Leaf Service EV System Adventures with P0AA6-1A and a Suspect 12V Battery

[Stanton]

I will NEVER use some stupid Lithium battery to replace a Lead Acid in a vehicle designed to charge lead acid batteries.

Wow. I'm not going to get into it, so I'll simply say: Lithium 12v starter batteries are designed to operate within the same parameters as the lead-acid counterparts they replace.
As for the rest, I suggest you do some research on the topic before spreading dis-information.

 

[boontis]

So I picked up my car today from the dealer after they checked over the 12v system. They reported that the 12v battery BARELY passed the load test only by a small margin, so they suggested I replace the battery as a starting point as it appears to be original. (confirming many of your comments on here!) They quoted $940 CAD to do the replacement - so I picked up a battery myself from the napa a block from the dealership for $162 and will install it this weekend

They also confirmed that something else is going on as there is no way a dead or dying 12v battery should cause the vehicle to stop like it did for me. (again confirming comments here!) I had shared some of my leafspy screen shots with the tech and he believes there is a pretty good chance I've got several weak cells that likely caused the main battery voltage to drop low enough that it also prevented the 12v charging from working long enough to drop the 12v battery below the computer's threshold - which is why I had BOTH of those errors showing. Seems to fit with the scenario?

The way this dealer works is they charge you 4 hours up front to do the diagnosis, and if it is something that Nissan will warranty then you get that money back. If it isn't something that Nissan will warranty you just lost ~$675. I get that its quite a bit of work but paying up front sucks - I guess that's my next step tho as I've still got 2 years/18k more km's under warranty and don't want to wait.

One last interesting thing - they charged my car up fully and I drove it home without any issues. I accelerated hard to try to see any sort of SOC rapid loss but nothing. It wasn't up the same hill tho - next time I try that I will have a battery and booster cables to avoid another tow charge

 

[knightmb]

I will NEVER use some stupid Lithium battery to replace a Lead Acid in a vehicle designed to charge lead acid batteries.
The system is set up to properly charge a Lead Acid Battery... LiPos or whatever rando
thing you want to put in there.. has different charge voltage/current requirements. Clearly the computer is very sensitive to battery condition... It CAN and It WILL disable the car if it isn't
seeing the expected battery conditions.
The smart thing is to use an AGM Deep Cycle Sealed 12v battery.
The dumb thing is to think some Chinese BMS built into your lithium thingus is safe, adequate, compatible, or reliable. Unless you believe in fairies. then do it ~!

I try not to argue with the opinions here when it is subjective. I will present counter-arguments in the presence of evidence though. The first claim that the Leaf 12V charging system is setup to only work with FLA batteries is probably not correct. No one that I am aware of has the engineering documents for the Leaf, so none of us know exactly what Nissan intends to do exactly, but we can infer based on the evidence of what we can measure and observe ourselves.

For starters, if the Leaf was intended to only work for FLA batteries, it would not be floating the 12V battery at 13.0V To properly take care of the FLA, the voltage would need to float between 13.5V and 13.62V Most Manufacturers recommend 2.25V to 2.27V per cell when the battery is "warm", like room temperature warm. When the battery is colder, the float voltage has to be higher to protect it's capacity. When the battery is hot, the float voltage has to be lowered, again to protect capacity. AGM batteries can float at a lower voltage, usually the recommended range is 13.2V to 13.6V. But, again the Leaf is not doing this. So, the Leaf fails on that compared to a typical ICE vehicle alternator that is keeping a constant +14V going on the battery at all times.

Next the Leaf never fully charges a FLA battery because it is charging based on a combination of voltage and power readings made by the battery current sensor. That is the logical way to protect the battery from being over-charged because the Leaf open voltage is 15V. This works fine when a FLA battery is brand new. As the FLA battery ages, the amount of power it can recharge with decreases. This means there is a way to get both a high charge voltage and small charge current that the system can not account for, instead it makes a best guess on the state of charge; of the 12V battery. Because there is no system counting power in and out of the 12V system, the Leaf has no idea if the 12V battery is actually fully charged. It's very easy to blast a FLA battery to 14.4V with 100 amps of power but there is a point where the amount of power going in will have to be decreased to prevent the voltage from climbing too high and causing capacity damage. Again, the Leaf is guessing, it does not know exactly how much power was in the FLA battery and it does not track how much it is putting in. It is working only on the voltage and current. The Leaf does not try to keep a 12V battery topped off like a battery maintainer would.

