They don't mention that 4, 6, 8 strings of 2200- to 4500-AH wet batteries can dump a few million amps into a short - and then you add in 4, 6, 8 -54V 400A Float Chargers running. (We'll ignore the End Cells, that's only 6V)
Which is why You Don't Make A Short.
As you crawl into the Live Front Panelboard to add another 600A circuit with 4) 750MCM THHN in parallel - Gee, why do you have multiple layers of pressboard, cardboard and Rubber Blankets? Almost looks like you built a tunnel in there...
Do COE Power for the Phone Company, that'll teach you some respect for "Only DC."