Although I am a fan of gasoline cars and even sneer at electric cars. However, the smoothness, quietness, acceleration and convenience brought by the Tesla Model S made me have to admit that this is the “future.” Guess what I thought of? Smartphones. Yes, extremely fast response, beautiful appearance, rich customized design.
But everything has two sides. The spontaneous combustion of smartphones has been resolved, but electric cars have not been able to escape this physical characteristic. According to the National Transportation Safety Board (NTSB), EVs account for a small percentage of vehicle fires annually, with an estimated 25 electric car fires reported per 100,000 vehicles in 2023. However, the unique characteristics of EV fires, such as prolonged combustion and called thermal runaway, warrant deeper investigation into their causes and prevention.
What Causes EV Batteries To Catch Fire?
Nearly all electric vehicle (EV) fires stem from lithium-ion battery failures, and at the core of nearly all lithium battery fires is a single, well-documented phenomenon: thermal runaway.
Thermal runaway is a self-sustaining, uncontrollable reaction where excessive heat triggers chemical breakdowns inside the battery, accelerating the release of more heat until the system fails catastrophically. While modern battery management systems (BMS), cooling solutions, and safety regulations have significantly reduced the frequency of these events, lithium-ion batteries remain susceptible to certain failure conditions that can initiate this process.
The Mechanism of Thermal Runaway
Under normal conditions, lithium-ion batteries operate within a stable range where charge, discharge, and thermal regulation prevent excessive heat buildup. However, when an abnormal condition—such as an internal short circuit, mechanical puncture, overcharging, or overheating—causes localized temperature escalation, the stability of the cell becomes compromised.
The process unfolds in several irreversible stages:
Stage 1: SEI Breakdown and Electrolyte Decomposition (~80°C–120°C / 176°F–248°F)
The solid electrolyte interphase (SEI) layer, a protective film on the anode that regulates ion flow, begins to degrade at temperatures above 80°C (176°F). As this layer decomposes, it exposes the anode to direct contact with the electrolyte, triggering unwanted chemical reactions that release heat and flammable gases.
Stage 2: Separator Failure and Internal Short Circuit (~150°C–200°C / 302°F–392°F)
As the heat continues to build, the electrolyte starts to vaporize, generating highly flammable gases such as hydrogen (H₂), methane (CH₄), and ethylene (C₂H₄). At around 150°C (302°F), the polymer separator—designed to keep the anode and cathode apart—begins to shrink or melt. If the separator fails completely, the electrodes come into direct contact, causing a massive internal short circuit. This drastically increases local current flow, injecting more energy into the system and further elevating the temperature.
Stage 3: Cathode Breakdown and Oxygen Release (~250°C–300°C / 482°F–572°F)
At this stage, the cathode material itself becomes unstable. For lithium-ion batteries using nickel-manganese-cobalt (NMC) or lithium cobalt oxide (LCO) chemistry, this means that the cathode structure begins to decompose, releasing pure oxygen (O₂). This is critical because, unlike gasoline fires that require atmospheric oxygen to sustain combustion, lithium battery fires generate their own oxidizers—making them extremely difficult to extinguish.
Stage 4: Full Thermal Runaway and Fire Propagation (>800°C / 1472°F)
If left unchecked, temperatures will escalate beyond 800°C (1472°F), causing violent cell rupture. At this point, the battery ejects flaming electrolyte, superheated gas, and molten metal, igniting surrounding cells in a chain reaction. This thermal propagation effect can quickly consume an entire battery module, pack, and ultimately, the vehicle itself.
Once thermal runaway has begun, traditional fire suppression methods are often ineffective. Large volumes of water are typically required—not to “put out” the flames, but to cool the remaining cells and prevent secondary ignition.
Key Triggers of Thermal Runaway
Mechanical Damage
EV battery packs are often located in the undercarriage to lower the vehicle’s center of gravity, but this also makes them vulnerable to road debris, high-speed collisions, and structural compression during accidents. If a hard impact punctures the battery casing, it can breach multiple cells, leading to an instantaneous internal short circuit.
