Elon Musk's Tesla battery in South Australia's Mid-North will no longer be the world's most powerful — with a new, bigger battery being built at Port Augusta.

Jay Weatherill at the launch of the Tesla lithium ion battery in December. ( ABC News: Nick Harmsen )

The new battery will be built by Whyalla steelworks owner Sanjeev Gupta, who secured a $10 million loan from the State Government through its Renewable Technology Fund.

The British billionaire, who purchased the steelworks last year though his company Liberty House, also bought a controlling stake in South Australian renewable firm Zen Energy — creating SIMEC Zen Energy.

The 120 megawatts/140 megawatt hours storage facility is larger than the 100MW/129MWh battery built by Tesla in Jamestown last year.

It will support the new solar farm being built at the Whyalla steelworks and will create up to 100 jobs during construction, which will begin later this year.

Premier Jay Weatherill said it would also benefit the broader South Australian community.

"We know that more renewable energy means cheaper power, and that's why we have increased our renewable energy target to 75 per cent and also introduced a new renewable storage target of 25 per cent," Mr Weatherill said.

"These targets will accelerate the transition from fossil fuels to renewables and lower bills for South Australians."

Mr Weatherill spruiked Labor's commitment over the past 12 months to fixing South Australia's energy problems.

"We cannot turn back, the momentum is growing. Here we are ending the campaign, two billionaires duking out who is going to have the biggest battery here in South Australia," he said.

"There are plenty more of those deals to be done and plenty more companies to attract to South Australia."

Mr Weatherill saved the announcement for the last day of campaigning with South Australians taking to the polls on Saturday morning.

Money for the latest battery was committed by the State Government prior to caretaker period, meaning the funding will not be contingent on the election result.

Tesla launched its battery last year after Elon Musk promised to build it "in 100 days or it's free".