That is a good point and I don't know enough to answer (if you have any good info sources about this I would appreciate them).

Aside from the Tesla battery in Oz (which is more about stabilization rather than primary supply) I don't know of any large-scale battery storage systems.

I get the feeling that we are ignoring the scaling part here (We Just have to scale-up). Since the battery systems would need to be big enough to cover dips in renewable output in a worst case scenario (brown-outs / black-outs are not going to be popular).

Is there any info on how many / how big / how long to manufacture these batteries and renewables would have to be to cover an example country?