Fire safety discussions around battery energy storage systems have traditionally focused heavily on what happens once a battery has entered thermal runaway or a fire has started: suppression, containment, preventing propagation and emergency response.
These measures remain essential, but the industry is increasingly looking further upstream, towards warning signs that appear before a failure develops into thermal runaway. For BESS operators, battery manufacturers and companies storing and managing batteries, identifying these conditions earlier creates a valuable window in which a developing problem can be investigated, isolated or cooled before it becomes a much larger safety event.
This isn’t an argument for replacing suppression; it’s about adding an earlier opportunity to intervene.
Thermal runaway isn’t the beginning of the problem
Whilst thermal runaway is the point when battery incidents become much harder to control, it isn’t the point when the underlying problems begin. Battery failures can develop from issues such as internal faults, electrical abnormalities, overheating or other forms of degradation.
Battery management systems and diagnostic tools provide information about what is happening within the battery itself, while external thermal monitoring can add another layer by identifying unusual temperature behaviour around batteries and associated infrastructure. These technologies aren’t alternatives; together, they provide visibility of different aspects of the risk.
Fiber optic distributed temperature sensing adds continuous temperature monitoring across large installations rather than relying on individual detection points, creating another opportunity to identify and investigate abnormal conditions before they escalate.
Detection is only valuable if you can act on the information
In recent conversations with a customer, we’ve learnt how they’re designing a battery system using fiber optic linear heat detection to identify defects and abnormal thermal conditions at the earliest point to prevent fires. Detection isn’t the end of their process; the system incorporates an automated robot to be used to move the affected battery into a designated safe zone once a problem has been identified. The defective battery can then be isolated from surrounding batteries and rapidly cooled to prevent the possibility of thermal runaway.
This shows how early detection can form part of an automated response rather than simply generating an alarm. The sensing technology identifies and locates the abnormality, while integration allows that information to initiate the next response: detect, locate, isolate and cool.
The objective isn’t simply to detect a battery fire faster, but to identify the developing problem early enough to act before there is a fire.
Why precise location matters
Early detection isn’t enough on its own; once abnormal thermal behaviour has been identified, operators (or automated systems) need to know where it’s occurring. This is particularly important in large BESS installations containing significant numbers of cells, modules, racks or containers. A general alarm can tell an operator that something is wrong within an area, but precise localisation makes a much more targeted response possible.
Distributed fiber optic sensing works by sending laser light through an optical fiber and analysing the naturally occurring backscattered light. Changes in that returned signal can be used to calculate temperature along the fiber. Rather than having isolated sensing points, this creates continuous temperature measurement along the sensing cable, with abnormal thermal conditions identified and located along the protected route.
This location information can be passed to fire alarms, control, monitoring or other third-party systems. For our customer’s robotic isolation concept, that becomes particularly important: the system needs to identify the affected battery before it can be physically removed and isolated. Precise localisation therefore supports a faster, targeted response, whether manual or automated.
Prevention doesn’t make suppression redundant
Early thermal detection shouldn’t replace established BESS fire protection measures. Suppression, containment, separation and emergency response remain critical. Standards and testing regimes such as UL 9540A specifically examine thermal runaway fire propagation and provide data that can inform fire and explosion protection strategies. Earlier detection introduces another opportunity to act before those measures become necessary.
Think of the strategy as a progression rather than a choice between prevention and suppression:
Step 1: Identify abnormal behaviour;
Step 2: Determine where it is occurring;
Step 3: Investigate or initiate an automated response;
Step 4: Isolate or cool the affected equipment where appropriate;
Step 5: Continue suppression and containment measures should the situation continue to escalate.
No single technology can address every stage of a developing battery incident. Early thermal detection adds another layer to that wider protection strategy.
From detecting fires to detecting abnormal behaviour
Traditional fire detection is designed to answer a simple question: “Is there evidence of a fire?”. Continuous thermal monitoring opens up a slightly different question: “Is something happening here that shouldn’t be?”
Smart alarm approaches can look beyond a single high-temperature threshold and consider factors such as absolute temperature, rate of temperature rise and deviations from expected thermal conditions. This matters because an abnormal thermal condition doesn’t mean a fire has started. It could instead provide information that warrants investigation before conditions deteriorate further.
Our customer’s robotic isolation concept shows where this could lead: sensing doesn’t sit separately from the response system; it provides information that enables the next action. As BESS installations grow, integration between detection, diagnostics, control systems and physical mitigation measures will become increasingly important. The opportunity is turning earlier, more precise information into action, not faster fire alarms.
The best battery fire is the one that never develops
Suppression will always matter, but by the time it is required, an incident has already reached a more serious stage. Battery diagnostics, BMS data, continuous thermal monitoring and integrated response systems create opportunities to act before that point.
The next development in battery fire safety may not simply be finding better ways to manage thermal runaway, but creating more opportunities to stop developing faults from reaching that stage in the first place.
Explore how Bandweaver’s fiber optic sensing technology enables continuous temperature monitoring and precise localisation across battery and energy infrastructure: https://bandweaver.com/linear-heat-detection/