ESS Dual Battery Management

[Gee-pah]

The way I look at it is that there is undue preoccupation with the "ESS factor". The Engine Stop Start function is straightforward; the engine stops and the engine starts.

Biases: I'm one of the few who doesn't have much issue with the ESS system. I do though trickle charge when parked at home and need to for ESS to engage when driving. This said, I completely get that people don't like being thrown a design that concerns them as it regards the additional wear and tear that cranking an engine has on the engine, starter and other components. Sure, that wear and tear is minimal compared to our "father's Oldsmobile," and the design incorporates so called heavy duty components, but "moving parts are subject to wear and tear."

This said, you're right...and the end of the day it's just (another form of) cranking and shutting down an ICE.

The complication is introduced by the insistence for drawing power while the engine is off under the premise that the practice can be exercised without impacting the effectiveness of the starter battery.

Sure--no questioning that with the 3.6L factory design, power draw, with no alternator to replenish the loss given a resting engine, drains the starter battery, but technically that starter battery might be considered the ESS/Aux battery, not the main battery. Regardless, the drain is lessened by the fact that both batteries are connected in parallel at rest, each contributing to the vehicle's resting power draw--not that you said otherwise---not that you're anything but correct.


Which battery is the cranking battery kind of depends on how you look at it. I say this because cold crank operation tests the ESS/Aux battery--as you probably know--and then that test successfully past, brings in the main battery in parallel to allow both batteries (yes, primarily the main one) to effect the crank. 3.6L's can start solely with an ESS/Aux battery, or as Jerry has shown us, with some wiring changes that make the 3.6L "think" its checking/tapping the ESS/Aux battery. And sure, model year 2019 3.6L JLs and beyond, or flashed 2018's can crank with either battery and not be stranded if the ESS/Aux battery fails its pre crank test.

Any system that ties two dissimilar batteries, or two batteries tied together that are tasked to different use is doomed to present troublesome experiences.

I agree. Question though...do you say this for reasons other than 1) moving energy takes energy, and 2) with dissimilar batteries and a design that ties the batteries to a particular function, either battery can be a parasitic drain on the other when connected in parallel, which for the 3.6L is all the time but for a second at cold crank and ESS events--especially when parked?

Adding the ability to disconnect the Jeep's two OEM battery scheme seems like a good idea. Utilizing the additional switching to reconnect the parallel connection may seem to offer a quick boost for the starting system, and it may seem like a quick and easy solution, but it is not the most efficient use of the potential energy you are transporting.

I think you ideally would opt for one big battery and in lieu of that 2 or more identical batteries in parallel, with no particular 3.6L task assigned to any one battery, but all batteries working together to effect all energy draw tasks. Is that about right?

Whereas that might be more efficient, doesn't the ability to separate the batteries (permanently, temporarily, or by logic (i.e. Geneses)) add additional fault tolerance?

The result of disconnecting the auxiliary battery and temporarily reconnecting it as a booster is that some of the downsides of running two dissimilar batteries are retained. The behavioral relationship between the two batteries is reversed. The aux battery will now sacrifice itself to charge the primary battery, where as in the unmodified system the primary battery tends to sacrifice itself to support the auxiliary battery. Regardless, of the configuration, the parallel circuit of dissimilar batteries will result in a system where battery life cycles are being squandered to charge batteries.

I hear this, but couldn't the ESS/Aux battery, properly charged, solely energize the crank, and then, with the alternator running, reconnect the batteries in parallel (immediately or at some point thereafter when voltages of the two batteries are, say, equalized) so replenishment of the main battery is a task that ultimately the alternator does, as parasitic draw from the main battery to the ESS/Aux is minimized by the main and ESS/Aux batteries getting replenish from the alternator?

For my part, when my auxiliary battery ages, I will remove it and send it to the core yard. I do not intend to replace it. It is unnecessary and I do not see any benefit to using it.

I respect that; it may even *for you* prove the optimal situation. Heck, other vehicles run ESS with 1 battery. But for many JL owners, who not only have optional gear that pulls power, but that may do so with the engine off, I'd think that the ability to separate batteries may make sense in increasing the chances for successful crank when in the middle of some overland adventure. Mind you, FCA didn't design it that way...but....

It's almost as if--if I hear you correctly, that acquiring the Geneses double battery tray and identical Geneses "group" rated batteries, and hooking them up parallel permanently, sucking up the 6 ESS events per crank byproduct, sounds appealing to you as well.

I am not debating with you....I'm just discussing pros and cons of various approaches.

