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Battery Off-Gassing

Image of a car fire with a battery symbol overlay. The vehicle's interior is engulfed in flames, illustrating the dangers of battery off-gassing and potential fire hazards associated with batteries.

Battery Safety: What is Off-Gassing and Why Does it Occur?

Batteries have become an integral part of our daily lives, powering everything from smartphones to electric vehicles. But have you ever considered the potential risks associated with the batteries that enable the seamless functioning of these devices? While advancements in battery technology have revolutionized the way we live, it’s crucial to explore the potential hazards these power sources pose.

Lithium-ion batteries are combustible and hazardous with the potential for dangerous thermal runaway that can have devastating consequences for the environment and property and also threaten human life. It is important to understand the first signs of a possible disaster – battery off-gassing. NevadaNano’s MPS™ sensors can detect hydrogen produced in a thermal runaway event as well as EMC and DMC electrolyte gases that signal the beginning of thermal runaway.

Electric Car Battery Pack in assembly

Understand Off-gassing: The Silent Emission

Off-gassing refers to the release of gases from lithium-ion batteries often as a result of battery damage, abuse, and/or misuse. When a battery is subjected to conditions such as overcharging, over-discharging, or physical damage, it can lead to the breakdown of internal components, causing the release of gases. These gases typically include carbon dioxide, carbon monoxide, hydrogen, and the vapors of volatile organic compounds – which are flammable and can be toxic for anyone who may come in contact with them.

Explaining Off-gassing Dynamics:

Off-gassing dynamics differ based on the specific battery design and battery-pack deployment scenarios. In enclosed setups like racks or small housings, off-gassing can accumulate within the confined space, increasing the risk of pressure buildup and ignition. In open scenarios, such as outdoor installations, off-gassing may dissipate more easily, but still poses risks in poorly ventilated areas.

How Off-gassing Occurs and the Timeline:

Although not always a guaranteed precursor to thermal runaway in lithium-ion batteries, off-gassing events typically occur early in their failure. Thermal runaway is used to describe the uncontrolled chemical reactions and processes that lead to a rapid increase in temperature and pressure within the cell. This escalation typically expels a significant quantity of flammable gases and vapors and ultimately results in the battery catching fire, posing significant safety hazards.

The timeline for off-gassing can vary depending on the severity of the abuse and the type of battery. In some cases, off-gassing may occur gradually over time as the battery undergoes repeated stress, while in other instances, it may occur suddenly due to a single event, such as overcharging.

Graph depicting the P-F curve, which shows the relationship between asset condition and time. The y-axis represents asset condition, and the x-axis represents time. The curve starts at a high level of asset condition and remains steady before beginning to decline. Key points on the curve include the point where failure starts, marked as 'P: Potential Failure,' and the point of 'F: Functional Failure.' The time interval between these two points is labeled as 'P-F Time,' indicating the period during which potential failure can be detected before it leads to functional failure.

Factors in which Off-gassing can occur:

  • Physical Damage: Any damage to the battery, such as punctures or crushing, can cause internal components to degrade, leading to off-gassing.
  • Overcharging: Excessive charging can cause the decomposition of electrolytes within the battery, leading to gas generation.
  • Overheating: Like off-gassing, excessive heat can trigger thermal runaway by destabilizing the battery’s internal chemistry.
  • Over-discharging: Discharging a battery beyond its recommended limit can also result in the release of gases.
  • Internal Short Circuits: Any malfunction that causes a short circuit within the battery can initiate thermal runaway.
  • Manufacturing Defects: Faulty manufacturing processes can introduce weaknesses in the battery structure, making it more susceptible to thermal runaway.

What are the dangers of Off-gassing buildup?

Off-gassing buildup can lead to the battery storage container turning into a pressure vessel that is just waiting for a spark to ignite. To mitigate this risk, it’s crucial to have a monitored ventilation system in place. Additionally, compliance with FM standards is essential, as BESS should maintain lower than 25% LFL or have a container that can open to vent gas, ensuring safety in case of off-gassing.

Why Early Detection of Off-gassing is Critical:

  • Preventative Maintenance: Early detection allows for timely maintenance and corrective action to address battery issues before they worsen. Routine monitoring of off-gassing can help identify underlying problems in battery systems, such as overcharging or internal damage, enabling proactive maintenance to mitigate risks.
  • Risk Mitigation: Off-gassing serves as an early warning sign of potential battery failures. By monitoring off-gassing levels, operators can implement risk mitigation measures, such as adjusting charging parameters or isolating malfunctioning batteries, to prevent thermal runaway and its associated hazards.
  • Enhanced Safety: Timely detection of off-gassing enhances safety for both personnel and property. It provides an opportunity to evacuate affected areas, implement emergency protocols, and minimize the impact of battery-related incidents on surrounding environments. Additionally, early intervention reduces the likelihood of injuries and property damage resulting from thermal runaway events.
  • Cost Savings: Detecting off-gassing early can help avoid costly repairs or replacements of damaged batteries and equipment. By addressing issues proactively, operators can extend the lifespan of batteries, optimize performance, and avoid unplanned downtime, resulting in significant cost savings over time.
  • Regulatory Compliance: Many regulatory standards and guidelines mandate the monitoring of off-gassing as part of battery safety protocols. Early detection ensures compliance with regulatory requirements and demonstrates a commitment to maintaining safe battery operations in accordance with industry standards.

Incorporating robust gas detection systems and technologies for early detection of off-gassing is essential for proactive risk management and maintaining the integrity of battery systems. By prioritizing early detection, stakeholders can safeguard against potential hazards, minimize disruptions, and promote the safe and sustainable use of battery technology across various applications.

MPS™ Sensor Technology – The Earliest Warning Of Battery Runaway

NevadaNano’s Molecular Property Spectrometer™ (MPS™) gas sensor is powering the next generation of combustible gas detection. The MPS™ delivers unprecedented reliability, accuracy, and worker safety by simultaneously detecting over a dozen of the most common combustible gases, including hydrogen, and the flammable vapors of common electrolytes (e.g. dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC)).

Picture of an electric car park and the charging stations

Key features of the MPS™:

  • Detects DMC/EMC & H2
  • No Calibration required
  • Supports 15+ year lifetime
  • Immune to Poisoning
  • Built in Self-Test
  • Certified Intrinsically Safe
Diagram illustrating the detection capabilities of the MPS™ Sensor. The sensor detects DMC, EMC, H₂, and hydrocarbons at various temperatures: 25°C, 130°C, and 700°C. The diagram shows different chemical reactions and emissions such as H₂O, HF, CO₂, CH₄, and O₂ at each temperature stage. At 25°C, the sensor detects O₂, H₂, DMC, and EMC. At 130°C, it detects EC, DEC, and EMC. At 700°C, it detects CO, CO₂, CH₄, and C₂H₂, with an indication of a potential fire. The image highlights the sensor's ability to detect these chemicals and prevent potential hazards.

The detection capabilities of the MPS™ results in earlier stage detection of an issue within the battery P-F failure curve, prior to generation of other toxic & flammable gases

Summary

The importance of using the MPS™ gas sensor lies in its ability to provide advanced accurate detection of hydrogen, DMC, and EMC during lithium battery off-gassing events. By promptly identifying the presence of these gases, the MPS™ sensor enhances safety measures, enabling proactive response to mitigate potential risks. With its comprehensive detection capabilities, the MPS™ sensor ensures the reliable monitoring of combustible gases, safeguarding against hazardous situations and contributing to a safer environment.


The MPS™ Gas Sensor gives the earliest warning of battery runaway.

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