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Moderation in Moderation
1995 YJ Wrangler SE
11,672 Posts
Discussion Starter · #1 · (Edited)
I did this because... why not?

SO... with all the additional auxiliary stuff going on in my electrical system that have been added and layered upon over the last decade, also coinciding with my optima red top finally kicking the bucket, i felt it was time to run a proper dual battery setup. I've always wanted to tackle this fun little DIY so here it goes.

Its not terribly difficult to weld some angle channel together and create your own battery tray (there are many resources and former write-ups on this topic that illustrate how to do so quickly and cheaply in this forum - look to the resource materials in the stickies). Seeing as how i had a store credit, and materials in Canada are ridiculously priced - deterring me from trying it myself - i used the store credit and topped off the rest to purchase a catalog item.

1. Dual Battery Tray - Rugged Ridge
2. Painless Wiring Dual Battery Isolator/Combiner kit

3. Make a few 2 gauge or better battery cables or buy them.
4. Positive and Negative multi stud busses (to clean up the terminals)

5. Battery terminals (many to choose from, i went with screw down type for exposed end cables)

6. *optional but a nice touch, because when you're in that deep. . . * Harness style weatherproof connectors.

7. Also optional but certainly useful are a way to monitor the voltage levels on your dual battery setup. I found two would fit my needs best as my overhead switch panel could accommodate. I upgraded my overhead USB to a dual port QC 3.0 USB setup, tossed the old 1.5A version as well as the original battery meter and picked up these:

Some may recall i did a rudimentary cleanup of my auxiliary items (lights, winch, OBA, etc etc etc) in the early winter of 2017. WHich included a relay/fuse panels. AT that time, i was happy with cleaning up all the relays all over the place and at least making what i considered a concise system at that point. Admittedly, i grew to be discontented with the overall result thought it was an improvement over the complete and utter lack of a "system" i had prior. I was proud at the time as wiring scares the bejesus outta me.

This time around i was gonna go all out and ensure i had zero paranoia, zero disappointment, and would never EVER have to worry about wiring again. For that, this project expanded from a simple dual battery project, to include a complete re-working of my auxiliary wiring components.

My thinking was to isolate any OEM electronic needs to my starting battery, and all other auxiliary fun doo-dads i added over the years to only draw current from the secondary/auxiliary battery. Only makes sense right? The write-ups i was looking at, though informative, were outdated. Simply running dual batteries in parallel was not what i was after in 2022. Technology of batteries has increased immensely since the dual battery write-ups of 2007-2014. These days, you can pick up one MASSIVE battery and be done with it. The point of this was to completely isolate and have the full controllability to combine when wanted/needed.

For this, i picked up an all encompassing multi fuse and multi relay box which would be designated as the housing station for all my auxiliary needs (including any i just NEEDED to add in the future).

Here is what i picked up:

This would allow me to re-wire everything i had, while allowing me 4 complete circuits for future use. Mind you, this is an open bottom box, hence i simply picked up a silicone baking mat off amazon for 5 bucks, cut it to size and used it as a gasket. It's a really thick and plush baking mat, thickest I've ever seen so it works well as the edges of thr box have something to bite into...sealing it pretty well. Unsure how well this baking mat would do for actual baking as a matter of fact. But GREAT gasket material for this application. 馃憦
Footwear Shoe Tire Automotive tire Bumper

Now obviously, this is going to look MUCH different than anyone else because as i always do.... i acquired a bunch of parts over the back half of 2021 which included PS inner fenders. Here they are mid-install.

I got hit with a turbulent depression for about 9 months before i could install any of these things. SInce they all were kind of required to make everything work. This simple dual battery project turned into a multi layered project which ended up being pretty nifty upgrade all around (form + function). It might not apply to everyone (as in, not EVERYONE will be installing everything i did for this "dual battery project"). This will simply be a tale of bruinjeeper's YJ. Take from it what you wish.

Needless to say - these fenders changed the dynamics and logistics of everything under the hood. These needed to get installed first before i tackled anything to do with the electrical. SO i grabbed a case of beer and a carton of cigarettes and went to work.

