OEM Battery Replacement

[Gee-pah]

On a 2020 JL, is there a benefit and/or need to bypass the ess battery? I am fairly certain that it is already showing signs of dying.

I believe the issue of not starting due to bad aux battery has been fixed by the factory. What other reason would I proactively bypass the aux?

Currently my plan is to bypass once it dies.

Here's the skinny on that Ronnie:

At least in the 3.6L engine, all JLs from model year 2019 and beyond (a.k.a. you) will, when the ESS/Aux battery fails to have sufficient power, not cold crank upon your first attempt.

On subsequent attempts the vehicle will move exclusively to the main battery, shutting the ESS/Aux battery out of supplying any electric, and attempt to crank off of the main battery.

If successful, the vehicle will show a diagnostic light that it has turned off ESS. That light will remain illuminated until the next cold crank, if any, where a charged ESS/Aux battery is detected.

Turning off ESS in these 1 battery situations is a smart response by FCA. You don't want this two battery ESS system running ESS with one battery that during an ESS event may rob that one battery of the power it needs to crank the engine.

The rub here is that the two batteries are connected in parallel 99.9% of the time, and as such, a battery in need of energy can suck energy from one with greater supply.

If you'd like to take matters into your own hand you can disconnect the ESS/Aux battery for good by going to the main battery's negative terminal and finding the cable which is bolted on to the terminal that is CLOSER to the passenger's front quarter panel (NOT father: that's the ground) and remove it. I'd rap the end in electric tape or some insulator.

This takes the ESS/Aux battery out of the picture. But remember, like I said, your first attempt to crank will fail here.

Don't do this on a 2018 3.6L without the PCM update flash TSB 18-092-19. On vehicles without this flash, inadequate charge in the ESS/Aux battery result in the vehicle not attempting a crank.

Long story..it's part of the fix by the factory that you referred to in your post.

I hope this helps.

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[Redbaron73]

Here's the skinny on that Ronnie:

At least in the 3.6L engine, all JLs from model year 2019 and beyond (a.k.a. you) will, when the ESS/Aux battery fails to have sufficient power, not cold crank upon your first attempt.

On subsequent attempts the vehicle will move exclusively to the main battery, shutting the ESS/Aux battery out of supplying any electric, and attempt to crank off of the main battery.

If successful, the vehicle will show a diagnostic light that it has turned off ESS. That light will remain illuminated until the next cold crank, if any, where a charged ESS/Aux battery is detected.

Turning off ESS in these 1 battery situations is a smart response by FCA. You don't want this two battery ESS system running ESS with one battery that during an ESS event may rob that one battery of the power it needs to crank the engine.

The rub here is that the two batteries are connected in parallel 99.9% of the time, and as such, a battery in need of energy can suck energy from one with greater supply.

If you'd like to take matters into your own hand you can disconnect the ESS/Aux battery for good by going to the main battery's negative terminal and finding the cable which is bolted on to the terminal that is CLOSER to the passenger's front quarter panel (NOT father: that's the ground) and remove it. I'd rap the end in electric tape or some insulator.

This takes the ESS/Aux battery out of the picture. But remember, like I said, your first attempt to crank will fail here.

Don't do this on a 2018 3.6L without the PCM update flash TSB 18-092-19. On vehicles without this flash, inadequate charge in the ESS/Aux battery result in the vehicle not attempting a crank.

Long story..it's part of the fix by the factory that you referred to in your post.

I hope this helps.

Great response, Thank you.

 

[WranglerMan]

If one chooses to you can remove the ESS battery all together and just run the positive cable up to the main and disconnect the ESS negative off the main and replace the main with a larger more robust battery, this way you don’t have to worry about that motorcycle battery or you can jumper N1 to N2 and do the same with the ESS neg and keep the ESS battery charged for an emergency, there are more costly options but you as the owner have to decide what your needs are.

 

[Gee-pah]

Thanks Will @WranglerMan :

You touched upon an additional topic I realized afterwards that I left out, that Ronnie @Redbaron73 might want to know.

Ronnie: maybe the diagnostic light in the dash bothers you. I think it's a "feature."

Heck, maybe you do too, as it automatically disables your ESS; which is recommended as stated above when running one battery.

