My only problem im running into is that i'm using these on older canon 420EZ flashes...and I think the circruity is f'd in two of them. You swap wooden batteries into one, and they don't work. swap normal batteries in and they work. So for now, i've got two on Battery packs, and the other two on NiMh...I'd like to have everything on battery packs, but for car shoots (as of now) NiMh is perfectly fine. Shooting a few hundred on NiMh at full power i've never run out, just sucks waiting around for them to charge.
NOW, when i have two shoots in a row and don't have time to go charge batteries that's where NiMh suck.
I built the boxes cuz...well hell...it's fun. I could probably swap the fake batteries into my 430ex and use the SLA as an on camera force, but i guess i'm afraid of using it with a $200 flash opposed to a $60 flash...catch my drift?
I'm running into problems now that my flash power isn't enough to light up the cars on a sunny day. I get screwed by the 1/200 sync, shooting iso 100, then shooting aperture around 6.3 or 7.1 to get the light down, then the flashes aren't 'strong' enough to light the car. The way i've been getting around it, is setting the camera into "hdr" mode (whatever it's called) and having the first shot fire the flashes at normal exposure, then the second shot (flashes wont fire) will be darker to catch the sky, then just merge them later in PS. cheezy, but hell it works...I can't overpower the sun yet (need more $ for bees!!)