This risk is well-documented.
- In 2013, a Tesla Model S struck a piece of metal debris on a highway, puncturing the battery and igniting a fire. This led Tesla to implement titanium shielding and underbody protection in newer models.
- In 2021, a high-speed crash involving a Model S in Texas resulted in a severe fire, requiring over four hours and 30,000 gallons of water to fully suppress.
Low-speed impacts, such as curb strikes or pothole damage, can also weaken the protective casing, creating a delayed failure mode where stress fractures allow moisture infiltration or internal degradation over time.
Overcharging & Overdischarging
Lithium-ion batteries operate within a strict voltage range (typically 2.5V–4.2V per cell). Deviating from this range can introduce serious instability risks:
- Overcharging (>4.2V/cell) causes excess lithium-ion deposition on the anode, forming metallic dendrites—thin, needle-like structures that grow over time and can puncture the separator, leading to an internal short circuit.
- Overdischarging (<2.5V/cell) can cause copper dissolution in the anode’s current collector. When the battery is recharged, these copper ions replate in unwanted locations, forming conductive bridges that increase short-circuit risk.
The dangers of overcharging were highlighted in GM’s recall of over 140,000 Chevrolet Bolt EVs between 2020 and 2021, where manufacturing defects in LG Chem’s battery cells led to a higher risk of internal shorts and spontaneous fires.
Thermal Management System (TMS) Failure
EVs rely on active cooling systems to keep batteries within an optimal temperature range of 15°C to 45°C (59°F to 113°F). If the thermal management system (TMS) fails, batteries can overheat—especially in hot climates like Arizona, Texas, or Nevada, where ambient temperatures already push cooling systems to their limits.
Cold temperatures introduce a different risk:
- In subzero conditions, lithium-ion diffusion slows, increasing dendrite formation.
- When the battery is rapidly fast-charged in freezing temperatures, existing dendrites can puncture the separator, leading to sudden failure.
Several Tesla fires in extreme weather conditions have been linked to thermal management failures, highlighting the importance of robust cooling architecture.
Water Damage & Corrosion
While modern EV battery packs are designed to be IP67 or IP68-rated, prolonged exposure to floodwaters, humidity, or saltwater environments can degrade insulation and cause electrical shorts.
This became alarmingly clear during Hurricane Ian in 2022, when dozens of waterlogged EVs in Florida spontaneously ignited. Saltwater intrusion created conductive pathways, leading to uncontrolled current flow and eventual thermal runaway.
Coastal regions, where salt exposure accelerates battery casing corrosion, also pose long-term safety risks if moisture seeps into the pack.
Electrical Malfunctions
Electrical malfunctions, including overcharging, short circuits, and faults in the battery management system (BMS), are responsible for approximately 9.7% of electric vehicle battery fires. Overcharging can lead to excessive current flow, overheating, and eventually called thermal runaway. In some cases, manufacturing defects in separators or wiring exacerbate these risks by creating weak points within the battery cells.
To mitigate this, companies like Nissan and Hyundai have integrated advanced BMS solutions capable of real-time monitoring, which can detect anomalies such as voltage imbalances or rising temperatures. These systems can isolate problematic cells or shut down the entire battery system to prevent escalation. The adoption of high-quality cell separators and reinforced wiring materials has further reduced the risk of electrical failures.
Thermal Stress
Thermal stress is a critical factor that significantly impacts the stability of lithium-ion batteries. Research indicates that when ambient temperatures exceed 35°C (95°F) and batteries are exposed to rapid charging cycles more than three times a day, the likelihood of called thermal runaway increases dramatically.
