I have a D700 and a MB-D10 grip.
I have put 8 fully charged Eneloop rechargeable AAs (1.2V) in the grip, 8 new alkaline AAs (1.5V) in the grip and a fully charged EN-EL3e battery in the grip. The number of fps stays at 5 in all three cases.
I have contacted Nikon Support about this but they keep saying all of the above methods will yield 8 fps.
I've watched some YouTube videos that say using a Nikon EN-EL4 battery (with a special adapter) will boost the fps to 8. Nikon Support did not comment on this idea.
Any thoughts or suggestions on this topic?