PacHy Kills 12v Battery - Crashes Vehicle

So let’s use this as an example with an electronic shifter and transmission . I if the battery dies you want the transmission to lock up to deter any movement ? , kinda strange because a battery can go bad anywhere . In a manual car you’d have to manually put into gear to negate movement , motorcycle as well . No power means no electronics , assists or safety features are present . If your house alarm fails and battery backup is dead you have no alarm , just saying . So if stellantis put code that when the battery goes dead to lockup the transmission , you’d grenade the internals and potentially die . So I think in hindsight common sense prevails for allowing any vehicle to have some kind of movement to get it out of harms way . So unfortunately you can’t have it both ways , and any vehicle has potential to move without power anywhere so bringing up scenarios like you have is complete conjecture .

stop-eject said:

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.

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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.

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):

Jvan said:

My best guess is the 12v battery failed and took out the transmission. Seems crazy that could happen.

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stop-eject said:

… 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.

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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.



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.



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.

GlenP said:

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.

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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.

js607191 said:

Sorry but how pretentious is that mailbox? More bricks than some houses. I agree with the Pacifica on this one. Had to be done.

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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.

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?