Aux battery bypass

[THAW]

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.

The separation and individual discharge of the batteries is the primary source of potential for one battery to critically damage the other.

When the objective is minimizing probability of parasitic battery damage (a goal overemphasized on this forum), disabling ESS makes disconnecting/removing the AUX (ESS) battery inessential, while disconnecting/removing the AUX (ESS) battery renders ESS status moot.

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[AndySpill]

The separation and individual discharge of the batteries is the primary source of potential for one battery to critically damage the other.

When the objective is minimizing probability of parasitic battery damage (a goal overemphasized on this forum), disabling ESS makes disconnecting/removing the AUX (ESS) battery inessential, while disconnecting/removing the AUX (ESS) battery renders ESS status moot.

You advocate disabling ESS to not allow the 2 batteries to separate, in so doing seeking to minimize ESS event based parasitic battery damage.

But as long as the owner has turned ESS off to minimize parasitic battery damage, that Aux battery is no longer needed, and disconnecting it, along with disabling the Power Control Relay (PCR) with a Fuse 42 pull, eliminates, not reduces the chance of parasitic battery damage as the batteries are no longer connected.

As other things aside from ESS events, even if it is main cause, can degrade that Aux battery, why keep it connected if not running ESS events, particularly but not limited to your claim that once that Aux battery is disconnected, running ESS events off solely the main battery is perfectly fine?

(Perhaps for few, with ESS off, that run some appliances offroad, the benefit of those 2 batteries linked, and being able to crank their way home is more important than the possibility of battery cannibalization. But I suspect this the exception, not the rule.)

We may disagree on running ESS events with one battery on a dual AGM battery JL, I suggesting it avoided, but I think we can agree that the vehicle is fine to run on its main battery alone when ESS events aren't happening, and the benefits of greater amp hours (not needed) running both batteries risks cannibalization by other causes.

An analogy: let's suppose we differ on taking steroids (the analogy here being the boost from the Aux battery) in bodybuilding. We probably don't, but suppose we do.

Regardless, we certainly agree that giving those steriods to healthy adults not seeking such muscle gains (the analogy being those not running ESS events and not needing the boost), given the side effects of the drugs (possible battery cannibalization), unwise, no?

 

[THAW]

As other things aside from ESS events, even if it is main cause, can degrade that Aux battery, ...

What "other things" cause uneven battery aging?

Even if one doesn't fully understand the physics, there are a convincing number of forum anecdotes from owners who disabled ESS on the first day of ownership and experienced normal (i.e. good for a JL) battery life from their combined AUX (ESS) and CR[an]K battery.

In any case, the OP has a reason for leaving the AUX (ESS) battery connected. You may not value the reason, but given he's disabled ESS he needn't be overly concerned about the AUX (ESS) battery aging faster than the CR[an]K battery.

 

[btm8]

What "other things" cause uneven aging of the batteries?

Even if one doesn't fully understand the physics/chemistry, there are a convincing number of forum anecdotes from owners who disabled ESS on the first day of ownership and experienced normal (i.e. average for a JL) battery life from their combined AUX (ESS) and CR[an]K battery.

In any case, the OP has a reason for leaving the AUX (ESS) battery connected. You many not agree with the reason, but given he's disabled ESS he needn't be overly concerned about the AUX (ESS) battery aging faster than the CR[an]K battery.

Yes, that is the conclusion I came to as well. I have been disabling ESS from the day I drove it off the lot until adding the Tazer a few weeks later. It maybe has seen 5-10 total ESS events in it's short life.

As mentioned, I have no issues running with both until it becomes a burden. When I have to replace it myself on my dime (a burden), it comes out permanently. The bypass won't ever work for me because of AUX maintenance that goes along with that. Charging won't work because of my condo rules and I don't plan on staying with family so I can trickle charge over night. Lol. Also, messing around with disconnecting/reconnecting and untaping/taping doesn't sound like something I'd be interested in unless absolutely necessary. Even if they made a protective clamp or something that could easily be removed, I would still have the charging issue.

 

[Mguy]

For those that are interested in battery science and not reliance on unsubstantiated claims of anecdotal evidence,

Combining dissimilar batteries into a single bank results in charging that is appropriate for a composite state of charge, not that for the individual batteries. Since AGMs are generally quite sensitive to accurate charging, the bank as a whole suffers.

Further, when charging is shut off, dissimilar batteries in a bank will cross drain (generally following Ohm's Law) until a combined resting state (equilibrium) is attained. This process will repeat itself over and over after each driving cycle, expending energy and thus resulting in bank capacity loss.

However, for a bank which is used only for vehicle starting and where the vehicle is properly maintained electrically, the above deficiencies will probably not be much of a problem. So, for an owner of an alternator equipped JL with a low risk tolerance for dealer pain on warranty claims, it makes sense to leave the JL electrically stock and just forgo ESS operation (and the accessory position on the start button). However, battery bank life will likely be shorter than if the main battery alone is similarly used after the aux negative/f42 was performed.

A further point regarding aux battery charging maintenance. After doing the aux negative/F42 disconnect, a fully charged healthy aux battery, due to AGM low self discharge rate, can be ignored for several months without damage. Reconnecting a few times a year for a day of driving, providing the engine/alternator is on for a total of 4 or so hours, should keep the aux battery going for several years. Disconnect promptly after charging to prevent cross draining.

 

[THAW]

Combining dissimilar batteries into a single bank results in charging that is appropriate for a composite state of charge, not that for the individual batteries. Since AGMs are generally quite sensitive to accurate charging, the bank as a whole suffers.

