Are the batteries really isolated during ESS stops?

[Flanders]

I guess we're going to keep at it. The issue of the common starter crank signal between the aux battery and the main battery indicating a connection between them had to be resolved

It was only ever an issue in your mind.

The difference between the traces was always the voltage between N2 and N1.

The scope could have been grounded anywhere in the circuit, even at MAIN+, and that still would have been true.

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[Flanders]

Has anyone ever wondered - why take the aux battery ground up to the top of the IBS on the main battery, THEN both over to the chassis ground instead of home-running the aux battery ground to the chassis?

Probably only people like me think about those things?

A better answer than my first for this arrangement:

Disconnecting the main at the chassis ground removes power from the vehicle electronics, except the IBS remains powered and doesn't reset (I think).

Not resetting the IBS is a nice feature. I'm reluctant to disconnect my batteries in the name of science because the charging system has been behaving sanely recently. It has not always.

 

[ShadowsPapa]

A better answer than my first for this arrangement:

Disconnecting the main at the chassis ground removes power from the vehicle electronics, except the IBS remains powered and doesn't reset (I think).

Not resetting the IBS is a nice feature. I'm reluctant to disconnect my batteries in the name of science because the charging system has been behaving sanely recently. It has not always.

That, and recent surgeries and such, good reasons not to go out and mess around with mine. It works fantastic, perfectly.
I need to get a new JSCAN license for my new VIN and check what the IBS says about the battery and so on. I wish it wasn't locked to that VIN. Instead, the new owner, who doesn't give a shit, can use JSCAN and you have to buy a new license.

 

[Andy29847]

A better answer than my first for this arrangement:

Disconnecting the main at the chassis ground removes power from the vehicle electronics, except the IBS remains powered and doesn't reset (I think).

Not resetting the IBS is a nice feature. I'm reluctant to disconnect my batteries in the name of science because the charging system has been behaving sanely recently. It has not always.

Youse guys are saying the Intelligent Battery Sensor is not really intelligent. I agree.

 

[jebiruph]

Late model Jeeps with batteries have 2 starting regimes. Let's call the first one "Cold Start." This does not mean that the engine (or weather) is cold. For our purpose, a cold start is one where the vehicle ignition was in the "off" position when you start. When pressing the start button on a cold start, the first thing that happens is that the Power Control Relay separates the 2 batteries. This is for the purposes of testing the auxiliary battery to determine the suitably for a future ESS start. The relay rejoins the 2 batteries in a very short time (~40ms). Once rejoined, both batteries are used to start and run the Jeep.

Actual oscilloscope test for cold start:

Simplified illustration for a cold start:

The second starting regime is an ESS start. The is where you are driving, you stop for a light, sign, or traffic, and the Jeep turns off (when you reach a full stop with the brake depressed). When you are ready to resume your drive, you let off the brake and the Jeep automatically restarts. When you make a stop with the ESS system turned on, and the engine shuts down, the 2 batteries remain connected together until you release the brake. Both batteries are keeping the electronics in the cab going. When the brake is released, the Power Control Relay separates the batteries. When the batteries are separated, the auxiliary battery powers the electronics in the cab, keeping things like the radio and AC on while you wait. Next the starter is energized solely on the power of the main battery. The batteries remain separated until the engine is started, and the starter turns off. Once the starter turns off, the Power Control Relay rejoins the batteries.

Actual test for ESS start:

Simplified illustration for ESS Start test:

Revelations?
For the purpose of a cold start, the 2 batteries function as one.

In an ESS Start, the auxiliary battery powers the cab electronics while the main battery starts the engine. The time that the batteries are separated on an ESS Start is decided by the time it takes to start the Jeep.

If you are running your Jeep as delivered (with 2 batteries), and you get an ESS Stop/Start message or the infamous Avengers warning light, this might be your first signal that your batteries are nearing end of life.

If you are running your Jeep with the auxiliary battery removed, then you should disable ESS Stop/Start. The reason for this is that when you experience a low battery condition (old or discharged battery drawn down by the power needed to run the starter) you might get a Powertrain Control Module (PCM) reset and error code. You could also damage some of the sensitive electronic in the cab.

Good job on illustrations.

 

[ShadowsPapa]

Youse guys are saying the Intelligent Battery Sensor is not really intelligent. I agree.

It is - and it's used on more makes and models than you'd think.
The issues arise with the driver/owner as much as anything else.

