I bought some 350 ma. and 1000 ma. Buck Pucks but haven't had time to test them yet. They are current regulators and they have only a 2 volt overhead if I remember correctly. I plan to make a headlight system using four 3 Watt Luxeons in series through a Buck Puck running off a 14.8V battery. You can simply short out one or two LEDs with a switch if you want high beam/low beam. Led Supply http://www.ledsupply.com/led-drivers-buckpuck.html has them from US$14.99 ea.