I have a Quantum I battery with module for an old Minolta flash. I use it now with my Nikon SB800.
The SD800 is now customized to hold the module in place. Looks neater than Quantum's SB800 module for a small fraction of the price.
I use them on all 3 of my SB-800 units. If it was possible to mount two of these on one flash, I would buy more! Best if you want to make the flash recycle faster, and of course take a more photos.