Looking for a wiring diagram for second battery

[Matthew bryant]

I was wanting to run a second wire from my alternator straight back to my secondary batteries with a battery isolator in the middle or do I have to hop off of my second battery under the hood?

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[Gears]

You can do either, typically its easier (depending on battery location) to run it off the battery. Just make sure you route it decent to avoid sitting up against hot things in car like the exhaust etc.