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Sep 02, 2023

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Extinguishing fires in electric vehicles (EVs) and lithium-ion batteries is a debated topic and is more relevant than ever as the number of EVs has increased considerably in recent years. These webinars answers many of the questions and also explains a recent project where a new method to extinguish EV fires was tested.

There are many questions about safety for the firefighter and the public, risks, environmental impact and how to extinguish the fire without using loads of water. We now offer two webinars where Per-Ola Malmquist (Utkiken.net) from the Swedish Civil Contingencies Agency / CTIF Sweden explains the research conducted in 2022 about how to safely put our EF-fires.

The first webinar, is produced by MSB.se. it goes into detail about lithium-ion batteries and EV-fires, and explains how the Swedish Civil Contingencies Agency (MSB.se) together with industry, tested various tools to safely put out EV-fires. The results were astonishing: in only 15 minutes and using only 750 liters / 200 gallons of water, a full scale electric vehicle fire was put out.

In the second webinar, put on by CTIF Associate Member Cold Cut Systems, Per-Ola Malmquist starts out with a short presentation on the above project, followed by two more studio guests.

The second part of the video features as presentation by Daniel Scott from Cold Cut Systems, which further elaborates on the use of cutting extinguishers in EV-fires, and the routine and safety checks to follow when responding to vehicle fires using these tools.

The last part of the seminar contains a real life Lessons Learned interview Håvard Hauge from Vestfold Fire Service in Norway, where the cutting extinguishing method was tried for the first time in an EV-fire.

We will soon return to Håvard Hauge´s experiences on this topic in a future article here on CTIF.org.

A report from tests made public by the Swedish Civil Contingencies Agency (MSB) shows that a cutting extinguisher can safely put out a battery fire in a very short time, with minimal use of water and without the risk of re-ignition.

The report is based on the results on a number of tests carried out in a collaborative project involving several stakeholders, including the CTIF Commission for Extrication and New Technology, and CTIF Sweden, where Tore Eriksson, Tom van Esbroeck & Michel Gentilleau have been part of the reference group. CTIF ´s Yvonne Näsman and Per-Ola Malmquist have been project members on behalf of MSB.se.

The tests were designed to examine whether injecting water into a Li-ion battery that had gone into a state of thermal runaway could effectively suppress and extinguish the fire without reignition.

Several different kinds of equipment was tested, including fog nails, pickaxes, traditional nozzles and various penetrating extinguishers (which use water mist to cut holes through the protective shell of the battery).

Please note, that for safety reasons, the use of fog nails or pickaxes (to break the battery shell before water was applied) are not recommended in the report.

Several tools and methods tested

As a stakeholder in the project, our CTIF Associate Member Cobra Cold Cut Systems provided their Cobra Ultra High pressure lance.

Also tested was the Murer extinguishing lance. Both tools extinguish fires from a safe distance through the use of a water mist which can penetrate walls and other hard surfaces.

In the case of the full scale, the Cobra Cutting Extinguisher was used to penetrate the protective shell of the EV lithium battery, with minimum introduction of oxygen to the cell.

Avoid jet flames and other risks by using the appropriate penetration tools

Several methods and tools were tested, and the high pressure extinguishing tools produced the best results. They also provided the safest methods for the operator, with the lowest risk of re-ignition or dangerous jet flames.

The reason for the more successful extinguishing with the cutting extinguishers, as opposed to other methods, is that those tools use high pressure water (sometimes mixed with an abrasive) to cut through the battery shell, minimizing the introduction of oxygen to the cell.

The extinguishing media used were:

Fog nails and pickaxes not recommended for safety reasons

Other methods tested, like the use of fog nails or pickaxes to break the battery shell before water was applied, are not recommended in the report.

The reason fog nail and pickaxes were deemed inappropriate is that those methods showed an increased tendency for dangerous jet flames to shoot out of the battery, and it also exposed the firefighter to a greater risk of electrocution from the remaining current in the battery.

The report from MSB underlines that operators wishing to try this do so only after a thorough risk assessment, and only after receiving the appropriate training in the use of tools approved for the purpose by the manufacturer. The report also stresses the importance of only using tools and methods approved by the employer.

