Auxilary Battery Died then Main Battery Died - Important Info

[Chocolyle]

Genesis Dual Battery Kit has been available for a long time.
https://www.genesisoffroad.com/jt-dual-battery-kit

Wow! They must be growing trees!??

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[ShadowsPapa]

Agreed, that is a terrible design and worse execution.

Good post on jump starting though, important to note that if you jump your vehicle you should immediately disable the auto start "feature" to avoid what happened here.

"Feature", LOL no it is a flaw.

If you have to jump start - the ESS should be disabled by the system anyway. Even if my batteries are low, but will still start the vehicle, ESS won't work. Get below 12.4 BATTERY volts and it's disabled.
We went though a lot of this with my wife's WK2 a couple of years back - ESS not working was the first clue the aux battery wasn't very good.

Like I have posted in a thread I started on my truck's battery voltages, the ESS not working is the first clue that you have a problem. Those who have disabled it permanently via tazer or whatever won't have that warning that there's a problem.
ESS not working is what told my wife there was a problem with her Jeep. She complained "why isn't it stopping at lights anymore" - and 2 weeks later, if the Jeep sat for a couple of days it had to be jump started. Simple process - connect cables as you would with any other vehicle, wait a couple of minutes, then start it. Too many connect and instantly try to start the dead vehicle. You should run the running vehicle at a high idle after connecting, and the dead vehicle should start.

ESS not working is a clue you may have a problem - a battery problem. It's a symptom of other things.

 

[OngsterA]

What's the lifespan of the aux battery, same as main roughly? How do you know if low in charge i.e. dying? Sorry I'm new to this dual battery world. Also, what gauge jumper from main + to N1 is acceptable? Good info though and great link above from @jebiruph !

Ahh, the ESS not working is an indication, just posted above. Thx!

 

[ShadowsPapa]

Many dealers are now saying 3 to 5 years.
It doesn't help when these never seem to get fully charged. Mine, for example, even after a very long drive, will never register as fully charged. It's a bit better since I charged the batteries individually and reset the IBS, but I still never get anything over 12.5x volts and stopping at a light with ESS kicking in, I get into the 11.8 volt range.
AGM batteries need to be charged at much higher voltages to get them up to full.
AGM batteries also have a problem with taking a set like some old phone batteries used to do years ago - if they are constantly only ever charged to 70% eventually you won't be able to charge them over that.

I'm not sure why the jumper thing on charging or jumping these - when you put 12 volts on the wires to jump start a vehicle, it's 12 volts along the entire chain of wires and cables. It doesn't drop the further down the wire you go (other than voltage drop induced by the cable itself)
So I gotta disagree with a need to use a special jumper or jump starting instructions.
The IBS monitors the main battery only. And the main battery is the "crank" battery.
The AUX battery is for the electronics. That's a light load - fractions of an amp.
Once you connect jumper cables at the main battery, you have the jumper vehicle's voltage present at the jumpee vehicle - along all wires and cables. Since it takes only 11+ volts to run the electronics, you are going to have that and much more from the vehicle doing the jumping once you connect the cables at the main battery. You can't see 14 volts at the main battery and less than 11 at the aux battery terminals.
Proof the vehicle electronics run on less than 12 volts is facing me every time my ESS kicks in and I have the cluster showing the voltage.

 

[WhyNotJeep]

My ESS has not worked since new, 150 miles now. There is no warning on the screen. The on screen voltage reads 12.4 to 13.8. Everything works but the ESS. I guess I want to get it fixed. Then I can look for a way to turn it off.

 

[Radio Guy]

My recollection of the wiring is the alternator charging cable goes directly to the main battery then charging current makes its way to the aux battery via the N2 and N3 connections. I would never try and jump start by connecting to the N1 terminal, the cable, connections and fuse were never designed to handle cranking currents and you will also have an added initial very high current while the batteries try to charge. Think of what that is doing to the PCR relay, I doubt its rated for cranking currents.

I would instead connect jumper cables to the main battery and common chassis ground then wait a minute or even several minutes while both batteries come up in voltage and are less of a burden on the alternator when the engine is finally running and you disconnect the jumper cables.

 

[Reddjeep]

The dealer connected a jump back to N1 when I was there. But maybe that was just to roll up the windows. Who knows. People have said they've had success jumping from N1. Can't believe this isn't a recall issue for jeep, but anything with emissions is.

 

[ShadowsPapa]

My ESS has not worked since new, 150 miles now. There is no warning on the screen. The on screen voltage reads 12.4 to 13.8. Everything works but the ESS. I guess I want to get it fixed. Then I can look for a way to turn it off.

LOL............ but on a non-LOL note, that's low voltage, quite low if the engine is actually running. The only time I have seen anything in the 12.7 range is when we'd driven several hours, were on the highway, all temperatures were fine and even and the alternator wasn't really needed for anything other than status quo. No charging needed, fans weren't needed at that speed (my wife was driving us home.........)

