Elon Musk has announced plans to build the world's largest lithium ion battery in South Australia.

The billionaire entrepreneur and Tesla boss said he the battery would be more than three times the size of the current record holder, speaking at a conference in Adelaide alongside Jay Weatherill, the state's premier.

The battery will be 100 megawatts, more than three times the size of the next largest battery, which is 30 megawatts, according to Musk. It will be able to hold around 129 megawatt hours of power, which Tesla estimates could power 30,000 homes.