Here is what i started with. Yes, my optima battery posts were being mugged - despite an original wiring clean up. At least at the time i knew i did everything safely instead of having crap all over the place and exposed to elements. Everything got labelled accordingly. But the relay box was simply just in an uncomfy position to work on and get to (firewall inboard of battery). I'm just a smidgen taller than Brad Marchand, and though i share the same drive despite being a smaller guy, i aint gonna lie - it was a *****. I had to work while kneeling on my fenders. Ouch.
Below you can see the shiny black 6 relay box to the left of the right of the battery.

and a few more because everyone loves photos, right?

you can see, although labelling and logistics were okay - it was convoluted needlessly.

Moderation in Moderation
1995 YJ Wrangler SE
11,672 Posts
Discussion Starter · #2 · (Edited)
I will start this section off by stating i had already upgraded/made 1/0 gauge negative ground cables in and around 2016, and at that time upgraded to the GC 136A alternator. You can see above due to space and a complete lack of ingenuity, i routed the new cabling through a 150A waffer fuse holder from alternator to battery. I mounted this atop my OEM PDC. This made things a ***** to simply replace a fuse in the PDC.

These 4 aforementioned 1/0 ground cables were re-used in this project. These are important with or without a dual battery project on a ~30 year old rickety YJ that has seen a lot of pavement and bumpy off road stuff. Everyone should be upgrading their grounds - it removes a lot of headaches and needless troubleshooting chasing down electrical gremlins in our YJs.

Ok back to the program.

After installing the inner fenders, i ended up with the below. I went ahead and ripped out the old battery tray and listed it for sale on a local ad of course. Here is a shot with none of the wiring or old fuse and relay panels touched yet and the RUgged Ridge dual battery tray installed. EVerything else is just loose and hovering in place at this point while i figured out how to lay things out.

What was evident off the get-go was i needed to separate that lead from the Alternator to the battery (through the 150A waffer fuse) from the top of the PDC as the PDC was never going to fit back in its original place with the new fenders in place and the dual battery tray. Hence, i could not use the crappy "PDC" relocation bracket that came with the RR dual battery tray kit. I had to get clever, here so what i did was remove the OEM PDC bracket and looked at how i could re-use this thing in order to secure the PDC to a new location not too far away to secure it properly (like from factory). Around my 7th beer that day i decided to mount the PDC sort of where it fell in the photo posted above.

I manipulated the original bracket (cut and bent accordingly) so that i could run the PDC length wise against the inner wall of the new inner fenders.

This allow me to drill two holes (shown above) in the bent piece of the bracket which i would locate with drilling holes and utilizing SS hardware to neatly bolt it in place through the inner side of the fender well. It worked out really well keeping things concise while allowing plenty of space to manipulate my OBA system if need be in the future. That worked out (love it when that happens after 7 beer). WIth that outta the way, logistically speaking, things started simply falling into place as i went into this with no game plan in terms of item placement.

I mounted the 150A waffer fuse and holder to the upper back side of the inner fender well as that seemed like the most thorough and natural routing for the alternator to battery + lead. I then just simply decided to mount the negative ground distribution bus just beside it at the top side of the flat inner fenders nearby. This positioning i found, fortunately might i add, allowed me to simply keep the original 1/0 gauge ground cables as their lengths were such - they had the proper length to still reach firewall, block, alternator, and the negative distribution buss.

I did run into a snag (minor) with the placement of the PDC, as this placement positioned the input wire to the PDC towards the front of the engine bay, and i had already made up my mind at this point to mount my Positive distribution busses on the fire wall above where the batteries would sit. The OEM cable was simply not long enough to reach back there. I got really lucky, and had just changed out battery cables on my Dodge Journey but retained the OEM Dodge cables. These just so happened to have not only enough slack to JUST reach the position of the distribution block, but also had a similar style rectangular perpendicular lug on the end. I simply had to drill a second hole in it to apply it to the dual studded application on our YJ's OEM PDC connection.

