The world’s largest lithium ion battery system is delivering power in South Australia. This Tesla ‘Powerpack’ system stores energy generated by a nearby wind farm, and it is capable of providing electricity for as many as 30,000 homes. It is three times more powerful than any other battery in existence. Activating this massive system fulfils a bold pledge by Tesla CEO Elon Musk who said that he would finish building the battery within 100 days or provide it for free. Musk made his risky vow on Twitter during an exchange with an Australian billionaire who was sceptical of the project. As it turned out the batteries were operating within just 75 days.