My weekend project is now complete, and I now have three “high capacity” battery packs for my Vivitar 285HV speed lights. The project was started mainly in a quest for faster recycle times without resorting to AC power, or the use of the HV port (which is conveniently broken on all three of my 285s). Not having to worry about batteries running too low was a secondary concern. With everything said and done, the secondary is the only thing actually achieved. Recycle time with a 6V 4Ah SLA battery is identical to the recycle time with four 2700mAh AAs at full power. I can, however, fire off full power flashes long after the AAs are dead, and that is certainly useful. At 1/4 or 1/16 power, the recycle is a little faster after maybe 5 or 6 consecutive flashes, but for those first 5 or 6 flashes the AAs keep up just as well.
All in all, it feels like I wasted time and money on this project. Being able to shoot more is useful in limited circumstances, but typically I know what I want to shoot, set up, shoot it, and move on. On the bright side of things, the packs are pretty heavy so at least I can use them to keep my light stands anchored. At some point, I’ll end up buying some AlienBees and everything else required to take them out and about. Until then, I’ll use my power packs with my 285HVs and do what I do.