Megapack fire at PG&E Elkhorn Battery, Moss Landing, California

In September 2022, a fire occurred in a single Tesla Megapack battery enclosure at the Elkhorn Battery Energy Storage System in Moss Landing, California, United States, owned and operated by Pacific Gas and Electric (PG&E). The site held 256 Megapack units. The fire started in the early hours of the morning. Safety controls automatically disconnected the facility from the grid, as designed. Shelter in place advice was issued to nearby residents while the local fire service attended. The fire was brought under control later the same day and remained confined to the single enclosure, without spreading to neighbouring units. No injuries were reported and there was no interruption to electricity supply to customers. The Elkhorn facility is separate from Vistra Energy's neighbouring Moss Landing Energy Storage Facility.

According to the findings published by PG&E, water entered the affected Megapack because its deflagration vent shield panels had been installed improperly, and that water intrusion led to the thermal event. The investigation found that 88 Megapacks on the site had experienced water intrusion from improperly installed vent shields. All 88 were inspected, damaged parts were replaced and the units were re-tested. PG&E and Tesla reported corrective actions covering the installation of the equipment, monitoring processes and additional automated features.

1. Confirm by test or analysis that the separation distances and enclosure construction used on site will contain a single unit failure without propagation, and record the basis of that conclusion in the site safety case.
2. Verify that automatic disconnection of the facility from the grid on a safety trip operates as designed, and include this in periodic functional testing.
3. Agree a written response plan with the local fire service before energisation, covering access, defensive strategy, water use and shelter in place arrangements for neighbours, and rehearse it.
4. Include physical verification of safety critical components such as vent shields, seals and enclosure covers in post-installation inspection and commissioning sign off, with photographic evidence retained.
5. Assess water ingress paths into enclosures, including rainwater, condensation and fire water, and inspect seals and drainage at defined intervals.
6. Where a defect is found in one unit, treat it as a potential fleet wide condition and plan in advance for an inspection or repair campaign across all identical units, including the spares and outage time this requires.
7. Establish a route for receiving and applying manufacturer design changes, firmware updates and alarm logic revisions, and record which units have been updated.

en.wikipedia.org/wiki/Moss_Landing_Power_Plant