 

[jebiruph]

Many dealers are now saying 3 to 5 years.
It doesn't help when these never seem to get fully charged. Mine, for example, even after a very long drive, will never register as fully charged. It's a bit better since I charged the batteries individually and reset the IBS, but I still never get anything over 12.5x volts and stopping at a light with ESS kicking in, I get into the 11.8 volt range.
AGM batteries need to be charged at much higher voltages to get them up to full.
AGM batteries also have a problem with taking a set like some old phone batteries used to do years ago - if they are constantly only ever charged to 70% eventually you won't be able to charge them over that.

I'm not sure why the jumper thing on charging or jumping these - when you put 12 volts on the wires to jump start a vehicle, it's 12 volts along the entire chain of wires and cables. It doesn't drop the further down the wire you go (other than voltage drop induced by the cable itself)
So I gotta disagree with a need to use a special jumper or jump starting instructions.
The IBS monitors the main battery only. And the main battery is the "crank" battery.
The AUX battery is for the electronics. That's a light load - fractions of an amp.
Once you connect jumper cables at the main battery, you have the jumper vehicle's voltage present at the jumpee vehicle - along all wires and cables. Since it takes only 11+ volts to run the electronics, you are going to have that and much more from the vehicle doing the jumping once you connect the cables at the main battery. You can't see 14 volts at the main battery and less than 11 at the aux battery terminals.
Proof the vehicle electronics run on less than 12 volts is facing me every time my ESS kicks in and I have the cluster showing the voltage.

The only time it would be 12 volts along the entire chain of wires and cables is when there is no current flowing through the wire. As soon as the current flows through the wire there is a voltage drop of amps x resistance (v=ar). As current flows into the batteries there is also a voltage drop that lowers the voltage available down stream.

If you're jumpstarting from the main battery, a jumper from from the main battery to the N1 terminal mitigates the voltage drop caused by the aux battery. The jumper wire itself should have less resistance/voltage drop than the factory wiring because you are bypassing ESS components and their electrical connections.

If you are jumpstarting with a vehicle that you can leave hooked up for a while to build the charge in the batteries, you don't need the jumper. But if all you have is a booster pack, efficient application of that limited power may mean the difference between getting started or not.

 

[mrmo]

Genesis Dual Battery Kit has been available for a long time.
https://www.genesisoffroad.com/jt-dual-battery-kit

Wow! They must be growing trees!??

They are pricey but a great solution. I have the diesel and they dont list for that engine, so that sucks. I have been trying to figure out a second batt and delete the aux, use same set up, isolator etc. I am going to install a 1000W inverter and run a 120V line and receptacle back to the bed using the factory system

 

[ShadowsPapa]

Since the two batteries are in parallel at all times, in order for the aux battery to be 11 volts, the main battery also must be 11 volts. The only time one can be more than the other is if they are not connected in parallel, and saw the main is 12.5 and the aux is 11 - connect them together and the current flows from the main to the aux until they are equalized.
But with these, they are connected in parallel, all the time it's sitting in your garage.
Putting jumper cables on the main is a direct line to the starter and the voltage will equalize save for the voltage drop in the wires themselves. Since the main is the cranking battery, and it's pos goes right to the starter..........

 

[jebiruph]

Since the two batteries are in parallel at all times, in order for the aux battery to be 11 volts, the main battery also must be 11 volts. The only time one can be more than the other is if they are not connected in parallel, and saw the main is 12.5 and the aux is 11 - connect them together and the current flows from the main to the aux until they are equalized.
But with these, they are connected in parallel, all the time it's sitting in your garage.
Putting jumper cables on the main is a direct line to the starter and the voltage will equalize save for the voltage drop in the wires themselves. Since the main is the cranking battery, and it's pos goes right to the starter..........

While the starter requires more power than the electronics, it doesn't seem to be as picky about voltage as the electronics. If the electronics don't get high enough voltage they don't boot up. From what I see, starting failures are typically (always?) due to the electronics not powering up and not the starter turning too slow, so the key is getting adequate voltage to the electronics.

When you connect a booster pack to the system, overtime the voltages will equalize, but it's not instantaneous. So in a situation where there is limited boost power available, attaching the booster pack directly to the electronics at N1 gets higher voltage to the system electronics quicker, before the system voltages equalize and possibly dropping the voltage available to the system electronics below the boot threshold.

Do some research and you will find lots of people saying jumpstarting from N1 worked when jumpstarting from the main battery didn't. This is an explanation of why that happens.

 

[FLGladiator]

Just watched a video on how to replace the aux battery, not too bad under the fuse box. HOW TO Replace the Main and Auxiliary Battery on a Jeep JL Wrangler and JT Gladiator Truck - YouTube

 

[Joe Gladiator]

other than the start/stop what else does the aux battery supply power too? can we eliminate it if its just the start/stop function.

 

[Mr._Bill]

other than the start/stop what else does the aux battery supply power too? can we eliminate it if its just the start/stop function.

The primary purpose of the ESS battery is to keep the computers stable so they don't reboot from low voltage while the truck is running. It also makes startup faster as it keeps the computers on all the time and you don't have to wait for them to boot each time the truck is turned on. The ESS system cannot be disabled or eliminated, it is always active and monitoring. The available mods and hacks just keep it from turning the engine off.

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