Fires in electric vehicles (EVs) and Battery Energy Storage Systems (BESS) have continued to make headlines in recent years. In January 2025, a massive BESS thermal runaway event at the Moss Landing Energy Storage Facility in California led to the evacuation of 1,500 residents. The fire, which was allowed to burn out due to the risk of explosion, highlighted the growing concerns over large-scale BESS safety.
Meanwhile, multiple EV battery fires led to further recalls across the industry. GM’s earlier $1.9 billion recall of Bolt batteries due to thermal runaway remains one of the most costly, but Hyundai, Ford, and BMW have also faced significant recalls linked to battery fires.
Although thermal runaway in BESS can result from manufacturer defects, clean energy technicians must implement advanced thermal management strategies. What is thermal runaway? It is a chain reaction where a battery cell overheats uncontrollably, leading to fire or explosion.
What Is Thermal Runaway?
Thermal runaway is a hazardous process where an uncontrolled rise in temperature triggers a feedback loop, releasing more energy and causing further temperature spikes. If left unchecked, it can lead to catastrophic failures in lithium-ion batteries, potentially resulting in fires or explosions.
This phenomenon is not limited to battery storage—it also occurs in chemical engineering (exothermic reactions), electrical engineering (power dissipation issues), civil engineering (concrete curing heat), and astrophysics (runaway nuclear fusion in stars).
What Is Thermal Runaway In BESS?
BESS thermal runaway occurs when a damaged lithium-ion battery cell releases flammable or toxic gases, triggering a chain reaction that spreads to adjacent cells. As this process accelerates, extreme heat and pressure build up, significantly increasing the risk of fires or explosions.
Preventing thermal runaway in BESS requires robust thermal management systems, early fault detection, and improved battery designs. With BESS thermal runaway incidents on the rise, the industry must prioritize safety measures to mitigate risks and ensure the reliability of energy storage systems.
How BESS Thermal Runaway Occurs
BESS thermal runaway happens when heat accumulates faster than it can dissipate, leading to a dangerous chain reaction. A key component in lithium-ion batteries is the separator, a porous membrane that keeps the anode and cathode apart while allowing ion transfer. If the separator degrades due to excessive heat, the battery short-circuits, triggering thermal runaway. This process can escalate rapidly, potentially causing fires or explosions.
Risks of Thermal Runaway in BESS
Thermal runaway in BESS poses severe risks to property, human safety, and the environment. If not properly managed, it can lead to uncontrollable fires, explosions, and the release of toxic gases. Once BESS thermal runaway begins, it is extremely difficult to stop, making proactive safety measures essential. Proper thermal management, system monitoring, and rapid-response strategies are critical to mitigating these hazards.
Factors Contributing to BESS Thermal Runaway
Several factors can initiate thermal runaway in BESS, including overcharging, overheating, manufacturing defects, battery misuse, and short circuits. In many cases, heat accumulates within the battery faster than it can be expelled. This causes the electrolyte to transition from a liquid to a gas, increasing internal pressure beyond safe limits. If venting fails, the pressure buildup can lead to catastrophic failure.
Preventing BESS Thermal Runaway
Intervening early in the process can prevent BESS thermal runaway, especially if the underlying abuse factor is addressed. However, if the battery separator is compromised, the positive and negative electrodes can mix, generating excessive heat and smoke—clear warning signs of imminent failure. At this stage, BESS thermal runaway is nearly unavoidable, reinforcing the need for robust safety systems and early fault detection in energy storage solutions.
BESS Thermal Runaway Containment And Prevention
BESS thermal runaway can occur rapidly due to various factors, leading to extreme temperatures, uncontrollable fires, and explosions. Once initiated, thermal runaway in BESS is difficult to stop, making prevention and containment critical for safety.
Dangers of Thermal Runaway In Lithium-ion Batteries
When a chain reaction triggers cascading thermal runaway, containment becomes increasingly difficult. The Arizona Public Service (APS) battery fire investigation revealed that a single battery cell defect likely caused BESS thermal runaway. Despite fire suppression systems functioning as designed, they could not prevent the chain reaction, highlighting the urgent need for improved prevention and mitigation strategies.
The thermal runaway in BESS at APS led to a buildup of flammable gases. When firefighters opened the door, the gases ignited, causing an explosion. This incident underscores the importance of proper BESS safety training for first responders and system operators to prevent unintended escalations.
BESS Thermal Runaway Containment Strategies
Lithium-ion battery fires are notoriously difficult to suppress, often requiring large amounts of water over extended periods. In some cases, containment is nearly impossible, especially in enclosed or remote locations.
