I'd suggest using the battery cable connection at the starter as a voltage source for the relays, with a 30 or 40 amp self-resetting circuit breaker inline. In case of a short, the headlights will flicker on and off instead of simply going out like a blown fuse would cause. You definitely DO NOT want an unfused straight battery voltage source with a heavy wire anywhere on the vehicle. That's setting the stage for a vehicle-destroying fire.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!