[RE-wrenches] How much Li battery?

[Mark Frye]

In the way back machine I remember being at a product roll out meeting 
for the brand new Outback FX inverter. I asked the engineer, what was 
the smallest battery bank that could be connected to the inverter. He 
said on the fly that probably you would want the battery to "weight" at 
least as much as the inverter. I thought that was a great answer.

Fast forward, with a 4000w Outback Radian, AC coupled with 2000w of PV, 
what is the smallest Li battery I would want for stable operation?

My loads don't really need more than 40ah of capacity.

What is the latest best practice on this?

Thanks.