Advancements in battery technology and BESS safety strategies have improved thermal runaway containment. Manufacturers must design batteries to prevent cell failures, while clean energy technicians must implement robust containment, ventilation, and monitoring systems in BESS facilities to mitigate risks.
Corrective System Shutdowns To Prevent BESS Thermal Runaway
Early fault detection is crucial in preventing BESS thermal runaway. Battery management systems (BMS) play a critical role, similar to how smartphones prevent overcharging. BESS battery management systems continuously monitor performance data to detect abnormalities before they escalate. However, not all failures are identified in time, reinforcing the need for multiple layers of safety.
Monitoring Indicators to Prevent Thermal Runaway
Detecting internal temperature spikes and off-gassing is key to preventing BESS thermal runaway. Off-gassing is often an early warning sign of battery failure, but detecting low concentrations of gases like carbon monoxide, methane, ethane, and ethylene requires specialized monitoring equipment, as conventional gas detectors may not be sensitive enough.
Corrective Shutdown Procedures for BESS Thermal Runaway
A well-designed BESS safety system should shut down a failing battery when excess gases are detected, allowing gas levels to return to normal. However, the affected battery cell will likely be damaged and require replacement. In some cases, Authorities Having Jurisdiction (AHJs), insurance providers, and utility companies mandate off-gas monitoring as a safety requirement.
Enhancing BESS Safety Measures
Early detection of failures can prevent extensive property damage and improve safety. Many BESS facilities now incorporate off-gas detection, advanced fire suppression, and ventilation systems to minimize the risk of thermal runaway in BESS.
Mitigating Dangers of BESS Thermal Runaway
Building BESS facilities with non-combustible materials and ensuring proper ventilation can help reduce fire risks. Adequate ceiling height and proper airflow prevent the accumulation of flammable gases. Additionally, BESS-specific firefighter training is essential, as traditional firefighting tactics may worsen BESS thermal runaway incidents.
Thermal Runaway Prevention
Preventing BESS thermal runaway is far more effective than attempting to contain it once it has started. Battery manufacturers can implement protective measures, such as adding protection circuits to regulate safe operation. These safeguards help prevent overcharging, rapid discharging, and short circuits—common triggers of thermal runaway in BESS.
Lessons from Past BESS Thermal Runaway Incidents
Examining past lithium-ion battery fires and explosions in BESS facilities provides critical insights into thermal runaway prevention. Investigations into these incidents have identified several key contributors to BESS thermal runaway:
Damage during construction – Physical damage to battery cells during installation can compromise their integrity, leading to internal shorts or other malfunctions. These issues often go undetected until the system is operational, increasing the risk of BESS thermal runaway.
Battery cell defects – Manufacturing flaws can cause overheating or internal chemical reactions. These defects may not be immediately apparent but can trigger thermal runaway in BESS when subjected to standard operating conditions.
Operating outside prescribed parameters – Deviating from manufacturer guidelines, such as improper charge rates, temperature limits, or overloading the system, can cause excessive heat buildup and cell stress, heightening the risk of thermal runaway.
Practices to Minimize Risks of BESS Thermal Runaway
A structured BESS commissioning plan is essential to prevent issues from the start. Proper handling and installation techniques protect battery cells from damage, while robust containment strategies, including ventilation and real-time monitoring, help detect early warning signs.
Comprehensive BESS safety training ensures operators follow proper maintenance protocols and do not run systems outside safe operating conditions. BESS facilities should also develop emergency plans for extreme weather, natural disasters, and other unforeseen hazards to mitigate thermal runaway risks.
Industry Standards for Thermal Runaway Prevention
To meet safety requirements, lithium-ion batteries undergo UL 9540A testing, which evaluates thermal runaway in BESS under fire conditions. This test documents critical thresholds, including the temperature at which thermal runaway begins and when venting occurs due to internal pressure buildup. UL 9540A test results help Authorities Having Jurisdiction (AHJs), insurance providers, fire departments, and building owners assess fire risks and improve safety measures.
Be Mindful of BESS Thermal Runaway Risks
Recent high-profile incidents have raised concerns about the safety of lithium-ion batteries across multiple applications, from electric vehicles to BESS facilities. As a clean energy professional, understanding thermal runaway prevention is essential for building trust in the energy storage industry and reinforcing a commitment to safety.
GreenLancer has a network of qualified designers & engineers who specialize in commercial or residential AHJs across the country to provide peace of mind through the permit and engineering process of your solar installation project. Fill out the form below to talk to a GreenLancer Rep, or sign up for a free account here and begin shopping services.
Comments