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Discussion Starter · #1 · (Edited)
There are three Parts to this thread. Yes, the Pacifica Hybrid is hard on 12v batteries, and this has been a debated topic. I now have cradle-to-grave data from a battery installed new in our PacHy in Jan 2019 and how the vehicle managed it for 4 years. That will be the second part of this thread.

First; What happened. Later, why it happened and finally, how I can fix my car so it should not happen again.

What Happened, recently (short version):

After 8 days of inactivity in our driveway, I found our beloved 2018 Pacifica Hybrid Limited completely dead and unresponsive to the remote on 1/4/2023. I manually unlocked the driver door, no usual dash indications, opened the hood and found the 12v battery system at 2.9v. As expected, it would not start and there were no responses or indications. There had been no warnings or indications of any problems prior to this (more on this later). The car prevented my 6 A charger from charging the battery while it was connected to the car. So I jump started the car with a known good battery, removed the jump, and allowed the engine to charge the car battery for a while. I decided to take no chances and replace the 12v battery. I turned the car to the OFF state via the dash push button. The car was never moved out of P park. I left it to go purchase a new 12v battery. I returned a little over 2 hours later with a new battery to find the car in the street, having rolled ~80 feet on its own and knocked over my neighbors 700-800 lb brick mail box across the street. A police report was filed, pictures taken, and I jump started the car with the new battery. It started normally and I backed it up under its own power into my driveway where I replaced the 12v battery without incident. The car has operated normally with no warnings or indications of a problem before and since this incident. While I was gone, the car on its own and while OFF had unlocked the transmission park pawl when the 12v battery was failing. This allowed the car to roll 45 feet down a very mild slope in my driveway (3/16”/ft avg), then across the street to crash into my neighbor’s mail box. There was no occupant, and no key fob was present. My quick search has found at least 3 other incidents with this same model, where the 12v battery failed and the car, on its own, unlocked the transmission allowing it to roll away. Of the 4 incidents I am aware of, 3 resulted in collisions and property damage.

NHTSA 11173732, also Pacifica Forum post: 528153, member: 64329 @AdrianaHybrid18
Brand new hybrid - completely died

Pacifica Forum post: 597914, member: 76986 @Inanni08
Battery dies on Pacifica Hybrid - Rolls out of driveway...

Pacifica Forum post: 543399, member: 66469 @luked1234
Battery dies on Pacifica Hybrid - Rolls out of driveway...

Kids play around here! and were nearby when this happened, but it was so quiet and slow that they did not notice. It didn't even trigger the motion activated video security camera across the street because it was so slow and moving towarrd the camera. It’s only a matter of time before someone is seriously injured or killed by this design defect. I have talked to my dealer about this but he suggests that I contact ChryslerCares first before they look at my car.

And for those who will ask: Yes, my wife and I have changed our behavior because of this incident. Normally flat-landers like us only set the parking brake when on a noticeable incline. The Pacifica has an inclinometer built in and does this automatically for us. But it is apparently not enough. With this car however, we now consider ALL surfaces as significant inclines and ALWAYS set the parking brake when turning the car off. This gives us some comfort, but consider that the parking brake is also under software control like the park pawl. Makes one wish for the days when we had a cable operated mechanical "emergency" brake that could be teased and under direct control of the driver instead of just a parking brake that we can ASK THE COMPUTER to apply and that is just ON or OFF.

I will make the car and battery available for inspection at the Dealer’s or Chrysler’s request.

I filed a police report. I consulted with my insurance agent and a lawyer. I filed an NHTSA complaint. And I have sent a PM to ChryslerCares.

We love this car, especially my wife. We use the heck out of it and it had 65330 miles on it at the time of this accident. But she has maintained it in showroom condition inside and out with regular hand washing, hand waxing and detailing. Prior to this incident, the car did not have a scratch on it and had never been in an accident. So she was livid when this happened and feels strongly as I do that this is a symptom of a dangerous design defect in the Pacifica Hybrid. Under no circumstances should a vehicle unlock the transmission on its own. There should be safeguards that prevent the haywire electronic behavior that causes this. Additionally, there should be a specific warning to the user that the 12v battery needs replacement. There is none. Those two topics will be the subject of the 3rd part of this thread. We hold little hope that Chrysler will fix the damage to our bumper, but that does not stop us from feeling that they should.
Wheel Car Tire Land vehicle Fire hydrant

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Discussion Starter · #4 ·
You missed the boat, he is not suggesting the transmission should lock if the 12v dies. He is saying that a locked transmission should not unlock because the 12v dies.

I've personally always used the auto parking brake setting that engages with park. With my kids you never know, and these stories certainly confirms it's a good idea. I'm so sorry the OP had to go through this, hopefully more folks that have this happened file reports.
Bingo! I couldn't have said it better myself. And thanks for the tip on the Auto Park Brake setting. I just went out and found it in settings and applied it.
Previously our pacifica (and I suspect all of them) must have an inclinometer built in. This is because when parking on a steep incline, it set the parking brake automatically when placed in park, but did not set it when on a moderate or low slope surface. I'm guessing this is to protect the park pawl mechanism from being over-stressed.
 

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Discussion Starter · #7 ·
I agree, a transmission, that is in park, should stay in park. I use the electric parking brake, all the time. Just a habit from driving manual transmission vehicles.

But FYI for the community -
The electronic parking brake on the rear wheels is power activatied and power de-activated. This means a 12v battery failure after you set the e-brake, means you can't release the brake manually. A jump will be required.
Yes, a jump will be required anyway if the 12v bat is below 10v, so it's no additional inconvenience. However I think we all can agree that a 5000 lb projectile with no driver and without warning rolling down your driveway, street or hill or even in your garage as in @Inanni08 case is more than an inconvenience.

And BTW, only @CANADAHYBRIDGUY has suggested engaging the parking pawl while driving. And I agree that would be a Bad thing.
I am preparing part 2 WHY IT HAPPENED, so hang tight.
 

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Discussion Starter · #9 ·
Hey, @drocketman, sorry it happened to you. I'm too lazy to search through our favorite video, if my memory serves me right, the parking pawl is driven by a motor. If the electrical power suddenly dies, the pawl should remain in the same state it was right before the failure. However, a slowly dying 12V battery may cause random actions from the van's computers. Unlikely, but not impossible. When the 12V battery died in my 2018 PacHy, it bricked the HV battery computer (BPCM) and the whole HV battery had to be replaced.
I looked back at the Weber Auto Pachy trans deep dive and you are correct. He refers to it as a motor that actuates the park pawl. A short pulse of power is required to engage or to disengage the pawl. Disengagement is positive where the pawl is always pulled from the Parking gear even if it is loaded by the vehicle on an incline. Engagement is spring loaded so that if the pawl comes down on a tooth of the parking gear, it allows the vehicle to move until the spring forces the pawl into the next tooth valley. In both cases, the pawl motor is energized for only a short time and completes the overcenter insertion or retraction motion. I do not know if the pawl motor has position feedback. I suspect not. Either way, if not powered, the pawl will not move and is spring loaded to remain in the last commanded position. However, I totally agree with you that IF the vehicle operating system can turn on wiper motors, flash lights, turn on AV systems, destroy speakers, destroy transmissions, and brick the HV battery, etc., during the "random actions", haywire operation and scrambled brains behavior when the 12v battery dies, it certainly might be able to momentarily power the parking pawl motor.
 

