Fire in battery unit during commissioning at Victorian Big Battery, Moorabool

In July 2021, during initial testing and commissioning of the Victorian Big Battery, a large grid-scale lithium-ion battery energy storage facility at Moorabool, near Geelong, Victoria, Australia, operated and owned by Neoen with battery units manufactured and integrated by Tesla, a fire began within one containerised battery unit. Smoke was first observed mid-morning. The fire spread to one adjacent unit before further propagation was halted. The affected units were allowed to burn out, consistent with manufacturer emergency response guidance, while surrounding equipment was protected, and the site was not declared under control until 2 August 2021, three days after the fire began. No injuries were reported. State fire services attended in strength, with reports of more than 30 appliances and around 150 firefighters on scene. A 25 metre perimeter was established and hose lines were used for exposure protection of adjacent battery units and transformers. Two of the site's 212 Megapack units were destroyed. An independent technical investigation was commissioned and its findings were published.

According to the published independent technical findings, the most likely root cause was a leak within the liquid cooling system of the first unit, which led to arcing in the power electronics associated with the battery modules and then to thermal runaway and fire. The report identified two significant contributory factors. First, the SCADA system required around 24 hours to establish full telemetry mapping for newly installed units, and the affected unit had been in service for only about 13 hours before being switched off at its keylock switch on the morning of the fire, so real-time monitoring data was not available to remote operators. Second, the keylock service-mode setting had disabled certain monitoring and protection functions that could otherwise have detected the fault. The report indicated that, absent these factors, the initial cooling system fault may have been detected and interrupted before it escalated.

1. Treat cooling system integrity as a safety critical boundary and carry out pressure testing and physical inspection of every liquid cooling circuit after installation and before energisation.
2. Do not energise newly installed units until telemetry mapping and alarm handling are verified as fully active, since multi-hour SCADA mapping latency during commissioning creates a monitoring gap.
3. Review service-mode and keylock arrangements so that essential alarms and protection functions remain active when a unit is placed in service mode, avoiding a period with no effective monitoring.
4. Following the investigation, the equipment manufacturer reported firmware, hardware and procedural changes including improved coolant inspection during assembly, additional coolant leak alarms, redesigned thermally insulated steel vent shields, and a battery module isolation loss alarm that removes affected modules from service; operators can ask suppliers whether equivalent measures are in place on their fleets.
5. Agree emergency response arrangements with local fire services before energisation, including whether a defensive strategy of allowing a unit to burn out while protecting adjacent assets is appropriate, and confirm the exclusion perimeter and water supply needed for exposure protection.

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