The Lumedyne Mini battery you linked to would need to be combined with a Supercycler to work with your Sunpak (or any other flash you might buy). That battery is part of Lumedynes modular flash system, and the weak point is how the modules fit together, so I'd recommend against it. The HV cyclers are the battery and rapid charging circuit in one package, very similar in concept to Quantum Turbo batteries, but a slightly different design. I've used both the Quantum Turbo system, and Lumedyne Mini battery/Supercycler combo, and I much prefer the Quantum system. I'm not aware of any "cheap" external battery system that will give you full power recycling in 1 sec.
I have no experience with the Sunpak TR-PAKII, and have no idea what one might be worth, or if it can be made to work with other flash brands.
Last edited by Groundloop; 04-11-2008 at 09:42 AM.
Reason: Added information