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Discussion Starter · #10 ·
Now WHY IT HAPPENED:

For you fellow intuitors out there, please try not to jump to a solution before there has been a thorough vetting of why it happened by all forum members who may have relevant input. The answer to the question of what is the ROOT CAUSE of what happened to me and my fellow roll-away victims is what we should be after here. As @stop-eject has pointed out, there may be some victims of other calamities caused by the same root cause. I follow the trail of evidence.

So first is research, data gathering and analysis.

What do we know that is common to all occurrences.

  • The 12V battery died or was dying when the rollaway occurred in all 4 cases.
  • The parking pawl was disengaged at the time of the rollaway in all 4 cases.
  • The vehicle was left unattended and was motionless for a significant period of time prior to the rollaway, in all 4 cases.
  • The initiation of the rollaway was observed in two of the 4 cases and it was verified that nobody was in the vehicle. In the third (garaged) case, the owner states that the car was left in park and nobody accessed the car when it rolled away. And in my 4th case, there is no evidence that anyone accessed the vehicle when it initated the rollaway.
  • In all 4 cases, the owners believed the car was left in park when the rollaway occurred.
  • None of the 4 owners have knowledge of what vehicle system functions may have been active when the car was in the OFF state, and the manufacturer acknowledges that the vehicle has automatic 12v functions when the vehicle is in the OFF state.
These questions occur to me:

1. Is there a high frequency of 12v battery failures in this vehicle?
2. If so, does it fail in a repeatable way or does the vehicle have random and varied response to the 12v failure?
3. Is there a definitive warning that the 12v battery needs replacement prior to its faiure?
4. Is there a routine service called out by the manufacturer that will make the owner aware of an impending failure?
5. Does the battery fail from old age or does it fail due to abuse by the vehicle?

Answers:

1. Yes. At the time of this post, a search on the exact words “dead battery” on only the 2017+ Chrysler Pacifica PHEV Hybrid Forum yields 138 results. A review of only one of these threads with only 30 posts on it, yielded 23 independent occurrences of PacHy 12v batteries dead, dying, replaced, or creating other problems. Another thread in these 138 threads had 421 posts on it. It is clear that there were thousands of posts related to dead or dying 12v PacHy batteries. Consider that this is likely only the tip of the ice berg as many owners are not familiar with or do not post on Pacifica Forums. Also consider that the Gas Pacifica uses the same battery, likely uses similar battery management hardware and software, and also uses considerable 12v battery energy during engine off times over and above other vehicles that do not employ Stop-Start technology. And a search on “dead battery” in the 2017+ Chrysler Pacifica Forums produces similar alarming results. For anyone who might question this conclusion, I suggest that they do their own searches and read a few thousand of the posts on the Pacifica and other forums before replying.

2, Random, definitely random. Both the conditions under which the 12v battery fails as well as what happens when and after it fails have some patterns but are quite varied. The battery has failed at different times: After a trip to the grocery store; After 1 night; After a few days; After charging; After about a week or more of sitting; Almost immediately after purchase, etc. It has failed under different conditions: During charging; With the motive battery at zero or 100%; In cold, temperate and hot conditions, etc. OEM batteries have failed as well as new replacement batteries. Besides the random conditions of failure, there are also random, seemingly unrelated problems associated with the 12v battery failure. Besides users just finding the vehicle dead and unresponsive with the 12v battery between 2 and 5 volt, they also have found the vehicle (without any control input) acting haywire with audible clicking, humming, or buzzing. It has been accompanied by strange instrument light behavior, AV screen flashing, loud popping in the speaker systems, windshield wipers operating, and parking pawl retraction. This haywire state also in multiple instances results in the vehicle in an unknown and unresponsive state that continues to drain the 12v battery with some lights and devices continuing to operate without the ability to shut them off.

3. No, in the vast majority of 12v battery failures, if not all of them, there is no warning to the user of impending failure. Users are completely surprised.

4. No, not to my knowledge.

5. It appears that the battery does not fail from old age in most reported cases. This does not mean that there are no 5-year-old Pacifica Hybrid batteries. But there is an unusually high rate of very early failure and failure in less than 4 years. The specified AGM battery is a deep cycle type battery, more expensive and more capable than standard liquid lead acid batteries. AGMs are often warranted for free replacement out to 4 years which is an indication of their durability and reliability. It is usually specified in two vehicle applications: 1. When there are heavy energy demands while the vehicle is OFF such as in a hybrid or a conventional ICE vehicle with Stop-Start operation. And 2. When the battery is located within the passenger compartment. Both are true of all Pacificas. However, there are some restrictions in charging these batteries that may become important to some users. I refer you to Low Voltage Hybrid and Electric Vehicle Systems presentation by Weber Automotive for more information on this:

An example of a modern vehicle AGM application that is neither a hybrid, nor a Stop-Start application is my son’s 2016 Challenger RT Hemi V8. Its H7 AGM battery is located in the trunk. The OEM battery lasted over 6 years and is a typical lifetime expected of an AGM in a non-hybrid, non-Stop-Start application. The bottom line here is that the specified H6 AGM batteries, OEM and replacements, in the Pacifica Hybrid application are not lasting as long as they should. There is now enough history to conclude that problems of short battery life in the Pacifica are not caused by the OEM batteries, nor a bad batch of batteries. So my investigation now focuses on the way the Pacifica Hybrid uses and charges the battery.

Here are a couple examples of forum members having serious vehicle failures that are strongly suspected as having been caused by the random haywire behavior of the vehicle’s systems during 12v battery failure (one doesn’t have to look very hard to find many other cases):

My best guess is the 12v battery failed and took out the transmission. Seems crazy that could happen.
… a slowly dying 12V battery may cause random actions from the van's computers. Unlikely, but not impossible. When the 12V battery died in my 2018 PacHy, it bricked the HV battery computer (BPCM) and the whole HV battery had to be replaced.
So at this point it is clear that the random response of the vehicle to 12v battery failure is likely the cause of the rollaway incidents. It also appears that the vehicle’s response to 12v battery failure may be the root cause of many more incidents of vehicle “bad behavior” than just the rollaway incidents. Given that there appears to be no indication to the user that the 12v battery is about to fail, it would seem prudent to apply a fix to the vehicle. Since battery failure is inevitable, the fix should concentrate on either warning the user that battery failure is imminent or preventing the vehicle “bad behavior” during and after battery failure, or both. This will be discussed in the third part of this thread: How I can fix my car so it should not happen again.

