Alternator Wiring with Kill Switch
I guess you haven't looked at modern cars, lately LOL. Relays everywhere. Most certainly in the ignition, charging, fuel system.
But yes, they do fail too.Your talking modern street cars, not drag race cars. If you need a batt. cut of, then most likely it is a drag car....Simpler, the better.
I have lots of relays, my fans run on thermos's with relays, different ones for different temps. My back up lights and trans brake, back the car up via reverse light switch in the shifter via relays, even though the reverse lights don't come on when the transbrake engages. Think about wiring that up for a min. My car is full electronics. I even get more exotic then that......Have you worked on a 2 million dollar RV wiring?...You want to talk about relays....LOL
I never touch a switch, or need to remember to tur a switch on when racing.
I would never interrupt my ignition, with a relay.....Have wired at least a 100 cars for street and race both...Who knows how many motorhomes I have had to straighten out.
Back to the original question...Just install a 4 post battery disconnect capable of the amp rating of your alternator, ignore all the other postings including mine!...