Aux Battery Cables

[AzCoronaDog]

Meaning, to accomplish total isolation of AuxBatt:

• Disconnect the AuxBatt POS cable end from the N3 terminal.
• Disconnect the AuxBatt POS cable end from the N1 terminal.
• Disconnect the AuxBatt NEG cable end from the PrimBatt NEG terminal
• Jump N2 to N1.

Results:

• PrimBatt is free of any pull down effect from AuxBatt.
• ESS continues to function as designed, ie, can disable by dash button each drive time.

Am I missing any understanding?

Correct!

If you want to keep the N1 circuit protected by the 150a fuse like the factory setup, jump N1 to N3 (instead of N2). But honestly, if N1 pulls more than 150a, your Jeep is probably on fire anyway!

Sponsored

 

[ScotM]

This thread is a mess and probably confuses more than it helps. I don't believe any puppies will die if it is deleted.

The N load studs, except at the N1 terminal, get power from the main battery connection to N2 and from the placement of the high amp fuse array. The N1 terminal distributes power to most of the Jeep's loads, including those essential for operation. N1 gets reliable power when,

1) the stock aux battery positive cabling is kept in place (regardless of whether the aux battery is connected or not), the fuse at N3 is maintained, and F42 is removed, or

2) a high amp jumper is installed from N1 to N2, or to any other N stud where the fuse is intact, or to a stud on the main battery bus.

The Jeep is metric. The N studs are M6 standard threading. 1/4 inch nuts sometimes work on M6 threads, but their use is not good practice. (Nor is it good practice to think of nuts and studs as conductive and part of the electrical connection, but that's another story).

I was only referring to what size battery eyelet you would need, as an M6 or 1/4” will work on the high capacity fuse array. It is never a good idea to mix thread types when securing a connection. I had hope that was obvious.

 

[alphawolff]

S/S wiring is as follows:

Primary -> N2 -> 150A FUSE N3 (VOLTAGE OUTPUT)-> PCR -> AUX POSITIVE -> N1


The N1 is the only post that powers the vehicle. The other posts are for the alternator, EPS, and starter circuits (plus the n2/n3).

This means that if the 150A fuse blows the primary is no longer able to touch the fuse box, it can only power EPS/STARTER circuits. If the fuse is blown the alternator also can no longer touch the aux battery. This causes the aux battery to power the entire vehicle until it depletes (rapidly). The primary effectively piggybacks onto the aux positive to reach the fuse box.

That 150AMP fuse seems serve absolutely zero purpose. It might've been a leftover from development. Its only theoretical use would be to stop the N1/PCR/Aux from shorting to ground, but it'll still short the aux battery as the fuse is way up circuit beyond the aux battery. The whole system is a massive engineering oversight. You can see their intended purpose (isolate the primary for starter/eps power supply), but failed to really think of the failure points.

 

[AzCoronaDog]

S/S wiring is as follows:

Primary -> N2 -> 150A FUSE N3 (VOLTAGE OUTPUT)-> PCR -> AUX POSITIVE -> N1


The N1 is the only post that powers the vehicle. The other posts are for the alternator, EPS, and starter circuits (plus the n2/n3).

This means that if the 150A fuse blows the primary is no longer able to touch the fuse box, it can only power EPS/STARTER circuits. If the fuse is blown the alternator also can no longer touch the aux battery. This causes the aux battery to power the entire vehicle until it depletes (rapidly). The primary effectively piggybacks onto the aux positive to reach the fuse box.

That 150AMP fuse seems serve absolutely zero purpose. It might've been a leftover from development. Its only theoretical use would be to stop the N1/PCR/Aux from shorting to ground, but it'll still short the aux battery as the fuse is way up circuit beyond the aux battery. The whole system is a massive engineering oversight. You can see their intended purpose (isolate the primary for starter/eps power supply), but failed to really think of the failure points.

N1 does power MOST of the vehicle, but N2 powers all the other Nx posts, specifically the power steering pump through N6 and the electric cooling fans through N5, and a couple of other less important stuff through the fuse block.

 

[alphawolff]

N1 does power MOST of the vehicle, but N2 powers all the other Nx posts, specifically the power steering pump through N6 and the electric cooling fans through N5, and a couple of other less important stuff through the fuse block.

Didn't think of the cooling fan I guess. All the really high load stuff. The aux battery is also powering them as well backwards through that n3 fuse (in parallel)

N1 powering the fuse box is like 99% of the vehicle. This is why if that fuse blows you need to provide power to N1 to get it going (either jumper wire or jump box on forced power)

 

[AzCoronaDog]

Didn't think of the cooling fan I guess. All the really high load stuff. The aux battery is also powering them as well backwards through that n3 fuse (in parallel)

N1 powering the fuse box is like 99% of the vehicle. This is why if that fuse blows you need to provide power to N1 to get it going (either jumper wire or jump box on forced power)

I purchased the full OEM repair manual for my '24, which includes hundreds of pages for the wiring diagrams. It is a complicated beast electrically! Pretty sure the wiring diagram for my '76 CJ7 fit on a single page... LOL
But the whole aux battery thing just feels like some engineering for engineering's sake, or a solution looking for problem.
Every other vehicle I have owned or rented with start/stop worked fine with just one battery. And if Jeep just programmed the system to remember the ESS setting between run cycles, we probably would never have this discussion!
I am glad I have a warranty, but the aux battery will be the first thing I get rid of when the warranty is up.

