Aux battery bypass

[btm8]

I stumbled upon the Aux battery issue after getting my Tazer setup to disable ESS and seeing this issue pop up in threads related to ESS. Anyway, I get the reasoning behind getting it out of the mix and will be doing so at some point.

I have a 2024 that is only 6 mos old and 2.5 yrs left on the basic warranty and do not want to affect that. I would have to reconnect it when I go in for service but do not have the option of maintaining the charge on it (nor would I want the hassle) after it's disconnected. I live in a condo with no access to doing a trickle charge overnight.

The only option I see is to leave it disconnected permanently and let it die a slow death (that it deserves). Which means I'm stuck with leaving it connected and it will have to sit on death row for 2.5 rys if I want to avoid warranty issues. If I'm missing something or if someone has a recommendation, please let me know.

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[Heimkehr]

Isolating the ESS battery is dead simple: Remove and tape off the related Negative cable, and remove Fuse F42 from the PDC (aka fuse box.)

Restoring ESS functionality for dealer visits during the warranty period is the inverse of the two-step disabling process. Done.

 

[btm8]

Isolating the ESS battery is dead simple: Remove and tape off the related Negative cable, and remove Fuse F42 from the PDC (aka fuse box.)

Restoring ESS functionality for dealer visits during the warranty period is the inverse of the two-step disabling process. Done.

The issue is I would not be able to maintain the aux battery in between dealer visits. It could be months in between and I don't think it would be ideal to be throwing a partially drained battery back into the mix. It may cause premature death of my main battery.

I guess maybe my lack of experience with AGM tech may be showing here. I know my Hulkman jump starter (lithium) is excellent at holding a charge and has maintained 100% charge in the past even after several months. I'm not so sure an AGM is in the same category for holding a charge in a dormant state.

 

[AndySpill]

Hi Bryan @btm8

While it is my guess that most dealers will not be concerned with whether you have disconnected the Aux battery and prevented it being isolated with a Fuse 42 pull I do appreciate your desire to put the vehicle back into factory configuration prior to deal service visits and how doing so could potentially tax your main battery, as that disconnected Aux has not seen charge and may be extremely low in voltage.

Periodically, and certainly prior to such dealer visits, if you place a battery charger's positive lead on the main battery's positive post (that's right, I said main battery) and the charger's negative lead on that temporarily uninsulated cable that you previously disconnected from the main battery's negative post (which originates at the Aux battery's negative post) this action will solely charge the Aux battery, provided it is capable of accepting charge.

After doing this I would test the Aux battery's voltage prior to reconnecting it to the main battery, placing the tester at the same locations I suggested above that you attached the charger, to see whether the charge took, and putting the two batteries back in parallel/reinserting Fuse 42, so as to not compromise the main battery, to see if it is okay to do.

Do separate/reinsulate that cable and pull Fuse 42 after the service visit, and turn ESS off.

 

[btm8]

Hi Bryan @btm8

While it is my guess that most dealers will not be concerned with whether you have disconnected the Aux battery and prevented it being isolated with a Fuse 42 pull I do appreciate your desire to put the vehicle back into factory configuration prior to deal service visits and how doing so could potentially tax your main battery, as that disconnected Aux has not seen charge and may be extremely low in voltage.

Periodically, and certainly prior to such dealer visits, if you place a battery charger's positive lead on the main battery's positive post (that's right, I said main battery) and the charger's negative lead on that temporarily uninsulated cable that you previously disconnected from the main battery's negative post (which originates at the Aux battery's negative post) this action will solely charge the Aux battery, provided it is capable of accepting charge.

After doing this I would test the Aux battery's voltage prior to reconnecting it to the main battery, placing the tester at the same locations I suggested above that you attached the charger, to see whether the charge took, and putting the two batteries back in parallel/reinserting Fuse 42, so as to not compromise the main battery, to see if it is okay to do.

Do separate/reinsulate that cable and pull Fuse 42 after the service visit, and turn ESS off.

After seeing your comment as well as seeing others who have actually had their dealers tell them outright that it's ok, I suspect many are just leaving it disconnected. If so, wouldn't the main battery be at risk during dealer troubleshooting? Most likely, they will be taking the vehicle out for a test drive and will most likely not disable ESS (Tazer will not be in play to disable). The main battery will be taking on the entire load that it wasn't designed to... And that could be several times depending on how many ESS events that tech puts your vehicle through.

 

[Phrank]

I've had my aux battery deleted for years. Half the time I forget to turn my ESS off until it stops the first time. It doesn't hurt anything.

 

[Roky]

I stumbled upon the Aux battery issue after getting my Tazer setup to disable ESS and seeing this issue pop up in threads related to ESS. Anyway, I get the reasoning behind getting it out of the mix and will be doing so at some point.

I have a 2024 that is only 6 mos old and 2.5 yrs left on the basic warranty and do not want to affect that. I would have to reconnect it when I go in for service but do not have the option of maintaining the charge on it (nor would I want the hassle) after it's disconnected. I live in a condo with no access to doing a trickle charge overnight.

The only option I see is to leave it disconnected permanently and let it die a slow death (that it deserves). Which means I'm stuck with leaving it connected and it will have to sit on death row for 2.5 rys if I want to avoid warranty issues. If I'm missing something or if someone has a recommendation, please let me know.