Given the above statements, the Leaf wasn't designed to only work with FLA or AGM batteries, it was designed to be compatible with them. Otherwise, why go through all the coding to make such a complicated charging system? Why not just blast +14V and be done with it? The Leaf could easily do that and it would be a much simpler system. The reason is safety related. Most vehicle alternators max at 100 amps. More of an average, you can find plenty that do less or more I'm sure. They are tuned to +14V and have the added benefit that the battery itself is the current limit along with the physical load on the alternator pushing back. The whole system has over a century of research and development to match up FLA batteries to ICE vehicle usage quite well.

Let's think about an engineering perspective on the Leaf. It's 200x and the Leaf needs a 12V power source to run everything except the drive motor and HVAC. The only viable technology that has years of testing and mass production to boot is FLA batteries. Seems like an easy choice, you only need it to switch on the main relays and then the HV battery takes over from there. Sure, now how do you charge the 12V battery back up? Well, use some power from that fancy 12V system you created. Ok, but how do this in a safe way? You can't just blast in +150 amps into the battery everytime. What if the battery was freezing? What if the battery has capacity damage from age or manufacturing issues? You need a way to control how much power you are forcing in. You also need to run all your 12V accessories without having them fail from voltage that is too high or too low. Nissan didn't built two "12 Volt" systems, they are using the same one to do both. That makes it literally impossible to have something that is designed around a certain battery chemistry and yet also runs the accessories at the same time with a regulated and predictable power level. That's why the whole system is a compromise at 13.0V. It keeps the accessories at a consistent power level and it is close to, but not quite there for keeping a 12V battery at the maximum state of charge. Nissan uses some workarounds like trying to get the 12V battery to 14.4V as fast as it can before leveling off at 13.0V but it's usually not enough time to keep any FLA or AGM battery at the maximum state of charge. Just like it's bad to leave a Lithium battery at 100% SOC for long periods of time, the opposite is true for FLA / AGM batteries, they need to be at 100% SOC all the time.

Where does LiFePO4 fit into all of this? It has the advantage of a higher operating voltage nominal voltage of 12.8V instead of 12.0V for the FLA / AGM family. That means it takes a higher voltage to damage the battery capacity, +14.7V or higher to be specific for most manufactuers. The Leaf doesn't have an issue with over-charging the 12V battery though, its problem seems to be not keeping a high enough state of charge. Again, LiFePO4 to the rescue, as part of the Lithium battery family, it also does not need to be kept at 100% state of charge all the time, it's operating range is 20% on the low end to 80% on the high end for the state of charge, that is where it functions best. It also has thousands more charge cycles than the Lead battery family, thus extending its life much longer. It also has a lot less self-discharge than the Lead family of batteries. Finally, most modern drop in 12V starter battery replacments using LiFePO4 have a BMS protection board that limits how much charging or discharging the battery can take to further preserve life and to act as a safety backup.

To claim that using a LiFePO4 is going to cause you issues with your Leaf or leave you stranded flies in the face of actual real world evidence from it's users both here on this forum and elsewhere around the world. The opposite is actually true, Leaf owners using a LiFePO4 have reported reliability that puts the FLA / AGM batteries to shame. It seems obvious that the design of the 12V system in the Leaf wasn't created specifically for 12V LiFePO4 batteries, but they just happen to operate very well in a Leaf because of its 12V charging limitations that disproportionally affect the Lead Battery family more than the Lithium battery family.

