Facts and myths about fires in electric vehicles

Martin Carlsson, a Naval Architect for Stena Teknik in Sweden spoke at the recent Electric Vehicle (EV) maritime safety conference in London. Following the event, he shared some information relating to legislative assessment for safety hazards of fire and innovations on ro-ro ship environments, details of which can be found below.

The growing shift towards EVs is a significant development in both passenger transport and maritime logistics. As these new energy carriers gain prominence, questions and concerns about the safety of EVs, particularly in relation to fire risks, have surfaced. In response, the LASH FIRE project, part of the European Union’s Horizon 2020 research programme, has addressed some of the most common misconceptions surrounding fires in EVs, especially in ro-ro ship environments.

This article builds on the PSS EV campaign with more key facts and looks some of the myths that have emerged about EV fires, based on the findings from LASH FIRE. However, as the recent conference highlighted, data related to EVs is still low due their current prevalence in the market and amount of research undertaken.

Myth 1: EVs burn more frequently than internal combustion engine vehicles (ICEVs)

One common misconception is that EVs are more prone to catching fire than ICEVs. However, current data shows that EV fires are less frequent than those involving ICEVs, relative to the number of vehicles in use. Common causes of passenger car fires, such as arson, hot brakes, or flammable liquids coming into contact with hot surfaces, are independent of the vehicle’s energy source. Electrical faults in the engine compartment are more typical in ICEVs than in EVs, further reducing the relative risk of EV fires.

Myth 2: EV fires are more intense than ICEV fires

Another myth suggests that EV fires are more intense or severe than those in vehicles powered by internal combustion engines. However, the total heat release from both EV and ICEV fires is comparable, with a range between 3.3 and 10 gigajoules (GJ) for an average-sized passenger vehicle. Most of the chemical energy in modern vehicles is stored in materials such as seats, interior elements, and tyres, rather than in the energy storage system (fuel or batteries). Therefore, there is no significant difference in the overall intensity of fires between the two vehicle types.

Myth 3: Jet flames from EV fires spread faster than ICEV fires

It is true that different energy carriers can result in different fire behaviour. For example, jet flames from gas pressure vessels or lithium-ion batteries in EVs may occur, but liquid fuels, such as diesel are more prone to causing fire spread through leaks and pool fires. In fact, plastic fuel tanks in ICEVs can catch fire much faster than lithium-ion batteries when exposed to external heat, challenging the assumption that EV fires spread more rapidly.

Myth 4: Battery fires can’t be extinguished and fire suppression systems are ineffective

While thermal runaway in lithium-ion batteries can be difficult to control, it’s important to note that fires generally do not start in the battery itself. Early activation of fire suppression systems, such as a deluge or drencher system, can effectively suppress fire spread by cooling both the vehicle and the surrounding environment. Data suggests that early intervention plays a critical role in containing EV fires, just as with ICEV fires.

Myth 5: EV fires burn hotter and can melt the deck below

The belief that EV fires burn at higher temperatures than ICEV fires is unfounded. The temperature of a fire depends on multiple factors, including the fuel source, atmospheric pressure, adjacent temperatures, and oxygen content. No data supports the claim that EV fires burn hotter than those in ICEVs, nor that they are more likely to cause structural damage such as melting the deck.

Myth 6: Extinguishing an EV with water poses a risk of electrocution

Another common fear is that using water to extinguish a EV fire could lead to electrocution. However, modern electric cars are equipped with extensive safety systems that automatically isolate the battery pack and break the electrical connection in the event of a collision or short circuit. To be electrocuted, a person would need to physically bridge the positive and negative poles of the battery, which is highly unlikely. Therefore, water remains a safe extinguishing agent for EV fires under normal firefighting conditions.

Myth 7: Hydrogen fluoride produced from EV fires is highly toxic

It is true that hydrogen fluoride, a highly toxic gas, is produced in higher quantities during EV fires than ICEV fires due to the combustion of lithium-ion batteries. However, the combustion gases from all vehicle fires, regardless of fuel type, are hazardous. Firefighters must avoid the smoke plume and wear adequate personal protective equipment, including breathing apparatus, when dealing with any type of vehicle fire. Studies have shown that fully equipped firefighters face minimal health risks from hydrogen fluoride exposure while smoke diving during EV fires.

Myth 8: Standard Fire Suits Don’t Protect Against EV Fire Hazards

Concerns about the adequacy of standard fire suits during EV fires have been raised, particularly in relation to exposure to toxic gases like hydrogen fluoride. However, research conducted by the Swedish Defence Research Agency (FOI) indicates that standard fire suits and equipment, when used properly in conjunction with BA systems, offer sufficient protection for firefighters operating in EV fire conditions. The exposure levels observed during testing were well within acceptable limits for a typical firefighting mission.

Myth 9: Overcharging lithium-ion batteries causes thermal runaway

Thermal runaway can occur if a Lithium-ion battery is overcharged at the cell or module level. However, EVs are equipped with Battery Management Systems (BMS) that prevent overcharging, making this scenario highly unlikely. While there have been reports of fires during charging, these incidents are often caused by external factors such as faults in the charging infrastructure or the cables, rather than overcharging of the battery itself.

Conclusion

As the global fleet of electric vehicles continues to grow, understanding the realities of EV fire risks is crucial for both the automotive and maritime industries. The LASH FIRE project, details attached below for info, has addressed some of the myths surrounding EV fires, highlighting that while these vehicles pose some different risks compared to internal combustion engine vehicles, they are not inherently more dangerous. By following proper safety protocols, equipping firefighters with the right tools, and maintaining early fire suppression systems, EV fires can be effectively managed, ensuring safety in ro-ro ship environments and beyond.