With the logistics starting to come together, i got to work on the daunting part of this project. WIring up the new auxiliary PDC. I did it right, took my time, and made daisy chains (first time ever) to limit the amount of wires heading in and out of a box this big. Whole 9 yards - crimped, soldered, heat shrunk - here is the time lapse of it getting more and more convoluted. Ideally you would like to use multicoloured wires to give yourself less of a headache... but so long as you understand how relays work (pins) and what goes where, you should be fine with a couple colours to save on how much wiring you would need to purchase.

And here is the spaghetti you're gonna end up with when done. Might look hard to follow, but again, can be done without colour coordination if you understand how relays and fuses and basic circuitry works.

Looks much neater when you turn it around eh? lol

OK. With that done. It didn't take many brain cells to figure out where this box would be best placed for future additions, inspections and just a location that overall made sense. Atop the new huge footprint of an inner fender - keeping everything electrical really close together and concise. This image was taken in stride - firewall was cleaned up and repainted afterwards and prior to dropping in two HUGE new batteries.

I started gaining some real momentum at this point, dropped the big batteries in and mounted my PDC with stainless hardware to the fender top after labelling each strand of wire coming out of the box. ANd started figuring out where to run the wiring in the most efficient and neat runs i could think of so they got their "muscle memory" and would stay in place neatly. I then quickly went ahead and created a functional, albeit rudimentary, but easy to read and comprehend 'legend' for the auxiliary PDC and taped it with clear gorilla tape to the inside of the PDC cover. ALso painted and mounted the 2nd positive distribution bus on the firewall (each positive bus were respective of their own battery, sticking with the plan to feed all OEM with one battery and anything i have added with the 2nd battery:


Moderation in Moderation
1995 YJ Wrangler SE
11,672 Posts
Discussion Starter · #3 · (Edited)
I slipped a little at this point, probably a little due to depression creeping back in, and partially probably because the next task (although not necessarily pertinent to some readers) was crucial to my context. It might be a bit off topic but i will include it here before moving onto installing the Painless dual battery isolator/combiner.

As i stated i did lose momentum but kept busy doing little things being sure not to drop it entirely. I tidied up wiring on the new driver side fender, relocated the horn, modified the air dam for the airaid) and installed LED side markers inside the fenders. Also got a chance to relocate the windshield washer reservoir a couple inches hire on the new fenders for much easier refilling - always hated how low it is positioned from factory. almost impossible not to spill the initial surge lol. Also had to add an aftermarket simple coolant overflow bottle as there was no good way to re-use the factory one. Mounted it inboard the air dam in unused space.

in between all of this i got it registered in Ontario from BC for the first time and took the opportunity to wire the license plate lighting more efficiently - re-utilizing a harness from a wiring kit i kept kicking around. Spliced in, and now future license plate removal is that much easier:

But i digress. . .

Tracing the wiring back to my overhead switchpanel was not going to be easy. Amateur and hasty former version of myself just wanted "it done" - and i knew this in the back of my head all along. Doubly i knew it might be just as frustrating tracing the wire runs to the actual sets of lights or whatever component the output leads powered. But i kept at it and the Octopus kept growing and becoming more complete.

Harness connectors were utilized at all conjunctions (inflow of the PDC and out flow of the PDC for easy disconnect in the future if needed (i praise the Lord it needn't be as the entire PDC was wired up, not solely the existing circuits - hence any future additions is simply a plug and play with a relay and a wiring connection (y)

as I completed the wiring, i may not have been able to drive it (or perhaps i am a completist at this stage in my life and wont allow myself to enjoy a reward prematurely) I simply wired up the starting battery to get the YJs juices flowing as the poor gal has been sitting much of the past two years.


