Nikon SD-800 Extra Battery Holder for SB-800 Flashgun
The SD-800 adds a fifth AA battery to the
flash. The SB-800 is designed to operate upon 6 volts of power, which is the
output of 4 alkaline batteries. NiMh batteries, however, have a lower specified
voltage which ideally requires 5 units to deliver ideal voltage to the SB-800.
For more information about, Nikon SD800 SD-800 Extra Battery Holder for SB-800 Flashgun .
Customer Reviews on Nikon SD800 SD-800 Extra Battery Holder for SB-800 Flashgun
Review by Sevket Gumustekin, 17/11/2011, Customer Rating:

Very usefull when you use 1.2V rechargeble batteries. 4 of them don't last long.
Review by Mike Rushworth, 09/03/2011, Customer Rating:

Fast and efficient service. Just what's needed. I shall use you again.