Before suggesting fixes, it is a good idea to examine as much data as possible. A few members including me have instrumented their batteries in hopes of understanding what loads are placed on the battery by the vehicle. It would be helpful if anyone has captured evidence of significant loads that could drain the battery a significant amount in a “short” time, or if anyone has additional evidence of abuse of the battery by the vehicle’s 12v system.

My recent battery failure punctuated a 4-year cradle to grave study of a new Champion H6 AGM (Johnson Controls) that was placed into service in our PacHy in Jan 2019. This was 2 months after we purchased the vehicle new.

At this point I would like to acknowledge all those who have contributed their stories of dying 12v batteries, especially @stop-eject for his relentless reporting of his plight in the thread Dead Battery Adventures. These inputs from frustrated owner who loved their Pacifica Hybrids as we love ours are why I preemptively replaced my 12v battery and instrumented my PacHy in Jan 2019 and why I am able to present the information below.

Two Significant Surprises in My Data:

Based on my understanding of vehicle charging systems, batteries and the problems reported in this forum prior to Jan 2019, I felt that continuously recording energy input and output from the 12v battery would be critical to understanding how the battery is used and managed in the Pacifica Hybrid. Borrowing from Solar Energy Battery Storage industry technology, I purchased and installed two energy meters in the storage area just above the battery in the left rear of our PacHy. The meters each display 4 parameters. The meters each measure and continuously display real time battery voltage. One of the meters is set up to measure and display real time current INTO the battery while the other is set up to measure and display real time current OUT of the battery using an included 100 A rated shunt placed in the ground circuit to the battery. The meters each internally multiply their voltage and current readings to obtain and display real time Power (Watts). This calculated Power is then multiplied by the Time since the last readings were made to obtain the incremental Energy in Watt-Hours (W-Hr). It performs these calculations at least once per second. Each increment is added to the previous displayed total W-Hr. So on the “Charge” meter, the current and Watt-Hours displayed by the meter are the real time current and the cumulative value of all energy INTO the 12v battery, respectively since the last manual reset. And the Discharge meter likewise displays the Current and Energy OUT of the Battery. The energy display capability of the meters only goes up to 9,999 W-Hr, so the meters had to be periodically reset to zero a couple dozen times during the 4 year life of this battery. At my discretion, I took snapshots with my phone of the meters during this 4 year life. I took a total of about 666 snapshots during the 4 years and recorded all 8 displayed values in a spreadsheet. Here are some interesting values recorded.

Minimum Discharge current seen: 0.00A. (Its assumed the minimum vehicle Off current is below 10 mA.)

Maximum Discharge current: 20.9A (larger values possible but not recorded)

Maximum Charge current: 68.36A (This occurred after restart following 2nd battery failure 1/4/2023)

Note that this high current is normal following a deep discharge in a normal vehicle. The applied voltage at the battery terminals was 14.4v resulting in 986.4 W in battery charging power alone. However, it should be noted that AGM batteries may suffer damage during extended duration high current charging that conventional liquid lead acid batteries do not. Again Ref: Weber Automotive Low Voltage Hybrid and Electric Vehicle Systems shown above.

Maximum Charge voltage: 14.87v (This occurred a few weeks after battery replacement 1/29/2019)

All during my recording of battery data, I was looking for signs of battery degradation. To see this, I looked for a radical departure in the plot of the difference between the charge energy and discharge energy. The slope of this line represents the battery’s storage efficiency. I expected to see a dramatic increase in the slope of this line that would indicate much more energy being used to charge the battery than was delivered to the vehicle during discharge. It just didn’t happen. This indicates that the battery is performing admirably and not near a normal end-of-life. Even after the first unexpected incident of finding the 12v battery dead after 8 days of inactivity on 1/23/2022, there was no indication of significant battery damage. The battery tested good, so was left in the vehicle and continued to perform normally for another year.

Rectangle Slope Font Plot Line


It was troubling that we were sure that we did not leave the vehicle with anything on at the start of that 8 days of inactivity. The HV battery was left at 0%. The recorded amount of energy which was drained from the 12v battery at some time during this 8 days of inactivity was approximately 788 W-hrs. This is a healthy amount of energy that could be expected from the discharge of a known good battery. This fact along with the battery accepting recharging without incident and testing good contributed to the decision to leave the battery in the vehicle. But it was a surprise to find such a large amount of energy drained in 8 days.

Another year went by without incident until 1/4/2023. After another 8 days of inactivity, the battery died again. After jump starting the vehicle and letting it charge the 12v battery for a short time, I made the decision to replace the battery. I turned the car to OFF and left to purchase a new battery. I returned a couple hours later to find the vehicle in the street having crashed itself into and knocking over my neighbor’s mail box.

I have since taken a closer look at my data. Again with this second dead battery event, the vehicle had discharged the 12v battery by an estimated 767 W-Hr of energy. Again the vehicle was left in the OFF state. I have no video or eyewitnesses of the event. I removed and replaced the Champion battery after the collision. At the time, I did not think to place the removed Champion battery on maintenance charge, but have since done so. I have offered it to Chrysler (Fiat Stellantis) if they want to test it and have told both my dealer and ChryslerCares this.

Grasping for straws, I decided to plot the discharge and charge energy separately for that battery’s 4 year life and made some significant findings.

Rectangle Slope Font Plot Parallel


Surprise!

What jumped out at me is the very large changes in slope of both curves and when they occurred. At first I doubted my data and began looking for reasons other than the obvious. First I eliminated the meters. Suspecting a scaling change, I checked current readings in the data from both meters and there was no significant changes to the typical values during the 4 different regions of slope indicating there was no change in scale factor. In addition, both meters would have to have their scaling factors change by the exact same amounts at the exact same times in 3 separate events, a statistical improbability. Then I considered changes to the environment and driving habits. There were none other than the normal mild changes of seasons. And those do not line up at all with the slope changes.