Using a LiFePO4 isn't a cure-all for the strangness that is the Leaf 12V system, but it seems to be able to operate best in that environment. That doesn't mean crappy LiFePO4 don't exist, it just means that with anything else in life, you get what you pay for. If I buy a cheap FLA or AGM it might only last a few years while a high quality version is able to live on for much longer. I know there are places that sell Lead Family batteries that can beat the OEM Nissan battery to death in reliability and lifespan just like the 12V LiFePO4 battery I chose +9 years ago continues to work today across (2) generations of Leaf syles and has never let me down in the coldest weather we get where I live 0F (-17.7C).

Finally, despite all the talk about the limitations of LiFePO4 in terms of performance and temperature, what often seems to be ignored is that FLA and AGM are also limited in cold weather performance. Most manufactures don't recommend charging them if the battery temperature is below 32F (0 C) because of (surprise ), capacity damage. At least the Leaf will reduce charging current to a trickle when it detects freezing outdoors temperatures, do you think a car alternator does that?

 

[knightmb]

So I picked up my car today from the dealer after they checked over the 12v system. They reported that the 12v battery BARELY passed the load test only by a small margin, so they suggested I replace the battery as a starting point as it appears to be original. (confirming many of your comments on here!) They quoted $940 CAD to do the replacement - so I picked up a battery myself from the napa a block from the dealership for $162 and will install it this weekend

They also confirmed that something else is going on as there is no way a dead or dying 12v battery should cause the vehicle to stop like it did for me. (again confirming comments here!) I had shared some of my leafspy screen shots with the tech and he believes there is a pretty good chance I've got several weak cells that likely caused the main battery voltage to drop low enough that it also prevented the 12v charging from working long enough to drop the 12v battery below the computer's threshold - which is why I had BOTH of those errors showing. Seems to fit with the scenario?

The way this dealer works is they charge you 4 hours up front to do the diagnosis, and if it is something that Nissan will warranty then you get that money back. If it isn't something that Nissan will warranty you just lost ~$675. I get that its quite a bit of work but paying up front sucks - I guess that's my next step tho as I've still got 2 years/18k more km's under warranty and don't want to wait.

One last interesting thing - they charged my car up fully and I drove it home without any issues. I accelerated hard to try to see any sort of SOC rapid loss but nothing. It wasn't up the same hill tho - next time I try that I will have a battery and booster cables to avoid another tow charge

Glad to read that you have a good idea of what is going on now. Sounds like the perfect storm of some HV battery issues and 12V battery issues happening at the same time to cause chaos.
$940 CAD ($697 USD) just to put in a new 12V battery!?
Was that the price for a Nuclear Battery or a stack of AGM batteries wired in parallel?

Since you have LeafSpy, keep a watch on the weak cells and yes, don't wait on getting some paperwork started for warranty work. The miles and time can come and go faster than you realize when you are busy living your life.

 

[woeful]

The Leaf is using IUoU charging to maintain its 12V battery. That requires a reasonably accurate temperature and current sensor (in the battery negative connector) and to monitor the voltage (done in the VCM, vehicle control module). It has two objectives and may have to compromise slightly for each: to maintain the 12V battery and to take minimum energy from the traction battery for doing that.

This charging regime blasts a large current into the battery until it's mostly charged, at nearly 15 V, then drops the voltage to about 13.5 V to finish charging much more slowly. There's a temperature adjustment for both those voltages. If the 12V battery is nearing the end of its working life, the change from the fast to trickle charging might well happen too soon, or other parameters in the charging algorithm might be off scale, so replacing that small battery may well be all you need to restore proper operation.

If the battery temperature and current sensor is faulty (inaccurate), this would properly mess up the charging system. Try replacing the 12V battery before worrying about the sensor, though. A bad connection somewhere in the 12V heavy cables which carry the charge current could also cause problems. Most other failures ought to show up as DTCs (fault codes), as there are checks and cross-checks in the car's electronics.

 

[nlspace]

they charged my car up fully and I drove it home without any issues. I accelerated hard to try to see any sort of SOC rapid loss but nothing.

That's great news, and you were able to drive home without the "turtle" or see any cells dropping low.

This appears to be yet another instance of an old, weak or worn out and depleted battery causing a multitude of issues. There is likely no issues with your HV Pack and you can verify this on your own using the Lspy and save a bunch of useless dealer
diagnostic fees.

