ESS Dual Battery System Operation

[jebiruph]

Did you ever come up with where the cluster and off-road pages come up with their voltage measurement?
Mine always is running 13.7 to 14.2 or even as high as 14.7 when I look. Today I was watching coordinates and altitudes and other stuff and noticed that my JT was running 12.8 down to 12.6 at times - it was sort of spooky as it was a hot day, we were booking it back home and still a state away from home when I noticed this - I saw your message and thought - oh, crap, hours from home on a nice warm day, we need the AC and a fuse is blown? But it made it hours and miles and later when I checked again it was running 13.8 volts.
Bugs me.
But - obviously that fuse is ok!

The consensus seems to be that the voltages you are seeing - high 12s to high 13s with occasional mid 14s are the result of a properly functioning system. The voltage seems to go high on deceleration and if the IBS shows the main battery needs charging. Otherwise high 12s to high 13s based on current system demands. This is based on the observation of others, for the 3 years I've been monitoring my JL, it's rarely been anything but the mid 14s. I did end up getting a warranty replacement on the main battery a few month ago right before the 3 year warranty expired. The 3 year old aux battery tested ok.

The thing about the fuse blowing is that there's no indication or feedback that there is a problem until the aux battery is drained. And I doubt that it's ever blown on it's own during normal operation, I think it's always a result of shorting out the disconnect main battery positive cable.

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[ShadowsPapa]

The consensus seems to be that the voltages you are seeing - high 12s to high 13s with occasional mid 14s are the result of a properly functioning system. The voltage seems to go high on deceleration and if the IBS shows the main battery needs charging. Otherwise high 12s to high 13s based on current system demands. This is based on the observation of others, for the 3 years I've been monitoring my JL, it's rarely been anything but the mid 14s. I did end up getting a warranty replacement on the main battery a few month ago right before the 3 year warranty expired. The 3 year old aux battery tested ok.

The thing about the fuse blowing is that there's no indication or feedback that there is a problem until the aux battery is drained. And I doubt that it's ever blown on it's own during normal operation, I think it's always a result of shorting out the disconnect main battery positive cable.

Have to thank you for all the info on the ESS connections and how things are routed. That info along with my background in legacy systems is helping me big-time figure this stuff out.

I'd suspect that since I never saw below 12.6 and at least with every other auto-related battery I've dealt with, a fully charged battery with the surface charge removed is at 12.6, the system never let the battery(ies) get below "fully charged voltage" and must be smart enough to handle the load otherwise. The truck operated PERFECTLY all the way there, all the way back, as far as ESS, starting, handling Pike's Peak and so on - it was just weird since I watch the volt meters in my other cars (the best way, far far better than an ammeter, to monitor what's going on with your classic car is a VOLT meter - ditch the ammeter - all but worthless, IMO)

 

[itsdapk]

I've been running for a week after deleting the ESS/aux battery with no problems.
I used this diagram to delete the PCR and a bunch of wires.
No problems or lights.

 

[itsdapk]

Does anyone know if you can delete the Intelligent battery sensor without issues? I've seen on some posts that you get a U113E code.
I have a 390amp alt I'm about to install and heard people had issues with bigger alternators.

 

[LaterGator]

The IBS is needed for the "smart" alternators. Wish there was a std alternator that could replace the oem version. Is your new alternator a smart alternator?

 

[ShadowsPapa]

Does anyone know if you can delete the Intelligent battery sensor without issues? I've seen on some posts that you get a U113E code.
I have a 390amp alt I'm about to install and heard people had issues with bigger alternators.

Like was said already about the IBS - but have you considered the wire sizing for the increased amperage just in case that extra amperage is ever called for and put out?

 

[itsdapk]

Like was said already about the IBS - but have you considered the wire sizing for the increased amperage just in case that extra amperage is ever called for and put out?

I run 2 1/0 powers and 2 1/0 grounds from the alt to my Lithium.
As well as 1/0 to the main batteries.

 

[itsdapk]

The IBS is needed for the "smart" alternators. Wish there was a std alternator that could replace the oem version. Is your new alternator a smart alternator?

Its a new alternator. I'll have to ask my alt builder.

 

[jebiruph]

The IBS is needed for the "smart" alternators. Wish there was a std alternator that could replace the oem version. Is your new alternator a smart alternator?

I don't think the IBS is needed for the smart alternator. The PCM monitors the load on the alternator and adjusts the output as needed. The PCM can also use information from the IBS to adjust the alternator output based on the status of the main battery.

 

[Delhux]

From October to May, my ESS system showed “battery charging”. Once the warm weather showed up, everything went back to working normally.

My guess is it is an issue with the main battery, but the dealerships told me both batteries passed all tests (including load).

Are there any known issues with colder ambient temps causing ESS to go into “battery charging” mode?

 

[ShadowsPapa]

I don't think the IBS is needed for the smart alternator. The PCM monitors the load on the alternator and adjusts the output as needed. The PCM can also use information from the IBS to adjust the alternator output based on the status of the main battery.

Ha - that's 'simply speaking' wired exactly as any typical alternator from the 90s and earlier.

