Going to dual batteries

So, I bought two new blue tops and two new battery boxes and enough cable to attach them to one another. I have heard of people putting a capacitor of sorts in between the two batteries. Is it necessary to do any thing other than neg. to neg. and pos. to pos. to run both? I forgot the justification that i was given way back when, i just remembered that something was supposed to go in there with em. Just curious, thanks!

isolator/combiner or perko switch would be a good idea if you want to use one as a starting batt and one for accessories like sound system, etc.

that must have been what I was told about. thanks. They sell those at basic automotive shops like auto zone, or is that more of a stereo shop item?

I went with an isolator on mine it was a pretty easy install I have one bat. for starting and one for the accessories

Blue Sea 7610 Isolator. I just put one in my boat. Looks clean, and works great. Get one off ebay. ~$100 with the switch

Or get a combiner. Those are about $40.

Here is a link from a previous post about the isolators and dual batteries.
http://www.wakeworld.com/MB/Discus/messages/3183/524141.html

I run with the Hellroaring battery isolator/combiner. I also added on the remote for it as well. Love and wouldn't run without one now. Hellroaring.com

I use the same Hellroaring unit as Kraig. Same results, wouldn't go without it in a boat.

There are a few ways to go when adding a second battery, they most popular that we sell is the battery separator, then you have Isolators and manual switches, for more info check out this site, Sure Power makes some great products: http://www.ase-supply.com/Sure_Power_Isolators_kits_s/20.htm