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Dual Batteries with 2012+ JK with 3.6L Engine - Finally!

20K views 53 replies 16 participants last post by  foo.c 
#1 ·
Ever since I bought my '12 JK over a year now, I've been searching for a way to get setup with dual batteries. I was ripped off by now defunct Benchmark Designs, who I paid $475 in hopes of obtaining a full kit. I eventually received part of a dual battery tray, but it was incomplete. I had to fab a top clamp, and having both batteries stacked vertically was inconvenient, and so I never utilized them properly (isolation, etc) due to the space and placement.

Here is an image of what that looked like:

As you can see, it doesn't look so great. There was a big gap on the side of the batteries, and I had to insert a wooden spacer so that the batteries wouldn't move and short out the side posts with the clamp. But, it otherwise worked.

Now, enter Mountain Off-Road Enterprises (M.O.R.E), who took the time to come up with a solution for dual batteries for the 2012 and up JK with the 3.6L Pentatstar V6. As soon as they announced it, I put my order in. $135 for the tray alone, very reasonable. I finally received my order and got it installed.

Here is a picture of the M.O.R.E tray with 2 Optima Yellow Top D34/78 batteries, test fitting before install:


The batteries are held down by a strap that uses a buckle to secure them as shown here:


Not a big fan of this, since they don't look as secure as when a solid top clamp is used. I didn't like this gap:


But, I must admit, that once installed, I felt better about it. They looked like they were there to stay. So, overall, I think the strap use is okay and will get the job done. Wish I could get it a little tighter. But, I'll evaluate how it performs, and I see several ways to modify that, including making my own top clamp, if necessary in the future.

Here is the tray installed, the TIPM is still in pieces:


Install requires that you cut down the factory bolts, wasn't a fan of this step, it was hard to get my sawzall in there and make the cuts without scratching up the tray, as you can see.


The old tray had to be cut off (this whole assembly is one big plastic piece that has the TIPM box, the battery box, and the intake box. You essentially cut off the battery box + expand some of the holes originally used to move it over a bit. It was a pain, you have to really cut as much as possible on the TIPM side, eventually it all bolts up. This is necessary to buy yourself as much space as possible.


Once you get that all worked out, you can re-install the TIPM and intake.


There were 2 plastic pieces in the kit, I assume they are to protect the batteries from the factory bolts that you cut down. I took additional steps using clear silicone to make it stick and cover the full bolt. Otherwise, its almost guaranteed they will fall off. I highly recommend that you do this.


Finally, with all that worked out, you can install the batteries!
 
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#2 ·
The final step

Last, I wired in a Cole Hersee Smart Isolator (48530), a 200 AMP dual battery isolator. It will sense the voltage of both batteries and automatically connect your auxiliary battery to the charging system once the main starter battery is charged (actually, when either battery reaches abover 13.2V for at least 1 minute -- this ensures that if your main battery is going bad, you can still top off the aux). It will also automatically isolate the batteries when the charging system is off and both battery voltages are below 12.7V for 1 minute. It features a BOOST function, which you can use to jump start yourself, or otherwise connect the batteries in parallel via a switch to increase available current for things like winching. Also has a STATUS indicator, which will tell you what the status of the batteries is (connected, or isolated).

Neat system, and to connect it, you simply connect the Smart Isolator between the positive lead coming from the main battery to the aux battery. The two batteries are grounded directly to each other. Then some pigtail wires are used for the boost switch and status LED.

Here is what it looks like, mostly done, still have to clean up some of the wiring and add some more tubing in certain areas:


This is what my internal monitoring system looks like:


I basically used a double pole double throw with center off switch to wire the batteries to a digital multimeter (this one has compensation functions, so you can dial in an accurate reading using a potentiometer). The boost switch is there, and at the time of this picture, the status LED was not in.
 
#26 ·
This is what my internal monitoring system looks like:


I basically used a double pole double throw with center off switch to wire the batteries to a digital multimeter (this one has compensation functions, so you can dial in an accurate reading using a potentiometer). The boost switch is there, and at the time of this picture, the status LED was not in.
Could you explain this in "amature weekend wrench turner" terms? I think you were in my thread when I asked about 2 analog voltmeters in an A pillar mount. Well the A pillar crapped out, so I was thinkning about a Rugged Ridge A pillar switch panel, and the very same voltmeter you used. I was going to use 2 taking up two spots each of the 4 switch A pillar mount, but I was wondering if the voltmeters stay on all the time, or can you rig it that they only light up with the ignition.
 
