This Dyna-Lite product is best suited for powering small on-camera flash units. Not the Uni 400 jr. that is packaged with this battery. The battery does not have any fail-safe mechanism to keep it from overheating and it's just not powerful enough for the Uni 400 Jr. flash head. I have 5 or 6 of these batteries and everyone of them has fried on a shoot at one time or another. We had one explode on a shoot yesterday (11/6/08) complete with a firecracker sound and smoke. Dyna-Lite doesn't offer up any solutions or fixes.[$] I can't recommend this product unless you are fond of high drama on photo shoots.
This thing has amazing recycle times with shoe mounts, even with handle mounts much faster than Q Turbo. Unfortunately, the first generation JR battery always burns itself out (literally), I hope this one is better.