Click for Coverage
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

January 2012 Randy’s Electrical Corner

Posted in How To: Electrical on January 1, 2012
Share this

If you are like a lot of Jeep guys I run into, the Jeep often gets parked in the winter until the snow gets too deep for the commuter car to handle. So, that often means that it sits through most of the fall and early winter neglected and the first big snowstorm finds you guys either hooking up the jumper cables or charging box or, worse, replacing the battery.

Hopefully this column comes before you end up doing any of that. Once I found out about this new automatic battery disconnect from Flaming River, I got one as soon as I could because I know how winter is for you guys. The idea is simple, really. This thing is a huge relay that can handle all the power your Jeep draws, including starting power. It is rated for 250 amps continuous and has a mind-bottling 2,500-amp surge rating. I wouldn’t run a winch through it, as a winch can draw more than the 250-amp rating when under load, but everything else in the Jeep should be good to run through this thing. It is IP 65–rated, which is a fancy way of saying “Drown it—it will take it.” And if you wire it up like the instructions say to, it works automatically when you shut the Jeep off.

The kit includes all the washers, nuts, and lock washers needed to attach the wiring to the disconnect unit. However, I had to add my own wire and terminals. First I built a platform so there would be a flat mounting surface near the battery, and then I used 4-gauge wire and solder-on terminals to run power from the battery through the disconnect and on to where it used to go in the Jeep. Any other wires I had running back to the negative side of the battery were moved over to the “output” side of the disconnect unit.

If you guys are honest with yourselves and your Jeep is a second or third vehicle, when you get home from driving it and shut it off, it could sit there just for the night, or it could sit there until your next Jeeping season. Wire this up the way it should be, and the battery is disconnected when you turn the key to the “off” position. So whether the Jeep sits a few hours or a few months, the battery will be 100 percent when you come back to it with no worries about battery drain.

I was surprised by the size of the automatic killer. It comes in at about 6x4x5 inches and is set up to be bolted to a flat piece of steel with four bolts. We went with the optional rubber terminal covers. You need to be very careful with the big terminals on this. If a piece of metal or a wrench or anything that conducts electricity falls across the terminals it could be bad. It probably wouldn’t be quite as bad as if you dropped a wrench across the terminals of the battery. But lets just say there are better ways to get your day jump started.

I was kind of surprised to find out that the manufacturer of high-quality steering parts was getting into electronics, but once I realized the company already made steering columns with ignition switches for hot rods and Jeeps that don’t get driven that often, this kind of made sense.

The wiring diagram that came with the kit left some room for interpretation, but I basically did what it said to do. I did this redraw with arrows and circles and stuff to make it easier.

For this story, I put the Automatic Battery Disconnect Switch in a carbureted Jeep with no radio or other electronic gizmos. Fuel-injected guys or guys with stereos or other things that need power for a memory, you might need to do it a bit differently. I’ll talk about your fancy Jeeps later.

Some newer computer-riddled Jeeps don’t run well if you pull the battery for any length of time, and you might want to bypass the disconnect to keep constant power to the computer. If you are thinking this might be the way to go but aren’t sure, disconnect your negative cable from the battery for at least an hour to see if there are any downsides with how the Jeep drives once you hook it back up. I tested just the radio in this Jeep while it was off, and it drew 0.18 amp. Bypass the disconnect all you want, but every bypass will have a cost.


Flaming River
Berea, OH 44017

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results