Wrangler NW Power Products

#100-120 Jeep TJ Dual Battery System

ELECTRICAL SYSTEM ISSUE - CHANGED RECOMMENDATION

We have made a few changes to our Project Jeep in recent days. One of these was the replacement of the Wrangler NW Dual Battery Tray we have previously recommended.

It is an excellent product, but we encountered some problems with the Odyssey PC-925 batteries required by that tray.

The top terminals on those batteries are supposed to take a small amount of rotation. We found that the small amount they quote apparently exceeds what they will really take.

We had one of our Odyssey batteries fail when the top terminal became disconnected from the plates inside the battery and began to rotate freely.

Some research has found that others have encountered similar issues. It seems that the terminals on the Odyssey PC-925MJT and PC-925LMJT batteries may be too weak for this application.

We still recommend the Wrangler NW Battery Manager.

It is the best way to handle the installation of two batteries in your vehicle.

We also recommend their alternators.

We have one in the Project Jeep and it really helped out when we had the problems with the Odyssey batteries.

We now recommend the Mean Green TJ Dual Battery Tray and two Optima Yellow-Top D34/78 Deep Cycle Batteries.

The following review is included for reference and to show the Wrangler NW Dual Battery Manager

Power. We all need it. We all crave it.

So do the lights, GPS systems, and radio gear that we all run on. Without power, they don't work. Without power, our Jeeps don't go anywhere.

If you are working in Search and Rescue, you need even more lights and more radios. You need even more power. That was the situation we found ourselves in after installing the primary radio gear in our Jeep. Just the radio gear in our Jeep - not including extra off-road lights - had the following power requirements...

That's 39.05 Amps if all of that is on and taking maximum power (transmitting, etc.). That's not likely to happen, but add in several 5 Amp to 15 Amp lights that may be running at the same time, and you start to see the need for more power. Add in the winch and the 1500 Watt inverter and you can see there is a real need for power, beyond the average daily driver or simple trail rig.

Our Project Jeep shipped from the factory with a "heavy duty" alternator rated at 117 Amps. I have not run a formal test, but I'm not sure it really is running at what it's rated for. We really should have a bigger one in there, and at some point in the next year we want to go with something around at least 175 Amps.

The less expensive way to get around for the moment is to go with a dual battery system. This would allow us to run two batteries, greatly extending our capabilities.

There are several solutions out there. The fact that our 99 TJ has air conditioning is a limiting factor. Some dual battery systems won't work if you have air conditioning, others require modifications to the A/C lines around the dryer. That's not cheap, and we wanted to find a bolt-on system that would work out of the box. The other thing we wanted was a solution for managing those batteries. It is not as simple as hooking them up together.

While at SEMA I met a couple of times with the folks from Wrangler NW Power Products of Portland, Oregon. They have dual battery systems that will work with just about every off-road capable vehicle out there. They offer a solution for the TJ with A/C, and a separate system for the TJ without air conditioning. Unlike most of their competitors, theirs is a complete solution including the cables and relay necessary to manage both batteries. The other main system you hear about, from Mean Green, does not include these parts.

The folks at Wrangler NW were nice enough to supply us with a system, and since you have to remove the battery tray to install the ARB Snorkel, we installed this at the same time.

I will note that this solution takes a couple of less-common batteries. You need two Odyssey PC-925 batteries, one of which must have reversed terminals - designated as a PC925LMJT. The other battery must be a PC925MJT. These are metal cased batteries (for high-temperature applications) with top brass terminals. It gets hot under the hood of the TJ, so that helps.

We also met with the folks from EnerSys/Odyssey Batteries at SEMA, and liked what we heard about them. They have been making batteries for military vehicle applications for many years. These are dry cell (starved electrolyte) batteries made with reinforcements holding the internal plates and extra strong parts overall. They are made to be heat resistant and vibration resistant - exactly what we need off-road. They will last for 8 to 12 years, and carry a 3-year warranty. They also provide true deep-cycle characteristics, and have excellent starting power.