Useless dealer diagnostics story: My mother-in-law had a leaf that lit up the dash with codes, and she had it towed to the dealer. They ran $1000 worth of diagnostics and determined that she needed a new Pack; full price since it was out of warranty. She determined it wasn't worth it to spend good money on an old car, so she got a Tesla and gave me the leaf. i put a new strong 12V in it, checked the Pack with LSpy, cleared the codes and gave it to my daughter to drive for 5 more years with no HV Pack issues.

 

[nlspace]

Just like on an alternator in an ICE car, the 12V DCDC Converter monitors the battery voltage thru a "Sense" line. If the battery is defective it can draw huge currents without charging, so current is leaving the DCDC (or Alternator) rapidly with little effect on the voltage of the S line. This is what causes Alternators to give their life and fail; the DC Converter is a digital controlled unit with smarts to throw codes and regulate itself from death.

Your Pack was squawking because it had insufficient low voltage power supply from the weak 12V battery; if the pack truly had low or unbalanced cells then those would still remain regardless of the battery.

Any DTC that occurs in conjunction with a low 12V battery is suspect as invalid; the CAN buss depends upon a good low voltage supply to operate and it can report garbage.

 

[cornbinder89]

I will not comment on the choice of a LI replacement other than to say it is a personal choice of the owner after weighing the pros and con's. There are both.
No, this wasn't a case of a 12 volt going dead causing the problem, it was a case of the traction battery causing a no charge of the 12 volt, that was confirmed by the dealer. It could not have "Caused" the car to do what it did.
The 12 volt did pass their test, although not with "flying colors". Replacing the 12 volt will not make the problem go away and saying so is false. It is up to the owner if they want to change it now, before the problem with the traction battery is resolved or not.
I disagree with some who say the float voltage is too low, You are comparing it to that of a starting battery/alternator system, not a deep cycle type charge regimen.
Woeful did a good job of explaining the 12 volt charge system on the Leaf, re read it!
I had a similar system to the Leaf's I built and installed and live on top of for many years in my trucks, Never had a battery failure either. It was slightly different in how it chose when to step the charging down, but worked almost the same. Only difference is I had voltage and current gauges on the dash.
Let me correct one thing, a bad cell will not put a massive load on the charging system, it will be about 25 amp or so max, well withing the ability of the Leafs charging system. I have witnessed it 1st hand.
Where I live, just a few weeks ago we were at -20F for several days, the high of the day reaching -15 to -17 F. When I drove my Leaf in those temps it started and drove in turtle with reduced power and the temp gauge in the blue. After driving a few miles and noticing the SOC, it would drop rapidly under a heavy load, from 80% to 50% and then recover. The Traction battery couldn't supply the current fast enough in those temps under that load. It came right back once I topped the hill. Mine was at "extreme low battery temps" and not at normal temps but is very similar to what Boontis saw at much higher temps. When you try and draw more current from the traction battery than some cells can provide, the SOC and battery voltage drops rapidly, in my case it was because the battery was too cold, in Boontis's case it is because of weak cells. When that happens the VCM can drop other loads and the DC-DC can be one.
We have had a "ton" of cases where the battery SOC drops a huge amount under load, This is the root cause, and replacing a 12 volt will not cure it. Any battery put under load and not charged will discharge, and that is what happened to your 12 volt, it lasted long enough under load to trip the low charge while driving and to provide power steering and brakes while you pulled to the side.
The Dealer, in this case did point that out. The problem for Bootis is if you pay the diagnostic fee and they don't determine it qualifies for warranty, then your out the money, it may be they can't reproduce the problem or don't really want to find it. If you have a few years left, I would continue to drive it, but if you are close to the end of the battery warranty I would push hard for the problem to be solved. If you start the paper trail before the warranty expires and continue to bring it back claiming they didn't fix the problem (and you will not pay another diagnoistic fee for their failure to solve the problem), you have the proof that the problem existed before the end of warranty and the original diagnostic fee is worth the cost to get Nissan to fix it. The dealer may try and charge a new fee but you should refuse, it is a "come back" (shop term for a car returning for the same complaint) not a new problem.
The best situation is if you know the conditions under which it happens and can reproduce them at will. You can take the tech or service writer out and show them. If they refuse and say they can't reproduce the problem say you want the zone rep involved, and show him, if they will not place a call to the zone rep call Nissan directly and/or file a BBB claim. In my days (long ago) working for a dealer, the zone rep would be available once a month or so to mediate problems with re occurring repairs and big problems near the end of warranty.
There is no question you have a traction battery issue as Stanton pointed out. It isn't going to get better, it will only get worse.