But the difference is likely the signal the alternator supplies for "sense".
It used to be "sense" was the system voltage. If it was under a certain number, say, 13.8, then more field current was supplied through the rotor. If it was over something, for example 14.0, then the field current would be trimmed. It happened really fast - you could see it on a scope as the transistor switched on and off managing field current, then later the PCM handled that.
In the 90s if the PCM voltage regulation function failed, you simply wired in a 1980s MOPAR voltage regulator in place of the PCM control and went on your way.

I know the smart alternators are a lot different - they can read the RPM of the alternator, load on each leg of the stator and much more - I never bothered getting into that as I've never been asked to restore an alternator later than about 1996.

 

[WXman]

So the question the average guy wants to know is: "How do I completely kill 12V power so that I can work on the vehicle safely?"

From those diagrams, it appears that removing the negative from the main battery AND separating the negative wires from that cable lug should do the trick. Would that be correct?

 

[jebiruph]

So the question the average guy wants to know is: "How do I completely kill 12V power so that I can work on the vehicle safely?"

From those diagrams, it appears that removing the negative from the main battery AND separating the negative wires from that cable lug should do the trick. Would that be correct?

There is one cable from the main battery negative terminal to the body that grounds both batteries. If you disconnect that cable at the body it should kill all power.

 

[Delhux]

@jebiruph I really appreciate you taking the time to share all of this.

I’ve had ESS charging issues and higher alternator output for a long time—particularly when the ambient temperature has dropped below 50-60 degrees for an extended period. Long story short, I’ve tended, had the batteries checked/load tested, the IBS both reset and replaced, but it seems to be ongoing (in cold seasons), while the battery voltage is almost always 14.5.

I recently added a Cascadia4x4 85W solar panel, and immediately saw my battery voltage drop from mid 14’s to low 13’s. A week later, the battery voltage started creeping back up all the way to 14.6.

I initially did troubleshooting on the solar panel and MPPT, but I’m curious if I should reset the IBS after adding the solar panel—I’d also like to switch on the parking mode for my dashcam, if the solar panel can keep working—would that additional drain/charge (cam/solar) influence the IBS data that gets passed to the PCM for smart alternator output?

Thoughts?

We've been hashing out the ESS dual battery system for a few years over on the JL forum and I think we have it fairly well sorted. Not all JT owners visit the JL forum, so I thought I'd start this post here for discussing how it works and it's various issues.

As an overview, the system consists of a small aux battery to power the interior electronics during an auto stop, conserving the main battery power for restarting. There is a PCR (Power Control Relay) that separates the aux battery and interior electronics from the main battery and engine electronics during an auto stop. The PCR is a normally closed relay, meaning when no power is applied, the relay terminals are connected. There is an IBS (Intelligent Battery Sensor) that monitors the electrical current into and out of the main battery and reports the main battery's state of charge and state of health to the ESS system. The aux battery is not monitored, instead the PCR is briefly activated during a cold start to separate the systems for quick aux battery test. If the aux battery fails the test, the auto stop/start throws an error and is disabled.

This first diagram shows the ESS related components and battery cables in their relative positions under the hood. Note that the negative cables at the main battery were switched at some point.

This diagram shows that when not auto stopped, both batteries are connected to everything. Since the batteries are connected to each other most of the time, if one goes bad, it can drain and impact the health of the other battery.

This diagram show how the electrical systems are separated during an auto stop.

This diagram shows that with the positive and negative terminals separated from the main battery, the aux battery is still connected the positive terminal. If the positive terminal gets shorted to ground, it will blow the high capacity fuse connected to the N3 terminal, separating the aux battery and interior electronics from the rest of the system.

With the high capacity fuse at N3 blown, the aux battery and system electronics are isolated from the alternator and the main battery. The aux battery becomes the only source of power for the system electronics and it is not getting charged from the alternator. Eventually the aux battery will run down and no power will be available to the system electronics, disabling the vehicle. At this point, attempting to jumpstart the main battery won't help because power will still not get to the system electronics.

 

[jebiruph]

@jebiruph I really appreciate you taking the time to share all of this.

I’ve had ESS charging issues and higher alternator output for a long time—particularly when the ambient temperature has dropped below 50-60 degrees for an extended period. Long story short, I’ve tended, had the batteries checked/load tested, the IBS both reset and replaced, but it seems to be ongoing (in cold seasons), while the battery voltage is almost always 14.5.

I recently added a Cascadia4x4 85W solar panel, and immediately saw my battery voltage drop from mid 14’s to low 13’s. A week later, the battery voltage started creeping back up all the way to 14.6.

I initially did troubleshooting on the solar panel and MPPT, but I’m curious if I should reset the IBS after adding the solar panel—I’d also like to switch on the parking mode for my dashcam, if the solar panel can keep working—would that additional drain/charge (cam/solar) influence the IBS data that gets passed to the PCM for smart alternator output?

Thoughts?

To start with, the negative side of the solar panel should be connected to pass through the IBS and not connected directly to the battery. How is yours wired?

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