In @WranglerMan's suggestion you run a fused wire between the N1 fuse in the Power Distribution Center (PDC) to either

the positive terminal of the main battery, or
the N2 fuse in the PDC. It makes no difference.

The PDC is that black box in the engine bay, on top, closest to the front passenger's seat. You'll need to lift its cover and the N1 fuse is the one closest to the driver's side, and closest to the front of the vehicle otherwise in the PDC.

Here is a link to such a cable:

Fused Wire

In the above product it will make sense to crimp on eyelets.

In order to keep the cable connected to the N1 fuse I would recommend, for easy installation and removal, securing it with appropriately sized wing nuts, M6 in size:

M6 wing nuts

Just add the wire ABOVE the existing factory nut, and the wing nut on top of that.

This action "fools" the PDC, in that calls it makes to the ESS/Aux battery
really end up at the main battery. This is NOT a substitute for disconnecting the negative terminal of the ESS/Aux battery as discussed prior, just a supplemental approach that avoids the light in the dash. Otherwise the techniques are identical, and one is no better than the other.

This N1-main battery positive supplemental method will NOT put the ESS disabled light into your dash: which is both good and bad.

If you go with this method please disable ESS. Whether that comes in the form of pressing the button each time you cold crank, or using one of the hacks to disable it,



or purchasing tech to do it like https://www.smartstopstart.com/ or https://www.zautomotive.com/ is up to you.

Many of the hacks to disabling ESS will produce the very diagnostic lights that the fused N1 jumper sought to eliminate. The tech will not.

 

[Redbaron73]

I have been considering the Genesis battery tray, but really have no need for 2 batteries. I do not use this for overlanding, nor do I run accessories with ignition off.

For now, I think the removal of the aux battery is the best option. Future upgrade to a group 94 battery would be long term solution. Thanks!

 

[Gee-pah]

I have been considering the Genesis battery tray, but really have no need for 2 batteries. I do not use this for overlanding, nor do I run accessories with ignition off.

For now, I think the removal of the aux battery is the best option. Future upgrade to a group 94 battery would be long term solution. Thanks!

Then Ronnie I would highly, highly recommend not purchasing it.

By no means should you conflate my recommendation with any disparagement of the Genesis product, which most report is great.

It simply is overkill for your needs.

 

[Redbaron73]

The only way genesis would make sense for me is to move the factory aux wiring for the 12v rear accessory, 12v front accessory, and the battery wire (part of tow package) to the secondary battery. Those are plugs that I currently use infrequently with no ignition. I have a battery cutoff circuit wired in on all of these and set to 12.0 volts, which is adequate protection.

My idea was to use a fuse jumper and relocate these to the Genesis aux battery.

I am not a fan of the continuous use solenoid, as it has a high phantom draw. I prefer some of the mosfet circuits, but have not found the right one. Plenty of marine dual battery setup, but none which are used the way this one is for the high charge rate we need.

 

[Htfan]

I'm waiting for the day a dual battery replacement tray becomes available for our 3.6L JLs. Then we can implement a redundant (ESS or not) battery system of our choosing.

If my main cranking battery fails before a product like this becomes available, I'll replace it with a larger group 94 battery.

 

[WranglerMan]

@Redbaron73 yes the Genesis system is like the Rolls Royce of battery options, there are less costly options like running a jumper full time and removing the ESS negative or taking the ESS battery out and moving some cables around but as @Gee-pah advised it’s best to not disable the ESS battery and use the ESS system, using ESS will tax the main crank battery a lot and after (6) cycles it will disable itself until the next ignition cycle and then reset but you are taxing the main by using ESS with just one battery, also not sure what the phantom draw is on the continuous use solenoid as I don’t have the specs, it does stay energized a lot but once the main crank drops below 12.7 +/- .1 it disconnects and draws no more power until startup when the smart isolator looks at the voltage, I’m sure if one had a mind to they could possible put a switch in to keep is open until needed but not sure what that would take.

I have been doing daily voltage checks since having the system and neither battery so far has dropped below 12.55ish and the below 12.6 has only happened right after I have been in and out of the jeep a lot so maybe a good test would be to check my charge on both batteries and then let it sit not connected to my smart charger for say 3-4 days and then see what the voltage drop is over those days.