They are putting this same technology to work in batteries for the civilian market, and the PC925 is no exception. Because of the starved electrolyte design, they don't spill and can be shipped via FedEx or UPS easily. Remember what I said about them being less common? If you can't find a local dealer, there are plenty of Internet sources. We have 4 dealers within 75 miles, one as close as 7 miles. Odyssey was nice enough to supply us with two batteries to use for this project - one PC925LMJT and one PC925MJT. Just what the Dr. ordered.

The PC925MJT has a reserve capacity of 52 minutes (meaning that they can power the vehicle without the alternator working for 52 minutes), are rated at 28 Amp hours, 765 cranking amps for 20 seconds, 380 CCA (which has worked fine for us in 20F weather), 625 HCA, and weigh in at 26 pounds.

A regular single battery for the TJ - say an Interstate MT-34 or MTP-78DT - will weigh in at about 40 to 43 pounds but can provide 800 CCA. However, they do not have the durability or deep-cycle capability that the Odyssey batteries do.

So you have about 10 more pounds in weight with the two batteries, but greatly enhanced capability. Now, on to the Wrangler NW Dual Battery Tray Kit.

When you open the box you will have everything you need - detailed installation instructions, a new battery tray, and a number of cables, and a relay. The installation is a bit involved, but easy to do. The best thing is that you don't have to mess with your air conditioning lines.

You start by removing the original battery, and then the factory battery tray. Ours looked quite nasty between the corrosion and the bits of Moab and other places that had made their way up there. There are 4 bolts that attach it to the Jeep. They may be a bit hard to locate if yours looks like ours did.

Keep in mind that there is a sensor in the factory battery tray that keep track of the temperature. You can see it in the center of the factory tray. This is used to help regulate the charging if it gets too hot. You will need to unplug that sensor to take the tray out of the Jeep, then move the sensor to the replacement Wrangler NW tray. There is a connector that will be somewhere behind the battery tray. Unplug that and the sensor will come out with the battery tray.

The Wrangler NW Dual Battery Tray is a bit wider than the factory tray, and is certainly well made. There is no comparison to the "quality" of the factory unit.

Here is a bottom view of the Wrangler NW Dual Battery Tray with the temperature sensor installed in it and ready to be put into the Jeep.

And here it is in the Jeep. It looks much cleaner than the factory unit did..

The basic installation is to install the tray, put the batteries in - with the PC925LMJT closest to the engine - and put the hold down bars in. Make sure the bar with the upward-facing studs is over the battery closest to the engine, and the studs are towards the rear. Here is what it will look like. Note that the Positive terminals are next to each other, and the negative terminals are on the outsides.

That relay is a necessary part of this installation. It - combined with the switch you will also be installing - allows the batteries to be isolated or connected in parallel for extra capacity when jumpstarting, when the main battery has run down, or when winching or using other very high current draw tools.

So now, here we go - starting with the PC925LMJT. This becomes the primary battery (doing everything that the original battery did - starting, headlights, etc). That one is easy.

The next one, the PC925MJT which is located on the fender side, is not as easy at it sounds. In the following picture you will note that the side of the Jeep has a part the extends over the battery. You have to find a way to maneuver the battery under that so that it can drop in next to the other battery. It took a few tries, but it can be done. It also leads to my only complaint - it is not very easy to get to the negative terminal on that battery. This is your aux battery, so you will be hooking your added lights, radios, winch, etc. to this battery.

I will jump ahead here and show you a photo of the initial testing stage - we have since cleaned up most of the wiring, but this will show you the clearance on the negative terminal on the far left side. There isn't much.

Once those are in, you are ready to start wiring the switch and the relay. All of the cables in this kit are well labeled and are easy to figure out.

You start with the small black wire that provides the ground connection for the relay. If this is not tight, the relay may fail to operate. It goes from the NEG COIL connection on the relay to a ground point. You can use one of the mounting studs the relay is bolted to, or a negative on the battery.

You then have a Positive that goes from the rear terminal on the isolation relay to the Positive terminal on the battery closest to the fender (the aux battery). You have a Positive that goes from the front terminal on the isolation relay to the Positive terminal on the main battery.

Last comes the factory ground - which is hooked to the ground on the battery closest to the engine - and an included 38" negative cable that goes from the ground on the auxiliary battery to a ground point - ideally a good ground point on the engine. We found one close to the alternator that metered out perfect.

