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04.11 EVs in flood water

What are the risks of EVs in flood water?

As global warming leads to more frequent flooding events, we can expect to see the total submersion of vehicles in flood waters more often over time.

 

There are three risks to emergency responders with electric vehicles in flood water & we've broken this page into three parts:

  • Electrocution risk

  • Removal from water

  • Increased risk of EV battery fire following submersion

 

We also recommend you follow EV FireSafe's IAIIM method for EV incident management.

In all cases, please follow your agency's SOPs & the manufacturer supplied Emergency Response Guide for removal & towing safe work instructions.

Please note, we don't have space to cover it here, but it is also vital for rescue agencies to be aware of the risk of ALL lithium-ion batteries in flood water, including personal mobility devices, golf buggies and home battery energy storage systems.

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Can an EV in water electrocute responding crews?

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An EV cannot electrocute a body of water & there is very low risk to responders entering water to facilitate EV removal, noting:

  • It is safest to assume the EVs high voltage systems are live & take extreme caution at all times

  • Full PPE should be worn

  • Electrical tools should be used where appropriate

  • Responders should avoid touching the vehicle where possible as exposed orange HV cables may not be visible underwater

Electric vehicles use direct current (DC) high voltage systems, typically 400V DC & upwards. DC power seeks to find a path back to itself, is independent of external systems & does not require 'grounding'. 

 

This means the EV should not electrocute a responder touching the car, or spraying an unbroken stream of water onto an EV on fire.

However, in the unlikely event a responder comes into contact with both sides of the battery system, positive & negative, & becomes the 'path of least resistance', there is an electrocution risk. This scenario may be possible where an EV has suffered major collision damage.

We have no recorded injuries, fatalities or near misses involving electrocution of responders during incidents where EVs have been submerged in bodies of water.

Great resources:

How to remove an electric vehicle from bodies of water using IAIIM

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Where an EV has been submerged in water, it is safe to recover the vehicle the same way as you would any other vehicle.​

A submerged EV does not electrify the water around it, however if bubbles are present in the water, move away from the vehicle as this may indicate thermal runaway is occurring underwater, & bubbles may contain toxic gases.

Where an EV has been submerged in water the following actions may be taken by emergency responders in accordance with our IAIIM method, however all responders should refer to their own agency SOPs:

​Identify:

  • Is the submerged vehicle an EV? How can you tell?

Assess:

  • Prior to recovery operations, look for risks to personal safety:

    • Check to see if the EV is connected to charging; exposure to live charging using AC grid power poses a serious electrocution risk

    • Exposed orange HV cables, arcing, sparking, scattered or floating battery cells

    • Signs of thermal runaway (battery fire) such as loud popping, hissing, whistling noises, large clouds of vapour or jet like flames 

      • Note that flames may appear underwater while the EV is still submerged​

    • Decide how you will protect yourself - full PPE/PPC is recommended

    • Decide how to connect towing to the EV with minimal time in the water

Immobilise:

  • Decide how to approach the EV while in the water, bearing in mind that movement may be unexpected, silent & rapid

  • How will you connect the EV to towing?

  • It is unknown how EVs float in water, so does it require anchoring to something solid while awaiting towing?

  • Once the EV has been recovered from the water it should immediately be immobilised using wheel chocks & placed into 'P' &/or hand brake applied

  • The EV should then be lifted to drain any water ingress from the battery pack:

Isolate:

  • Once the EV has been removed from the water isolate the high voltage systems using a cut loop, pull plug or pull fuse

    • Review the ERG ​for this method, bearing in mind some EVs do not have a manual isolation method

    • NOTE: DO NOT attempt to pull the Manual Service Disconnect as this is designed for trained mechanics, not emergency responders

    • NOTE: Disconnecting the 12V battery DOES NOT isolate high voltage systems

Monitor:

  • Using a thermal imaging camera, monitor the battery pack for any increase in temperature above ambient

  • Be alert to the signs of thermal runaway 

  • Thermal runaway may occur several weeks or even months post-submersion, so it is advisable to quarantine the EV until it can be fully assessed

Why does a submerged EV have a higher risk of battery fire?

It is perfectly safe to drive through heavy rain & puddles in an EV. Electric vehicle safety systems & battery packs are designed to be safe in water, even if fully submerged (however all emergency agencies do not recommend driving through flood water).

 

However, EVs that have been submerged in water, particularly salt water, for an extended period of time - typically hours to days - may have a higher potential risk of experiencing a battery short circuit, which may result in a battery fire.

While our research indicates ingress of water to an EV battery pack increases the risk of thermal runaway, there is no data to indicate likelihood. 

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