Successful extinguishing of an EV battery in 4 minutes - with only 63 gallons if water

Several standalone battery modules and also a full scale EV were tested by bringing the batteries into a state of thermal runaway, resulting in battery fire. Water was introduced after 15 minutes from the first signs of propagation, to simulate a typical fire service response time.

In the full scale fire test, the total duration of the extinguishing effort, from the time water was first applied on the vehicle fire, to the time the lithium.Ion battery was determined to be inert, was only ten minutes for extinguishing the entire vehicle fire. The total time for extinguishing the battery alone was 4 minutes.

The water consumption for extinguishing the lithium-Ion battery was calculated to be only 240 liters / 63 gallons.

Including the time to extinguish the entire vehicle fire, a total of 750 liters / 200 gallons in total was used, in a combined effort with the Cobra cutting extinguisher and traditional fire extinguishing with water.

This can be compared with real life examples of some fire services using up thousands of gallons of water, requiring several tanker trucks, in dealing with a single EV fire.

Many fire services have also witnessed on cases where several teams have been dispatched, spending hours trying to contain EV fires, with sometimes very mixed results.

No sign of reignition with minimal use of water

After only ten minutes of being flooded with a relatively small amount of water, the batteries showed no sign of reignition. The voltage measurements of the battery modules also showed that in all the tests, that the affected battery cells and the neighbouring cells were cooled and showed a drop in voltage. Other battery cells maintained either a full charge or residual charge.

Some of the battery cells where the Cobra Cutting Extinguisher had been applied showed no residual voltage at all.

The most important observation is that in all cases the affected battery cells, and neighbouring cells, were cooled by the introduction of water and showed a drop in voltage. This also stopped the propagation of fire in the battery and stopped the fire from spreading further.

read a summary of the report on cold cut systems home page

Below is a 28 minute educational video demonstrating how the tests were made.

The tests were carried out in 2022, after a set of preliminary trial tests showed promise in 2021.

Several different types of tests were made, including fire tests on isolated EV batteries, and also a full scale fire test on a lithium-Ion battery inside an electric vehicle.

The file "Putting out battery fires with water" is the official report on the project by MSB. It is downloadable as a pdf above.

This is a machine translated version of the original Swedish document. A professionally, human translated version of the document will be published soon.

Water must be applied simultaneous with penetration - or dangerous jet flames will occur

The tests show clearly that it is important to be able to apply water simultaneously as the protective shell of the battery is being penetrated. Other methods, which involve breaking the battery shell first, allows time for oxygen to enter the cells, which can lead to the battery reigniting. The cold cutter allows for flooding the battery with water before oxygen can enter the battery cells, which makes the battery inert in a shorter time and provides a safer working environment for the operator.

No reignition in the fire tested batteries

Reignition of lithium-Ion batteries which have previously burned is quite common and can pose problems for tow trucks and junk yards. Although the results of these tests are not necessarily conclusive when it comes to reignition, the methods tested show promise. The text below is translated directly from the Swedish report:

"Monitoring to detect possible re-ignition was limited to 15 min, which may be acceptable in an engineered test situation. However, experience from the field has shown that re-ignition can occur after a considerable time - hours or days from the time of the fire. During the two and three days that the battery pack was stored after the fire and before disassembly, there was no re-ignition".

Cold Cut System´s own video:

The video below from Cold Cut Systems´ YouTube channel shows some of the methods used in the tests. The method of extinguishing EV battery fires with Cobra is based on the Swedish Civil Contingencies Agency (MSB) report, "Demonstration of extinguishing method of lithium-ion batteries". This film is made to visualize the tests that were made on the full EV and is not from the actual tests.

Methodology

A review of existing research literature on Li-ion battery fires was carried out to ensure that all the known risks were fully understood as well as the mechanism of spread of fire within Li-ion batteries.

One of the overall findings from this research was that the most effective suppression of a thermally propagating Li-ion battery is achieved when coolant can be applied as close as possible to the core of the heat source within the battery.

