A Tesla Megapack in Moss Landing, California

Andrew Evers | CNBC

Renewable energy giant Neoen plans to turn its Tesla megapacks back on this week in the Victorian Big Battery in southeast Australia after a fire at the energy storage site occurred in late July.

Victoria’s Electricity, Gas and Pipeline Safety Regulatory Authority has given Neoen and Tesla permission to “re-energize the Victorian Big Battery,” Neoen said in a statement emailed Monday.

The Victorian Big Battery is owned and operated by Neoen and is one of the world’s largest energy storage systems. It is intended to help avoid power outages in the region and to supply households with electricity from renewable energy sources such as sun and wind.

Paris-based Neoen developed the site with partners such as Tesla Energy and AusNet, with some parts built by Cimic Group’s UGL. Tesla has not disclosed its suppliers for the project or what types of battery cells it used in the megapacks, which are lithium-ion battery-based storage systems.

Tesla did not immediately respond to a request for comment.

The fire at the battery site in Geelong, Victoria, occurred on July 30th. Two Tesla megapacks went up in flames in the 300 megawatt (450 megawatt hours) facility. No casualties were reported, but the fire set off an alarm for toxic air in surrounding neighborhoods.

About 150 firefighters from the Country Fire Authority and the local Fire Rescue Victoria, along with dozens of fire trucks and rescue vehicles and drones to monitor the temperatures of the two affected Tesla Megapacks, were called in to fight fires. Flames did not spread to the other mega-packs of about 210 that make up the system.

Elon Musk speaks for Tesla at Hornsdale wind farms, Australia

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On August 1, two days after the outbreak, the firefighters stopped using water on site. The facility was declared under control on the afternoon of August 2nd.

The Country Fire Authority, WorkSafe Victoria, Energy Safe Victoria and the Environment Protection Authority then asked Neoen and Tesla to suspend some operations in Geelong so they could conduct parallel investigations.

Next Steps

Neoen expects the results of a full, independent investigation – conducted by the Energy Safety Response Group and Fisher Engineering – to be released to the public in November.

“The cause of the fire was identified by short circuits in two specific places, which were probably triggered by a coolant leak outside the battery compartment,” said the spokesman. “These occurred while the Megapack was offline in a service mode that removed the fault protection. This improbable sequence of events meant that the fault could go undetected and cause a fire in the adjacent battery compartment.”

Neoen also said that Tesla took “mitigating measures” after the companies conducted a root cause analysis, adding that Tesla is making changes to its Megapack firmware and monitoring

The system is scheduled to be switched on again from September 29 for test purposes in order to prepare the large battery for commercial operation until the start of the Australian summer season in December.

Neoen and Tesla are under pressure to keep Australian regulators happy for their joint work in a separate location. Last week, the Australian Energy Regulator (AER) sued Neoen, saying that another large Tesla battery it was developing, the Hornsdale Power Reserve, failed to provide backup power as expected during a four-month period in 2019 that it was paid for.

SEE: In Tesla’s Megapack system