Moderation in Moderation
1995 YJ Wrangler SE
11,672 Posts
Discussion Starter · #4 · (Edited)
Once i got everything traced, connected, mounted and verified functionability, it was time to move making this a dual battery install. The Isolator/combiner.

atop the battery tie down are two appropriately space studs upon which i chose to mount it.
Running the Painless kit wasn't rocket science, it all comes together pretty easy. I did choose to tap one of the empty single blade ports in the cab which feeds 12v to the switch to limit the amount of wiring going into the bay needlessly, then took the 5/8" hole saw and cut a designated hole into the fire wall next to the others i have made, grommetted and fed the wires through and attached them where they needed to go according to instructions.

I mounted the switch and LED lights where the hardtop control cut outs were located. They have been disconnected as i don't really utilize my hardtop any longer. I bought a package of xwitch blank out plates drilled two hols for the lights and popped it into HC control slot 1 and wedged the ultra beefy switch into HC control slot 2. Not ideal but it is in there rock solid. I am thinking i will be grinding out the hole enough with a dremel to fit - but if i ever go back to hardtop - and or ditch this setup . . . . . im stuck with an awkward hole. SO for now it stays.

Red = Batteries are isolated but both charging. This is an option while the vehicle is off, key on, or running.

Green = Batteries are combined and fully charging. This is an option only available while the vehicle is in key on or running.

No light (mid position) = Secondary battery Isolated completely from system/charge. Starting battery operating normally/charging.

Link up your new Voltmeters into the daisy chain up overhead:

Link up your battery cables accordingly cut as concise to length as possible because it got tight on me real quick despite all the measures taken to clean up wiring lol.


Premium Member
4,857 Posts
WOW! Just simply wow! Yes. It should be a sticky. That is an amazing write up. Amazing detail but even more amazing in the quality of the work.

Just be forewarned though that a sticky would require an entire schematic of your Jeep that is clearer that a factory schematic for the said year. ;) JK. You could do that with a couple of crayons. :ROFLMAO:

Dude. I am an electrical guru. I am now thinking about letting you wire my Jeep. Very, very clean work. Well done. Once again. An equally amazing write up.

As far as your reference to working on a Jeep while only being as tall as Marchand, remember, I am even shorter than Theoren Fleury. Take that! Knees on the fenders does not get it. I can get my tiny little feet inside next to the engine on the frame rails. In fact, that is what I will be doing in a few. Not to hi jack you but my Mopar plastic valve cover arrived today. It was not available forever, it did not cross reference to anything. I have looked for them for a long time. The OMIX one I bought that was supposed to fit with a lot of other stuff done was a disaster. It would have worked if the OMIX cover held any clearances at all. Just a POS in the end. When I googled again, I found an OEM one on Flea bay listed as an AMC Eagle part. Unboxed it tonight. It is the real deal, but some how the internal baffles at sometime became unattached to the inside of the cover. They were wrapped in separate paper and included in the cover packaging. Kind of shady in a way, but yet I feel like I got the last correct OEM valve cover for Daisy on the planet. I will deal with it.

Amazing though. Your choice of what to use, the quality of connectors, everything. Very well done.

You have as I have stated before, possibly the most electrically advanced YJ on the planet. You have disputed it but somewhere in this post, you spoke of different versions of USB. You need to swallow your pride and tap out on that one buddy.

Freaking awesome write up. Possibly the best that has ever been on this site. I once again recognize the true professionalism of the work and components.


Mind blown.

Last thought. You got this far in 7 beers. WTH would you accomplish with a 30 pack??? JS.

Moderation in Moderation
1995 YJ Wrangler SE
11,672 Posts
Discussion Starter · #8 ·
WOW! Just simply wow! got this far in 7 beers. WTH would you accomplish with a 30 pack??? JS.
I have evidence archived somewhere of what happens after 14 beer ..... 8.8 spring perch on the driver's side was welded closer to an SOA position than the necessary SUA position. Which wouldn't have been necessarily a bad thing had I not already welded the passenger side to its correct SUA position/angle (mind you, the passenger side was done before I hit the foggy 7 beer state of mind lol.

.........wouldn't have been a good thing or as easy a fix if my inputs were mashed up with my outputs from the PDC box lol
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