Why not have the aux battery replaced since you’re still under warranty? Then deal with it when you’re more comfortable doing so…. What am I missing?

 

[THAW]

The issue is I would not be able to maintain the aux battery in between dealer visits. It could be months in between and I don't think it would be ideal to be throwing a partially drained battery back into the mix. It may cause premature death of my main battery.

I guess maybe my lack of experience with AGM tech may be showing here. I know my Hulkman jump starter (lithium) is excellent at holding a charge and has maintained 100% charge in the past even after several months. I'm not so sure an AGM is in the same category for holding a charge in a dormant state.

The self-discharge rate for AGM batteries is similar to that of Lithium batteries - generally, a couple percent per month.

 

[AndySpill]

After seeing your comment as well as seeing others who have actually had their dealers tell them outright that it's ok, I suspect many are just leaving it disconnected. If so, wouldn't the main battery be at risk during dealer troubleshooting? Most likely, they will be taking the vehicle out for a test drive and will most likely not disable ESS (Tazer will not be in play to disable). The main battery will be taking on the entire load that it wasn't designed to... And that could be several times depending on how many ESS events that tech puts your vehicle though.

I am not worried about the occasional ESS event that runs on solely the main battery in an Aux battery disconnected JL Wrangler like yours.

 

[btm8]

Why not have the aux battery replaced since you’re still under warranty? Then deal with it when you’re more comfortable doing so…. What am I missing?

From what I understand on this subject, the aux is a parasite. I prefer to avoid parasites as others have. Many recommend to take it out of play as soon as possible and that sounds reasonable and some have seen issues with that battery as early as a year in as well. Either way, I'm gambling.

 

[Roky]

From what I understand on this subject, the aux is a parasite. I prefer to avoid parasites as others have. Many recommend to take it out of play as soon as possible and that sounds reasonable and some have seen issues with that battery as early as a year in as well. Either way, I'm gambling.

Yeah, I get that for sure, I yanked mine out as soon as it started acting up ( lasted almost 4 years). But I never used the ESS since day one, I pushed the button until I got my Tazer)

https://www.jlwranglerforums.com/forum/threads/crystal-rubi-build….61821/post-1782952

But I don’t care about the dealership and since you seem to be worried about that, that’s where my confusion comes from……That aux battery isn’t going to hurt anything as long as it’s not dying so that’s why I suggested you should just replace it….then when the warranty is up, yank it outta there…

 

[btm8]

Yeah, I get that for sure, I yanked mine out as soon as it started acting up ( lasted almost 4 years). But I never used the ESS since day one, I pushed the button until I got my Tazer)

https://www.jlwranglerforums.com/forum/threads/crystal-rubi-build….61821/post-1782952

But I don’t care about the dealership and since you seem to be worried about that, that’s where my confusion comes from……That aux battery isn’t going to hurt anything as long as it’s not dying so that’s why I suggested you should just replace it….then when the warranty is up, yank it outta there…

Yeah, I'm probably leaning that way. I'm thinking delete when it comes time. As mentioned, I'm not thrilled on having to maintain it leaving it unconnected and don't want the hassle. I think I'm in the delete camp as far as delete/bypass goes. If it dies before warranty ends, I'll replace and once warranty ends, yank it and put in a good Everstart or something at the same time. By then, that main should be getting close anyway.

 

[btm8]

I am not worried about the occasional ESS event that runs on solely the main battery in an Aux battery disconnected JL Wrangler like yours.

As mentioned, I'm going to stick with the little parasite for now and delete in a couple of years when warranty is up. Thanks for the input on the occasional ESS events not hurting the main. It'll be good knowing my main (whatever it is at that point) will be fine with an ESS event here and there when taking in for service.

 

[THAW]

From what I understand on this subject, the aux is a parasite.

As mentioned, I'm going to stick with the little parasite for now and delete in a couple of years when warranty is up.

The AUX (ESS) battery is not a parasite by default; it can become one when it's aged significantly more than the CR[an]K (main) battery - which can be difficult for the average Jeep owner to detect.

The true issue with the AUX (ESS) battery is its small capacity is heavily taxed under the often large load it supports alone during ESS events, making a long life unlikely with frequent and/or long ESS engagement. If you plan to leave the AUX (ESS) battery connected, the best way to prevent parasitic damage to the CR[an]K (main) battery is to turn off ESS - as you've done.

 

[AndySpill]

The AUX (ESS) battery is not a parasite by default; it can become one when it's aged significantly more than the CR[an]K (main) battery - which can be difficult for the average Jeep owner to detect.

The true issue with the AUX (ESS) battery is its small capacity is heavily taxed under the often large load it supports alone during ESS events, making a long life unlikely with frequent and/or long ESS engagement. If you plan to leave the AUX (ESS) battery connected, the best way to prevent parasitic damage to the CR[an]K (main) battery is to turn off ESS - as you've done.

Yes, *if* you plan to leave the Aux battery connected, it will be less taxed if you don't run ESS events. On this I agree.

But if you've committed to not running ESS events you don't need the Aux battery and I can't help but think that whatever it adds in amps being connected in parallel to the main battery is more than negatively counterbalanced by its potential to die before the main battery: even if never having to run an ESS event, and in so doing, lead the main battery to a premature death as well.

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