The Fire Started in the Cooling Loop: A Storage Safety Lesson
Some lessons arrive as statistics. This one arrived as a fire that burned for four days. On 30 July 2021, Australia's largest battery energy storage project — the Victorian Big Battery near Geelong — caught fire during commissioning. News reports and the official investigation pieced together what happened. One container was fully involved. Thirteen tonnes of lithium cells burned. Two containers were lost. The fire took four days to contain, with the site evacuated and, thankfully, no one hurt. The most probable root cause, per the investigation: a leak inside the container's cooling system led to a short circuit. The short ignited electronics. Local overheating then drove thermal runaway through the adjacent cells, and from there into the neighbouring container.
Read that sequence again, because the industry did, and it changed procurement meetings afterwards. The cells were not the instigator. The wiring was not the instigator. The event began with the fluid that runs between the cells — a heat transfer fluid doing an ordinary job on a hot afternoon. At Glacier Coolant we build industrial coolant for exactly these circuits, and this event is the reason our storage conversations start with the fluid, not the price list.
The chain, step by step
Safety failures in battery storage are chains, and this one is worth walking slowly, because every step is a design question.
| Step in the chain | What happened | The question it should have triggered |
|---|---|---|
| Leak inside the cooling system | Fluid escaped its circuit within the container | What limits the consequence when our coolant escapes? |
| Short circuit | Fluid reached energized electronics | How conductive is our fluid at that moment? |
| Ignition of electronic components | Local fire inside the enclosure | What burns, and what feeds the fire? |
| Local overheating | Heat accumulated faster than it spread | Would stable cooling have contained it? |
| Thermal runaway | Neighbouring cells cooked off in sequence | — |
| Spread to the next container | Fire crossed the container boundary | — |
The fluid sits at the very top of that table. It is the quietest component in the container. It is also the one that travelled farthest from its design intent in that fire. Everything below it happened after the fluid went where it should not have gone. Everything below it happened after the fluid went where it should not have gone. Stop the fluid, and the chain has no first link. That is why coolant choice in battery storage is a safety engineering decision, not a maintenance line item. Our industry reached that conclusion slowly, and paid for the delay. The correction is cheap by comparison. It is a specification line, written before delivery, and kept honest by monitoring afterward. Nothing on that list is exotic. All of it was available in 2021. All of it is available now. The difference between the two years is only whether anyone asks for it in writing. Procurement asks. Engineering checks. The container runs cool for fifteen years. That is the whole program, and it fits on one page of a tender.
Why storage coolant is a harder duty than it looks
A battery container asks more of an industrial coolant than most industrial loops. Four reasons, each of which became a formal requirement in procurement specs written after 2021.
First, the metal list. Battery compartments pack copper busbars, aluminium structures, stainless circuits and cast components into tight quarters. Two dissimilar metals sharing one electrolyte form a galvanic pair; the fluid must be chemically calm toward all of them at once. The corrosion behaviour of a candidate fluid on each metal family belongs in its datasheet, not in a verbal assurance.
Second, the service life. Storage plants are designed for fifteen to twenty years. The fluid must remain chemically stable across that horizon. The specific risk is oxidation at raised temperature. Glycol-based fluids oxidize faster as temperature rises. Acidity climbs. Corrosive by-products accumulate. A coolant that drifts acidic in year eight is a slow leak factory.
Third, the seals. Every joint in the cooling circuit — and there are many inside a container — relies on elastomers such as EPDM, silicone rubber and FKM. A coolant that swells, hardens or extracts from those materials manufactures its own leaks over time. Seal compatibility is therefore a coolant property, verified by testing, not a mechanical contractor's afterthought.
Fourth, visibility. Conductivity, pH and concentration are the fluid's core readings. If they are not monitored, the first sign of trouble is the kind of event this article opened with. Online monitoring of the loop is the cheapest fire-prevention hardware in the building.
These four requirements are written out as acceptance tests in our energy-storage coolant spec, which pairs with this piece as the operating checklist.
What a safer fill looks like
The lesson, translated into a fill decision: choose a coolant engineered for the container, from a supplier who can prove behaviour on your metal list, your seals, and your service horizon.
