South Australia’s big Tesla grid battery is being taken to court by the Australian Energy Regulator (AER) after failing to provide grid stability measures despite being obligated to do so. Known officially as the Hornsdale Power Reserve, the 150 Megawatt (MW), 77 minute grid battery built by Tesla was the largest in the world at the time of construction. However, AER has instituted proceedings against the battery’s owner after the Australian Energy Market Operator (AEMO) alleged the Tesla big battery failed to ensure frequency control between July and November 2019. Maintaining grid frequency is a critical requirement in ensuring energy supply and stability, but almost all batteries are unable to perform this function due to technical limitations. This means that should frequency have dropped during this period, the battery would have been unable to support the grid potentially resulting in energy instability and blackouts. “It is vital that generators do …