I am installing a second battery into my truck. i have purchased an isolator, 90amps to match my altenator. i have purchased a second battery; a yellow top deep cycle marine life battery. but I don't understand how i'm supposed to actually install it. I've read the directions that came with the isolator and it isn't making to much sense to me. and i've attempted to do research on the internet but i keep reading different things on how to wire up the two batteries, isolator, and altenator. can someone explain what i need to do.

Also i plan to place the second battery and isolator in a metal box and place it within my toolbox, because there is no room in my engine. But i'm concerned they may be overheated. is placing it in my toolbox something to be concerned about?

i also have 2gage wire that i plan to use on the second battery for a ground and run to the isolator. is that a problem or should i use 4gage as the altenator and 1st battery have?

thanks