I asked this same question about 4 weeks ago!
1 item you need to resolve. The "+" positive terminals length! The previous rechargable batteries I was using(after-the-fact note) always gave me problems in my 550EX,580 EXII, and Canon ring flashes, both models.
Turns out that those battery manufacturers had reduced the size of the "+" terminal and it was NOT making proper contact with the battery compartment terminal.
I could never figure out why a freshly charged battery drove the associate eqpt nuts! Well it was the above.
Since then I went to ENELOOPS. Not a bit of problem!!
Dan
I always use the 5'th battey option in my SB-800. It prevents me from losing the holder, and I can shoot an entire flash heavy wedding on one set of Eneloops.
