I had to throw away a couple of rechargeable Energizer 2500mAh AA batteries that I used in my SB800 speedlight. Below are the two batteries I threw away. Notice the white blotches on the side wall of the batteries and white powder residues on the edge of the negative terminal. I don't know what caused the white blotches and the residue -- the negative terminal is made of one piece, like those pressed aluminum cans of Coke, so it's not like something leaked out. In any case, I threw these two batteries away and bought some new Duracell 2000mAh Pre-Charged rechargeables. These Duracell rechargeables behave like the Sanyo Eneloop rechargeables in that they will maintain 80% of their charge for up to a year, unlike normal rechargeable batteries.
Just to be clear ... you should not mix the different types of batteries when used in the speedlight. I will keep the Energizer set separate from the Duracell set.
For more information on the Duracell Pre-Charged Rechargeables:
http://www.duracell.com/en-US/product/pre-charged-rechargeable-batteries.jspx