"Dissimilar" capacity is not the same as dissimilar internal resistance. And similar capacity doesn't guarantee identical internal resistance.

 

[Mguy]

"Dissimilar" capacity is not the same as dissimilar internal resistance. And similar capacity doesn't guarantee identical internal resistance.

This is not informing, it’s trolling.

Can you substantiate your anecdotal claim? I’d love to see a report from a JL owner who got 4 years on the stock setup, without external charging, by simply not using ESS and/or other techniques.

@Roky?

 

[Roky]

This is not informing, it’s trolling.

Can you substantiate your anecdotal claim? I’d love to see a report from a JL owner who got 4 years on the stock setup, without external charging, by simply not using ESS and/or other techniques.

@Roky?

Yeah, I have never used ess from the day I picked it up to the present, either by pushing the button or Tazer….. maybe 3 or 4 times where I forgot to press the button, but as soon as it reminded me the button was pushed…..I got 4 years ish out of my original stock batteries before the aux took a shit…. At that time I yanked it out, got a yellow top, and everything has been great for near 3 years now….. I’ve recently been plugging my rig into my Norco Genius 10 when i know I’m not gonna be running it for a few days …..

 

[THAW]

This is not informing, it’s trolling.

It's not trolling, they're facts. It's unfortunate you take simple statements of fact personally.

I’d love to see a report from a JL owner who got 4 years on the stock setup, without external charging, by simply not using ESS and/or other techniques.

I assume you mean without separated external charging. Otherwise, you sound confused about your own "dissimilar" battery charging claims.

Here's a 4-year example (owner stated no external charging as of 3.5 years).

 

[THAW]

However, battery bank life will likely be shorter than if the main battery alone is similarly used after the aux negative/f42 was performed.

Can you substantiate your claim that with ESS disabled and similar use the battery bank has a shorter life than the main alone?

 

[Heimkehr]

I’d love to see a report from a JL owner who got 4 years on the stock setup, without external charging, by simply not using ESS and/or other techniques.

I installed an ESS defeat harness the day the new Jeep was driven home from the dealer.

My OEM H6 AGM lasted four years, almost to the day. It spun the starter just fine the evening prior, and then was dead as a doornail the following morning. I replaced it with an Interstate H7 AGM, isolating the ESS battery at the same time and via the accepted method. Done.

Not once during my ownership have I had a battery charger of any type connected to the batter(ies) in my JLU.

 

[Mguy]

@Roky and @Heimkehr, congrats on your battery longevity achievements, and thanks for reporting same. Obviously many with stock wiring don't do as well, ESS operation likely the primary reason.

@THAW, first, regarding your statements on battery capacity and internal resistance, the problem is they are just that, statements. Rather than ask a question about batteries, you posted useless tautologies. Just as Lucy doesn't need to know much about football when playing with Charlie Brown, you don't need to know much about batteries to cite a technical term or two. But I'm not going to be Charlie Brown in your trolling game.

As for substantiating my assertion that among non-ESS users dual battery stock setups will likely not do as well as those with the aux negative/F42 disconnect, readers still interested and unsure should look again at my first post in this thread. JLs with a single battery don't suffer from the two deficiencies there identified. Some may note the small capacity increase from the aux battery. While not mentioned, I think it common knowledge among regular users of 12 volt AGM systems that good charging maintenance--which single battery setups promote and make easy--can overcome other battery characteristics, including small capacity differences. So I'm not sure, but believe it likely, that single battery JL setups will last longer.

Finally, for anecdotal evidence regarding JL single battery use, we'll have to wait. The aux negative/F42 disconnect mod wasn't even invented until June, 2022, less than three years ago.

 

[Nokones]

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 OP has a 2024. I believe his/her 2024 is similar to my 2023 and most likely has the 48V Lithium Aux battery that is located towards the rear of the vehicle and is water cooled/heated by his on-board vehicle cooling system thus, does not have the F42 fuse. Also, if my memory serves me right, the Aux battery is warranted for 7 or so years.

I have the Auto Stop Eliminator and it works great and does not interfere with anything. I also have the Mobilistic system and that systems works great.

 

[btm8]

The OP has a 2024. I believe his/her 2024 is similar to my 2023 and most likely has the 48V Lithium Aux battery that is located towards the rear of the vehicle and is water cooled/heated by his on-board vehicle cooling system thus, does not have the F42 fuse. Also, if my memory serves me right, the Aux battery is warranted for 7 or so years.

I have the Auto Stop Eliminator and it works great and does not interfere with anything. I also have the Mobilistic system and that systems works great.

I don't think that's correct. From what I understand, the etorque is no longer available starting in 2024, for either engine. Regardless, I have an alternator which means it's the two battery system. It's funny that the manual only has a small paragraph in the entire manual related to having a two battery system if you have ESS. But they have several pages dedicated to the EV. All that it says about the 2 battery system is that both batteries must be disconnected to discharge the 12V system... That's it! Nothing else in the entire manual about the traditional batteries. I thought I had the wrong manual at first but there's just one for all Wrangler variants.

 

[Jebiruph]

Finally, for anecdotal evidence regarding JL single battery use, we'll have to wait. The aux negative/F42 disconnect mod wasn't even invented until June, 2022, less than three years ago.

The aux battery first started being bypassed in 2018, the jumperless bypass was the 2022 improvement. https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/post-423590

@Rhinebeck01 was the bleeding edge and has been running it ever since.

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