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[Yellow Cake Kid]

I appreciate the thoughtful discussion.

Thank you.

 

[WranglerMan]

@Jebiruph here is the answer I received from Genesis in regard to the IBS connection to the aux battery connection.

The IBS is connected through the factory wiring and wiring harness to the factory negative post clamp. Because of the orientation of the batteries in the dual battery system, that post clamp attaches to the newly added accessory battery negative. It has more to do with the factory wiring than with anything we decided for or against in designing the system.


Sincerely,
Genesis Offroad, LLC

 

[Yellow Cake Kid]

"The IBS is connected through the factory wiring and wiring harness to the factory negative post clamp. Because of the orientation of the batteries in the dual battery system, that post clamp attaches to the newly added accessory battery negative. It has more to do with the factory wiring than with anything we decided for or against in designing the system.


Sincerely,
Genesis Offroad, LLC"


When the batteries are connected in parallel the IBS will represent the resistance of the battery array and the voltage of the battery array which are two useful parameters to consider. It is unlikely that the temperature reading will represent the actual temperature of one or the other batteries' cells, but it is also unlikely that the OEM system does a great job of this either. Neither battery will be charged with an optimal strategy for their individual circumstance, but the parallel connection will tend to mollify the deviance from best case possibility.

When the batteries are disconnected from the parallel array it would seem that the IBS should be connected to the battery that is being charged otherwise the charging system can not provide an optimized charging cycle.

Placing the IBS on the disconnected secondary battery while charging only the primary battery introduces some possibilities that warrant further consideration. My first thought is that the Body Control Module will be instructing the alternator, via the field control and current regulation, to charge the battery in accordance with a strategy befitting the state of the battery that is disconnected, while the battery that is actually connected is being charged with no regard for the state of the art of Intelligent Battery Charging.

That seems like something worth pondering.

 

[Gee-pah]

Some (hopefully) yes/no questions:

1) Is it correct to say that the "Separated Batteries" wiring of https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/post-1291331, while a perfectly acceptable method of, say, running appliances off one of the batteries while the 3.6L is parked, and preserving the other, is a setup that would not allow, at the point of cold cranking, the vehicle, if an un-flashed 2018 3.6L, to turn over?

I say this because from the factory the ESS/Aux battery is tested for voltage prior to cold crank, and if absent, the 3.6L JL from 2018 won't attempt a crank, and because without the ground connected on the ESS/Aux battery, as in this setup, no voltage can be detected.

Again--in no way am I seeking to find holes in this design, just understand it. Clearly one could, using the techniques above, easy reconnect this ground prior to cold crank.

2) Is it correct to say that the original hack from 2018, where a fused jumper between N1<-> N2, and the grounds of the two batteries are connected might be considered yet a 4th variation from the three of the picture linked above that represents the polar (no pun intended) opposite of the "Separated Batteries" wiring in that BOTH the jumper and grounds are connected, whereas in the "Separated Batteries" scenario, neither are?

Thanks.

 

[Gee-pah]

It is an over simplification to regard the parallel interconnection of a fully charged primary battery and the partially charged secondary battery as acting as one, and that is the basis of my interest in this subject.

And I think you say this because in a hard wired parallel connection there is no logic as to when one battery might be connected to the other to say, avoid the parasitic drain you speak of, whereas in a Genesis like setup, when those batteries are connected in parallel could have both logic and user overriden "Boost" button aspects to it?

It seems as if Genesis has put a lot of thought into providing a solution, but it appears that the Genesis system charges the secondary battery by placing it back in the parallel array so it may be charged.

If that is so, the secondary becomes a parasite to the primary battery until the system reaches equilibrium.

Fair--but this parasitic drain's impact might be reduced by a cranked 3.6L JL's alternator charging both batteries, correct? And when the batteries are connected in parallel with the rig at rest, and the parasitic drain you speak of is absolutely the case, that parallel connection might represent the lessor of two evils, the worse one being the inability to crank the engine, especially if you or sensible logic controls when the connection occurs, yes?

(I am NOT poking holes. I am trying to understand. )

A system could be devised that dedicated the charging to one or the other battery and not both at once.

That is the kind of dual battery management that appeals to me.

Do you feel this way because it offers the operator more control? If the alternator can handle the charging needs of both batteries, is it the ability to less tax the alternator when two batteries aren't needed, or faster charge one battery where you are going with this?

