The growing number of electric vehicles (EVs) on our roads has increased awareness of the potential fire hazard that these vehicles’ lithium-ion (li-ion) batteries pose. But the dangers associated with EVs go beyond dead batteries; they also include a host of other issues that might lead to car fires. Let’s examine the intricacies of the fire risks related to electric vehicles in this extensive guide, including not only the function of lithium-ion batteries but also additional elements like the materials utilized in contemporary cars. We hope to offer important insights into comprehending and reducing the dangers related to EV fires through an analysis of current research findings and industry advancements. This is a comprehensive view of managing fire threats in the age of electric mobility, covering everything from the development of EV technology to the difficulties encountered in fighting fires.
Fire Hazards with Electric Vehicles: It’s Not Just the Battery
Lithium-ion (li-ion) batteries, which allow electric vehicles to perform similarly to those with internal combustion engines, have raised concerns. Several codes have been updated to address issues with these batteries. Manufacturers are improving battery safety, but fire protection specialists should be concerned about other automobile technologies as well.
Vehicles and Batteries
Most of us only have familiarity with lead-acid batteries used to start diesel or gasoline automobiles. Concerns about greenhouse gas emissions have prompted the development of all-electric automobiles. The first electric vehicle (EV) was on the road in the 1830s, over 50 years (1) before the internal combustion engine (ICE) was invented. This early car lacked practicality due to its use of replacement batteries rather than rechargeable ones. In the late 19th century, numerous firms developed viable, rechargeable electric vehicles. When Henry Ford and others introduced affordable, dependable ICE vehicles to the market, they were quickly forgotten.
Today’s EVs are not like those from the past. Li-ion batteries are commonly used due to their high energy density (KWH/pound), fast recharge times, and quick discharge, enabling rapid acceleration. Battery packs for today’s automobiles weigh approximately 1,000 pounds (2). These packs are made up of multiple separate battery cells (similar to D-cell batteries) connected together and placed in a protective casing. Properly designed cases protect batteries and prevent them from releasing their stored energy. When they fail, fires frequently occur.
EV Battery Failures
The primary risk with an EV battery failure is thermal runaway. Thermal runaway happens when heat builds up inside a cell, causing a chemical chain reaction. Heat and internal pressure can cause the battery casing to fail (3). The flammable electrolyte produces a vapor cloud, which can ignite into a fireball. Closely packed cells in the battery pack increase the likelihood of nearby cells failing.
When EVs catch fire, they frequently generate front-page or even national headlines. As a result, it’s easy to assume that such incidents are commonplace. In reality, they are uncommon. In 2020, the NTSB reported about 200,000 fires involving ICE vehicles. There were just 52 involving all-electric vehicles (4). Even though ICE vehicles outnumber EVs on the road, they are 20 times more likely to catch fire than EVs (5).
Moving forward, it is anticipated that the risks of EVs will be reduced even further. Rivian and Ford plan to use Lithium Iron Phosphate (LFP) technology for their EVs starting in 2024, replacing li-ion batteries. In 2024, Tesla will employ this technology, with the exception of high-performance vehicles. LFP provides various advantages over lithium-ion batteries. One benefit is a lower chance of thermal runaway (6). LFP batteries have a lower energy density and release rate compared to Li-ion batteries, which could explain this. LFP batteries have a non-flammable electrolyte; thus, if a cell breaks, no flammable fumes are emitted.
If Batteries Aren’t the Only Problem: What Else is?
In 2015, research in France examined hundreds of vehicle fires in parking garages. Only 1% of fires from 1997 to 1999 involved more than five automobiles. That figure climbed by a factor of 8 (7) between 2010 and 2014! EVs were exceedingly uncommon at the start of the previous decade. Li-ion batteries, therefore, cannot be the cause of this sudden rise.
Plastics are considerably more likely to be the culprit. The materials used in current furniture, which can reach flashover in 3-4 minutes, are also contributing to the increased intensity of car fires. Originally, cars and trucks included steel body panels, fiber insulation, and natural fiber seats. Modern vehicles employ polypropylene body panels with polyurethane insulation and padding. Even the gasoline tanks are made of plastic.
A typical car contains almost 400 pounds of group A plastic, which accounts for 10% of its weight but 50% of its volume (8). This does not include the additional weight of synthetic fabrics (100 pounds) and synthetic rubber (200 pounds). To estimate the amount of fuel these synthetics contribute to a fire, consider that a 20-gallon gasoline tank contains around 120 pounds of hydrocarbons (140 pounds for diesel). The modern car uses four times more gasoline than the liquid fuel it operates on, rather than preventing fires from spreading.
Suppressing EV Fires
Car fires will happen. The goal of sprinkler designers should be to reduce fire spread. Previously, guidelines focused on closed parking garages, presuming that fires would not spread in open garages. Recent accidents highlight the need for sprinklers in open garages above 48,000 square feet, leading to a 2021 IFC rule. (903.2.10). The 2022 edition of NFPA 13 identifies parking garages as OH2 rather than OH1 (A188.8.131.52). This is a positive step forward.
Testing will be required to determine whether this is a suitable classification.
The 2023 edition of the 88A Standard for Parking Structures mandates sprinklers in all parking structures to comply with NFPA 13 and 13R (6.4.1). NFPA 88A may not have a significant impact on I-Code enforcement because the IFC does not recognize it.
While worries about fire threats related to lithium-ion batteries in electric cars (EVs) have been raised, it’s important to understand that there are other risks involved with EV fires besides battery failures. The use of plastics in modern vehicle construction greatly increases the intensity and spread of vehicle fires. The fact that EVs are statistically less likely to catch fire than conventional internal combustion engine (ICE) vehicles is nevertheless important.
Furthermore, the use of lithium iron phosphate (LFP) batteries and other developments in EV battery technology promise to substantially reduce the likelihood of thermal runaway and battery-related fires in the future.
It is imperative to establish complete fire protection measures, such as adequate sprinkler systems and revised building rules for parking structures, in order to properly handle fire threats in the era of electric mobility. Fire protection specialists can proactively handle the evolving issues provided by electric vehicles and ensure the safety of both vehicle occupants and property by keeping up to date with the latest research findings and industry advancements. An all-encompassing strategy for fire safety will be essential as electric vehicles become more commonplace on our roads to protect infrastructure and communities from the possible dangers of EV fires.
Courtesy: Rob Geislinger, Field Service Coordinator, Area 9 for the NFSA.