Jumperless Aux Battery Bypass

[Mtrctylarry]

I have some questions about start/stop and the aux bypass. I replaced my battery a couple weeks ago with a new Interstate battery (the larger one) and did the bypass. After driving a half hour or so, start/stop started working as typical. Within a day or two, it stopped working and I started getting the battery charging message. Even though it was a brand new battery, I stuck it on my trickle charger overnight to top it off. Start/stop started working again as typical. A week or so later it stopped working again and the battery charging message came back. After charging it again overnight, start/stop is not working and I continue to get the charging message. According to the dash, the battery is reading 13.8 to 13.9 while driving around. At idle it reads 13.8. I‘m thinking that the new battery is defective and that the next step would be to load test it. Thoughts? Thanks, in advance, for any guidance.

I believe your right about having a bum new battery, my 2019 JLRU is still on the original main batt and bypassed stop/start couple of years ago. Still reads 14.7 Volts while driving.

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[OldGuyNewJeep]

I have some questions about start/stop and the aux bypass. I replaced my battery a couple weeks ago with a new Interstate battery (the larger one) and did the bypass. After driving a half hour or so, start/stop started working as typical. Within a day or two, it stopped working and I started getting the battery charging message. Even though it was a brand new battery, I stuck it on my trickle charger overnight to top it off. Start/stop started working again as typical. A week or so later it stopped working again and the battery charging message came back. After charging it again overnight, start/stop is not working and I continue to get the charging message. According to the dash, the battery is reading 13.8 to 13.9 while driving around. At idle it reads 13.8. I‘m thinking that the new battery is defective and that the next step would be to load test it. Thoughts? Thanks, in advance, for any guidance.

You should not use ESS if you have done the bypass. Jeep literally added a second battery to support ESS - that’s its sole purpose!

Either train yourself to press the button each and every time you drive, invest in a SmartStopStart or Tazer, or undo the bypass.

 

[OldGuyNewJeep]

I believe your right about having a bum new battery, my 2019 JLRU is still on the original main batt and bypassed stop/start couple of years ago. Still reads 14.7 Volts while driving.

14.7 volts is what your alternator is putting out, not how many volts your battery has at rest.

A number that high means IBS sees your battery is depleted and is trying to charge it in a hurry.

When my group 94 Odyssey is fully charged my display will read between 12.6-13.1.

 

[Mtrctylarry]

14.7 volts is what your alternator is putting out, not how many volts your battery has at rest.

A number that high means IBS sees your battery is depleted and is trying to charge it in a hurry.

When my group 94 Odyssey is fully charged my display will read between 12.6-13.1.

Your absolutely right...I didn't think about the gauge while driving is showing the charge rate going into the Battery. My Wrangler is not a daily driver, so I keep it on a battery tender while not driving. My Craftsman voltmeter after driving shows 13.4 right after a drive, but next time I'll wait a few days and see how its holding.

 

[jeepdawg706]

Hi guys. Just finding this thread after going through the ringer with a main battery dying, replacing it, then it dying again to only end up replacing the aux. I had the NEW main battery replaced today under warranty because it died again today. ESS still doesn't work (stuck on battery charging).

I want it gone but I have a winch and lights hooked up. Is that a contraindication to do this?

Thanks in advance

 

[DKAwildcat]

I did the auxiliary bypass a month ago and had no problems immediately afterwards. The ESS worked as normal. About a week ago I noticed the radio would sometimes make a popping sound when the engine restarted at an intersection. I haven't heard of anyone else having this issue. Will this damage the radio in time if I don’t push the ESS button immediately after starting the engine? When I do hear the popping noise, it does remind me to press the button.

 

[joliett]

I had that sound. You have to just reset the radio.

Put car in RUN mode:
I have been simply holding down the volume button until the screen goes black and then it seems to reset. Voila.

 

[DKAwildcat]

I had that sound. You have to just reset the radio.

Put car in RUN mode:
I have been simply holding down the volume button until the screen goes black and then it seems to reset. Voila.

I did the radio reset twice and the speakers still makes a popping sound on occasion when the engine restarts at a stoplight. I recently updated to the newest version of Uconnect so I wonder if it has anything to do with that? In any event, I’ll keep trying to remember to press the ESS shutoff button after starting.

 

[IceCactus]

I just purchased a 2021 Wrangler Eco Diesel. Im pretty sure the aux battery is dying, it stopped does ESS and the screen on the dash constantly says charging ESS battery.

Im thinking the starting and stopping isnt great, especially for diesel so I want to get rid of the aux battery so it doesnt drag down my main. Ive read through all the pages and it seems there is conflicting methods.

If i want to take the AUX completely out,

1) Pull F42 fuse
2) Remove aux battery

Do I need put the + and - to the main battery?

Or do i tape off both + and -?

Or do attached + to main and tape off -?

 

[AndySpill]

I just purchased a 2021 Wrangler Eco Diesel. Im pretty sure the aux battery is dying, it stopped does ESS and the screen on the dash constantly says charging ESS battery.

Im thinking the starting and stopping isnt great, especially for diesel so I want to get rid of the aux battery so it doesnt drag down my main. Ive read through all the pages and it seems there is conflicting methods.

