The world's largest lithium ion battery has been switched on in South Australia.

The world's largest lithium ion battery promised by Tesla boss Elon Musk has been switched on in South Australia. The battery is designed to ensure a constant power supply to the state during extreme weather events. In Jamestown, north of Adelaide, the world's largest lithium ion battery is officially up and running. Built at South Australia's Hornsdale Wind Farm, the Tesla energy storage system was launched on Friday - more than a month ahead of deadline. South Australian Premier Jay Weatherill unveil the giant battery.

Largest lithium-ion battery launch in SA Source: AAP