Jumperless Aux Battery Bypass

[Rhinebeck01]

ESS with main only from the factory?

In regard to a stock JL ..... IF you only have only one cable on the Main batteries negative side, you do not have a dual battery system, JL. You do not have an Aux battery on that JL.

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[KOKOKO]

IF you only have one cable on the Main's negative side, you do not have a dual battery system, JL. You do not have an Aux battery.

I understood your first observation. No secondary wire on main battery = no aux battery. I do have ESS so was simply inquiring in a puzzling manner how it was being powered. I didn't know there were 3.6 Wranglers using the main battery to power the ESS system.

 

[Rhinebeck01]

I understood your first observation. No secondary wire on main battery = no aux battery. I do have ESS so was simply inquiring in a puzzling manner how it was being powered. I didn't know there were 3.6 Wranglers using the main battery to power the ESS system.

I believe you have an eTorque, JL...

To tell ... eTorque or not...

Pop the hood and in say 15 seconds you can take a looksee and tell if it is an etorque JL or not....

With eTorque ........and the JL, you will see the factory has placed a solid metal jumper between N1 and N2 in the Power Distribution Center (PDC).

You will also find that there is NO, Aux battery negative cable attached to the Main batteries Neg terminal... you will just see an available stud on the Main battery neg terminal, with no cable attached to it...

And indeed, the plastic box under the PDC/ hiding behind the passenger fender flare, is there... but does not have an Aux battery in it.. it is just an empty box.

And of course, if you crawl under... with eTorque, you will see, the 48v battery box will be these... - (with battery) just ahead of the rear axle on the drivers side.

And yes, there are also other differences......

 

[KOKOKO]

I believe you have an eTorque, JL...

To tell ... eTorque or not...

Pop the hood and in say 15 seconds you can take a looksee and tell if it is an etorque JL or not....

With eTorque ........and the JL, you will see the factory has placed a solid metal jumper between N1 and N2 in the Power Distribution Center (PDC).

You will also find that there is NO, Aux battery negative cable attached to the Main batteries Neg terminal... you will just see an available stud on the Main battery neg terminal, with no cable attached to it...

And indeed, the plastic box under the PDC/ hiding behind the passenger fender flare, is there... but does not have an Aux battery in it.. it is just an empty box.

And of course, if you crawl under... with eTorque, you will see, the 48v battery box will be these... - (with battery) just ahead of the rear axle on the drivers side.

And yes, there are also other differences......

I believe you have an eTorque, JL...

To tell ... eTorque or not...

Pop the hood and in say 15 seconds you can take a looksee and tell if it is an etorque JL or not....

With eTorque ........and the JL, you will see the factory has placed a solid metal jumper between N1 and N2 in the Power Distribution Center (PDC).

You will also find that there is NO, Aux battery negative cable attached to the Main batteries Neg terminal... you will just see an available stud on the Main battery neg terminal, with no cable attached to it...

And indeed, the plastic box under the PDC/ hiding behind the passenger fender flare, is there... but does not have an Aux battery in it.. it is just an empty box.

And of course, if you crawl under... with eTorque, you will see, the 48v battery box will be these... - (with battery) just ahead of the rear axle on the drivers side.

And yes, there are also other differences......

Correct on all counts. Thanks for the knowledge.

 

[Fudster]

Not questioning which cable is which. I only have one cable attached to the main neg terminal. I assume the aux is bonded at the chassis or frame. Asking if anyone can confirm where?

Noted...sorry...didn't know when I responded

 

[lakebuster]

Pulled #42 fuse and removed auxiliary battery negative cable with heat shrink and tape. 2 things happened when It 1st started the 2020 Jeep Wrangler it started beeping and must have finally timed out, never heard this type of sound and voltage was high on digital read out.
Has anyone else had this happen?

 

[lakebuster]

Okay need some help, removed all grounds from negative post. 1 Negative wire had 2Volts it was the larger of the two ground wires, the smaller ground wire had 13 volts so bolted that to the negative post. (Also have F42 pulled) and even with 13 volts the Jeep is not starting nor does it have any power past the battery.

I need some help please!

 

[azwjowner]

Okay need some help, removed all grounds from negative post. 1 Negative wire had 2Volts it was the larger of the two ground wires, the smaller ground wire had 13 volts so bolted that to the negative post. (Also have F42 pulled) and even with 13 volts the Jeep is not starting nor does it have any power past the battery.

I need some help please!

I think you have it backwards. The smaller ground wire is the aux battery lead, that's the one you want to disconnect. The larger ground wire stays connected to the main battery.

 

[Fudster]

Okay need some help, removed all grounds from negative post. 1 Negative wire had 2Volts it was the larger of the two ground wires, the smaller ground wire had 13 volts so bolted that to the negative post. (Also have F42 pulled) and even with 13 volts the Jeep is not starting nor does it have any power past the battery.

I need some help please!

To restate @azwjowner's thoughts, which I concur with, your removal of both black factory cables from the main battery takes the main battery out of the vehicle's electrical schematic and is wrong. Then separating both of these removed cables from one another takes the ESS battery out of the electrical schematic of the vehicle as well. At least if you had kept these two disconnected from the main battery's negative post cables connected, you'd have power from the ESS battery to furnish the vehicle.

Many vehicle appliances have current returned to the vehicle's battery/ies negative post by using the metal of the vehicle itself as the "ground wire" if you will, to which the body ground connection I describe below then channels to the negative post of either of both batteries to complete a circuit. It sounds like the cable leaving the vehicle's body ground is not connected to anything.