So I am forced to consider the vehicle’s charging system. I first assumed that the vehicle’s charging system was functioning as designed. There are two modes of operation:
  • Discharging – This occurs when the vehicle is OFF and the HV battery is not being actively charged. In other words, whenever the vehicle DC-DC converter is OFF. The HV charge cable may or may not be plugged in. Loads are placed on the 12v battery by the user as well as the vehicle’s automatic functions during this time, and the battery is discharged by whatever amount of energy is required to perform the function.
  • Charging – This occurs whenever the vehicle is plugged in and actively charging the HV battery and for short periods when this is complete. It also occurs whenever the vehicle is in the Run mode and for short periods after shutdown, so essentially whenever you are driving. And it occurs whenever the vehicle’s programming decides that it needs to. In other words, the 12v battery is charged whenever the vehicle DC-DC converter is ON.
As designed, the vehicle’s DC-DC converter is functionally equivalent to an ICE-only vehicle’s alternator system. The significant differences are that the DC-DC converter in the PacHy has a much higher current capacity than a normal alternator system and it can operate without the ICE running. As in some modern alternator systems, it can vary the voltage that it outputs to the system. Whenever the DC-DC converter operates it is always outputting a voltage that is significantly higher than the open circuit battery voltage. So when it’s on, the battery by definition is being charged. This is not always true of weaker and RPM dependent alternator systems, but it is true of the Pacifica Hybrid.

So when operating properly, the DC-DC converter, when ON, delivers makeup energy to the 12v battery to restore what has been drained while it has been off. Because of battery inefficiencies, the energy used to recharge is always more than what was drained. This is evident in the generally positive slope of the Net Energy curve above and also by the Charge Energy curve being generally higher slope than the Discharge Energy curve. I must admit that I was looking for damage to the battery by the charging system because of the exceptionally long duration of higher voltage applied to the battery over its lifetime. But that was not the case. The charging system was responding correctly to the battery drain. It consistently recharged the battery proportionally to what was previously drained while the DC-DC converter was off (with only two exceptions). So my 12v system behaved correctly until the two 8 days of inactivity. During those two times the battery was not charged and its voltage dropped below the 10v DC-DC converter start minimum. So the battery died from some unknown load(s) that continued to deplete the battery to the 4.9 and 2.9 volt readings when it was finally discovered. So the charging system was working apparently as designed. But what I did find were dramatic shifts in loading by the vehicle (discharge) of the 12v battery during its 4 year life.

Referring to the Discharge and Charge History chart above, the rate of discharge of the 12v battery for the first 27 months after installation was relatively constant at an average of about 1953 W-Hr per month. Then for no apparent reason that I can see, on or about 4/11/2021 the rate of discharge suddenly increased by a factor of more than 3.5 to a relatively constant rate of 6849 W-Hr per month. It remained at this increased rate for more than 9 months until the battery was first found dead on 1/23/22 after 8 days of inactivity. Very suspiciously, after disconnection, recharging and reconnection of the battery, the vehicle returned to the original discharge rate of 1953 W-Hr per month. Again it remained at this lower discharge rate for about 10 months until again for no apparent reason on or about 11/14/22 it jumped up to the same higher rate of about 6849 W-Hr per month. Not surprising, this time the battery lasted less than 2 months at this higher discharge rate before again being found dead on 1/4/2023 after another 8 days of inactivity. I want to stress that the vehicle was in almost daily use for this entire 4 years with the exceptions of the two 8 day periods of inactivity. Also of note is that the Charging curve is what I expect of a properly operating charge system, only recharging the battery in response to the discharge rate for the entire 4 years. The only failure to recharge occurred during those 8 day periods when the vehicle was off and the battery was not charged, allowing it to die.

So what was the load that killed the battery these two times? I do not know what the load was but I can ball park the current it took to drain the battery using the W-hrs that were indicated during discharge. The first dead battery event took an approximate average power drain of at least 4.1 Watts if constant over 192 hours. Assuming an average battery voltage of 12.3 volts, this would equate to an average current over those 192 hours of about 0.334 A or 334 MA. Of course, the load most probably was higher than this to drain the battery in less than the entire 8 days. For the second dead battery event using the same calculation, the minimum drain would have to be at least about 324 MA.

To summarize:
I believe that the charging system is heavy handed, but functions adequately to recharge the 12v battery when allowed to operate during charging or driving. There was a definite and consistent 3-1/2 fold increase in the vehicle off state discharge of the 12v battery that started 27 months after battery replacement and again 46 months after battery replacement. Both dead battery events occurred while this increased load was present. The depletion of the battery in less than 8 days in both events was most likely due to this increased discharge loading in the absence of HV charging or driving. The cause of the increased discharge load is unknown at this time. The increased discharge load disappeared and the discharge rate reverted to the lower initial value when the battery was disconnected and reconnected following the first dead battery event.

In any event, I am anxious to hear of any similar findings or comments. I hope this will lead to simple solutions to the vexing issue of dying 12v PacHy batteries and the related bad vehicle behavior. I have ideas on how to do this in the third part of this thread, but it should wait until what I have presented here is thoroughly discussed.
 

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Discussion Starter · #13 ·
My 12v died after about 4 years during a recent cold snap when we had snow/ice and did not drive the vehicle for a few days. Not sure if any thing else was going on out of the ordinary with it other than several days of freezing temperatures and the car not being driven, I think it was plugged in. Since all systems were dead, I had to manually open the side sliding door and climb into the back to replace the battery, the rear lift gate could not be opened. Luckily we have a flat driveway, sounds like as a precaution one should block the wheels when swapping out that battery.
Yes, lesson learned. After my rollaway, I blocked a front wheel while I replaced the battery. My driveway is pretty much visually flat, and barely exceeds the minimum slope required to drain water of 1/8" per foot. So your suggestion is good for ANYTIME the battery is failing or has failed, even in a visually flat driveway. I think it especially important if the 12v battery is lingering in, or about to enter, the 5-10v range. That seems to be where the bad behavior happens. My suggestion would also be to disconnect the ground strap from the battery if it is found below 11 or 11.5 volts while the car is OFF and in a No-Load condition or loaded less than 3A. There has just been too much evidence of bad behavior below this voltage to chance it. Any battery that is found below 11.5 volts when loaded less than 3 amps is an impending failure. Of course, you can still probably start the vehicle when it is above 10 volts, but think about what you need to do to potentially save yourself some real grief.
 

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Discussion Starter · #14 ·
Sorry to see this happened to your gorgeous White Pachy, total bummer for sure. Glad nobody was hurt by this. Hope you can resolve this dead battery roll issue & get her back to her pristine condition soon. Best of luck.
Louise (my wife has a personal relationship with our PacHy) has been operating without incident for 600+ miles on the new battery and we are still working out how the bumper is fixed and who will fix it.
 

