I've been preparing to install my winch (Smittybilt X2O 8) and have decided to go with a dual-battery setup. I've heard that you don't really need an auxiliary battery to run the winch unless you are doing some serious pulls. And to be honest, I don't intend to get myself in that situation (ah, but do we ever?!? <img src="/forums/images/graemlins/shiner.gif" alt="" />). However, the auxiliary battery can also come in handy when camping, like for powering a cooler, lights, etc, as well as giving you a second battery for a self-jump start. All of that sounds good to me...

So here's my plan, which I have just put into action this weekend (work in-progress): I'm going with 2 Optima batteries (one red top for the main, one yellow for the aux). Because the space is way-too tight under the hood, I'm going to move both batteries to the rear and install the battery isolator in the stock battery tray, along with a 500 amp battery isolator relay. For those not familiar, the isolator will allow the batteries to discharge independent of each other (so you won't kill both batteries with the winch), but will manage the charging of both by the alternator. Some people run dual batteries in parallel without isolation, some use a high-current switch to control the battery configuration manually, while others use relays alone to isolate the batteries. From what I've gathered, the diode-type isolators are the only means for automatic control of charging while still isolating the batteries. And that's what I wanted. The relay will be used to cut power to the winch when it's not in use and to keep people from playing with it when I'm not around... <img src="/forums/images/graemlins/mrt.gif" alt="" /> And it adds a mechanism for cutting power quickly, should an emergency arise (runaway winch or the like). This is where the solenoid can shine, because it will be controlled by an arm/disarm switch inside the cab. Most people install manual switches under the hood. But you can't get to anything under the hood quickly (enough) when you're in the middle of a pull. <img src="/forums/images/graemlins/zombie.gif" alt="" /> With the solenoid, you just flip the switch...

Mounting batteries in the rear: After spending a few hours measuring and staring (I tell my wife I'm "visualizing"), I decided the most efficient way to relocate the batteries was to send them to the back of the bus - by cutting out the factory jack's "hidey-hole" and building a dual-battery box that sits under the body, between the rear axle and the cross-brace behind the rear bumper. Basically, I'm just making the jack's storage-box deeper so it will hold 2 group 34/78 batteries side-by-side. I started that part today. The box has been cut out and a new mounting frame has been mocked up using 1/8" steel angle (a mix of 1.5" and 2" because that's what I had laying around the garage). The batteries will fit comfortably in the new box. And the box will ride at a safe-height between the axle and rear cross-brace (low risk of getting bashed). I will post some photos soon...

The last bit of trivia that applies to moving the batteries to the rear (or installing a winch, in general) is wiring. My winch is spec'd to pull 410 amps when under full-load. That's a lot of juice (and that's why I bought a 500 amp relay). The power cables that come with a winch are always bigger than stock battery cables. However, if you're running the power over a longer distance (battery under the hood vs battery in the "trunk"), you need even bigger cables. How big? That seems to be point of debate. By electrical specs, I would need at least 3/0 gauge wires for the winch circuit, with 4/0 being preferred. I've read of others running 1/0 or 2/0 without a problem, even 2 gauge for some. I decided to air on the side of caution and go with 4/0, just in case. This is partly because I'm a wuss and fear getting myself into a situation that I couldn't get out of because I chose to skimp on the pennies and fried my winch circuit pulling myself out of the Taco Bell drive-thru <img src="/forums/images/graemlins/baby.gif" alt="" />... and partly because I was able to get bigger cables for less than what my local welding supply-shops quoted for smaller-gauge cables, simply by shopping online (no tax and free shipping too). <img src="/forums/images/graemlins/kewl.gif" alt="" />

OK, let's sum up the blah-blah-blah:

1 red top Optima battery (main for starting)
1 yellow top Optima battery (deep cycle for aux/winch)
1 500 amp relay (power-interrupt for winch)
1 200 amp battery isolator (allows me to move up to a 140 amp alternator one day... though the 140 amp isolator would have worked just as good, costs about $10 less and will fit in the stock battery tray <img src="/forums/images/graemlins/rolleyes.gif" alt="" />)
4/0 gauge wire for the winch's pos and neg power cables (to solenoid) and the main battery's ground cable
1/0 gauge wire for the main batt-to-starter cable (starter doesn't pull the same load as the winch, so I can save some pennies there)
2 gauge wire for the charging circuit (isolator to batteries, with each battery having it's own wire)
A variety of cable lugs and switches (small taters, in the scope of things)...

Yep, that's where I'm going next!!! <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" />


1997 Sportage 4x4, auto-trans, Warn manual hubs, 4" UPYOURKIA front lift, TJ 106AA rear springs, 2-5/8" body lift, 31x10.50 treads, SmittyBilt SRC front and XRC rear bumper, swing-out tire mount, OBX LSD front diff, Track Finder rear locker, 5.38 R&Ps and... really crappy gas mileage! <img src="/forums/images/graemlins/shiner.gif" alt="" />