All the high-power LEDs used in bike headlights are designed around Lithium cells as a power source, consequently the LEDs require ~3.7 V for operation.
You should look into these for building lights. Better yet, just buy one ready to use and quit wasting your time with all these novelty 12 V automotive aftermarket LED devices.
Last edited by seeker333; 02-26-12 at 06:17 PM.