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Discussion Starter · #16 · (Edited)
Sorry but how pretentious is that mailbox? More bricks than some houses. I agree with the Pacifica on this one. Had to be done.
:giggle:
Agreed. Beauty is in one's eye. They are all like that in our subdivision, though. They are over 30 years old and the developer built them on fairly poor foundations so they are relatively easy to knock over with a collision when our clay soil is wet. Four that I know of have been accidentally hit. Three were demolished, but our PacHy was apparently moving so slow that this one was the only one that stayed whole. I was able to build a better foundation for it and right it for about $40 in materials and 3 days of sweat equity. My neighbor was pleased that he now has a better foundation for it. But the mail box is not the issue. The $2000+ damage to our PacHy is, as was the risk to kids playing in our neighborhood. The risk in our neighborhood was likely less than most others. That's why I made this thread.
 

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Discussion Starter · #17 ·
Periodic Update:
1/04/2023 Rollaway incident, Police report, and 12v battery replaced,
1/25/2023 PM to ChryslerCares, NHTSA complaint filed, and started this thread.
1/31/23 ChryslerCares reply requesting mileage and VIN.
2/1/2023 My response with the requested information.
2/7/2023 ChryslerCares requesting personal contact and additional information.
2/9/2023 My response with all requested information and additional background.
 

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Discussion Starter · #18 ·
A little more on Why It Happened:

Most will agree that the best predictor of Future behavior is Past behavior. So I will recount my own personal experience which has been repeated countless times by others and I will also quote from this 2020 post:

Fixing Dodge-Chrysler-Plymouth 3G Minivan Instrument...

To condense the story, modern vehicles have more processors in them than ever before. They communicate over one or more data busses. If a data bus has an open, short, poor connection, or noise on it, communication is stopped or scrambled. The data busses communicate measurements, commands, error codes, on-off statuses and any kind of data you can imagine. They operate at very high speed. The info on them is digital which means there is a specification of voltage that is considered high (on or 1) and a specification for a voltage that is considered low (off or zero). And when switched on and off very fast, it is a binary stream of ones and zeros that make up “words” of the language the processors speak to each other. The worst failure for these data busses is to have a noisy connection and/or a voltage supply which is out of specification. These can be caused by a high resistance connection, a corroding connection, an intermittent connection, or a failing supply voltage.

To quote from the above link:

“In the late '90s, as cars began to get more and more complex, they relied on several computers, and they all had to talk to each other. If one couldn't figure out what another was trying to tell it, they all crashed.

Chrysler's third generation minivans were no exception to this issue. In fact, they are now rather known for it. All the computers in these vans from the powertrain controller to the body controller to the transmission controller to even the instrument cluster, radio, and heater controls are all connected together over one single computer network called the Chrysler Collision Detection bus, or CCD bus for short. A single pair of wires running throughout the vehicle enables this.

When there are no problems with this computer bus, everything works well, as intended. But if anything should happen to that bus, like a connector pin failing intermittently or a short circuit, the whole thing either crashes and brings the van to a stop at worst, or haunts the wipers or instrument cluster like a poltergeist at best.”




A poor connection is the most common cause of problems and can result in noise on the data bus. Noise is often rejected, and modules just shut down and malfunction codes are generated. But noise can sometimes be interpreted as valid commands or data and information can be misinterpreted. This was the cause of our 1998 Voyager speedometer cluster haywire behavior. A cold wave soldered joint on the back of the speedometer cluster on the data bus line resulted in wild fluctuations of all instruments with needles banging audibly on their full scale and zero stops, wild light and warning behavior, unrelated failure codes for modules all over the vehicle, or a completely blank and dead speedometer cluster. This all while the vehicle would otherwise start and run ok. This was just one cold solder joint manufacturing defect on one pin of a circuit board. In most cases, the flaw was not visible to the naked eye. It was repeated hundreds or perhaps many thousands of times. It resulted in countless and needless module replacements, people selling their cars, and was a tremendous source of frustration for owners. To my knowledge, it was never acknowledged as a factory defect by Chrysler. But thanks to some industrious person, it was identified and communicated to the masses that an hour or so of labor, a soldering iron and a few cents worth of solder could permanently fix it. I fixed ours.

It is known that the PacHy operates some electrical loads and processors while it is in the OFF state. A slowly failing supply voltage caused by a draining 12v battery can, in theory, also indirectly produce noise on data bus lines. When a 12v battery fails by being drained slowly, electronic components may not operate properly. Processors, voltage regulators, and other loads may operate erratically or turn off altogether. This can create an instability in the voltage supplied by the battery. As loads drop off, battery voltage may momentarily recover higher allowing some loads to attempt restart. This can cause a rollercoaster effect of voltage noise possibly from loads turning on and off, possibly by components operating out of specification, and possibly because of interrupted communication. You can see and hear this rollercoaster effect in the PacHy by watching the voltage and listening under the hood when attempting to recharge a deeply discharged 12v battery (< 6v) with a charger capable of less than 6 amps while the battery is still connected to the vehicle. You will see the voltage rise and fall and likely hear clicking sounds under the hood as loads are applied and then dropped erratically. Most everyone has experienced the gibberish displayed on battery operated devices when the batteries are dying. Communication over a data bus may be similar to what humans speak when their oxygen is slowly diminished and they become hypoxic. It is confused, senseless and often just plain wrong. And when the oxygen or voltage is restored to proper levels, the human or processors may or may not even remember what happened. So there may be no failure codes as in my case.

I know that this is just a theory as to why haywire behavior has been observed when the 12v battery is failing in PacHys. But owners must ask themselves: Does it explain the behavior we have seen? Is it consistent with prior problems with other vehicles? And are there any better explanations?


Finally, why did my battery fail?

Here are the facts:

1/11/2019 New 12v AGM H6 installed in 2018 Pacifica Hybrid Limited.

1/23/2022 Battery found dead after 8 days of inactivity, recharged, tested good. (estimated average load over 8 days >334mA)

1/4/2023 Battery found dead after 8 days of inactivity, recharged, tested NO good, replaced. (estimated average load over 8 days >324mA)

Increased battery drain started at 27 months (9.5 months before the first failure) and again 1.6 months before the second failure, despite no known change in the way the vehicle was being operated.

Very high overall energy drain of 143,858 W-hr over the 1454 day life of that battery (when compared to normal ICE non Stop-Start vehicles).


My conclusions:
  • The unexplained sudden increase in battery energy drains in the months before failure and during the 8 days prior to finding the battery dead may be due to multiple causes and is presumed to be inherent in the design and unchangeable.
  • The high overall energy drain on the battery is a factor in its shorter than expected life (It’s just a more stressful application than in other vehicles). Also relatively deep discharge during periods of several days without being charged cumulatively damages the battery and contributes to the shorter than expected life.
  • The Second battery failure occurred after a shorter exposure (1.6 as opposed to 9.5 months) to the increased (3.5 fold) vehicle off discharge rate. The second failure resulted in a greater depth of discharge and delivered less energy to get there. This indicates that the battery was likely damaged by the first failure, so it failed sooner, failed to a lower voltage, and delivered less energy during the second failure.
  • Both failures occurred after some cumulative damage, during January, after 8 days of inactivity, and after vehicle discharge rates increased. All these are suspected as contributing factors.
How to prevent battery failure and failure propagation to other systems:

The simple answer is to never let the 12v battery “deliver” less than 10v in the vehicle OFF state.