Fresh water is the most readily available medium for first responders and was therefore the chosen agent for these tests. One objective of the tests was to see if safe tactics could be developed for first responders to use in applying water to cool the interior of a Li-ion battery in thermal runaway.

All the tests were carried out using Li-ion batteries with 100% state of charge. Thermal runaway was initiated using a heating plate that was installed pre-test. The battery units were also modified to overcome some safety systems; the modifications had no impact on the cooling effect of the water.

In tests ii) and iii), once thermal runaway had been initiated in one cell of the battery, there was a delay of 15 minutes before extinguishing media was applied. This was to simulate the time taken to call the emergency responders and for them to arrive at the scene. The tests were terminated when visual inspection indicated no continuing thermal propagation and the temperatures recorded on the Thermal Imaging equipment were below 50°C.

The three tests, in sequence, were:i). Three stand-alone subpacks – four battery modules at 24 Volts, 6.54 kWhii) One stand-alone traction battery at 14.8 Volts, 2.8 kWhiii) One full size electric vehicle with traction battery – 27 modules at 14.8 Volts, 2.8 kWh

The tests were carried out on four different types of setups:

• sub-battery

• stand-alone electric car battery

• complete electric vehicle

• battery module.

The tests were carried out over two days in April 2022 on a practice field at Södra Älvsborg's emergency services association. This is an advanced practice field with many years of experience testing cold cutting tools for various applications.

A total of eight trials were carried out, distributed over four different tests. The tests were preceded by a risk analysis where all tools were evaluated based on specific conditions. The risk analysis also took into account the design of the test objects.

The risk analysis showed that there could be difficulties with access to the battery and electrical safety if only the existing standard equipment on modern fire engines is used. Therefore, it was decided to include two commercial tools in the demonstration, the cutting extinguisher and the extinguishing lance.

The following conclusion regarding other methods is translated directly from the Swedish source document:

"When we made holes while adding water, no new jet flames appeared. However, when we made holes without adding water, jet flames appeared. Two extinguishing attempts were carried out with self-constructed tools assembled from equipment assumed to be on a modern standard fire engine: jet pipe and narrow hose and pickaxe, which was used for punching holes. Although it worked in the demonstration, this type of approach is not recommended because the technology is difficult to implement in a real vehicle fire where access to the battery is limited and would require working inside a burning vehicle."

"The risks associated with handling a burnt battery with a significant amount of residual energy must always be weighed against the benefits of shortening the response time. Note that also lithium-ion batteries which have been allowed to burn out may contain residual voltage and should always be treated with this in mind until it is confirmed that the battery is electrically dead. During the demonstration, both a thermal camera and a thermocouple were used. It is important to note that the thermal imager is sensitive to reflection, so it can be difficult to get a completely truthful picture of the heat spread inside the battery. In the event of a fire in an electric vehicle and its battery, it is of the utmost importance that the response personnel take note of the vehicle manufacturer's safety and response information in the vehicle's rescue card (Rescue Sheet) and rescue instructions (Emergency Response Guide, ERG) in order to be able to make response planning based on the specific conditions in the current case."

Summary of the tests:

This is only a summary of the tests, however the full report can be accessed (in Swedish) through MSB.se.

An English summary of the test can be read on the Cobra Cold Cut System home page

Results and methodology:

The tests were very successful and demonstrated, among other findings, that:

Test ResultsIn the first two tests, all three methods for injecting water into the battery itself worked to the extent that they were able to reduce the heat in the affected battery cells and extinguish the fire. The batteries did not reignite after being extinguished in any of the tests.

However, use of an axe to make the water access hole in the battery casing caused an initial increase in intensity of the emerging jet flames from the battery until the pipe was connected and water was able to flood the battery cells. This method was also the least accurate in terms of targeting the water to those cells in thermal runaway or in thermal propagation.