 

[Andy29847]

It is - and it's used on more makes and models than you'd think.
The issues arise with the driver/owner as much as anything else.

Don't bicker with me!

The fact that the Jeep system with its IBS and dash voltmeter tell the driver almost nothing when one of the batteries starts causing problems makes me feel differently. The reluctance to reset the IBS because "charging is working good now" is another nail in the coffin. What info can you get from the IBS if you have a tool to read it?

 

[ShadowsPapa]

Don't bicker with me!

The fact that the Jeep system with its IBS and dash voltmeter tell the driver almost nothing when one of the batteries starts causing problems makes me feel differently. The reluctance to reset the IBS because "charging is working good now" is another nail in the coffin. What info can you get from the IBS if you have a tool to read it?

The problem is that it doesn't give a driver a "you have a failing battery, you fool, you idiot" message, it shows you voltages and you have to read the trends and behaviors.

There are several sections, the info will be in the BCM because it's the hub for pretty much everything. It even feeds the PCM info about things, rather than the PCM receiving it directly.

Intelligent Battery Sensor (IBS) Data 3:
Intelligent Battery Sensor Lifetime Charge Received: 2861.75 A/h
Intelligent Battery Sensor Lifetime Charge Released: 2765.75 A/h
Intelligent Battery Sensor Voltage Before LIN Wakeup: 7.58 V
Intelligent Battery Sensor Wake Up Reason: Not defined
Intelligent Battery Sensor (IBS) Data 4:
Intelligent Battery Sensor Calculated Battery Resistance: 2.00 Ohm
Intelligent Battery Sensor Resistance at 100 % SOC and 25 Deg.C: 1.74 Ohm
Intelligent Battery Sensor Accumulated Time Since Last Reset: 28 sec

 

[Andy29847]

The problem is that it doesn't give a driver a "you have a failing battery, you fool, you idiot" message, it shows you voltages and you have to read the trends and behaviors.

There are several sections, the info will be in the BCM because it's the hub for pretty much everything. It even feeds the PCM info about things, rather than the PCM receiving it directly.

Intelligent Battery Sensor (IBS) Data 3:
Intelligent Battery Sensor Lifetime Charge Received: 2861.75 A/h
Intelligent Battery Sensor Lifetime Charge Released: 2765.75 A/h
Intelligent Battery Sensor Voltage Before LIN Wakeup: 7.58 V
Intelligent Battery Sensor Wake Up Reason: Not defined
Intelligent Battery Sensor (IBS) Data 4:
Intelligent Battery Sensor Calculated Battery Resistance: 2.00 Ohm
Intelligent Battery Sensor Resistance at 100 % SOC and 25 Deg.C: 1.74 Ohm
Intelligent Battery Sensor Accumulated Time Since Last Reset: 28 sec

Respectively, those readings, except for State of Charge", are items that pertain to the IBS, not the systems in the vehicle. Even the Resistance and SOC are not very useful because it is measuring both batteries together. More important, the numbers are not available to the owner.

 

[Great Offender]

Another Zombie thread.

 

[jebiruph]

I made a relay with a test point, it is green trace. The probe is connected to the output of the stater relay. Trigger near 7.8V rise. The test point measures less than 1 ohm to GND. It is the coil of the starter solenoid. Main battery ground.

I've never heard of making a relay with a test point, any details on how you did it?

 

[J Sierra]

Take the relay case off, drill a hole in the top . Solder a test point on.

 

[jebiruph]

Respectively, those readings, except for State of Charge", are items that pertain to the IBS, not the systems in the vehicle. Even the Resistance and SOC are not very useful because it is measuring both batteries together. More important, the numbers are not available to the owner.

I think that IBS information is specific to the battery it's connected to. Here's an image of other information available from jscan https://www.jlwranglerforums.com/forum/threads/new-twist-on-aux-unavailable.158752/post-3270587

 

[Andy29847]

I think that IBS information is specific to the battery it's connected to. Here's an image of other information available from jscan https://www.jlwranglerforums.com/forum/threads/new-twist-on-aux-unavailable.158752/post-3270587

Ah, but it is hooked to both batteries. This is my last reply on this issue.

 

[ShadowsPapa]

Respectively, those readings, except for State of Charge", are items that pertain to the IBS, not the systems in the vehicle. Even the Resistance and SOC are not very useful because it is measuring both batteries together. More important, the numbers are not available to the owner.

The IBS can't report on systems. What are you looking for specifically?

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