SA's giant battery 50 per cent complete

The clock is ticking on entrepreneur Elon Musk's promise to build the world's largest lithium-ion battery in South Australia within 100 days or provide it for free.

But with the facility already half finished, the US billionaire looks set to get paid.

Mr Musk travelled to Jamestown, in SA's mid-north, on Friday where construction of the 100-megawatt battery is well advanced.

The Tesla boss said the South Australian project was an example of how to replace fossil fuels with renewables.

"This is a great example to the rest of the world of what can be done," he said.

"When this is done in just few months, it will be the largest battery installation by a factor of three."

The SA battery will be paired to a neighbouring Neoen Hornsdale Wind Farm to bring added reliability and stability to the state's power supplies.

It is thought to be costing taxpayers about $50 million and forms part of the state government's $550 million energy plan.

Other elements of the energy plan include installing emergency generators at two sites in Adelaide, a push for more gas-fired power generation and a solar-thermal power plant near Port Augusta.

It was prompted by a series of power issues, including a statewide blackout when a freak storm brought down transmission lines a year ago and another event last summer when heavy demand and a lack of electricity flowing through the interconnector with Victoria cut services to thousands of properties.