This is particularly true when the state of charge (SoC) exceeds 80%, as high SoC levels exacerbate internal heat generation. Frequent fast charging at high temperatures can degrade the thermal stability of battery cells, leading to accelerated electrolyte decomposition and increased internal pressure. To address this, automakers such as Rivian and Ford have implemented advanced liquid cooling systems within their battery packs, ensuring that operating temperatures remain below 30°C (86°F) even during rapid charging. These systems use high-efficiency heat exchangers and predictive thermal management algorithms to distribute heat evenly and prevent localized hotspots, effectively reducing the occurrence of electric vehicle battery fires.
Chemical Instability
The choice of battery chemistry plays a crucial role in determining susceptibility to lithium ion battery fires. High-energy-density batteries, such as those using nickel-cobalt-aluminum (NCA) chemistry, are more prone to instability compared to safer alternatives like lithium iron phosphate (LFP) batteries. LFP batteries, with their lower energy density, provide greater thermal stability, making them a preferred choice for many manufacturers, including BYD and Tesla’s standard-range models. Meanwhile, significant advancements are being made in solid-state battery technology by companies like Toyota and QuantumScape. These batteries replace flammable liquid electrolytes with non-flammable solid materials, significantly reducing the likelihood that EVs will catch fire.
Signs of Impending Thermal Runaway
Electric car fires rarely occur without warning, and recognizing the early signs is critical to preventing catastrophic outcomes. The most common indicators include a significant increase in cell temperature, which may exceed 60°C before accelerating to a runaway state. This temperature rise is often accompanied by physical swelling of the battery cells as internal pressure builds. During this process, flammable gases such as hydrogen and methane may be released due to the decomposition of the electrolyte. These gases, when combined with heat, create an environment highly conducive to ignition.
Advanced detection systems are essential in identifying these warning signs before escalation. Technologies such as thermal imaging cameras can monitor temperature anomalies across the battery pack in real-time, while gas sensors detect the presence of volatile compounds at extremely low concentrations. For instance, Tesla and Hyundai have incorporated multi-layered early detection mechanisms into their EVs, enabling rapid intervention by the battery management system (BMS) to shut down affected cells and prevent further damage. Additionally, research indicates that integrating predictive analytics into BMS software can enhance the ability to forecast thermal events based on patterns of use and environmental conditions.
Do EVs Catch Fire More Than Gas Cars?
Contrary to popular belief, EVs catch fire less frequently than gas-powered vehicles. According to the National Transportation Safety Board, ICE vehicles experience approximately 1,529 fires per 100,000 vehicles annually, compared to just 25 per 100,000 for EVs. However, the causes and consequences of these fires vary significantly. For ICE vehicles, the majority of fires are attributed to fuel leaks, electrical system failures, or overheating engines. These incidents often occur on highways or in urban traffic, causing substantial economic losses and occasional fatalities.
In contrast, electric vehicle battery fires are primarily linked to called thermal runaway within lithium-ion batteries. While less frequent, they are often more complex to extinguish, requiring specialized firefighting equipment and prolonged intervention times. For example, data from NFPA indicates that extinguishing an EV fire can take up to 24 hours and involve 20,000 gallons of water, significantly straining fire department resources.
The financial impact of electric car fires can also be severe due to the high cost of battery replacement and potential damage to surrounding infrastructure. For instance, a single EV fire in an underground parking garage can result in millions of dollars in damages and lengthy repair timelines. Additionally, EV fires pose unique challenges to emergency responders, as the release of toxic gases such as hydrogen fluoride requires specialized protective gear and ventilation systems.
Understanding the differences in fire dynamics and leveraging data-driven strategies are crucial for improving fire safety across all vehicle types. Manufacturers, regulators, and fire departments must collaborate to develop targeted solutions, such as improved fire suppression systems and enhanced safety protocols for both EVs and gasoline fires.
After understanding the question of why do EVs catch fire?, how to solve the problem of EVs Catch Fire? Up to now, there is no liquid that can prevent EV fire from continuing to burn. The most effective way to put out EV fire is to contain the spread of EV fire. Safeprotex has developed an EV fire blanket specifically for EV fire. Just like the car fire extinguisher, we recommend that you keep one in the trunk, which will definitely help you at the critical moment.