I have 3 of the Quantum batteries that I use with Sunpak 555's. A bit on the bulky side, but they last much longer than AA batteries. I use them on my 555's all the time, on events and in studio, for background lights, and for main lights when bounced off umbrellas (today's cameras are marvelous at higher ISO's). I'm always on the lookout for these flashes (I have 8 now) and quantum batteries to power them on Craigslist. I place them in various locations throughout the reception with different power settings (that's the best part about these flashes is its ease in setting power ratio's) and they can last all night.
been using 555's forever (well, almost). Used on a 12' Bogen Masterstands and, powered by a Lumedyne megacycler w/ mini battery (2 outputs w/2 strobes) - for Altar Returns) or OLD Lumedyne AC converters (4 outlets w/up to 3 strobes) - at reception site & placed in corners). One could also use a Turbo w/y cord for 2 outlets to power up 2 strobes. Turbo or Megacycler (mini battery) can refresh 2 stobes (one @1/2 pwr, other @ 1/4 pwr.) in less than 2 seconds. The AC converter refresh rate is RIGHT NOW.
