Canon Compact Battery Pack E and Transistor Pack E Set. Canon's Speedlite 540EZ, designed for the Canon EOS-1N/1N RS 35mm AF SLR camera, can be attached with two optional battery packs for faster recycling time, which is useful for professional photographers. These accessories are the Compact Battery Pack E and Transistor Pack E Set. Of course, the 540EZ can be used with any EOS models with or without these two battery packs. But if you need fast recycling for it, these accessories are among the options available, aside from independent makes. Six AA-size alkaline batteries are needed to power the Compact Battery Pack E. Rechargeable AA-size Ni-Cd batteries can also be used. However, lithium AA batteries are not recommended to be used with this external power pack. The newer Compact Battery Pack CP-E2, which is similar to the E version, is designed to accept AA-size lithium batteries. The Compact Battery Pack E is actually a small, light transistor pack with quick-charge and low-voltage quick-firing functions; and can be attached to an EOS body using the tripod fixture supplied. Compact Battery Pack E in its case How it is attached to the 540EZ Basically, the idea of using this optional battery pack is to enable a faster recycling time when shooting events and other functions where successive shots of the required scenes are important. This is the case for many professional photographers who prefer to shoot with either ISO 50, 64 or 100-speed films. Using an ISO 400 or 800 speed film, the need for a faster recycling Speedlite may not be necessary since the illumination given out by the flash is less, thus conserving battery power and allowing the photographer to shoot continuously without waiting for the flash to recycle. The six batteries inside the Compact Battery Pack E are only designed to speed up the recycling time of the Canon Speedlite it is connected to but the said flash unit still needs its own four AA-size batteries to perform the required illumination. If the batteries inside the Speedlite are weak, the recycling time can be affected, too. The same goes for the six units inside the Compact Battery Pack E as any drop in the voltage will also affect the recycling time. The six photos below of Bangkok's China Dolls singing duo were shot with the Speedlite 540EZ with the EOS-1N using the Compact Battery Pack E loaded with alkaline batteries. China Dolls' expressions captured in succession << Back to Main . 1 . 2 . 3 .