Adds a fifth battery to shorten recycle time to as little as 2.9 seconds on full power manual.

The SD-800 Quick Recycling Battery Pack allows for the added use of a fifth AA battery to the SB-800 Speedlight.

The SB-800 is designed to operate on 6v of power, which is the output of four alkaline batteries. 

Because Ni-Mh batteries have a lower voltage, five are required to deliver the ideal voltage to the flash.