
Applies to the 580EX II.
The 580EX was recommended to use a dummy battery in the gun to get the full benefit from the pack ~ was never an aficionado of that myself. The flash flattened its own batteries first but boosted by the pack.
The way I use mine, it's still moreorless the same way and I've found when I run out of juice, simply swap out the batteries from the pack to the gun an away you go again.


I've let it setup whatever way it came, happy out, so have not looked in detail, but the whilst I found the manual incorrect in practice for the 580EX it is configurable and works as stated in the manual for the 580EX II.
Actually, I have a 580 EX II so it is recommended that I can leave regular batteries in the flash unit while the CP-E4 is attached? can you use rechargeable batteries on CP-E4 and regular Alkalines in the 580 EX II or do all batteries have to be the same type (rechargables or alkalines)?