Afternoon everyone, I got a call a few days ago from someone who wants to get rid of some old flash equipment, specifically the SunPak 511, 611 and 544. The 511 is an old friend, I carried one of those to all manner of news events. It was big enough and put out enough light to cover most situations. The 611 I always though of as something with a little more kick and some tech upgrades. There are two 511's and one 611 and all three work. The 544's I don't know. The 511 will run on 4 AA batteries and the 611 on some C cells but both also had a separate power back that used the 512 volt battery that sped recycles up considerably. They weren't cheap but very nice to have. I can probably look around and find some factory power packs for these but does anyone still make the 512V battery? The more practical question might be to ask if Quantum or someone else makes a pack that will plug into either of these flashes. I know, they are quite old and there are better current flash units but I plan to use these on the Nikon F2 or a Nikkormat if I get them at all, he's just giving them away so it might be fun. Rick H.