I for one run the Genesis system along with a Smart Stop/Start module as I truly dislike the ESS feature so I can use the additional amp hours to run my compressor when needed along with winch and just have the extra power from the additional battery to run my stereo and aux items without fear of running my battery to low, also be advised that if you choose to run with one main battery and remove the ESS one everything that is powered thru the PDC ( which is everything ) will pull power from the main battery so if your parked and have lights and radio on you can pull the main down pretty quick and with the ESS battery removed you will not have a backup.

Doing the ESS battery hack is fairly inexpensive and my guess would be less than a $20 investment for a fused jumper and a few wing nuts but as the complexity goes up to work around this poor design so does the cost so you as a Jeep owner have to evaluate your needs.

 

[Gee-pah]

Some color commentary to Will @WranglerMan:

With each cold crank to the 3.6L JL, the current (read: right now, not "electric") software logic is such that if after 6 ESS events, if voltages of the ESS/Aux battery and main battery are seen**** as identical, ESS will be disabled until the next cold crank where the 6 ESS events test starts all over again.

**** or what the vehicle "thinks" are the ESS/Aux and main battery, care of the above referenced "wiring magic"

I think that FCA's thought here was that if the voltages are identical that some failure of the components is causing the batteries to remain connected in parallel, and that voltage reading that is being taken is a composite voltage of both batteries tied together, when the batteries should have been separated as per factory, and highly unlikely to individually have the same voltage.

What Will describes also happens with the Genesis product, which again is not to in any way meant to look upon this product as anything but excellent; just something that not all owners need. This 6 cycle thing has nothing good or bad to do with Genesis wares, it's just a vehicle design thing.

Jeff @Htfan, a 2 battery (of equal size) tray that fits in the space, that the basic alternator (I don't have the towing package with the heavy duty alternator) provides enough capability to charge both batteries
is my wish too....a so called "Genesis light" where only the batteries, not the electronic tech, runs them. : - )

 

[WranglerMan]

@Redbaron73 do you know what the 200 amp Cole Herseey relay/solenoid draws since it’s a continuous duty solenoid, I do know once the main crank battery drops below 12.7 +/- .1 ish that it opens as I have tested this but have no idea how much power it pulls to stay closed.

 

[Bob Burd]

@Redbaron73 do you know what the 200 amp Cole Herseey relay/solenoid draws since it’s a continuous duty solenoid, I do know once the main crank battery drops below 12.7 +/- .1 ish that it opens as I have tested this but have no idea how much power it pulls to stay closed.

700mA

 

[MauiSteve]

I watched the Genesis video, it looks like a great product that provides some real battery capacity. I didn't catch whether it throws any codes but it looks like it may not. On my list for later, well built product.

 

[WranglerMan]

700mA

Thank you Sir, that seems pretty high but in the scheme of things with these newer vehicles all having a parasitic draw this just adds to the pile plus if it opens/disconnects at 12.7 +/-.1 on the main crank battery it should be fine.

I think the biggest issues with these AGM batteries is they need to be charged in the 14.4-14.6 voltage range and I don’t believe the smaller tenders can do that, they are fine I think if connected to a fully charged system to keep the batteries topped off from the parasitic draw but I don’t think tenders like Deltran can do the job adequately if the batteries are low.

As I said I have been doing daily checks and both batteries are in the 12.6-12.8 range but since the solenoid is closed 99% of the time they would be close to the same voltage

Here is an interesting thread that discusses the Cole Hersee parasitic draw, I found it very interesting, it starts discussing the voltage draw around post #35

https://www.jeepgladiatorforum.com/...d-ess-6-cycle-limit-anyone-with-issues.27325/

 

[Gee-pah]

I watched the Genesis video, it looks like a great product that provides some real battery capacity. I didn't catch whether it throws any codes but it looks like it may not. On my list for later, well built product.

Steve:

As touched upon above, the only "issue"--which really isn't much of an issue IMHO that I know of installing the Genesis kit is that after 6 start top events in one cold crank, the vehicle will stop the ESS system until the next cold crank, where that counter of 6 cycles restarts.

If you're curious the reasoning is above and is an FCA, not a Genesis thing.

IMHO the Genesis product is an excellent well made accessory that I otherwise don't own because, like many others, I don't need its functionality, but would buy without reservation in a second if I did.

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