.South Australia had (maybe still has) the "world's largest battery" (installed by Tesla | Musk) which is an integral part of the SA state power grid that carries it through night times with no wind . . .

If there's "a major grid outage" no large scale battery (or gas fired plant or coal fired plant, etc) will prevent blackout .. as there is "a major grid outage" preventing power from being delivered.

Individual homes would be left to do what individual Australian homes do during bush fires, floods, tree falls, etc and turn to gas lanterns, home generators, and any community hubs that feed local rooftop solar through a local small scale battery (not common as yet, but they're about and increasingly so).