The Benchmark-Designs kit...
The Benchmark-Designs kit is compact and tidy. The primary battery is closer to the engine. Accessories, such as the winch that we have on this Jeep, are connected to the auxiliary battery. Optima Yellow Top AGM batteries add 750 cold-cranking amps (each) and deep-cycling capability to our dual-battery setup.
Off-road adventures demand that you be properly equipped. One thing that we all seem to have experienced is not having enough battery juice after a long winching session, using lights with the engine off while a buddy fixes his junk, or just plain leaving accessories on too long. Running dual batteries may be the solution.
The simplest dual-battery setups give you twice the reserve capacity, allowing you to do something wrong longer before being stranded. There are quite a few smart systems available now that isolate one battery at specific times so you always have enough juice to start the engine.
Benchmark-Designs offers two electronic packages that work on any Jeep. With its K.I.S.S. kit, both batteries charge and are available for heavy power loads when the ignition key is in the run position. When the key is off, the batteries are isolated. One is available for running accessories while the other is preserved for starting the vehicle. The Smarty system is the premium kit, and it monitors the condition of the batteries, charging them together or separately as needed. Both are available when power loads require, but the system isolates them when voltage drops below 12.7, leaving enough power in the primary battery to start the vehicle. This system does a better job of maintaining both batteries at optimum charge, reducing the load on the alternator, and thus preserving one battery to start the vehicle. Both electronic kits are completely automatic.
There's a lot of junk under the hood of a JK; it seems that everything on the passenger side is attached to the battery tray. The kit instructions take you through 38 steps to remove the factory plastic tray and replace it with a new steel one. It took us three and a half hours to do the whole conversion. Everything fit well, which is a small miracle in this cramped space.
Benchmark-Designs offers two different electronic-control packages and a dual-battery tray that fits all JKs. We like that the kit comes with mounting hardware, the electronics are designed to fit together, and that the mount accepts standard-sized batteries. The Smarty kit comes with everything shown here. No additional items were needed for our install.