Originally Posted by
Looigi
You might want to keep in mind that bike lights are usually optimized for efficiency to get the most light and life from a limited size battery. Motor vehicles don't have that limitation so lights designed for them may not necessarily be as efficient.
I don't know about the efficiency, but its been my experience that most automotive headlights like the ones linked tend to start at about 50 watts, and it creates too much drain for the battery I'm willing to carry. Lots of light, but probably more than I need. As a cyclist, I don't have the need to see as far ahead at 15-20mph as a motorist might at 60-70mph.