Electric cars do not burn more often - but differently

Since the end of July, pictures of the burning freighter Fremantle Highway have been going around the world. On board were almost 3,800 new vehicles, 498 of them electric cars. What could have caused the fire? And what does the accident mean for the potential danger and future transport of electric and hybrid vehicles? An overview of the current studies and findings by Sebastian Meerschiff, mobility expert at ERGO.

For days, salvaging the burning freighter Fremantle Highway of the Japanese shipping company Shōei Kisen seemed out of the question - the danger of the ship capsizing was too great. On Monday, however, the freighter - still on fire - was successfully towed to a temporary anchorage in calmer waters, far from the shipping lanes, 16 kilometres north of the islands of Schiermonnikoog and Ameland.

It is not yet clear what exactly caused the fire on board. Initial speculations were that it could have been a so-called thermal runaway. This is a chemical process in the battery of an electric vehicle. Within milliseconds there is an extreme rise in temperature, the energy stored in the battery is released and spontaneous combustion occurs. With 4,000 vehicles parked close together, the fire can then spread quickly.

Transport and entry bans are being discussed...

The results of the investigations will show whether such a thermal runaway was actually the cause of the fire. Above all, however, it is important to look at the situation objectively and holistically. For in the recent past, there have been repeated situations in which the alleged fire risk from electric vehicles has been discussed in a way that has attracted public attention.

For example, on 1 March 2022, the Felicity Ace sank about 166 kilometres southwest of the Azores. It was loaded with numerous luxury vehicles worth around 200 million euros. As some electric vehicles and plug-in hybrids were also on board, some shipping companies reacted by issuing a general transport ban for vehicles with electrified drives - without it having been proven beyond doubt that an electrified vehicle had caused the fire.

And not only at sea, but also "underground", similar debates have already been held with regard to electric vehicles. For example, the city of Kulmbach and individual homeowners' associations wanted to prevent electric vehicles from being allowed to park in underground garages because of their alleged fire hazard. In the case of the homeowners' association, the Wiesbaden District Court ruled in favour of the electric car owners (Case No. 92 C 2541/21), while the town of Klumbach voluntarily lifted the ban on entry after the fire brigade was provided with special fire-fighting equipment.In a survey conducted in June 2023 by ERGO Mobility Solutions and the ERGO Customer Workshop, 20 percent of respondents also stated that a fire or spontaneous combustion was among their greatest fears regarding the battery of an electric vehicle.

...but does the perceived danger match the reality?

Basically, all experts summarise it as follows: The fire risk posed by electric vehicles is not greater than that posed by internal combustion vehicles - it is actually lower. However, once an electric vehicle is on fire, it burns "differently" and alternative extinguishing methods are necessary.

In general, it is true that vehicle fires have become more challenging in recent years across all drive types. According to the ADAC, the reason for this is simply that significantly more flammable materials are being used - in insulation, tyres and upholstery.

Whereas in traditional vehicles it is primarily the fuel, in addition to these flammable materials, that causes a fire, in electric vehicles it is thermal reactions inside the battery. In somewhat simplified terms, the following happens: The cell overheats and oxygen is released, causing the mixture to catch fire on its own. This "self-supply" with oxygen is also the main reason why other extinguishing methods have to be used for electric vehicles.

Classical extinguishing methods aim to remove the oxygen from the fire. For example, a special extinguishing foam can be used. Below deck on the Fremantle Highway, CO2 was the method of choice. This should displace the oxygen and thus suffocate the fire. However, this method is ineffective on burning electric vehicles.

Burning lithium-ion batteries are primarily extinguished with water. The aim is to cool the vehicle down enough to interrupt the thermal chain reaction that jumps from cell to cell. This requires large amounts of water, not least because the batteries - for safety reasons - are designed in such a way that no water can actually penetrate from the outside. It is important to keep the battery temperature stable below 80 degrees, otherwise there is a risk that fires that appear to have already been extinguished will re-ignite.

Analogous to the testing of new vehicle, battery and charging technologies, new extinguishing methods for electric vehicles are therefore also being researched - including special extinguishing blankets, extinguishing containers or even extinguishing spikes with which the battery housing is deliberately damaged to allow more water to enter the battery (source: ADAC).

Even though burning electric vehicles may be new territory, the German Fire Brigades Association clearly takes the position that no particular danger results from these fires. "Due to the current reporting in various media, it seems important to emphasise that electric vehicles can also be extinguished by the emergency services of the fire brigade. [...] This may be somewhat more difficult than fighting fires in conventionally powered vehicles. However, it is no more complex or dangerous than, for example, a fire in a gas-powered vehicle. [...]"

Electric vehicles do not burn more often

But do electric vehicles now really burn more frequently than other types? Due to the great public interest, several authorities have taken up this question. The ADAC concluded in 2022: "Currently, there is no evidence that electric cars are more likely to burn than cars with internal combustion engines, with or without being involved in an accident."

DEKRA also commented as early as 2021: "The fact is that, according to our findings, electric cars do not pose a higher fire risk than conventionally powered cars." This is also confirmed by the German Association of the Automotive Industry (VDA). With regard to the fire on the Fremantle Highway, a spokesperson told the press: "Electric vehicles do not pose any particular danger, the fire risk with an electric car is no higher than with a combustion engine."

Analogous statements also exist from the German Insurance Association (GdV): "Electric cars do not burn more often than combustion engines, but they burn differently." The GdV also criticises the decision of some shipping companies not to transport electric vehicles in the future - and instead pleads for more modern extinguishing systems on board the freighters.

And TÜV Nord also expressed its opinion as early as 2021, prompted by the aforementioned measure by the city of Kulmbach to deny electric vehicles access to underground garages. "There is a big gap between media reporting and the real situation. Every year, 15,000 cars burn down in Germany. The vast majority of these are internal combustion vehicles. Unlike e-cars, however, these fires are usually not worth reporting. In fact, petrol cars in particular, but also diesel cars, have a significantly higher fire risk due to the technical and physical conditions: They run on a flammable liquid fuel that tends to vaporise and can explode. If the fuel escapes from a leaking petrol pipe, for example, a fire is inevitable. Incidentally, the fire in Kulmbach is also said to have been caused by a burning petrol engine."

These statements are further confirmed by a study of the American insurer AutoinsuranceEZ. It examined current data, including from the National Transportation Safety Board (NHSB), on vehicle fires following collisions. The rate of electric vehicles catching fire was just 0.025%, whereas it was 1.5% for internal combustion vehicles. The highest rate, however, was 3.5 per cent for vehicles with hybrid drives.

A similar study from Sweden confirms these figures. In 2022, a total of 23 electric cars caught fire - for a variety of reasons. This corresponds to a rate of 0.004 percent - measured against the total number of electric vehicles registered in Sweden. For internal combustion vehicles, the rate was 0.076 percent, which was significantly higher.

Conclusion

Even if current studies do not show that electric vehicles burn more frequently than classic petrol or diesel models, this does not mean that there is no need for action. In particular, there is a need to respond to the "different nature" of the fires. This includes the installation of suitable extinguishing methods or the appropriate training of fire brigade personnel.

The "Albero" project (transport of alternatively powered vehicles on RoRo ferries), funded by the Federal Ministry of Education and Research, has been working on the development of a holistic safety concept for RoRo ships (ships where the cargo is driven on and off the ship) in the period from 2018 to 2021. At EU level, the LASH FIRE project is researching new fire protection concepts for RoRo ships. "The aim is to develop and demonstrate operational as well as design solutions to improve fire prevention and ensure better fire fighting on all RoRo vessel types."

Text: Sebastian Meerschiff