If i want to take the AUX completely out,

1) Pull F42 fuse
2) Remove aux battery

Do I need put the + and - to the main battery?

Or do i tape off both + and -?

Or do attached + to main and tape off -?

Let me assume your JL is equipped with dual AGM batteries: not all JLs are.

The simplest step is to identify the black cable (there are two) which connect to the main battery's negative terminal, whose other end is NOT the body ground connection on the passenger's side quarter panel just under the hood.

Leave that cable connected.

It is the other cable, (whose distal end connects to the negative terminal of the Aux battery BTW) that you disconnect, and wrap its now loose end in insulative material so it doesn't risk coming in contact with metal and causing a short.

At this point, the second attempt to crank your vehicle will get you going (the first will fail). The ESS light will turn on.

That is the bare minimum that needs to be done provided (I say for those reading, if not the questioner with his 2021) you are running a dual AGM battery JL later than the 2018 model year. Let's take it a step further. After disconnecting this cable but before attempting a crank you can also pull Fuse 42. This should result in the first attempt at you cranking being successful and not turning on the ESS off light. Do though turn ESS off by pressing the button or buying aftermarket tech to turn ESS off for you as running ESS on one battery, could, under the "perfect storm" cause you problems. You can leave the Aux battery in the vehicle. Pulling this fuse silently prevents the batteries from every being isolated such that all calls for current to either battery individually or together now end up only at the main battery.

Let's take it a step further.

You want to take the optional step of removing the Aux battery. You can do so from above or from the side, the latter is easier and safer I think, but I recommend that you read up on how to do this and acquire some spare fender liner pins as it's common to break some of these inexpensive pins as part of the side removal process. If you need references on either side and/or top removal write back here.

If you remove this battery I'd remove the black cable as well that leads from its negative terminal, whose other end you already disconnected.

The two positive cables off the Aux battery I would imagine should best be connected together, or yanked along with the PCR, which by virtue of the Fuse 42 pull, won't be energized.

See this diagram. Notice that there is not direct positive connection between the batteries, unlike on the negative side. They connect thorough terminals N1, N2, and N3 of the PCR.

https://www.jlwranglerforums.com/forum/threads/ess-jumpstarting-main-battery-vs-n1-terminal.87726/

BTW: I don't agree with acquiring the Genesis Offroad system to address this issue.

It's not that it won't. It's not that the product isn't excellent. It's just that there are cheaper ways to address this than the Genesis Offroad setup, which shines for people who run overlanding appliances while their vehicle is parked, and who need to maximize and manage this power while still being able to crank the vehicle for the trip home after camping.

 

[Mguy]

Some JL owners with aux batteries, particularly those with warranty coverage still making dealer visits, may find it more convenient to 1) replace fuse 42 with one that was previously blown, 2) use a short piece of rubber hose rather than tape or heat shrink to isolate the aux battery negative cable.

 

[AndySpill]

Some JL owners with aux batteries, particularly those with warranty coverage still making dealer visits, may find it more convenient to 1) replace fuse 42 with one that was previously blown, 2) use a short piece of rubber hose rather than tape or heat shrink to isolate the aux battery negative cable.

The removal or blowing or Fuse 42--either one--prevents isolation of the batteries and is a remedy here. Replacing Fuse 42, either because it has been previously disconnected or blown can only be counter to remedying the questioner's desire to remove the Aux battery , unless they desire the vehicle to shut off ESS with an EVIC warning light (late model dual AGM battery 2018's or later) or fused jumper terminals N1 and N2 in the PDC: the original technique before its inventor @Jebiruph discovered and published the Fuse 42 pull.

Perhaps I misunderstand your advice.

I have no issue with your method of insulating the disconnected cable.

 

[IceCactus]

Thanks @AndySpill for the detailed post!

The two positive cables off the Aux battery I would imagine should best be connected together, or yanked along with the PCR, which by virtue of the Fuse 42 pull, won't be energized.

I assume you mean connect together the 1 positive from the aux to the positive of the main?

 

[Ratbert]

You want to take the optional step of removing the Aux battery. You can do so from above or from the side, the latter is easier and safer I think, but I recommend that you read up on how to do this and acquire some spare fender liner pins as it's common to break some of these inexpensive pins as part of the side removal process. If you need references on either side and/or top removal write back here.

With his diesel you just take out the main and pull out the aux from underneath it. No need to mess with fender liners.

 

[AndySpill]

Thanks @AndySpill for the detailed post!
I assume you mean connect together the 1 positive from the aux to the positive of the main?

As I think about it, with the Aux battery disconnected or removed, what you do with the cables that begin at its positive terminal probably is likely to cause you the least headache if you simply insulate any exposed metallic cable ends and just leave them in place.

Those cables are indirectly connected to the main battery's positive post via factory setup at one end, and now, absolutely no place at the other end. They no longer serve a function and to connect them together or to some other place is not only not required, but could cause issues if connected to the wrong place. Yank them or keep them in place (my preference) and insulate their exposed ends.

When I say indirectly it also means that when the dual battery AGM JL is running as per factory that those battery are separated for an instant at cold crank and during ESS events. The Power Control Relay (PCR) that effects this separation relies on Fuse 42 being in place. Removal of the fuse prevents the batteries from being disconnected, provided an Aux battery is in place and connected, which in your case it is not.

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