Adding a Second Battery for Audio

Hey Guys,

I'm new to the site. Looks like there is a wealth of knowledge among the forum. I'll get straight to it. I'm planning on installing a sound system in my 22ft boat. I currently have a head unit installed with component speakers. I want to isolate the entire system on a separate battery, which not a problem. The problem is being able to push amperage back into the battery using the engine coils. At the stern of my boat, I have a dual circuit switch (1, 2, or Combined) The motor does not have an alternator, so it looks like it's drawing power from the coils. My question is it as easy as adding a positive wire (gauge wire will depend on the distance run ((thinking 4 gauge) from the 2nd positive on the circuit switch to the positive terminal on the battery, and a negative wire to the ground bus bar? I'm thinking this will keep separate circuits on each battery and separate charges for each battery...or would I need to hook the battery up in parallel or series with the other main battery?

Thanks,

 

Yes, it is that easy.
Bear in mind that the "audio battery" is only charged when the switch is turned to Combined. Outboards usually do not have a separate alternator but use one or two coils under the flywheel to provide charging current; for your wiring it isn't relevant.