often asked whether a fire agency should buy a fire blanket, cutting tool or extinguishing agent, & our answer is; no, there is no need to purchase extinguishing tools for EV battery fires.​

While this response does not make us popular with those manufacturers, currently (as of 2024):

  • EV battery fires are rare

  • These tools are typically very expensive

  • They may be too large & heavy to be comfortably carried on a truck

  • Often come with no manufacturer operating procedure or training

It should also be noted that some of these products may actually increase risk to emergency responders, even when being used correctly.

Having said that, there are some scenarios in which these tools may be useful, & all considerations are outlined in the comparison table here.

EV battery fire suppression - fire blankets
Large thermal fire blanket that is placed over an EV to contain flame.


Pros:

  • If used in time, blanket will contain flames & stop fire spread to exposures

  • Can be left on EV as it's moved from scene


Cons:

  • ~25kgs for one car-sized blanket, so must be used by two firefighters in breathing apparatus

  • Cannot 'extinguish' or stop thermal runaway (despite manufacturer claims!)

  • Thermal runaway will continue under blanket & may slow down (as opposed to the Burn method), the process

  • Vapour cloud (off-gassing) will continue under the blanket

  • More independent testing is required to ensure efficacy & safety for responders

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Increased risk:

  • Where a blanket is lifted by wind or a person, the build up of gases under the blanket may cause a localised vapour cloud explosion

  • Blankets often come as single or multi use, but there are no agreed, safe decontamination procedures for multi-use blankets

For responders:

  • We do not consider it necessary to buy & make space on a truck for a fire blanket for the sole purpose of EV battery fire management at this time

  • Where blankets have been purchased by a high-risk site, fire blankets should be used with caution to avoid causing vapour cloud explosion

  • As most thermal runaway events occur prior to fire crew arrival, fire blankets will typically be most useful post-incident to contain a potential secondary ignition

For private sector businesses:

  • Sites where EVs are parked, stored or charged in normal operating conditions do not require fire blankets

  • Higher risk sites such as where EV or lithium-ion battery repairs, servicing or manufacturer occur may consider purchasing a fire blanket, but;

  • A standard operating procedure should be sought from the manufacturer or written by the site, including:

    • NO staff should be trained to cover an EV in active thermal runaway due to high risk of injury or death

    • Blankets should be used by attending fire crews only

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