Glacier Coolant has formulated industrial coolant and secondary refrigerants since 1994. The chemistry behind our storage-relevant products rests on the M3 super-film rust inhibition technology, which forms and maintains protective films across mixed metals, and the Modify2000 compounding technology, which tunes packages to the actual duty. The Box7 full-scope test method verifies a candidate fluid against the container's conditions before delivery — metals, temperatures, and seal materials together, because that is how the loop actually lives. Metals, temperatures and seals are checked together rather than one at a time; a fluid can pass a single-property test and still fail the container. Thirty-plus invention patents and four thousand customers stand behind those methods, but the argument that matters here is simpler: the fluid should be chosen the way the fire investigation reads — starting at the top of the chain, where the fluid sits.
| Procurement line | The question behind it |
|---|---|
| Corrosion data per metal | What proof exists for copper, aluminium, steel in this fluid? |
| Oxidative stability at temperature | What happens to acidity in year eight? |
| Seal compatibility table | EPDM, silicone, FKM — tested, for how long, with what result? |
| Conductivity starting point and band | What is the consequence if this fluid reaches a busbar? |
| Monitoring plan | Who watches conductivity, pH and concentration, and how often? |
The wider context: heat management in storage
Coolant is not the only thermal technology in the storage yard. Phase change materials cooling appears in adjacent designs, absorbing heat at fixed temperatures to buffer excursions, and thermal energy storage applications use similar media at grid scale. These approaches complement liquid cooling rather than replace it; the container loop remains the front line, and the fluid in that loop remains the component with a failure chain attached. Evaluating a coolant supplier with the same rigour as a cell supplier is the practical takeaway — a process we have written up as a checklist in our supplier evaluation.
Three sentences to add to your next specification
The lessons compress well. If a storage project takes one page from this editorial, it should be these three specification sentences.
| Sentence | What it closes |
|---|---|
| "Coolant shall document corrosion behaviour for every metal in the container." | Verbal assurances on mixed metals |
| "Coolant conductivity and pH shall carry supplier-defined warning lines." | Silent drift toward the leak scenario |
| "Coolant shall state its behaviour on EPDM, VMQ and FKM seals." | Leaks the fluid itself manufactures |
None of the three costs money at the specification stage. All three cost dearly to add after an incident review. That asymmetry is the fire's real tuition, paid once in 2021 and available to every project since at the price of one page.
FAQ
What caused the Victorian Big Battery fire?
Per the official investigation reported at the time, the most probable root cause was a leak inside one container's cooling system, which caused a short circuit, ignited electronic components, and drove thermal runaway through adjacent cells. Two containers burned over four days; the site was safely evacuated.
Why is battery coolant a safety item?
Because the coolant circulates near live electrical components and flammable cells. If it escapes the circuit, its conductivity determines the short-circuit risk, and its behaviour determines what feeds or limits a fire. Fluid choice is therefore part of the fire safety design, not just maintenance.
What coolant is used in battery energy storage?
Water-based inhibited glycol fluids are common in container cooling circuits, chosen for freeze protection and heat transfer. The differentiating factors are multi-metal corrosion protection, long-life chemical stability, seal compatibility and a defined conductivity band.
How does a coolant leak start a battery fire?
Escaped fluid can bridge energized electronics, creating a short. The short generates intense local heat; adjacent cells heat beyond their safe window and enter thermal runaway, which then propagates cell to cell and, as seen in 2021, container to container.
What should I ask a coolant supplier for a storage project?
Corrosion data on your exact metal list, oxidative stability documentation at your operating temperatures, seal compatibility results for EPDM, silicone and FKM, the conductivity starting point and its rationale, and a monitoring plan for conductivity, pH and concentration.
How often should storage loop coolant be tested?
Continuously for conductivity and pH where instrumentation allows, with scheduled laboratory checks for concentration, inhibitor residual and appearance. Any top-up or repair event should trigger a sample.
Does coolant quality affect insurance and compliance?
It increasingly does. Fire investigations now trace root causes to component level, and a documented fluid specification with monitoring records is evidence of engineering control. Undocumented coolant is an unpriced liability.
What is the single most important fluid property for storage safety?
No single property carries it. The safety case rests on the combination: low, stable conductivity for leak consequence; multi-metal film protection to prevent the corrosion that creates leaks; and long-life chemistry so the fluid does not become the hazard over a fifteen-year horizon.
Ask for the acceptance sheet
Send us your container's metal and seal list plus the design service life. We will return a storage coolant acceptance sheet built on the four requirements above, with the data behind each line. The product collection is the starting catalogue, and the four acceptance tests are the operating companion to this piece.