 

[cornbinder89]

I read back through and found this is a 2018, so you have 6 years on the 12 volt, as shown it still has a little life but near the end. Personally I wouldn't replace it until the end, but you are at best looking at months not years of life left. Mine was replaced by the p/o at 7-8 years of life from the date code on the new battery. 6 isn't wasting money.
All this being said, it will not cure what put you on the side of the road. It may or may not allow you to restart on the side of the road when it next "bricks".

 

[knightmb]

Today is the last day I am going to leave the original "suspect" battery earlier in this topic in my wife's 2018 Leaf. I made sure to keep it topped off Monday, but she used it the entire week with daily driving and noticed no problems. If she had no prior knowledge of the issues this suspect 12V battery had, everything would appear fine to her. So, as one last test, I wanted to do an experiment to see how much power her Leaf would charge a completely "depleted" 12V FLA battery if I just switch in into drive mode and did nothing else buy let it charge. No driving, no accessories, etc. I made sure to switch every possible thing off before starting. I already know how much capacity this 12V battery has, so when completely depleted, will her Leaf take it all the way back up 100% SOC (as best as it can) before it floats the 12V bus at 13V.

This part was an easy setup, I just use some small space heaters to burn power until the battery reaches 10V or as close as I could get it. I was trying not to totally tank the 12V battery because it would make the experiment fail. It needs to have enough power to at least start her Leaf one more time.

After depleting the 12V battery externally, I then waited another 10 minutes to see what voltage the battery would settle on. Interesting, the battery was about to recover up to 12.10V before I started my charging experiment.

Before starting the experiment, I get LeafSpy connected. I begin logging the amount of power going into the battery at 1:35PM and to fast forward, the Leaf finally decides the 12V battery is full @ 2:28PM. So nearly an hour of non-stop charging. The charging power maxed at 71.23A @ 14.4V or (71.23 x 14.4) = 1025.7 watts and tapered off the entire hour of charging. Rather that post up hundreds of LeafSpy screenshots, I just plugged everything into a spreadsheet to calculate the watt second power, then calculate to watt minute and finally to watt hour.

This is a minute by minute breakdown (chart below) of how much power was being pushed into the 12V battery every minute. Without reading this entire chart, the total comes to 91 watt / hours of power. The battery performs 108.14 watt hours under ideal testing. So the Leaf only charged this suspect 12V FLA battery to 91 / 108.14 = 0.84 or 84% of it's tested capacity under ideal conditions as it was only 62F outside. The 12V FLA is not cold or hot. I did not calculate any efficiency loses because this would produce some heat in the 12V FLA for example, so my numbers are ideal and more than likely even less power was absorbed by the 12V FLA but only a small percentage of loss that probably would not make a big dent on the actual amount the battery has now, so it might be 83% SOC for example, but beyond the scope of my experiment. Regardless, my experiment simply shows that the Leaf did not reach 100% state of charge for this 12V FLA in this ideal test.

Extra Notes: After the 12V FLA charging, the battery is still lightly discharging power as noted in the last LeafSpy screenshot before I stopped the experiment. I would suspect it's because it's balancing with the now lower 12V bus voltage, so a 13V float still results in a small power usage of the 12V FLA until the voltages balance.

