Nope, just one relay is all that is required. Run the trigger wire from the toggle switch to your hibeam circuit instead of a constant on 12v source.

Wired as shown below, the relay will only be powered on if:
A. The hibeams are on, and:
B. the toggle switch is on.

If you want the light usable regardless of when the hi's or lows are on, connect the switch to another source, like the running lights for instance.



I strongly recommend that wherever you hook the trigger wire up, it is to a source that shuts off with the key, that way you wont accidentally leave the lights on and drain your battery.

 

Actually, I believe using one relay will cause voltage to be back fed into the High Beam fuse and turn on your high beams:


You can avoid this by using a 12 volt diode on the path from the High Beam fuse or you can do this with 2 relays:




I posted this before I saw that Happy posted his drawing... but the logic still applies. The note that he had about using an ignition hot circuit is great advice. There are many places in the fuse box under the hood to do this, just whip out the multimeter.

 

yup, using two sources to the same line would give you issues, that is why i used the highbeam power with an inline switch as the trigger. Seemed like the simplest setup to me and used what i already had in the light kit.



It was that...

or this:

 

that's the first schematic i posted.

 

Since my google products search for thermonuclear particle decay machine did not return any results, i'll have to stick to the battery... for now. Thanks for the info.. i'm gonna order up the KC's as soon as my tax return shows up in my account.