Potential solutions:
  • Replace the 12v battery every 24 months.
  • Run or actively charge the vehicle for a minimum TBD minutes every TBD days.
  • Connect a battery float charger to the 12v battery whenever it is parked and off.
  • Minimize the number of vehicle waking events caused by opening doors or touching door handles. If done more than TBD times, immediately perform 2 above before putting the car to sleep.
  • Turn off headlight run after shutdown in settings.
  • Install a battery that is not susceptible to depth of discharge damage or damage from not being maintained near 100% SOC.
  • Install a fail-safe circuit that can only activate during vehicle OFF state (and <TBD mA draw) that disconnects the 12v battery when its voltage drops below TBD volts. Manual reset with soft start circuit to allow vehicle restart.
  • Install a lightweight rechargeable lithium auxiliary battery that is charged whenever the vehicle DC-DC converter is active and operates as a trickle float charger to the 12v battery when the DC-DC converter is off.
  • Does anyone have other possible solution ideas?
 

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Discussion Starter · #21 · (Edited)
What are you trying to accomplish with them btw?
Two things:
1. I presented my case where I believe the PacHy is designed (not intentionally) to eat 12v batteries resulting in premature failures - premature in time of vehicle inactivity as well as battery life expectancy. This by itself is not a serious problem. But in combination with the following, it is. There is no routine service of the 12v battery that would discover its impending failure and no messages or warnings leading owners to suspect impending failure. There is no Fail-Safe. It can just fail after sitting any length of time without any warning. And finally I believe that there is sufficient evidence that battery failure in the PacHy can, on occasion, accompany if not cause internal damage to the vehicle as well as external damage to property and people. I believe that Chrysler/FCA/Stellantis should consider taking responsibility for the damage that is attributable to this design and operational defect as well as attempt to fix this defect. But all I am asking is that they fix our bumper damage that I believe was caused by this design defect.
2. I have not yet been able to get the Z11 recall performed and asked for help.
 

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Discussion Starter · #23 ·
So It looks like I need to separate my two problems into two different threads. I will be moving my Z11 recall difficulties to this existing thread:

And I will use this thread only for the roll-away incident.

Periodic Update:
1/04/2023 Rollaway incident, Police report, and 12v battery replaced,
1/25/2023 PM to ChryslerCares, NHTSA complaint filed, and started this thread.
1/31/23 ChryslerCares reply (Hannah) requesting mileage and VIN.
2/1/2023 My response with the requested information.
2/7/2023 ChryslerCares (Hannah) requesting personal contact and additional information.
2/9/2023 My response with all requested information and additional background.
2/14/2023 ChryslerCares response (Hannah) "Your concerns have been fully documented...Expect your case manager to be in contact shortly..."
2/15/2023 Received voice mail from Chelsea at ChryslerCares reminding me to schedule Z11
2/16/2023 I returned call Chelsea not available so left message to call.
2/16/2023 Received voice mail from Chelsea at ChryslerCares reminding me to schedule Z11
2/17-19/2023 I made multiple failed attempts to get Z11 Scheduled with AutoNation CDJR Katy Tx.
2/20/2023 Received call from Chelsea at ChryslerCares. When asked about fixing my bumper, she said cannot help with roll-away bumper fix. Dealer will charge diagnostic fee. Stated that I could rent a car and submit for reimbursement later for the Z11 fix.

So I guess that I will not be using Autonation CDJR to fix the roll-away incident damage to our bumper caused by the design defect in the Pacifica Hybrid.
As expected, very disappointed.
 

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Discussion Starter · #27 ·
Could it be an undiagnosed parasitic drain that's not a design flaw?
Yes. I am doing drain recording sessions now off and on. So far the largest drain I have found that sticks around indefinitely is about 80 mA with the car off and the hatch open. That's about 1 watt. All other cases so far time out and go to something under 10 mA. Still investigating. Interestingly, the time out durations seem to be somewhat random.

On another subject, does anyone know if there is a reset procedure for the battery BMS device (located on the 12v battery negative terminal). Or is there a reset in the vehicle software. Or is it supposed to adjust to a new battery over time. I ask this because the DC-DC converter routinely places a higher voltage on the battery than it should and may contribute to overcharge damage. The highest I have recorded is 14.89 volts with a 1.20 A charge current applied. That was on Feb 16, a full 43 days after the new battery was installed. The new battery is being kept at 100% SOC and yet is still being charged significanty above trickle current.
 

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Discussion Starter · #28 ·
Does anybody else see that the PacHy 12v battery application seems almost perfect for a LiFePo4 drop in? Of course I would have a voltage drop device for charging and the LiFePo4 would have its own BMS. It would be lighter and have at least twice the energy storage capacity. It would not have a damage risk at deep discharge like a lead acid AGM. So the current requirement to keep it at 100% SOC would be eliminated. Also, the BMS will auto shut down the battery if it is ever drawn down to 10v so the risk of haywire vehicle operation while unattended also goes away. And life expectancy would be at least as long as the HV battery. This would make it cheaper than installing multiple Lead Acid AGM batteries in the long run. It would solve all the problems of the current lead acid AGM battery application.
I wonder if all the "phantom" loads that the PacHy has were originally assumed by the designers to be taken care of by a LiFePo4, but at some point a decision was made to keep the price down for the vehicle. LiFePo4 bats are much cheaper and better now than they were before 2017.
 

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Discussion Starter · #30 · (Edited)
Never heard of them until now. Looks like the only downside is they require climate control to take a charge when temps are below freezing.
Yep, it damages them to charge below 32 degrees. But there is no problem discharging them below freezing. There are many with built in heaters. The BMS can use a small amount of the battery's own energy to keep the temp just above freezing if necessary. Many of the packaged 12v units have this feature now. The LiFePo4 charge profile is very much like the AGM. A few years ago, one of the experts on this forum pointed out that the warning on the factory PacHy 12v H6 AGM battery ("Do Not Exceed 14.4v charge voltage") was very similar to the max voltage charge limit of a lithium battery. The LiFePo4 reaches 100% SOC at about 13.6-13.8v (right at the float voltage of a lead acid) and the upper limit is 14.6v.
I would build my battery, purchasing the cells and BMS. A 4 cell unit that super outperforms the H6 AGM can be produced for about $600 or less. The BMS interfaces by BT to a phone app and shows all parameters including SOC and individual cell voltage. It protects the battery from over temp, under temp, over voltage, overdischarge (undervoltage), short circuit, overload, and automatically balances the cells. In the PacHy application, it should last 6 to 10 years or more.
Here is a good place to start a learning process. It compares by testing the performance of several flooded and AGM lead acid batteries against an off the shelf LiFePo4 battery. Very thorough and enlightening. LiFePo4 stands for Lithium Iron Phosphate. The surprising result is that none of the lead acids delivered their stated capacity and the LiFePo4 exceeded its stated capacity.
12v battery compare LiFePo4 AGM Flooded

