Tesla has finished installing the world's biggest lithium-ion battery array within 100 days of signing a contract for the project.

The 100-megawatt battery ain South Australia is designed to provide security to the state's electricity grid. It will store enough energy to power 30,000 homes for about an hour, connected to a wind farm run by French renewable energy company Neoen. According to reports, Tesla used Samsung battery cells.

Tesla's chief executive Elon Musk had said the battery would be free if it was not installed within 100 days. It appears the company will meet the 1 December installation deadline.

The state will have the right to use the battery array's entire output to avoid "load shedding" blackouts - when power demand outstrips supply.