Adelaide, Australia — The world's biggest lithium-ion battery has plugged into an Australian state grid, an official said Friday, easily delivering on Tesla Inc. chief executive Elon Musk's 100-day guarantee.Musk promised to build the 100-megawatt battery within 100 days of the contracts being signed at the end of September or hand it over to the South Australia state government for free.South Australia Premier Jay Weatherill announced on Friday the battery began dispatching power into the state grid on Thursday afternoon, providing 70MW as temperatures rose above 30°C."South Australia is now leading the world in dispatchable renewable energy, delivered to homes and businesses 24/7," Weatherill said.The official launch came a little over 60 days after the deal was signed. But crucially, it came on the first day of the Australian summer — the season when power usage soars due to air conditioning use.Tesla says the battery has the capacity to power 30 000 homes for up to an hour in the event of a severe blackout, but is more likely to be called into action to boost supply during peak demand periods.The battery power packs are installed near the Outback town of Jamestown, about 200 km north of the state capital Adelaide. They store energy generated by the neighbouring Hornsdale Wind Farm, owned by French renewable energy company Neoen, to bring added reliability and stability to the state grid.Tesla partnered with Neoen to build the battery, which is more than three times larger than the previous record-holder at Mira Loma, California.The Tesla 100 MW/129 MWh Powerpack system in the rural town of Jamestown, 200km north of Adelaide. (Handout, Neoen via AFP)South Australia, which relies heavily on solar and wind-generated energy, has been scrambling to find a way to bolster its fragile power grid since the entire state suffered a blackout during a storm last year. Further blackouts plagued the state over the next few months.The battery farm is part of a 550 million Australian dollar ($420 million) plan announced in March by Weatherill to make the state independent of the nation's power grid. The cost of the battery has not been made public.The Australian grid operator has warned of potential shortages of gas-fired electricity across southeast Australia by late next year. The shortage is looming as Australia is expected to soon overtake Qatar as the world's biggest exporter of liquid natural gas. Australia is also a major exporter of coal, which fires much of its electricity generation and makes the country one of the world's worst greenhouse gas polluters on a per capita basis.