Now you can get on with the Battery Manager installation. This consists of a switch that is mounted inside, and connects to the isolation relay to control it. There is another wire which needs to be hooked to an ignition-switched Positive power source, and plugs into the Battery Manager cable. Here is what the cable assembly looks like...

There is plenty of cable included. We placed the Positive sensing cable behind the glove box, and found the perfect source for it, provided by the factory. We never hooked anything to it as it is only rated for 3 Amps.

And we know that we won't exceed 3 Amps because the Wrangler NW sense wire is fused at 2 Amps.

We placed the switch low on the center column bezel, right next to our CB speaker. It fits right in and stays out of the way.

The cable from the switch is routed through the firewall and the three wires in that cable are connected to the isolation relay. The white wire goes to the top connection on the relay. The red wire goes to the front terminal on the relay, and the black wire goes to the NEG COIL terminal (bottom) on the relay.

Once these are all hooked up, you are ready to go. Once again, here is what it looked like before we cleaned everything up...

You really don't have much interaction with this system other than occasionally changing the switch setting in the cab.

The DUAL ON position (left - green LED) allows both batteries to charge but keeps them isolated. Vehicle starts off of the main battery. This is where you normally want it.

The DUAL OFF position (center - no LED lit) causes ONLY the main battery to charge. Anything hooked up to the auxiliary battery will still work, but that battery won't charge. Can be used if you want to charge the main battery from a deeper discharge, or if the aux battery has gone bad on you and you don't want to hurt the charging circuit. I don't see this happening with these Odyssey batteries, but this same system can be used with other batteries.

The EMERGENCY ON position (right, red LED) ties both batteries together in parallel (12VDC, NOT 24VDC). This will give you the full current capacity of both batteries, and is useful for winching, jump-starting another vehicle, or if you ran your main battery down and need extra power to get your own vehicle started. It jump starts your main battery via the aux battery. This position even works with the engine off.

So after over 6 months of hard use, I can tell you that this system has never once failed us. Both the Wrangler NW system and the Odyssey batteries have performed well in below freezing temperatures and in temperatures of over 105F. We have a ton of extra lights, all of the radio gear, and the winch hooked up the auxiliary battery, and everything works fine.

Sometimes in the shop we put the key in the accessory position and run the radio. We did this while testing the Eclipse AVN-7000, and it was such an engrossing product that we ended up running the main battery down. The Jeep wouldn't start. I just flipped the switch to EMER ON and got it started instantly, then switched it back to Dual On and drove around for a bit, and all has been well.

I have had some people question if the Odyssey Batteries are really good enough, or if we would be better off using a different dual battery system and some Optima Yellow Top batteries. The D34/78 Optima batteries used by the Mean Green dual battery setup provide 750 CCA's and have a higher reserve capacity. However, they also are not constructed as well as the Odyssey Batteries, and they weigh in at 43 pounds each. That means you are running 86 pounds of batteries in the Mean Green setup versus 52 Pounds for the Wrangler NW Dual Battery system. That's a savings of 34 pounds.

The Odyssey batteries also offer a superior warranty (3 years versus 12 months free then 12 months prorated), and can be deep-discharged over 400 times.

What I can say is that running all of the radio gear, lights, winch, and inverter that we have, the Wrangler NW Dual Battery system has been more than adequate. It has held up under some pretty severe off-road conditions (think Moab, and plenty of rough dirt and rock roads), and under extremes of weather. While the tray itself could certainly hold the extra weight, a complete Wrangler NW system weighs less than the other options, and it includes EVERYTHING you need. Without the battery management parts, any other dual battery system won't work out of the box.

Wrangler NW does, and it's what we recommend.

-- James Bell Jr.

For More Information, Contact:

Wrangler NW Power Products

810 N Graham Street

Portland, OR 97227

800-962-2616 Voice

503-517-0753 FAX

Click HERE To Visit The Odyssey Factory Site

Click HERE To Visit The Wrangler NW Power Product Site

Click HERE To View The Installation Instructions For The #100-120 Wrangler NW Dual Battery Tray