01:35:00 PM​	10.1​
01:36:00 PM​	17.1​
01:37:00 PM​	6.5​
01:38:00 PM​	5.3​
01:39:00 PM​	3.2​
01:40:00 PM​	2.5​
01:41:00 PM​	1.6​
01:42:00 PM​	1.5​
01:43:00 PM​	1.5​
01:44:00 PM​	1.5​
01:45:00 PM​	1.4​
01:46:00 PM​	1.4​
01:47:00 PM​	1.3​
01:48:00 PM​	1.3​
01:49:00 PM​	1.2​
01:50:00 PM​	1.2​
01:51:00 PM​	1​
01:52:00 PM​	1​
01:53:00 PM​	1​
01:54:00 PM​	1​
01:55:00 PM​	0.9​
01:56:00 PM​	0.9​
01:57:00 PM​	0.9​
01:58:00 PM​	0.9​
01:59:00 PM​	0.9​
02:00:00 PM​	0.9​
02:01:00 PM​	0.9​
02:02:00 PM​	0.9​
02:03:00 PM​	0.9​
02:04:00 PM​	0.9​
02:05:00 PM​	0.9​
02:06:00 PM​	0.9​
02:07:00 PM​	0.9​
02:08:00 PM​	0.9​
02:09:00 PM​	0.9​
02:10:00 PM​	0.9​
02:11:00 PM​	0.9​
02:12:00 PM​	0.9​
02:13:00 PM​	0.9​
02:14:00 PM​	0.9​
02:15:00 PM​	0.8​
02:16:00 PM​	0.8​
02:17:00 PM​	0.8​
02:18:00 PM​	0.8​
02:19:00 PM​	0.8​
02:20:00 PM​	0.8​
02:21:00 PM​	0.8​
02:22:00 PM​	0.8​
02:23:00 PM​	0.8​
02:24:00 PM​	0.8​
02:25:00 PM​	0.8​
02:26:00 PM​	0.8​
02:27:00 PM​	0.8​

 

[cornbinder89]

It seams the data got cut off,
We used to have a saying about battery operated lifts, the 1st 85% of a charge takes the first 90% of the time, the last 15% of charge takes the second 90% of the time!

 

[boontis]

I read back through and found this is a 2018, so you have 6 years on the 12 volt, as shown it still has a little life but near the end. Personally I wouldn't replace it until the end, but you are at best looking at months not years of life left. Mine was replaced by the p/o at 7-8 years of life from the date code on the new battery. 6 isn't wasting money.
All this being said, it will not cure what put you on the side of the road. It may or may not allow you to restart on the side of the road when it next "bricks".

I called the dealer this morning after reading this - they told me the 12v battery only has 3 years/60k kms. They also added that since it BARELY passed, even if it was within that time, they would not cover the replacement under warranty. (because of course they won't - they will recommend it gets replaced but not under warranty hahaha #stealership)

 

[knightmb]

It seams the data got cut off,
We used to have a saying about battery operated lifts, the 1st 85% of a charge takes the first 90% of the time, the last 15% of charge takes the second 90% of the time!

Yeah, I hit enter by accident while trying to copy/paste out of the spreadsheet, lol. It should be updated now.

 

[nlspace]

They also confirmed that something else is going on as there is no way a dead or dying 12v battery should cause the vehicle to stop like it did for me.

Except for the hundreds of times this has happened and been reported on this and many other EV forums over the past ten years or more--and it was caused by an old, weak or worn out 12V battery. Go back and read this forum, do a search and see all the posts on this subject.

You and the dealer have assumed that the LSpy data was valid or had any meaning after the 12V failed. This is an invalid assumption.

Once the 12V has been verified good to go, then use the scan tool to troubleshoot any DTCs or unbalanced cells, etc.

 

[nlspace]

Today is the last day I am going to leave the original "suspect" battery earlier in this topic in my wife's 2018 Leaf... she had no prior knowledge of the issues

Happy Wife, Happy Life, and You dodged a bullet on this one...

 

[cornbinder89]

You and the dealer have assumed that the LSpy data was valid or had any meaning after the 12V failed. This is an invalid assumption.

