New transformer in works for Australia’s most powerful battery, but return to full service pushed out again

The catastrophic failure of one of the transformers at the Waratah Super Battery in New South Wales last year was triggered by a “significant internal fault” that led to the rupture of the tank wall, a new update has revealed – although the cause of that fault is still being investigated.

In an update on the status of the most powerful battery in Australia, and quite likely the world, owner Akaysha Energy revealed it is likely to continue to limp along at around half of its promised capacity for most of the year, with delivery of a replacement transformer expected in the second half of 2026.

The transformer failed in mid-October 2025, just as the 850 megawatt (MW), 1680 megawatt-hour (MWh) facility, located at the site of a former coal-fired generator at Munmorah on the NSW central coast, was preparing to complete the last of its “hold point” tests ahead of full commissioning.

The huge battery had already been delayed by up to at least six months due to a series of events – mostly blamed on bad weather, according to public pronouncements by its owner Akaysha Energy.

In its update on Wednesday, Akaysha says delivery of the replacement transformer is now scheduled for sometime in the third quarter of 2026, with the manufacturer, Wilson Transformer Company, having kicked off production after securing the necessary long-lead items required for the build.

Until then, the Waratah Super Battery continues to operate with just one transformer in service, with a second transformer also remaining offline as a precautionary measure.

Remediation of the second transformer will be incorporated into a “defined program of work” to ensure all three transformers are operational at the site later in 2026, the company says.

In terms of its System Integrity Protection Scheme (SIPS) obligations – Waratah is contracted to act as a kind of giant “shock absorber” to smooth the impact of any network events – the battery is operating at about half of its promised capacity, at 350MW (740 MWh), with the remaining capacity scheduled to come online by the end of 2026.

“The original HVT3 transformer experienced a significant internal fault, resulting in damage to the windings and an overpressure event,” the Akaysha update says.

“This overpressure led to the rupture of the tank wall near the base, causing the transformer to self-drain into the surrounding (bunded) area. Investigations into the cause of this fault are ongoing.”

The company says a detailed design review process for the new transformer, completed by the Super Battery’s contractor Consolidated Power Projects and Wilson Transformer Company, alongside other consultants, has confirmed that the design of the new transformer meets requirements.

“The previous decision to engage an Australian-based transformer manufacturer has enabled Akaysha Energy to expedite the investigation, site works and replacement programs,” it said on Wednesday.

“This approach has facilitated immediate engineering engagement, a strong on-site presence, and rapid mobilisation of manufacturing resources.”

Akaysha says it will continue to provide updates on the project’s progress.

In the meantime, the battery is still regularly being called into action by the Australian Energy Market Operator to prevent blackouts when NSW electricity demand surges or its ageing coal-fired power generators drop out of the mix.

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