Active safety in lithium batteries: gas sensors and aerosol fire suppression systems

When it comes to industrial lithium batteries, safety is one of the central issues. In the world of industrial applications, where machines often operate continuously and autonomously, the safety of lithium batteries is not optional but rather a fundamental requirement. This is even more relevant when considering the range of chemistries available on the market: not all lithium solutions offer the same level of stability.

For this reason, at Flash Battery we have chosen to offer the option of integrating additional safety measures such as gas sensors and extinguishing systems built into the battery that are capable of detecting early warning signs and acting proactively to address them.

Not all lithium batteries are the same: several chemistries exist, each with different characteristics in terms of energy density, lifespan and above all thermal stability and intrinsic safety.

Some, such as NMC (Nickel-Manganese-Cobalt) lithium cells, provide high energy density but also carry a higher intrinsic risk of thermal instability, especially under extreme operating conditions or in the event of a malfunction. Under abnormal stress (such as short circuits, impacts or overloads), these cells may experience dangerous phenomena such as thermal runaway, a chain reaction that leads to the rapid release of gas and heat, with potential risks of fire or explosion.

By contrast, the LFP (lithium iron phosphate) chemistry adopted by Flash Battery stands out for its far more stable and predictable behaviour, even under stress. In fact, LFP cells have a high decomposition temperature and are less prone to thermal instability, a combination that ensures a high level of safety even in the event of an internal short circuit.

 However, while LFP cells are intrinsically very safe, as with all types of energy storage the risk is never zero.  For example, a hot spot may develop due to improper tightening, which could ignite the sheath of a cable or surrounding plastics.

For this reason, battery safety must be addressed with an integrated approach that combines the selection of a stable chemistry, advanced electronic design and intelligent monitoring and response systems.

In the world of lithium batteries, safety cannot be an afterthought, but must be a guiding principle integrated from the very earliest design stages. This is why the manufacturer plays a decisive role in defining the safety level of a battery pack, and this process begins as early as the research and development stage, where technical criteria, chemistries and protection logics are defined.

The process then moves into design, which must follow specific criteria, and continues with the selection of the most suitable materials and the actual assembly of the battery pack. Choosing a lithium-battery manufacturer with experience and the right know-how is therefore critical to ensuring the safety of industrial machines. Behind a finished battery pack lies a truly complex world of study, research and development, technical testing and above all careful selection of components and electronics, factors that – besides influencing the performance of the application – are essential to ensuring a lithium battery is safe and reliable over time.

One of the central elements in this architecture is the BMS (Battery Management System), which does far more than read data: it communicates constantly with the vehicle and the charger, monitoring the voltage, temperature and state of health of each individual cell in real time. In the event of anomalies, the BMS can interrupt charging and discharging, act on the contactors and isolate the battery to prevent any operational risk.

Overheating is one of the main issues to prevent to ensure the safety of a lithium battery, and to achieve this constant monitoring of the battery’s internal temperature becomes essential. One of the various functions of an intelligent BMS is precisely this: ensuring the constant checking of the temperature and the voltage of individual cells, to interact with the vehicle and with the battery charger in order to stop it from charging and discharging in the event of a critical issue and to trip the main contactors.

Gas sensors make it possible to detect the formation of volatile electrolyte gases that may escape from a damaged cell well before obvious symptoms appear, such as rising temperatures or visible smoke.

In the event of overheating or an internal short circuit, various specific gases may be generated inside the battery pack from the decomposition of materials in the cell such as hydrogen, carbon dioxide, carbon monoxide and other vapours from liquid electrolytes.

These gases are a sign of an early stage of cell damage, even before visible smoke or the onset of full thermal runaway, and therefore represent a signal that cannot be ignored.

This is where gas-detection sensors come into play and why they can make the difference in determining the safety of a battery pack.

As soon as gas is detected inside the battery pack, this device communicates in real time with the Battery Management System (BMS), which interprets the signals and can trigger targeted actions: notifying the vehicle of the anomaly, actively cooling the modules, activating extinguishing systems or sending alerts to the control centre.

Unlike traditional thermal sensors, which only signal an anomaly after the temperature has exceeded critical thresholds, gas sensors make it possible to gain precious time to activate countermeasures and prevent more serious consequences such as thermal runaway.

In the chart above, a cell was overloaded until it reached thermal runaway. As can be seen from the temperature line, at minute 4:30 the cell opened its safety valve and immediately afterwards the sensor detected the presence of gas, alerting the BMS.

The temperature sensor didn’t detect an increase related to thermal runaway in the cell until 12 minutes had passed.

The adoption of a gas sensor inside a battery pack can thus speed up detection by several minutes, improving the safety of the entire system and providing valuable time to respond.

Among the solutions adopted, aerosol fire suppression systems are an important active containment measure.  In the field of active safety solutions for lithium batteries, aerosol suppression systems represent a highly effective technology, designed to act quickly in the event of an incipient fire.

In fact, condensed aerosol fire suppression systems are an advanced solution for protecting batteries and energy storage systems (BESS), especially where traditional methods such as water or gas are ineffective or harmful.

These devices are activated automatically when they detect an abnormal rise in temperature, releasing a suppressing agent in the form of aerosol that can quickly put out the start of a fire without collateral damage to the electronics.

 Unlike systems based on water, gas or powder, the aerosol agent acts at the core of the combustion process, interrupting the chemical chain reactions that feed the fire, rather than simply smothering the flames or cooling the environment.

The extinguishing agent, released in the form of ultra-fine particles (less than 10 microns), binds to the free radicals generated by the fire, neutralising the propagation process.  This mechanism is particularly effective against lithium-ion battery fires, which can escalate rapidly and are difficult to contain with conventional systems. Moreover, aerosol doesn’t damage sensitive electronic components, enabling targeted and safe action within battery compartments or confined spaces.

Aerosol suppression systems offer a range of tangible benefits that make them particularly suitable for industrial applications and energy storage systems (BESS).

One of their main strengths is the speed of response: activation takes place within seconds of detecting a thermal anomaly, a crucial factor when dealing with events such as thermal runaway, which can evolve very quickly.

Furthermore, the ability to operate in enclosed, complex spaces makes aerosol an ideal solution where pressurised or water-based systems cannot be used or would be harmful. The absence of pressurisation and the compact size of the devices simplify integration into modular architectures.

There is also an additional advantage: the suppressing agent leaves no harmful residue, protecting the integrity of power electronics and reducing restoration times after an event.

Finally, it’s a safe solution from an environmental perspective as well: the suppressing agent is halon-free, non-toxic and compliant with the Montreal Protocol. In terms of integrated and sustainable safety, aerosol is therefore a technologically advanced and highly effective choice.

Today prevention is one of the most strategic values in the design of advanced energy systems. Detecting an anomaly in its early stages and promptly identifying a potential hazard means protecting people, environments and processes before more serious consequences occur.

In an industrial context that is increasingly automated and interconnected, safety cannot be left to chance or tackled reactively. It is not simply a question of adding one more device, but of adopting a proactive, intelligent approach in which technology, data and automation work together to ensure the highest standards of efficiency and safety. This has been our method since our founding in 2012: design by thinking ahead, because true reliability stems from the ability to prevent, not just to react.

Bibliografia

^{[1] https://www.figarosensor.com/product/feature/lithiumionbattery.html}