#3 ·
WORD OF CAUTION: Use locktite or some kind of thread locker when installing the tray. When I removed the old benchmark tray, I found that the bolts were no longer tight, all of them were loose. So, this time around, I made sure to use thread lock on all the bolts. This is not in the instructions, but those bolts will rattle loose in my opinion. I properly torqued them last time, and was surprised to find them a bit loose, one almost off. Its cheap insurance that this won't happen. It really shouldn't be that huge of a deal if it does, since it is such a tight fit, but if you're going to do it, just do it right the first time :)
 
#4 ·
Great write up! I'm looking to do this soon.
 
#5 ·
Nice job.

Sticky?
 
#7 ·
x2 this should be a sticky. great write up that I plan on using :)

Thanks man! :punk:
 
#6 ·
Very nice! I still need to add a couple of voltmeters to my set up. May I suggest a couple of pairs of Marine Terminals? I think they are like ten bucks a pair and will help clean up the wiring alot.

How do you have the Smart Solenoid mounted?
 
#17 ·
Yes, thanks, I did purchase some marine terminals, but didn't find them until after I'd taken the time to make the cables. Since I'd adhesive lined shrink tubed them and pressed them in all nice, I decided not to upgrade and do it all over again. Aside from the 2 voltmeter cables, nothing else is going to get connected to the batteries, so things should stay neat (hopefully, otherwise, will have to swap out the terminals). I ran a 4 AWG wire to a 150 amp circuit breaker that feeds into one of those Blue Seas fuse boxes. So, all aux wiring will end up at the box away from the battery. But, as you mention, the marine terminals are definitely the way to go for someone starting off from scratch.

I mounted the smart isolator to the battery strap using zip ties, and applied some hot glue to the bottom to secure it further. It won't move, and can actually pretty much stay that way, but I plan to get some plexiglass and make a bracket for it. Choosing plexiglass because its not conductive, but metal can work too. I didn't like the idea of using metal, which I had, and I'd cut to hold the isolator, but decided against it. It seemed that if for some reason, the bolt holding the bracket to the side of the Jeep came off, I'd have a big metal solid piece that could bridge the + and - terminals and start a fire. If plexiglass came loose, at least it wouldn't short the terminals. I tried to minimize the risk of shorting anything out. I think it might have been you who suggested to add liquid electrical tape to the isolator terminals in a different thread, which I ended up doing, for added protection :thumb:. Will try to get that plexiglass tonight and hope its rigid enough not to vibrate when installed. Otherwise, I might have to go with the metal piece. I suppose I can plastidip the metal piece to reduce risk of shorting... hmmm... light bulb...
 
#9 ·
You carry a spare tire, right?
Same idea. NASA type thinking. Redundancy.
We're running winches, extra lights, compressors, sat-nav, laptops, fridges, and the occassional espresso machine.
A spare battery is cheaper than a tow from the middle of nowhere...
 
#16 ·
Maybe.

Do you need a lot of what we carry? Not always, and not for every trip.

I needed 11 rope-style tire plugs the other day on my way home from work; I picked up a huge bushing in my tire and put a hole in it over 3/4" wide ---- was in a spot where jacking was a bad idea and didn't want to ruin my $700 wheel...
So I needed my tire repair kit and my compressor; was glad to have them.

Your build and your budget have to suit your needs and desires. If you want a spare battery and can't afford this sort of set-up, carry a spare in a box. Charge it once in a while; an Optima won't mind.
But if you're on a vehicle-dependant overland-style journey, self sufficient, self-reliant, and away from civilization for a few weeks, you'll be wanting that battery. I know people who've spent the better part of 3 days in a winchfest to get themselves through a sticky spot. It's hell on a single battery and you'd be walking.
 
