Relocating and Upgrading Aux Battery?

[Tncdrew]

Defeat the Start/Stop, and get rid of the fkn thing! ?

Boom! A certain degree of unnecessary complexity eliminated!

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[Mguy]

There isn’t really a fundamental problem with parallel batteries. If there was a good reason then they wouldn’t do it. The only slight disadvantage is that over the lifetime of the battery, the smaller battery will not get the amount of cycles as the larger battery, it will cycle more. This is due to the imbalance of how each battery shares or divides the current either during charging or discharging. When there are two batteries in parallel, current will slosh around between them for a little bit until they balance. This action will shorten the life but not by much. If the batteries were the same size and in parallel, from the same manufacturer, the balancing would be better but there are variations from battery to battery. The balancing is worse when the battery sizes are different but like it said it doesn’t affect the life that dramatically.

Respectfully, I disagree. Unlike with traditional lead-acid batteries, AGM manufacturers provide specific multi-stage, multi-voltage, charging routines because their products require it. These routines are substantially defeated when applied to a paralleled bank of non-identical batteries. I do agree non-identical traditional lead-acids do much better (they generally can handle single stage "dumb" charging).

 

[THAW]

Hey Thaw, you asked "What are the physics of dissimilar size batteries causing battery wear?" The question was reasonably related to the thread's topic and discussion flow, and it seemed to be asked in good faith and not as some sort of rhetoric or sarcasm. The answer--the science behind maintaining AGM performance and longevity--is not context specific.

By the way, based upon well established electrical engineering principles, unless aux battery relocation to the rear calls for wrapping cables three times around the seats, any concern regarding a resistance differential from extended cable length is adequately addressed by cable gauge.

Best of luck in your electrical endeavors.

I did not intend offense.

Your answer didn't address the ESS system taking the batteries out of parallel, which was part of my question (though, admittedly, that fact may have been unclear).

Can you elaborate on the principles you mentioned? What voltage drop do you estimate for a car length of appropriately sized battery cable?

 

[THAW]

Respectfully, I disagree. Unlike with traditional lead-acid batteries, AGM manufacturers provide specific multi-stage, multi-voltage, charging routines because their products require it. These routines are substantially defeated when applied to a paralleled bank of non-identical batteries. I do agree non-identical traditional lead-acids do much better (they generally can handle single stage "dumb" charging).

Does a Wrangler's alternator provide that charging routine?

 

[JL.FR]

There is probably a Wrangler sales volume effect in the USA vs EU and this is the reason for a lot of problems in your country. And an idea... exported batteries may be of better quality. it is easy to remove the ESS, disconnect the engine hood contact and the ESS will no longer work.

 

[Carolina Jeeper]

There is a basic problem with the different amp rated parallel batteries in our Jeeps. They will not discharge and charge at the same rate. We can debate it, but it's not going to eliminate that one main issue.

One of the batteries will be repeatedly be low in charge level and pull the other one down. There's nothing to debate here. It will happen. This even happens in identical parallel batteries when a cheapskate replaces just one battery. One will pull the other down and then you'll end up replacing both again sooner than later.

I've seen this scenario play out over and over in big semi trucks with 2, 3, and 4 batteries in parallel. All commercial truck mechanics have seen this happen.

Don't misunderstand me and think I'm not aware of the other factors at work here. I am and I'm just giving clarity on this one really big issue that all by itself is a major flaw in this factory setup. If it had been such a good design instead of an engineering failure, then we wouldn't be reading all about it here in this thread.

Moving any or all of the batteries out of the engine bay will extend their life. Engine bay heat shortens the life of batteries. So, it's a really good idea to put them anywhere but there. Better upgrade to a larger gauge cable though.

 

[AndySpill]

There is probably a Wrangler sales volume effect in the USA vs EU and this is the reason for a lot of problems in your country. And an idea... exported batteries may be of better quality. it is easy to remove the ESS, disconnect the engine hood contact and the ESS will no longer work.

Casa, please, stop.

First you wonder why American owners complain about ESS batteries then you write one ambiguous sentence about yanking, I think, the battery.

It's not that simple, although it's not, on the other hand incredibly difficult.

You suggestion, "remove the ESS."

The ESS what, system or battery? In the same sentence you use ESS, it seems, to reference both.

If you mean battery in the first part of your sentence do know that it's far easier to simply disconnect this battery, not yank it. Second, doing so without also fused jumpering N1 to N2 in the PDC, or pulling Fuse 42 will prevent early model 2018s from cranking, and later model dual AGM battery JLs from cranking on the first attempt, throwing an ESS off light in the dash thereafter.

 

[THAW]

There is a basic problem with the different amp rated parallel batteries in our Jeeps. They will not discharge and charge at the same rate. We can debate it, but it's not going to eliminate that one main issue.

Batteries charged in parallel and isolated to power different loads do not discharge at the same rate. The different discharge rates cause deviation in age related capacity, regardless of starting size.

 

[AndySpill]

Batteries charged in parallel and isolated to power different loads do not discharge at the same rate. The different discharge rates cause deviation in age related capacity, regardless of starting size.

This bodes well Foster with my desire, I think, that not only would equally sized AGM dual batteries in the JL have been a more robust factory approach, but having them automatically switch off the roles as Main and Aux to even out wear...

....if not, in fairness and critique to my own desires here, added complexity to the system...

 

[Carolina Jeeper]

Batteries charged in parallel and isolated to power different loads do not discharge at the same rate. The different discharge rates cause deviation in age related capacity, regardless of starting size.

Thats not a parallel battery system. Parallel batteries have the positive poles tied together and negative poles tied together.

 

[THAW]

Thats not a parallel battery system. Parallel batteries have the positive poles tied together and negative poles tied together.

Right, but it is the Wrangler battery system (and the subject of this thread).

 

[Carolina Jeeper]

I understand that. The point I was trying to make is how dissimilar battery sizes just don't work well together. I used true parallel batteries as a prime example. So in our Jeeps The alternator can't fully charge both batteries since they evidently are tied together during charging.

When the charge and discharge rates are too far away from each other even from age, it's going to reduce the life of both batteries.

Even if I can't word it just right, the issue exists. It's a simply a bad design.

 

[THAW]

I understand that. The point I was trying to make is how dissimilar battery sizes just don't work well together. I used true parallel batteries as a prime example. So in our Jeeps The alternator can't fully charge both batteries since they evidently are tied together during charging.

When the charge and discharge rates are too far away from each other even from age, it's going to reduce the life of both batteries.

Even if I can't word it just right, the issue exists. It's a simply a bad design.

Right.

So the question becomes how much does battery size mismatch matter relative to the variance in battery aging caused by continually switching them out of parallel to power different loads?

I don't think anyone has a precise answer, but the forum tends to focus on battery size and suggestions that matching it would somehow prevent one battery failing before the other and wreaking havoc on the electrical system.

 

[JL.FR]

Stopping the stop and start is simple, there are a lot of topics here on this forum. Simply unplug the engine hood switch. There are 2 switches, I don't remember which one, but you can easily find them on this forum. The auxiliary battery is an aberration. There is room to put a longer and stronger battery, remove the little piece of plastic at the bottom, why JEEP did not take this option. Why do only JEEPs have this weird assembly??

 

[Carolina Jeeper]

Right.

So the question becomes how much does battery size mismatch matter relative to the variance in battery aging caused by continually switching them out of parallel to power different loads?

I'm pulling from my commercial truck electrical training here, and will say battery size mismatch and age difference matters enough to be covered in it.

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