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Dual Battery System

4/24/2018

13 Comments

 
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As discussed previously on a few web forums, I’ve wanted to move the WK2 to a dual-battery setup for quite a while now. The goal will be to move all the auxiliary electrical units (HAM and CB radios, fridge, lighting, device charging, etc.) to the deep cycle battery – hereinafter referred to as the House battery – and get them off the starting battery. By alleviating their power draw from the starting battery, we’ll be lowering the chances of a dead car in the middle of nowhere.

I knew the spare tire was going to be moved to a swing-out tire carrier, which opened up the possibility of mounting the new House battery underneath the rear deck I built last summer. Once the majority of parts were ordered (every single one of them available on Amazon with 2-day delivery) I got to work laying out how this project would go along. The full parts list will be updated once the project is done, but currently is as follows:
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The full parts list will be updated once the project is done, but currently is as follows:
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-  Universal Battery sealed 100ah AGM
- Wirthco 150A Intelligent Battery Isolator
-  Blue Sea Systems 12-post fuse block w/ negative bus
-  8”x5” ABS plastic project box
-  2x InstallGear 150A in-line fuses
-  2x 10-foot sections of 4AWG wire in red & black
-  Crimp-on 4AWG cable ends
-  Battery terminal ends
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Acquiring Gear For Installation
So the first step here was to remove all my gear from the back of the Jeep. This included my Pelican case of recovery and winter camping gear, kept in there in case of an emergency while New England is getting pummeled with adverse weather. Luckily that time of year is almost over. I then pulled the fridge out and removed the rear deck I had built last year. Next up came removing the OEM included gear, the spare tire, jack, and plastic storage cubbies that fit around the wheel. This left me with the open wheel well, from which I removed the plastic surround trim piece.

I purchased a 4’x4’ piece of 3/4" plywood from Home Depot from this project, and had it set up on two sawhorses in the garage. A quick trace with a Sharpie and I had a template to fit inside the wheel well. The Jigsaw made quick work of this and within a few minutes I had a fitted piece of decking to use as a base for the electronics.

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Factory Trunk Design
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Spare & Jack Removed
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Trunk Trim Removed
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Tracing the Trunk Deck
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Test Fitting

Once the deck was sanded, Dani asked what color I was going to paint it. While my initial thought was just to do it black, she asked for silver… so it’s metallic silver. This actually will work to my benefit, as it will push me even more to keep the wire routing clean, even though it’ll never really be seen. With paint dry, I moved the deck into the house and turned the living room into my mad science laboratory getting the fun part of the project underway.

I unfortunately spent an hour or so cutting up the existing wiring system in the Jeep, pulling out the control box and re-routing the existing auxiliary lighting and radio harnesses to the rear trunk area for use in a few days time. The relay control box was pretty tired after months of working with it and moving it to a resting spot, so I went ahead and ordered a new ABS project box to be installed in the new spot in the back. I chose one that’s a bit larger to allow for future expansion, after measuring and ensuring that it will fit on the deck.

I played around with the parts on the deck once it was in the living room and figured out a clean layout for the equipment. Battery will be on the passenger side, with the Wirthco Intelligent Isolator mounted on a bracket in front of it. In-line fuses to the side and again in front of the (+) post of the House battery. The Blue Sea Systems fuse panel and relay control box will live on the driver’s side of the compartment, and wiring will be routed between the two without needing much distance at all.

It took a quick trip to Harbor Freight to buy a handheld hydraulic crimper to tackle the 4AWG connections, but it seems like a good tool to have for the future. As of now the basic wiring is set, and I’ve pretty much gotten as far as I can before the last bit of parts arrive and I move this set-up into the back of the Jeep.

Lots of photos, and plenty more to come…
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After getting the system tested with temporary wiring, I went ahead and got to work making the necessary wiring looms to get all of the electrical components (lighting, radio/comms, fridge) bought back to the Blue Sea Systems fuse panel and connected appropriately. This took quite a bit of time, and was sort of a pain in the butt, but I think the cleanliness of the end result was worth it. 

In order to get the wiring into the trunk area I was hoping to use some kind of brush-plate from home A/V installs, but in my searching I found a computer-desk type grommet for wiring, which turned out to be perfect for my use. It measures about 2.25" across, and using a hole saw I cut out the appropriate hole in the trunk/tire surround trim to allow wiring to pass through. It's high enough to clear the rise in the floor of the vehicle and allows wiring to fit in the minimal gap between the suspension air tank and the floor. This took some tricky snaking, but the end result was worth it. I used adhesive silicone to seal the grommet to the plastic trim, and though it's not 100% perfectly adhered, it has done a good job making it look clean.

