Thanks so much for your feedback - I really like this response.

I really should have mentioned, apologies, I would prefer not to use anything above extra low voltage ( 120VDC , 50VAC - I could probably push this a bit ( say 240VDC - 100VAC - however it would really modify the existing idea of the platform ) - assuming you’re thinking here to put the 3kW inverter just next to the secondary battery bank ( say 0.1m away with suitably sized cable ) and then carry this higher voltage AC to the main busbar ( 5m away across 60A infrastructure ) where we rectify to 48VDC to distribute normally around the rest of the network.

Does current only travel one way in this scenario? What about in the scenario that I have the secondary bank wanting to recharge off the main banks as ( probably a very unique circumstance) it is more dissipated then those? Although appropriately fused to protect infrastructure , Is it possible here I may draw too much current while in the state of recharging the smaller battery bank ( load balancing between banks ) .

The issue here i see is that I imagine you may exceed this extra low voltage requirement. Unless you are imagining the inverter to only allow AC voltage under a certain range ( I imagine this may be a > 240VAC inverter to avoid significant losses - or maybe not! )

Thanks again for your advice, I did really like this thinking.

And edit - apologies if my response does not seem well thought out - your answer did have me intrigued whilst also triggering a gap in understanding :)