Dual battery selection
 

I'm getting ready to install a dual battery system with a Cole Hersee isolator. I wanted to go with a auto battery for the main and a marine battery for the second. Does it matter? Or should both batteries be the same?

Both batteries should be the same. I went with 2 diehard platinum marine batteries in my setup.

I cannot say I fully understand why marine batteries are not recommended as primary batteries. Only that they may not provide the initial power for start up (so I have read). I need reliability in very cold and hot climates.
I assume your dual marines are running fine.

Is the isolator the only thing needed to run the dual battery set up??

First let me say, I am not an expert on this at all. I wanted to install a dual battery setup and have been reading a lot on it and this is what I have found out. So others may have more accurate information.

Other than the dual battery tray and some extra cable. The isolator can also option out with a boost switch or indicator light etc. but it (isolator) doesn't have too. It just gets connected to each battery and runs on its own. Isolating the batteries when necessary not to overload the alternator and not drain your main battery when running your accessories.
Probably tmi, but take a look on the forum or look at the packaged kits out there by companies like rugged ridge.

I am planning to put in a dual set up too. I would like my second battery to be a marine unit with lots of amp hours to use. Does anyone know if a 31 series battery will fit in place of the stock 34? Is the Rugged Ridge dual battery tray okay or should I look for something else? I am also interested in the wiring and switching design that lets you boost yourself in the event your main battery dies. I won't be winching btw, my main loads will be lighting, OBA, and a few accessories. Because we're pretty remote up here the dual batteries are more for safety and reliability than for lots of winching etc.

You need a certain isolator. I would get the die hard 34 group battery as its a odyssey rebrand battery. Pm and I can give you more spec. I can't post them on my
Phone

I went with 2 platinums auto batteries. I still think maybe I should have gone with the marines. (both have same cold cranking amps)

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You have the best setup for the money. I would stick to auto batteries, the platinum have amazing no charge time on them. As they are re=branded Odyssey batteries one of the best on the market right now. Stay the hell away from optima.

I used to have the same opinion on Optima, but now even their marine batteries have a two-year full replacement on them. As long as they keep this type of warranty, I'll keep them running in mine. Before the warranty changed I lost some money on them, but I couldn't be happier now.