After pulling all the loose ends of the aux. component wiring into the trunk space I then had the fun (read: tedious) task of cutting them all to the appropriate lengths so they fit cleanly and were able to be loomed up together in the trunk. Testing each fixture one at a time, reappropriating the right fuse size to the connection point, and checking the dash panel switches as I went to make sure everything was functioning appropriately from a control standpoint. Once all was great I used some more of the adhesive tie-downs to secure everything in an organized manner, then took some photos and put the storage deck back on top, calling it a day.

For now the system is fully functioning and seems to be doing so flawlessly. In the next few weeks I'm going to install a 12v meter by the fridge so I can monitor the house battery without lifting the storage deck lid, and also a switch to disable the isolator system. Because it's intelligent and not just passive, it draws a tiny amount of power to see if the starting battery is on or not... where I travel a lot and the vehicle sits in the garage, I'll be able to use the switch to disengage the grounding wire of the isolator to shut it off, essentially disabling the charging capabilities of the second battery until I turn it back on. I've got miscellaneous switches in the basement, so when I've got a meter and time I'll add those to make the entire setup even easier to use.

Final Dual-Battery Install Photos:

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13 Comments
Dan
5/5/2018 06:51:08

Looks good! I’ve been wanting to do the same and was looking at the wheel well approach. What’s the plan for the spare, roof it?

Reply
Ryan McKee
8/25/2018 18:26:51

I ran the setup locally with no spare for a few months and then recently installed a Wilco Hitchgate Solo to carry spare fuel and the spare tire for Overland trips.

Reply
Dan
8/25/2018 18:02:54

How did you get a good trace on that? Does the tub have no bottom?

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Ryan McKee
8/25/2018 18:25:35

Hey Dan,

If you look at the 5th photo you can see the tub liner laid out on the plywood decking. I used a combo of the interior dimensions and exterior dimensions to make the cut. Luckily I was able to pull it off in just one pass with the jigsaw.

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Michael w
2/7/2019 10:08:20

Love this. Really considering this myself along with a solar panel to boot. However. I gotta ask. How does the alternator hold up with this set up? Did you need to upgrade? If not have you had any issues with your current alternator?

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WOODYxWOOD
6/23/2019 22:46:48

Yes! Is there a larger-amp alternator you need to get to run a dual battery setup? What about dry cell batteries?

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Luke T.
12/6/2020 19:04:12

Hello, I too am a trailhawk owner and these cars come standard with a higher output alternator as well as a higher output water pump as stated on my window sticker parts list. I do not know if this year trailhawk came equipped with it but I know the newer years do indeed. Additionally the higher out alternator is not needed for a dual battery setup because the draw is not significant enough to need it. If running multiple lighting systems, speakers, and trailering it would be recommended. Just my opinion.

Ian Serio
2/21/2019 11:20:41

How did you run your wires from the factory battery into the tire well? I see you used the grommet to run through the plastic of the well, but where did you run the wires from there to the battery?

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Robert Odwyer
11/2/2019 01:48:48

I love this set up and have begun assembling what I need for a similar design. One question. Your 2017 WK2 is equipped with a variable voltage alternator. Does your auxiliary battery stay charged with the isolator? I've read that isolators are not very effective on newer vehicles due to their "smart" alternators. Redarc recommends using a BCDC charger in lieu of an isolator for smart alternators; but not sure how much of that is marketing hype to sell another product. Looks like you've been running this set up for awhile now. Any retrospective feedback on charging performance? Thanks, Rob

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Dave
11/28/2020 21:59:12

Would you be able to show how you connected to the Jeep battery?

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Colin
6/16/2021 21:26:39

I've added a 100 Amp circuit breaker with manual reset between the spare battery and fuse box (https://www.amazon.com/gp/product/B01F76VJT2). This allows one to easily disable all auxiliary power (easily in the sense that the trunk is empty and one can access the spare battery...). I've also added a secondary switch to break the ground of the battery isolator behind the rear passenger seat so that one can easily switch it off when the WK2 is garaged for extended periods (the isolator has a small parasitic drain on the starter battery).

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oto
10/30/2023 22:18:24

Hi
Beautifull work
However you lost space at the back for nothing.
There is space for a full starting battery (if you want) or deep cycle under the passenger seat.
Also a DCDC charger will make sure you don't wreck the batteries prematurely It all fits in fairly easily. You will need to fashion a battery tray though.

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Phillip McCoy
9/18/2024 04:50:50

Hi you.

I am profoundly Deaf Man.

I need more information for battler wires by how to do it!


I live in the UK 🇬🇧!

Your area in the UK and email address!

Please send me by email!

Reply



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