How to make an alternative to a quantum pack from Ken Rockwell.com:
Wedding photographers carry fat external batteries for fast recycling and tons of shots. The SB-800 has a socket for this. The SB-800 even has a bizarre external single AA holder which lets you use odd sets of 5-AA cells for somewhat faster recycling compared to just using the 4 internal cells (It seems weird to me: my sets and charger come in 4s, not 5s.) Other companies like Quantum make big external batteries that plug right into the SB800 while the SB600 has no such connection. In the old days we just rigged up our own connections to flashes, usually with wooden dowels the size of AA batteries and thumb tacks, and used a 6V gel-cell around our waists. Personally I just swap alternating sets of Ni-MH AAs and I'm happy.