Hey i have a system that uses a large amount of power, in my last car i had my main battery that ran to a relay, the relay was grounded at one point and the other point went to the ignition or something. Then from the relay it ran to a second battery and then to my amps. I bought the relay in order to have current flowing through it between batteries with the car running, but not flowing when it is sitting off with the key in so i can listen to music off the back battery and not pulling from the engine battery. My question is, where do i wire the ignition side of the relay to? Obviously the ignition, but last time i was thinking i could wire it to a switch turning it on and off myself. but that sounds kind of annoying. I drive a 97 toyota 4runner, curious where i wire this ignition side to? I attached a picture its simple really. I just dont know if there is a certain part of the ignition or really how it works at all... I just want current to flow when the engine is running and that is it. This might be a battery isolator? Much of a difference? Thanks hope to hear back.

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if you wanna do it manually, just wire a switch to a +12 volt source.

if you wanna do it automatically, i have just about hacked my radio wiring harness to tap everything easily.

from lights, to ACCESS to ON to everything you need is laid out easily at the that harness...

 

what are the specs of the system? and what electrical upgrades do you have if any? also what kind of car did the system come out of? I only ask these questions because running more than one battery is rarely the proper solution unless it's a strickly comp. system.
I know I didn't answer your question, but if you answer mine I can be of more help