 

[Jebiruph]

Some (hopefully) yes/no questions:

1) Is it correct to say that the "Separated Batteries" wiring of https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/post-1291331, while a perfectly acceptable method of, say, running appliances off one of the batteries while the 3.6L is parked, and preserving the other, is a setup that would not allow, at the point of cold cranking, the vehicle, if an un-flashed 2018 3.6L, to turn over?

I say this because from the factory the ESS/Aux battery is tested for voltage prior to cold crank, and if absent, the 3.6L JL from 2018 won't attempt a crank, and because without the ground connected on the ESS/Aux battery, as in this setup, no voltage can be detected.

Again--in no way am I seeking to find holes in this design, just understand it. Clearly one could, using the techniques above, easy reconnect this ground prior to cold crank.

2) Is it correct to say that the original hack from 2018, where a fused jumper between N1<-> N2, and the grounds of the two batteries are connected might be considered yet a 4th variation from the three of the picture linked above that represents the polar (no pun intended) opposite of the "Separated Batteries" wiring in that BOTH the jumper and grounds are connected, whereas in the "Separated Batteries" scenario, neither are?

Thanks.

The only reason I know for the separated batteries configuration is for individual charging of the batteries which some users report doing frequently. It's not intended as a running configuration and as you state, an un-flashed 2018 would not start with a bypass jumper installed.

With the 2 variables of the switch and the fuse, there are 4 different combinations available. I mention the 3 that I thought are relevant to this discussion.

 

[Yellow Cake Kid]

Fair--but this parasitic drain's impact might be reduced by a cranked 3.6L JL's alternator charging both batteries, correct?

I think a proper answer to your question would require some work in a lab with access to the cells wired in series that are found within the typical automobile battery form factor.

So, here is an abstracted example of some of the challenges:

- Assuming the batteries are wired in parallel and being charged.
- Assuming the engineers were well aware of the nature of parallel circuits... which they are.

Let us imagine that you have two batteries sitting at differing charge levels. For the sake of discussion let us say that one battery is charged at 13.2vDC and the other is charged to 12.1vDC. It would not be unreasonable to assume that the battery with the greater charge presented a resistance of 1.5ohms, while the other battery measures 1.0ohms.

1.5 ohms and 1.0 ohms placed in parallel will appear as .6 ohms, so a reading of .6 ohms could be extrapolated backwards to determine that you have two batteries, one at 1.5 ohms and the other at 1.0 ohms. But .6 ohms could also be extrapolated backwards to equate to one at 1.2 ohms and the other at 1.2 ohms.

The resistance readings, combined with the voltage reading provide valuable information that can be used to track and predict the health of the battery so that charging cycles can be applied more effectively.

Furthermore, the resistance readings are most useful when they are collected as a corpus of data correlating to the lifespan of the individual battery, which is data that the IBS system is perfectly suited to provide. The opportunity to make and collect these observations has previously been impractical but now the measurements and collection are especially convenient.


With the voltage measurements you have a similar challenge.

If you have a battery at 13.2vDC and another at 12.1vDC and they are wired in parallel, the system sees 12.65vDC. The system does not know how one battery differs from the other, and it doesn't know if the 12.65 extrapolates to the pairing described above or perhaps to a pair made up of a 14vDC and 11.3vDC battery, which also presents itself as 12.65vDC. So, the system doesn't know when it is beginning to sulfate one battery while continuing to charge the other. That is not an ideal situation. Now, it is true, and I think that this is what you are referring too, that the internal resistance of the batteries will tend to mollify the negative effects of trying to service two dissimilar batteries at once, but the option of charging each battery independently would be preferable, especially when the technology has finally matured to make the possibility of optimizing charge cycles available to a vehicle's onboard charging system.

These are incredible simplifications of small aspects of the issue, but it seems frustrating, to me, that just when we have achieved the ability to track and manage for both optimal battery health and charging system energy efficiency, the gains made by this applied technology are undermined by clumsily slapping a second battery onto the circuit.

Do you feel this way because it offers the operator more control? If the alternator can handle the charging needs of both batteries, is it the ability to less tax the alternator when two batteries aren't needed, or faster charge one battery where you are going with this?

I feel this way because technology exists that could manage this automatically while making use of the latest improvements in battery charging technology, but for lack of a few parts and features in the current implementation(s), this opportunity has yet to be realized.

Best regards.

 

[WranglerMan]

I don’t believe the Genesis system charges both batteries at once or at least thats my understanding, I believe on startup that it first looks at the voltage on the main crank battery and once it sees that voltage at 13.2 for several minutes it then allows the solenoid on the smart controller to be energized and the current flows to the second battery and this is done to not over tax the alternator, not sure how the original Jl charging system work.