#28 ·
:) No classified data here. I will post pictures as soon as I get a chance. The Jeep is spending the night at the dealer getting serviced, and we're taking a trip Friday - Monday, so I might not get to it till Tuesday or so. But, meanwhile, I used this:
Bussmann Hi-Amp Circuit Breaker - 150 Amps : Amazon.com : Automotive for a circuit breaker, 150 amp Bussman. In the picture on my post that shows the isolator on the batteries, the big red cable at the far left slides right onto the side of the batteries. That Bussman breaker is mounted to the side of the Jeep there and that cable connects to one side of it. The other side of the breaker has a big cable that I routed along with the factory wires, so its no longer visible, but it runs along the top with that wire loom that runs on the top of the fire wall, all the way to the other side of the Jeep where there is a lot more space. I made a little bracket to hold the Blue Sea Systems Fuse Box in place. It is this one: Amazon.com: Blue Sea Systems Fuse Block Ato 6 Circuit with Ground: Sports & Outdoors
 
#29 ·
Thanks, LB. That's what I thought you said, but the switch terminology always gets me. You should have seen when I tried asking the OTRATHW guy about the switch I used for the dual battery set. After he nicely went through a very detailed explaination as to how the switch worked, I was like, "I just need it to work with my Smart Isolator to connect the batteries, and I need an LED that will light when the batteries are connected and fit in an sPod." :D
 
#30 ·
I trust Blue Sea switch materials; used that on my Conqueror trailer.

What kind of trailer do you have?

BTW, I run 3 huge batteries when I'm overlanding. The big main and two remote Optima D31Ms. I carry a genny, just in case, but the PW has always been able to charge things back up.
I just love my ARB fridge...
 
#34 ·
I have an m416 trailer. It's a fun project, a lot more work than I anticipated it would be. I appreciate the commercial off-road trailers and their pricing now. DIY projects end up costing almost the same, more when you factor your own time costs. I've seen your trailer in a few threads. It's an awesome machine. :thumb:
 
#31 ·
Great post. I installed dual batteries in my 03 Rubicon shortly after picking it up from the dealership. The spare battery has saved me several times. My Jeep often sits for weeks at a time without being started...and though I usually have a solar trickle charger on it, sometimes the main battery is run down. On modern vehicles, something is always using power even when the vehicle is off. I also have a fridge/freezer mounted in it, and dual batteries make it so that I can leave it running in the wilderness without having to worry about being stranded out there with nothing but a tray of ice.

The 03 tray was made by Mean Green. Since the batteries had to be mounted on their sides, I had to use Optimas. One nice thing about the Mountain Off-Road tray is that the batteries are mounted upright and you can use the OEM battery as the main or backup. The new Jeep will be here in a few weeks. One of the first things I plan to do is install dual batteries.


I'll look into the Isolator you mentioned. Sounds like it might have been easier to install than the one I used from Hellroaring Technologies. If I remember right, I had to run a wire to the alternator also.
 
#35 ·
I'll look into the Isolator you mentioned. Sounds like it might have been easier to install than the one I used from Hellroaring Technologies. If I remember right, I had to run a wire to the alternator also.
I definitely recommend it. In general, a smart isolator, either MOSFET or intelligent solenoid based is a good idea. There are several Diode based (or silicone controlled rectifier) isolators, and they tend to have the typical 0.7V forward voltage drop of a diode. This tends to have a negative effect on charging batteries, and often leads to them not being fully topped off. I've seen other manufacturers with lower forward voltage drops of around 0.3V, but that's still not ideal. I saw a couple of these at the local auto parts chains for around $40. I recommend staying away from those.

I chose the Cole Hersee 48530 because it was rated for 200 Amp Continuous current, some others rate by peak current, which is cheating. I also like that the Quiescent Current (how much current the actual devices uses when its doing nothing) was very low, 5mA typical, 8mA max. I also really liked that they are SAE rated for protection against RF, EMI (Electromagnetic interference is an important consideration when you will sit this thing next to some high current winch cables and all sorts of clicking power loads), Shock (off road use can shock this unit quite often), Vibration (again, off road it will be subject to this frequently), Thermal Shock (this one is important if you see snow or really cold weather. It can go from freezing to very hot in a short amount of time sitting in the engine bay and its nice to know that this thing is rated to survive such a thermal shock). Oh, an IP65 ingress rating, so its not just waterproof, you can hit it with a pressure washer if you want (don't recommend that). What else? its made in the USA, and I'm probably forgetting a lot more.

As far as the alternator goes, in this case, it does not get separated since it can do an inline sense. So, the alternator and starter cable stay in their factory location tied to the positive battery post :thumb:. So, yeah, if you had to install one that separated them, this will be a breeze in comparison.
 
#32 ·
LBrito,
Thanks for your great write up. Here at Mountain Off Road we listen to our customers and their critiques. We have made is simple change to the strap location by lowering the slot down below the top of the battery the strap will now synch both batteries down tight. Thanks for everyone interest in our Dual Battery Tray for 2012 JK. Happy Wheelin!!!!
 
