I'd just like to say that 18awg is definitely NOT a large enough wire to accommodate 55W headlights. Sure, the wire might be rated to carry 10 amps (which many are not, depends on the wire you have) but wire has to be de-rated for the conditions its used in. You have to take into account voltage drop, ambient temp, wire spacing, etc. I wouldn't run anything smaller than 14awg for anything you're using.