electricalforum.nz

What are others thoughts in following AS/NZS 5139:2019- Electrical Installations-Safety of battery systems for use with power conversion equipment.
I know this standard is not cited but it appears to be the most up to date information regarding battery systems to follow as a guideline.

Exactly.
So why wouldn't you?
Always a good idea to imagine yourself in Coroner's court trying to answer why readily available guidance wasn't followed.
That scenario puts "no rule saying I have to" into perspective
and if the reason not to follow is mainly cost, then it gives us something to measure the perceived cost against.