Rather--and this is just a restatement of @azwjowner's thoughts, identify the vehicle's body ground. This is under the hood on top of the passenger's front quarter panel half way between the front of the vehicle and passenger's compartment. One of the cables that starts there needs, at its other end, to be connected to the main battery's negative positive. It seems you disconnected it.

The other factory cable's end you disconnected from the main battery's negative temrial should be wrapped in insulative material (so it doesn't electrically short on any vehicle metal) and set to the side. The other end of that dangling cable attaches to the ESS battery's negative post.

This action I describe, where only one, and the correct cable is dangling, will take the ESS battery out of the electrical schematic of the vehicle and reinstate the main battery into it. Done in concert with the removal of Fuse 42, which you stipulate, your vehicle will be unable (a good thing) to energize a relay that separates the two batteries, which happens for an instant at cold crank and during ESS events.

Now, all calls for electrical current will go to all connected batteries, which for you is just the main battery now.

Do disable ESS from engaging. To allow it to engage would tax your one cranking battery during ESS events: the very thing the two battery design was design to prevent when that relay you prevented from being energized by pulling Fuse 42 separates the batteries during ESS events and runs the vehcile's appliances off of the small battery.

 

[lakebuster]

To restate @azwjowner's thoughts, which I concur with, your removal of both black factory cables from the main battery takes the main battery out of the vehicle's electrical schematic and is wrong. Then separating both of these removed cables from one another takes the ESS battery out of the electrical schematic of the vehicle as well. At least if you had kept these two disconnected from the main battery's negative post cables connected, you'd have power from the ESS battery to furnish the vehicle.

Many vehicle appliances have current returned to the vehicle's battery/ies negative post by using the metal of the vehicle itself as the "ground wire" if you will, to which the body ground connection I describe below then channels to the negative post of either of both batteries to complete a circuit. It sounds like the cable leaving the vehicle's body ground is not connected to anything.

Rather--and this is just a restatement of @azwjowner's thoughts, identify the vehicle's body ground. This is under the hood on top of the passenger's front quarter panel half way between the front of the vehicle and passenger's compartment. One of the cables that starts there needs, at its other end, to be connected to the main battery's negative positive. It seems you disconnected it.

The other factory cable's end you disconnected from the main battery's negative temrial should be wrapped in insulative material (so it doesn't electrically short on any vehicle metal) and set to the side. The other end of that dangling cable attaches to the ESS battery's negative post.

This action I describe, where only one, and the correct cable is dangling, will take the ESS battery out of the electrical schematic of the vehicle and reinstate the main battery into it. Done in concert with the removal of Fuse 42, which you stipulate, your vehicle will be unable (a good thing) to energize a relay that separates the two batteries, which happens for an instant at cold crank and during ESS events.

Now, all calls for electrical current will go to all connected batteries, which for you is just the main battery now.

Do disable ESS from engaging. To allow it to engage would tax your one cranking battery during ESS events: the very thing the two battery design was design to prevent when that relay you prevented from being energized by pulling Fuse 42 separates the batteries during ESS events and runs the vehcile's appliances off of the small battery.

When I connect the larger wire and taped up smaller wire, I get an audible alarm and the alternator pegs out at 14.3-14.5 post number #355 shows the alarm I am talking about.

 

[Leisure Freak]

My 2019 Sport didn't see the k

When I connect the larger wire and taped up smaller wire, I get an audible alarm and the alternator pegs out at 14.3-14.5 post number #355 shows the alarm I am talking about.

I had something similar when doing this F42/Aux Ground removal on my 2019 Sport. Firsts start quirk where asked I use key against start button and first time ever chime going off. I started the jeep and chime continued until I pressed OK on the steering wheel. Chime ended and has never returned. Normal operation ever since. I will say my volt display has been in the 14s from day 1 ownership even with both batteries. Even when it gets into the high 12s after a road trip's 8 hour drive it returns to the 13s and then 14s the next days. Jeep told me -- normal, of course.

 

[Fudster]

When I connect the larger wire and taped up smaller wire, I get an audible alarm and the alternator pegs out at 14.3-14.5 post number #355 shows the alarm I am talking about.

David, for me to help you I need you to identify the cables as the one "whose other end is the body ground," and the other, which I assure you came from the factory connected at its distal end to the ESS battery's negative terminal.

 

[lakebuster]

David, for me to help you I need you to identify the cables as the one "whose other end is the body ground," and the other, which I assure you came from the factory connected at its distal end to the ESS battery's negative terminal.

Thanks for the help the large ground cable read 0 V but once I connected to negative terminal on top of the IBS it is now working.
Thanks for the help

 

[JL MADDOG]

So I pulled the aux battery cable and removed F42 as noted by the OP.

Everything works fine except I get the error message when starting the engine and the ESS fault symbol lights up in the EVIC.

Is there a solution to that?

 

[Fudster]

So I pulled the aux battery cable and removed F42 as noted by the OP.

Everything works fine except I get the error message when starting the engine and the ESS fault symbol lights up in the EVIC.

Is there a solution to that?

Hi Michael:

As you may know, when you pull Fuse 42 you prevent a relay from being energized that separates the two batteries; itself an event that only happens under factory conditions for an instant at cold crank, and during ESS events.

With Fuse 42 yanked calls for electrical current from either battery go to all connected batteries, which in your case is just the main battery.

With this said, the pre crank check of the ESS battery, in your case, gets routed to the main battery.

Is it possible your main battery is on its way out? Is it possible some other factor that disables ESS, like misaligned hood close pins, is at play?

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