The external Canon Compact Battery Pack CP-E4 improves flash recycle times significantly and increases the number of firings before batteries need to be replaced.
The pack takes the CPM-E4 rapid-change magazines that can be loaded with 8 AA-size batteries prior to a shoot to ensure fast and smooth transitions from one battery set to the next - important in critical shooting situations or to keep up momentum in the studio.
The updated "E4" version has been improved with better dust and moisture sealing at the contact points, to get it to match the weather-resistance characteristics of the 580EX2 Speedlite.
