Scrap of the Soul Cloak: "Restore 7% max Supercharge after using a Supercharge ability. This does not stack with Extended Supercharge Tactical Mod." It does stack with the "Extended Supercharge Tactical Mod" (Helmet, Home Turf Mod)
There is no "Extended Supercharge" head mod. The description of the artifact refers to the "Extended Supercharge" CHEST mod, which doesnt stack. The "supercharged" head mods are not the same thing as the "Extended Supercharge" chest mod. You gotta be sure to read desciptions carefully or mistakes will be made.