A key factor was the assumption that in the extreme case of battery modules not being harmed, their voltage would stay intact, while the other extreme case would be that a completely burned-out battery module would show no residual voltage. Thereby the remaining voltage of individual battery modules was considered an indication of the extent of damage caused by the thermal runaway propagation. In all the tests, the affected battery cells and the neighbouring cells were cooled and showed a drop in voltage. Other battery cells maintained either a full charge or residual charge.

The final full EV test involved a vehicle that was fully involved in fire (i.e. the vehicle cabin was fully involved and cells within the Li-ion battery were in thermal runaway. The vehicle cabin was extinguished using a conventional firefighting nozzle, then Thermal Imaging equipment was used to show the hottest spots within the battery. Cobra was then used to penetrate both the car bodywork and the battery casing and then apply water within the battery itself. The total period of fire suppression was 10 minutes from the first approach with Cobra to the conclusion of firefighting when all surface temperatures had fallen below 50°C. 15 minutes after extinguishment, the whole vehicle was twice lifted 1 metre using a forklift truck and then dropped to simulate rough handling – no reignition occurred. The car was then placed in a quarantine location for two days with no reignition.

The Cobra was used for around five minutes using 240 litres of water. The firefighting nozzle was used for four minutes using 510 litres of water giving a grand total of 750 litres. This is significantly less than the 1670 litres used in a test conducted by Exponent and The Fire Protection Research Foundation reported in 2013.

The use of Cobra permits the operator to act from a safer distance when establishing an ingress hole for water injection.

At the first sign of propagation, a countdown was started from 15 minutes to mimic the normal emergency service response time.

The extinguishing attempt was then started. To control the fire, water mist from the cutting extinguisher was used to knock down the flames and try to extinguish the cabin fire.

When it was possible to open the rear door, thermal imaging was used to scan the interior of the vehicle and look for hot spots in the battery pack.

It was done by measuring thermal gradients in the cabin floor. Wind and control of gases using a PPV fan (Positive Pressure Ventilation) meant that one side of the vehicle was difficult to access due to thick smoke and flames.

The cutting extinguisher was used in the gimbal tunnel and lance extenders were used to facilitate access and avoid contact with the bodywork. During the time which the fire extinguisher was in operation, a conventional jet pipe was used as personal protection for the fire extinguisher operator.

When the fire calmed down and the flames closest to the fire extinguisher operator were extinguished, the person with the protective beam (the beam operator) continued with the focus on extinguishing the compartment fire. Note that the x beam operator's primary duty throughout the operation was to protect the fire extinguisher operator from flash and flames. The test was terminated when the thermal imager showed a stable temperature below 50 °C.

After the extinguishing effort was interrupted, continuous monitoring of the temperature with a thermal imaging camera continued for 15 minutes, to ensure that the propagation stopped. To simulate a removal of the vehicle, the vehicle was lifted about half a meter a couple of times with the help of a forklift, and dropped to the ground to see if it was possible to provoke a reaction that could lead to re-ignition.

Conclusions

Background:

A preliminary study was carried out by Cold Cut Systems in Kungsbacka in 2021, where the Swedish Agency for Community Safety and Preparedness (MSB) participated as a reference. The purpose was to investigate whether it was possible to interrupt the thermal process in a propagating lithium ion battery by establishing an internal water flow in the battery pack.

Cold Cut Systems used a cutting extinguisher (Standard Cobra lance) in the pilot study with good results. It was determined there was enough evidence to motivate further studies and tests to develop guidelines for offensive extinguishing efforts of lithium-ion battery fires.

This demonstration is an activity within the scope of this work.

The overall aim of the demonstration was to contribute with experimental experience of the methodology of flooding lithium-ion batteries with water in the event of a fire and to show that it can contribute to a faster and more efficient extinguishing, provided that it is possible to access the battery in a safe way.

The goal of the extinguishing efforts was to stop the thermal propagation in the lithium-ion battery.

The demonstration was limited to test objects composed of lithium-ion cells with a maximum nickel content of 60 percent in the cathode material. More nickel-rich and energy-dense electrode systems have higher reactivity and must be investigated separately.

Both prismatic cells and pouch cells are represented in the sample objects. Cylindrical cells have not been studied in this demonstration.