JJC FB Series Compact Battery Pack for CANON Flashes JJC FB-1(II) replaces CANON CP-E4. Compatible: CANON 580EX,580EXII flash It has a total capacity to hold 8 AA batteries. It can be used with any type AA battery. Total minimum flash recycling time can be as fast as 1.5 seconds when used with AA Ni-MH batteries, and the capacity per round of batteries is about doubled. Batteries must be in place in the flash in order to operate.