Generally a fuse should protect the whole circuit from shorting to the frame, so close to the battery and before the switch is best. As long as your wire and switch are rated for the amps you don't need a relay. (eg, a 10 amp switch and #14 wire should be heavy and physically robust enough for this small of a load. You could probably go smaller but won't save much money.
Originally Posted by max384
Sanjoh, I got your lights in yesterday (Holy crap! FAST shipping. I ordered Thursday afternoon and they arrived at my door on Saturday with standard shipping selected!). I went to install them and realized automotive wiring is definitely not my thing. I want to wire them independent of any of the headlights so that I can flip them on and off regardless of whether the high or low beams are on or whether the keys are on, etc.
In my simplistic mind, it makes sense that I can just add an inline fuse and switch to the hot wire and just run the negative wire to the negative terminal of the battery. Here is a quick diagram of my proposed wiring plan:
Would I need a relay or a voltage regulator or anything? Is that diagram complete crap?
If anyone else has my answer, please feel free to jump in. This isn't just directed toward Sanjoh.