My new setup has only been running for a very short time but I have done daily voltage checks on both the crank battery and aux battery and both have been pretty identical in voltages but i expected that since the Cole Hersee solenoid has been energized as the main crank battery has been 12.7 or above but this a.m on my last of the 7 day check the crank voltage had dropped to 12.59 as I was checking and I heard a click and then I took a resistance reading across the solenoid and it had opened and isolated the two batteries as the crank was at 12.59-12.6 and aux was at 12.75 and after starting within a few minutes they reconnected and both were again at 12.75-12.8

I will have to say that my charging system seems to be a lot more efficient as when I start it after being parked for 10-12 hrs it displays above 14+ on the EVIC and the metered voltage at the batteries is usually 13.7-13.8 and after driving for 20-30 mins the displayed voltage is usually 12.9-13.1 and I had not seen that on my original setup for a long time and after parking it’s been at 13.1 and after the 10-12 hrs it usually drops to the 12.6-12.8 so I can’t complain so far

 

[Yellow Cake Kid]

That part where it says Reconnected... and both batteries are hooked up to the charger... that's when both batteries are being charged despite the fact that one would seem to be "full".

Here is a very rough and regrettable analogy:

 

[Jebiruph]

"The IBS is connected through the factory wiring and wiring harness to the factory negative post clamp. Because of the orientation of the batteries in the dual battery system, that post clamp attaches to the newly added accessory battery negative. It has more to do with the factory wiring than with anything we decided for or against in designing the system.


Sincerely,
Genesis Offroad, LLC"


When the batteries are connected in parallel the IBS will represent the resistance of the battery array and the voltage of the battery array which are two useful parameters to consider. It is unlikely that the temperature reading will represent the actual temperature of one or the other batteries' cells, but it is also unlikely that the OEM system does a great job of this either. Neither battery will be charged with an optimal strategy for their individual circumstance, but the parallel connection will tend to mollify the deviance from best case possibility.

When the batteries are disconnected from the parallel array it would seem that the IBS should be connected to the battery that is being charged otherwise the charging system can not provide an optimized charging cycle.

Placing the IBS on the disconnected secondary battery while charging only the primary battery introduces some possibilities that warrant further consideration. My first thought is that the Body Control Module will be instructing the alternator, via the field control and current regulation, to charge the battery in accordance with a strategy befitting the state of the battery that is disconnected, while the battery that is actually connected is being charged with no regard for the state of the art of Intelligent Battery Charging.

That seems like something worth pondering.

How does it know the resistance of the battery array?

 

[Yellow Cake Kid]

It measures the voltage drop at start ups so the resistance may be calculated.

 

[Jebiruph]

It measures the voltage drop at start ups so the resistance may be calculated.

Wouldn't you have to have a current measurement and a voltage measurement to calculate resistance? The IBS in the Genesis configuration does not measure cranking current.

 

[Yellow Cake Kid]

The current measurement is actually a voltage measurement made across a shunt resistor.


edit to replace this
As you may have concluded, in the OEM implementation with the voltage drop measured during start ups, the Power Control Relay is open and the voltage measurement is specific to one battery .

with this
In the OEM implementation with the voltage drop measured during start ups, is the Power Control Relay still open or has it closed. Is the voltage measurement specific to one battery or are the batteries in parallel when the measurement is made, which inplies the voltage drop would be indicative of how both batteries react?


Nevertheless, the charging strategy determined by the info is applied to the two batteries. Go figure.

In the modified systems we have been discussing, where the PCR is bypassed, it's more complicated or simple depending on how you look at it.

In the Genesis system it appears that voltage and current would be measured at some start ups but not all, and then the info would, perhaps, be erroneously attributed to the battery that Jeep had intended the IBS to be mounted on.

Good times.

 

[Jebiruph]

The current measurement is actually a voltage measurement made across a shunt resistor.

As you may have concluded, in the OEM implementation with the voltage drop measured during start ups, the Power Control Relay is open and the voltage measurement is specific to one battery .

Nevertheless, the charging strategy determined by the info is applied to the two batteries. Go figure.

In the modified systems we have been discussing, where the PCR is bypassed, it's more complicated or simple depending on how you look at it.

In the Genesis system it appears that voltage and current would be measured at some start ups but not all, and then the info would, perhaps, be erroneously attributed to the battery that Jeep had intended the IBS to be mounted on.

Good times.

I saw in the IBS thread you posted a link to a different IBS system. Here's a screen shot from the JL system. I don't see any reference to system resistance calculations.

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