I've posted this elsewhere but there is a cheaper option if you are willing to back yourself.
Adding up the costs for a proper DC/DC charger + a dual battery kit + an extra 2x D34A Optima batteries is quite a bit of cash.
Capacity wise, at the end of it, you end up with 55Ah for each D34a.
Using the second battery only for accessories when the car is off, and only discharging to 50% that leaves you with 27Ah of power to go through, pretty poor return on the 1k+ that the setup costs.
Another option is to go with a drop in AGM battery replacement for the main battery like
http://www.batteriesdirect.com.au/sh...n66-tall).html which is a 70 Ah battery. Total setup cost is $390
Discharging this to 50% gives you 35Ah of power to use, much better value.
You would obviously need to have low voltage cut outs on whatever accessories you are using, I haven't tested if the Wrangler would start even when the battery is discharged to this level but I bet it would - i'll let you know when I buy one of these and set it up.
35Ah is enough to run a moderately sized fridge overnight and you can add a solar blanket to keep it charged up during the day when you aren't driving.
Other downsides are that you don't end up with a "spare" battery to jumpstart with or use as a spare replacement main battery in the event of total failure of the primary.
