I would like to put dual batteries in my KJ. Are there any manufactures for this and would I need to install a bigger alternater? Planning on trying to take it thru Canada into the Arctic Circle.

try WranglerNW.com for prefab kits, or for components try hellroaring, or NationalLuna for info.  Overland Journal did a great write up on dual battery systems, if you can get your hands on a copy...

 A dual battery arrangement is different than two batteries. If they are in parallel still get 12v but using the second battery as an alternate battery to run equipment and not for starting can be a bit interesting. I have a second (actually third) battery that is charged by a solar panel that I use to operate the ARB cooler, independent of the vehicle battery setup.  But, since my system is 24v (two in series) I could not tap off one battery for the 12v items without  causing one to be drained before the other. So, without a new charging system it was actually more cost effective to install a third battery. 

It will depend on the use of the second battery as to your arrangement and placement of the battery. I understand that the LR has room under the bonnet for another one. You are in luck having so many possible arrangements to solve your problem, and so many here on the site that have the experience to give you advice.

Happy trails

I have one of these kits  that is brand new if you're interested. It is the in-dash dual LED mount. The 12voltguy.com design is intended to run accessories off the primary saving the second battery as a backup to combine with the primary for emergency starting or winching. I'll sell if for $100 saving you $30 + shipping?

 I ended up going with a National Luna setup for the monitor option and also to run the accessories off the second battery.

p.s. He also has Jeep-specific switch panels but I don't see the KJ as an option. One of the others (TJ/XJ etc.) might be interchangeable.

Hi Bill:

Sorry for the late reply.  You probably know this by now but here goes:

There are dual battery systems and twin battery systems. 

A twin battery system is simply two identical batteries wired (normally) in parallel to provide big starting power; diesels usually have a twin battery set-up due to the high compression ratio of the motor.  These batteries must be identical and in the same condition (don't mix old and new; replace as pairs).  These are "house" batteries that provide power for the motor to start and the vehicle to run as intended by the OEM.

A dual battery system adds a second (or third in the case of a deisel) accessories battery to the electrical system.  This battery is isolated from the house system by a system/device that ensures that the accessories battery gets charged but does not drain the house battery.  The accessories battery is a deep cycle type designed to be run down and recharged as opposed to regular vehicle batteries that do not like being discharged too low.

If you research battery isolators and accesory power systems you will find lots of great reading.  Here are a few links to get you going:

http://www.hellroaring.com/bic75300.php

http://www.ccis.com/home/mnemeth/12volt/12volt.htm