Here is a DIY 280 A-hr LiFePo4 battery demo. (that's over 2.5 times the capacity of the H6 AGM.
DIY 12-Volt 280Ah LiFePO4 Battery

Because of the much lower internal resistance and higher storage efficiency of the LiFePo4 battery, it will be a much lower load on the PacHy's DC-DC converter.
Do a google search of LiFePo4 batteries and search YouTube. They are the future and will replace most all other chemistries, just like LED replaced incandescent, flourescent and HID.
The only reason they are not prolific in cars yet is their cost, and that has come down dramatically in the last few years. It is still a big chunk of change in the initial cost of a new car even though it is cheaper in the life cycle cost of the car. The auto industry is so competitive that the designers find it easy to kick the cost down the road onto the owners since they are used to replacing batteries every 4 years anyway. The reliability, safety, performance and cost of the lithiums are improving by leaps and bounds while the lead acids are topped out and cannot improve much.
 

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Discussion Starter · #32 · (Edited)
Quite the opposite- PacHy is designed to wake up and recharge the 12V battery every 3 weeks. Of course, this will not help if the battery is genuinely defective, as many of them are.
I have a LiFePo4 in my bike and it's been good so far. I can feel that its voltage is a bit higher because the starter is more enthusiastic. Because of the excellent cranking capabilities, most of them have lower storage capacities to keep the cost down. My bike battery is 60WH, while its lead equivalent is more like 150WH. Since PacHy needs capacity rather than cranking power, a good battery for it can be pricey.
You are right. What good is a planned charge in 3 weeks if the battery drops below 10v in 8 days. What I meant to convey above is nobody INTENDS to design a parachute to open AFTER you hit the ground, but that is what we have here. The intent was not to be defective, but that's what the PacHy is.
I disagree that the AGM batteries are defective. I would say the Pachy AGMs are mis-applied and crippled by the Pachy, not defective. Lead Acids are good batteries for specific applications and the AGM is a really good lead acid battery. They are just a poor fit in the PacHy and they are abused beyond their capabilities, so they don't last.
I believe what you are sensing in your bike as increased enthusiasm of the LiFePo4 is the increased voltage under load with the LiFePo4. The resting voltage is not much higher, but the discharge voltage is much higher because of lower internal resistance. The slope of the voltage during discharge is also flatter so higher voltage under load is delivered from 100% to 10% SOC. Not so for lead acid.
The AGM is not as tolerant of high current charging as flooded lead acid batteries. And all lead acid batteries are damaged by deep discharge that is not immediately recharged. This is how the PacHy 12v AGM is cumulatively damaged during charging in the PacHy. After a deep discharge of my PacHy's AGM, I have seen long duration charge current as high as 68 Amps. This is not good for an AGM. In addition, charging it above 14.4v is not good for it either. And finally discharging it mildly 10-20% and leaving it there for more than a couple of days is also not good for it. We just need to realize that a lead acid chemistry just will not last in a PacHy. This is proven by everyone who has a Pachy. Show me one PacHy battery (original or newly replaced) that lasted more than 4 years. Contrast that with my son's original AGM that lasted until late last year in his 2016 Challenger RT with V8 hemi. Lead acid batteries are fine for vehicles with milder off state energy demands. But Pacificas with Stop-Start and especially PacHys are just a torture chamber for lead acids.
Consider that both my laptop and my phone have battery life extension modes where they are charge limited at 80 and 85% SOC, respectively. The Lithiums love it there.They are stressed when above 90% and below 10%. I keep telling my wife not to discharge her phone to zero, but she doesn't listen and has had to replace the battery after 2 or 3 years. Keeping a lead acid at 85% for an extended time would kill it quickly. The actual usable capacity of a LiFePo4 of the same physical size is typically 4 or 5 times that of a lead acid even though its stated capacity is only twice what the stated capacity of the AGM is. There is a vast difference in the stated capacity and the actual usable capaciy of the two. And the LiFePo4 can last for 6000 to 10000 cycles and be left deeply discharged for weeks or months with no damage. It's a no-brainer.
You might be surprised that the 4 cell LiFePo4 application in the PacHy will need a voltage limiter/regulator to keep it below 14.6v during charge. This is because I have seen the PacHy charge voltage as high as 14.89v. I suggest watching those two videos I linked in post 30. The DIY battery demo uses 280 Ah cells and results in a battery that if discharged between 10 and 90% SOC would deliver around 2733 W-hrs routinely. Contrast that with what you dare draw out of an H6 AGM. And the 4 cell block (without case) will be about 6.9" deep x 8.2" tall x 11.5" wide and weigh about 46.7 lbs. The current markets that are driving the development of LiFePo4 12v batteries are RV users, solar storage banks, and fishermen who use trolling motors. But common usage in autos is not too far away. Current BMS boards for LiFePo4s are capable of 100 A or higher charge and discharge current.
 

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Discussion Starter · #33 · (Edited)
Why does the Pachy have such a high charge voltage when the manufacturer of the battery clearly says DO NOT EXCEED 14.4V CHARGE VOLTAGE?
Most likely because the design engineers boxed themselves into a corner. Designing a great car with great features resulted in heavy OFF state energy drains and put them in a dilemma. This resulted in the PacHy's OFF state energy discharge dropping the SOC earlier than in other vehicles. The difference is not in the total energy used while the vehicle is off. Rather it is in what loads are applied and when. Meaning, when other vehicles are OFF, they may drop a few % SOC over days or weeks because they self discharge and have a few very small loads applied. However, the PacHy has more loads and may drop much more SOC over the same time span. The largest energy drain on ICE only vehicles may be the cranking energy. But this occurs just before the battery is charged back up with the engine running. Lead acid batteries don't mind this because of the short time between discharge and recharge. If you look at the PacHy, there is no starting load on the battery. The largest energy drain on the PacHy occurs when it shuts down and slowly powers down its systems, and also when a door or hatch is opened during periods of inactivity and it again goes thru a power down ritual. In addition, the PacHy may do other things in the interest of convenience, system maintenance and monitoring that other cars do not do. Agreed, these are relatively small energy loads, but the key is when they occur. The engineers at Chrysler likely knew this but it was probably too late in the design process to do anything about it other than raise the charge voltage (DC-DC output). This is a balancing act between a rock and a hard spot. They likely knew the drains, if left without quick recharging, would have a detrimental effect on the battery life so charging the battery back up ASAP was needed. The quickest and cheapest (but not best) solution to this was to raise the DC-DC output voltage but that also has a detrimental effect on AGM battery life. Hence the rock and hard spot. The OEM suppliers of the H6 batteries to Chrysler may have been involved with this decision process and may have seen it as a product liability issue. That may explain why they printed in red letters on the top of those H6 AGM batteries to not charge above 14.4 volts. Ya think?