 

[mbrose1994]

N1 does power MOST of the vehicle, but N2 powers all the other Nx posts, specifically the power steering pump through N6 and the electric cooling fans through N5, and a couple of other less important stuff through the fuse block.

In effort for simplicity,

• IF I put the PrimBatt POS cable on N1
• And jumped N1 to N2
• And disconnected all AuxBatt cable ends
  • NEG off PrimBatt NEG post
  • POS off N1
  • POS off N3

I have eliminated the AuxBatt (electrically) and have a single battery system.

Any expected issues with so doing?

 

[AzCoronaDog]

In effort for simplicity,

• IF I put the PrimBatt POS cable on N1
• And jumped N1 to N2
• And disconnected all AuxBatt cable ends
  • NEG off PrimBatt NEG post
  • POS off N1
  • POS off N3

I have eliminated the AuxBatt (electrically) and have a single battery system.

Any expected issues with so doing?

That should work fine, and ESS should still function.

 

[Mguy]

In effort for simplicity, do the aux battery negative/F42 disconnect, enjoy the reliability of a single battery 12v system, and use ESS if you still want.

• IF I put the PrimBatt POS cable on N1
• And jumped N1 to N2
• And disconnected all AuxBatt cable ends
  • NEG off PrimBatt NEG post
  • POS off N1
  • POS off N3

I have eliminated the AuxBatt (electrically) and have a single battery system. Yes, and you would make fans of Rube Goldberg proud.

Any expected issues with so doing? Yes. Due to the peculiarity of the Jeep hardware for N terminals, your custom work will be either unnecessarily difficult to do, or have an unnecessary level of unreliability.

My comments to your post in bold, above. I don't see your reason for moving lugs and installing a jumper. There are, in fact, not many. It seems like you're trying to reinvent the wheel.

 

[alphawolff]

In effort for simplicity,

• IF I put the PrimBatt POS cable on N1
• And jumped N1 to N2
• And disconnected all AuxBatt cable ends
  • NEG off PrimBatt NEG post
  • POS off N1
  • POS off N3

I have eliminated the AuxBatt (electrically) and have a single battery system.

Any expected issues with so doing?

Correct. You'll just have a bunch of wasted cabling laying around. Lot easier to just install a jumper between N1&N2 and leave everything else intact. If the aux battery eventually fails you can isolate it then.

 

[mbrose1994]

My comments to your post in bold, above. I don't see your reason for moving lugs and installing a jumper. There are, in fact, not many. It seems like you're trying to reinvent the wheel.

LOL! I appreciate the Rube Goldberg (RG) reference too.
But, I contend, unwinding the AuxBatt is difficult because Jeep created a RG design.
Establishing a simpler, single battery system is worth the effort.

And, unfortunately, my Jeep did not like quick easy AuxBatt NEG cable off, pull Fuse 42 state.
So, my extra effort to eliminate (electrically) the AuxBatt entirely.

Moving the PrimBatt POS from N2 to N1 is just simple, direct connect logic.
Then doing jumper from N1 to N2 is simple way to power rest of Jeep.
Yes, I have 3 useless AuxBatt cables doing this.
But, Jeep's RG design is to blame for that.

Crossing my fingers because Jeep's RG design might reject this effort to simplify.

 

[THAW]

If for some strange reason you want to remove the aux battery but still have ESS operative, a jumper from N1 to N2 or N3 and leaving fuse 42 in place is the solution. The aux cables can then be removed. The relay does't come into play, but the computer will notice if F42 is not there.

In effort for simplicity,

• IF I put the PrimBatt POS cable on N1
• And jumped N1 to N2
• And disconnected all AuxBatt cable ends
  • NEG off PrimBatt NEG post
  • POS off N1
  • POS off N3

I have eliminated the AuxBatt (electrically) and have a single battery system.

Moving the PrimBatt POS from N2 to N1 is just simple, direct connect logic.
Then doing jumper from N1 to N2 is simple way to power rest of Jeep.
Yes, I have 3 useless AuxBatt cables doing this.
But, Jeep's RG design is to blame for that.

A separate jumper is not required; just move the AUX (ESS) battery positive cable terminal connector to the CR[an]K/main battery positive post.

 

[THAW]

The best way to think about N1 is: it's the Jeep (fuse box). That is, N1 is where the battery/batteries and/or alternator/PPU are sending power.

 

[AzCoronaDog]

The best way to think about N1 is: it's the Jeep (fuse box). That is, N1 is where the battery/batteries and/or alternator/PPU are sending power.

Mostly. The cooling fans and electric power steering are on other N terminals, as they are very high amperage. (So is the alternator output)
So the best way to think about it is N1 and N2 have to have power 100% of the time for everything electric to function.

 

[AzCoronaDog]

There are certainly several ways to successfully eliminate the aux battery, but when my warranty is up and I do that fix, I will use a jumper from N1 to N3, so the original factory setup of N1 having a 150a fuse back to the main battery remains.
Even though my warranty is good for another 2 1/2 years, I built a jumper to keep in the jeep for future use.

It is made of 14g aluminum, plenty of current carrying capacity, won't rust, and fits with the fuse box lid on. The two nuts allow me to put it in place on top of the originals.

I threw in a 10mm socket and adapter to fit the factory ratchet, and it all fits in the factory tool kit.

I will use the jumper, remove all the aux battery cables, box, etc., and keep F42 in place so ESS can still work if I hit my head and think it is a good idea for some reason.
I already have an ESS module thingy that turns ESS off every time the Jeep starts (10 second removal if needed), so my aux battery is there just to avoid any warranty issues.

Sponsored