#37 ·
Glad to hear! Great build quality on the tray!
 
#36 ·
Did the digital multimeter come with the isolater system or was this a part your sourced independently? If the latter, where and a part number, please?
It strikes me as a good add-on even with a 1-battery system if you're putting a hard load on the alternator (during winching, etc.).
Another post asked if you were going to add a more heavy duty alternator. Is this potentially needed given the extra load that 2 batteries might require, or does the isolator manage the load such that the required amps don't exceed what the alternator can deliver.
 
#39 ·
Regarding the voltmeter, I sourced the part independently. I got mine from Amazon: Amazon.com: Stinger SVMB Voltage Gauge - Blue Display: Car Electronics
They also come in red.
The isolator is pretty much passive, all it really does is control when the batteries are connected together, and when they are isolated, based on conditions. But, the batteries do have some reserve, so if you exceed the alternator output, then you'll start to tap into the battery reserve.

I responded to the question on the alternator via PM, forgot I never updated this post. Here is a copy/paste of my response:

Forgot to respond to your question on the thread, but no, I don't think a higher output alternator is needed. At idle, the stock 160amp puts out about 100 amps, I think full capacity starts at around 1500rpm. I'll have to measure the current at higher RPM, but, that's plenty of juice. It will charge my fully drained optima in about 30 minutes. Both would be topped off within the hour.

The way the isolator works, it charges the main battery first for a bit, then connects the aux battery, so it doesn't put an unneeded strain on your alternator (not that it couldn't handle charging both, but it might be a strain if you're running a full set of off-road lights, say 4 x 100W, which would draw about 40 amps, plus a bunch of other junk. But, if you're just running normal vehicle stuff, you can overwrite the wait period to charge up the main and start charging them both up together by pressing the Boost switch on the isolator, and it will pair them both to the alternator. The alternator will just see it as a higher capacity battery.

I looked at the offerings for upgraded alternators, and they're really not worth it unless you plan to do a lot of winching. When you think about it, a winch will draw about 200 amps at load, and if 150amps from the alternator go to the winch, then the other 50 amps have to come from batteries. If you have a Optima D34, that's a 55 Amp Hour battery. That means it can deliver 55 amps continuously for 1 hour. So, you can winch, non-stop, for 1 hour, before it dies. I doubt anyone would exceed that. So, with duals, you can extend that to 2 hours max (you probably want to limit it to 1.5 hour, to ensure you can still start the vehicle). This is also talking continuous operation, any time you stop winching, that alternator will keep putting out the current that will charge your batteries back up a bit.

So, something like a Mean Green 200 Amp alternator is still a bit overkill, it makes more sense with a single battery though, instead of doing duals. Cause then you can recharge that battery in about 20 minutes, and the extra juice you'd get from a second battery for winching can be somewhat replaced by a higher output alternator.

But, I don't run all the high current items at once, that may be different for someone who runs 4 x 100W off road lights (40 A), plus 100W Ham radio (10A) going + other stuff, then it might make sense to upgrade so that you don't have to wait so long to recharge the batteries if all those things are running.

Jeep got it right when they chose 160Amps, plenty of juice for most folks. Now, if money wasn't an object, then I'd upgrade. But, because of the way that the engine handles all the electronic, we are limited in our choices of alternators, and the cost of a small upgrade is pretty ridiculous for not so much benefit.
 
#48 ·
If I get the dreaded Pentastar dead head, I will fight with them if I have too. The issue is so well documented that I can't see them getting out of it.

If I get an electrical problem, I'm pretty sure I'll be on the hook for it.
 
#53 ·
The battery light is coming on in the mornings now. If I restart, it seems to go away until the next time it sits a while. I think it's these batteries. I have had terrible luck with Optimas, and these are of unknown age. (They came with a trailer I bought.)

I'm going to replace the primary battery with my OEM battery and see if it goes away. I'll probably get a Diehard Platinum as a replacement.
 
#54 ·
I've been having this issue with my reverse lights staying on.

The dealership said the insulation on the wire which goes to the reverse switch in the trans had rubbed through. They said it rubbed on the aftermarket battery tray or a bracket that was part of the tray. (I'm going to see if they can show me so that I can add some extra protection there.)

Keep an eye on this.
 
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