Just for argument sake lets take two vehicles that both use AGM lead acid 12v batteries that are both located in the rear of the vehicle inside the cabin and away from engine bay heating and vibration: A 2016 Dodge Challenger R/T with hemi V8 and a 2018 PacHy Limited. Also lets just assume that the Off state energy loading of both of these is the same. This assumes the minimal energy drains of the Challenger when Off added to its large starting energy are equal to the energy drains of the Pachy while OFF. So you might assume after a couple of days sitting inactive, that the same amount of energy drained and the same amount of energy recharged should have the same effect on the battery. NOT SO. The key is when the drains occur. The bulk of the drain on the Challenger (starting load) occurs just prior to recharging, but the drain on the PacHy occurs right after shutdown or throughout the 2 days of inactivity. If they are immediately charged back up, lead acid batteries are not damaged by trivially small energy drains and only very slightly damaged by large energy cranking drains. High cranking current damage is different from damage caused by leaving a lead acid in a mildly discharged state for a day or more. Both are cumulative, and slowly reduce the performance of the battery over time. However in the PacHy, leaving the battery in even a slightly discharged state for more than a day is more damaging than the Challenger's cranking load, leading to early failure in the PacHy (3-4 years) and not in the Challenger(5-7 years). The selection of AGM batteries for both these cars was driven by several factors. First, the AGM is more tolerant to deep discharge and time in a discharged state than a flooded liquid lead acid battery. But it is not immune to it. Second, the batteries were to be located in the passenger compartment, so needed overboard venting of charge gasses. AGMs have this feature, flooded lead acids do not. Finally, it is interesting to note that the Challenger has an H7 AGM and the PacHy has an H6. The larger battery in the Challenger was needed for cranking amps capacity, not energy storage capacity. In hindsight, it may have been better to equip the PacHy with the H7 for its increased energy capacity, but this is only speculation. The benefits may have only been minimal because the root cause (PacHy's large OFF state energy drain and its detrimental effects on lead acid batteries) would still be there. So the engineers at Chrysler may have decided that the added weight to an already overweight vehicle was not worth the gain. So, since I cannot redesign the OFF state loads that are designed into the PacHy, the solution as I see it is to eliminate the root cause by reducing the cumulative battery damage. Again I arrive at the LiFePo4 solution. The benefits far outweigh the down side.

Benefits:
Two or three times the life.
At least twice the usable capacity.
No degradation caused by inactivity at less than 100% SOC.
Lower energy demand from the onboard DC-DC converter
The same or lower weight.
Auto disconnect if drained below 10v so no gremlins if it dies.
Convenient and complete battery health information.
Piece of mind.

Down Side:
About 2 to 4 times the initial cost (but total life cycle cost are the same or lower)
Voltage limiter required on + lead
It is something new and may involve unforeseen problems (that's what engineers do).
 

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Discussion Starter · #34 · (Edited)
Quite the opposite- PacHy is designed to wake up and recharge the 12V battery every 3 weeks. Of course, this will not help if the battery is genuinely defective, as many of them are.
I have a LiFePo4 in my bike and it's been good so far. I can feel that its voltage is a bit higher because the starter is more enthusiastic. Because of the excellent cranking capabilities, most of them have lower storage capacities to keep the cost down. My bike battery is 60WH, while its lead equivalent is more like 150WH. Since PacHy needs capacity rather than cranking power, a good battery for it can be pricey.
BTW,
The lower LiFePo4 capacity of the replacement in your motorcycle is not only to keep costs down. It is because the difference between usable and total (stated) capacity. It seems like the two should be the same, but they're not. A battery is supposed to deliver its rated capacity in watt-hrs by the time it discharges down to 12.2 volt but lead acids rarely can produce their capacity by the time they reach this voltage (yes, most lead acid battery capacity statements are lies). That is why you usually do not see the capacity (W-hr) on auto batteries (product liability). You see cold cranking amps and amp hours and some silly thing like reserve capacity (Amp hours is not equatable directly to energy capacity). If you review the battery comparison video I linked above it will make this clear. In order for a lead acid to truly deliver its capacity it has to typically go down to 11.8 volts. Not so for a LiFePo4 battery. They will usually deliver more than their rated capacity under the normal conditions that they and lead acids are used. Also lead acids have a higher internal resistance, so they are taxed more to deliver cranking amps under all conditions than LiFePo4s. The bottom line is that you have to have a higher capacity lead acid to meet real world needs of your motorcycle in all the conditions it needs to perform in. I have been looking at 280 A-hr cells for a hypothetical PacHy battery. But that is probably a tremendous overkill. The A-hr capacity stated on the label of the typical H6 AGM replacement for the PacHy is only 70 A-hr. Because the usable capacity is greater in a LiFePo4 of the same rated capacity, one could probably get away with a 60 or 50 A-hr LiFePo4 in the PacHy.

FWIW, you can purchase a 100 A-hr LiFePo4 already assembled commercially available. And it typically weighs only 25 lbs or less and will have almost twice the USABLE energy capacity of the typical H6 AGMs in PacHys.
Do a search.
The trick will be to limit the voltage on the PacHy 12v battery positive lead to 14.4v (14.6 is max). Another trick may be to game the existing PacHy BMS output. So understanding what the PacHy BMS does for the PacHy operating system is needed. Questions like what influence (if any) does the BMS have on the voltage delivered by the DC-DC converter? And if it does have influence, how does it do it. For example, it may be possible to game the BMS control signal to limit the DC-DC output voltage to 14.4v without additional circuitry. For a drop in conversion to work, all a "managed" LiFePo4 needs from the PacHy is a voltage source between 13.8 and 14.4 volts capable of charge currents. Its built in BMS will do the rest and can charge the LiFePo4 cells at and above any current that I have ever seen delivered from the PacHy to the H6 AGM. Even if the 14.4v limit is exceeded, the LiFePo4 BMS will prevent damage to the battery, but my design requirement would be to have a system that operates as intended to limit the voltage delivered to the BMS for charging. It would be a perfect battery for the PacHy. Lighter, smaller, safer, smarter, more capable and cheaper in the long run.
 
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