The Canon Compact Battery Pack CP-E4 is a compact, lightweight, external power source designed for use with the Canon 580EX II, 580EX, 550EX, MR-14EX, and MT-24EX Speedlite. When it is connected to the Speedlite, the recycling time is reduced to approximately one-third of the original value, and the number of flashes is increased by approximately three times. (Using alkaline batteries (LR6), connected to 580EX II Speedlite; based on Canon's testing criteria.) If also features the same dust- and water-resistant performance as the EOS-1D series cameras.
Notes: Do not directly attach the Compact Battery Pack CP-E4 to the tripod socket on an EOS DIGITAL camera other than an EOS-1D series camera, attach an optional battery grip to the camer's tripod socket, then attach the Compact Battery Pack CP-E4 to the tripod socket on the battery grip.