Um, why are you setting the CF12 to external only? It should be left at "0". [assuming you are using batteries in the 580 as well] It will automatically draw/add the external power to the onboard power.
By setting it to 1 you only use the external pack to refresh, and the in-flash batteries are only for controlling the flash electronics, not flash output which is more power-consuming. That way it's less likely you'll have to change the internal batteries at all--less hassle when in the middle of a shoot.





