I think the idea here is to have one target as “first-come first-serve”, meaning that 6A target would always be fully supplied before other 18A target (IV → LU transformation) are given energy.
Manually this could be done by setting up a Insane Voltage (IV) battery box filled with batteries and and “Energy sensor” cover into it. Running a redstone signal from that cover into “Cover controller” that opens up a “Shutter cover” (connected to same power cable) only if redstone signal is applied could work. This way 6A target (battery box) would always be filled to desired level before any energy would be given to 18A transformation.