Alert Bouncing off Long Term Support, page-18

here is an excellent research piece on the effect and payback periods on batteries... this one is not grid scale - but it uses Tesla hardware - which is all modular anyway... so one could conclude the bigger the density - the bigger the potential for scale discounts and benefits. It also means that if an individual power pack fails... the whole system does not go down... the faulty item is simply removed and replaced... or the system as a whole just operates with a smaller total capacity.

https://sustainability.uq.edu.au/files/11868/EPBQtyRptq12020.pdf

Well worth the read if you have the time... or you can skip to near the end of the document where they compare the cost/Mw vs Wivanhoe PH setup...

TLDR... batteries are profitable... short payback periods and rapidly deployable.

Use of transmission lines such as Liddell would lead to AGL being able to get large scale batteries deployed into the grid in a remarkably short period of time.... Moss Landing (in the USA) will eventually be able to supply

The largest currently planned battery in the world will eventually be able to supply 1500mw for 4 hours (1500/6000)

https://reneweconomy.com.au/australias-tesla-big-battery-is-no-longer-biggest-battery-in-the-world-30125/

Four hours seems to be the current expected ceiling of batteries ... any supply needed longer than this and you need to look to pumped hydro ~8-12 hours or gas firming to fill the gaps in renewable supply.