No, he didn't "assume" the car lost power, it did. He didn't assume it would not keep going it wouldn't. He didn't assume the car went into turtle, it did. He didn't imagine the drop in traction batter SOC he saw it, He didn't imagine that it came back when he reduced the load it did. All signs of a problem in the traction battery.
The traction battery couldn't supply power either to the motor or the DC to DC charging system, so both failed and that is what caused the car to stop.
It will happen again, and for the same reasons. Replacing the 12 volt will not solve the underlying problem. The dealer knows this, I hope the owner knows this. As for you. I hope it never happens to your car, but when it does and you keep buying 12 volts and it keeps happening, well may be you'll learn and expensive lesson on how things work in the Leaf.
Keep buying 12 volt batteries if it makes you feel superior, for the rest of the people, diagnose to the root issue and you'll know you have solved the problem once and for the minimum of cost.

 

[mux]

I can confirm that a bad 12V battery will cause all kinds of weird issues, including a car randomly stopping at freeway speeds. We've had customers coming in with these problems multiple times (across ~300 serviced leafs).

That being said, the OP's issues can't be caused by a dead 12V battery. P0AA6 is a very serious error that indicates insufficient insulation between the HV system and the car, often pointing to a failing lithium cell or undue contact between a high voltage-carrying cable/busbar and ground. Commonly also: water in the battery. Any P0AA6 we encounter means: open up the battery and see what's going on.

 

[nlspace]

then I remove service disconnect from the center of the pack. I use my multi-meter to check both contacts down in the plug to see if any voltages appear between both sides of the pack and vehicle ground. After a long wait for the capacitance to finally zero out the voltage, I am about to confirm that no voltage leaks were found while testing the battery pack.

So he did first check for a P0AA6 HV/insulation leak to chassis, then addressed the 12V problem.

Based upon the hundreds of EV forum reports and posts with similar symptoms, i would have recommended to address the 12V issue first, then re-scan for DTCs.

Have you ever heard or found an actual HV short to chassis, or have these always been faults of the leak detect circuit?

 

[knightmb]

To update this topic, it's been 2 weeks and still no issues for my relative. They were using my loaner 12V battery from my 2020 (the original FLA I just keep in storage) with no issues despite many days of freezing cold weather this month. They finally decided to go with an Optima AGM battery. I checked for any DTC codes in the last few weeks, all still nice and clear on LeafSpy. Topped off the new 12V battery with my charger and installed the new 12V battery (they had to wait for it to be shipped to battery place, OPT8073-167 Optima Yellow Top AGM 450CCA BCI Group 51R ) and I gave them back their original 12V battery so they can go get a core refund for recycling. If anything else happens, especially if that P0AA6-1A DTC comes back, it will be more serious as I won't be suspecting the 12V battery anymore.

Having written all that, there is something I will point out. Not as a finger wag at my relatives for using their Leaf exactly as they wanted to, but maybe more of a warning to anyone else that might suspect they have a weak or failing 12V battery and comes to read this topic years later. My relatives, as we like to say here, live "out in the country" on a small farm. That means, the closest city or town is 20 miles away (being mine basically). As such, light pollution is a lot less. When they drive their Leaf at night, they use all the lights possible. This includes the fog lights, or lower set of lights on the Leaf relative to the main headlights above. On the 2018 (and even on my 2020), these are Incandescent lights. They use a lot of power, a lot more that you would suspect for such small lights compared to the massively brighter LED head lights.

Because of where they live, they use a dash setting in the Leaf that leaves all the "lights" on after you turn off the Leaf for a preset amount of time. They use the highest setting of 3 minutes (180 seconds) because they don't have street lights where they live. This is to aid in the night time when walking around outside of their home. The very first sign that something was odd is when this no longer seemed to stay on as long as it used to. They are not technical, so did not think much about it. I ran a quick test on my wife's 2018 to see how much power just having these lights on without the HV providing backup power. I was surprised that having the fog lights / head lights / cabin lights running in this "delay" mode consumes close to +240 watts of power. You can cut this down by another +80 watts by switching off the fog lights and a few more by turning off all the cabin lights, but I don't suspect a typical Leaf owner is going to worry about that.

What kind of impact does this have for 3 minutes? I used my spreadsheet to calculate it's about 4 watt hours per minute or roughly 12 watt hours every time. That's not a lot compared to the overall capacity of the 12V battery, so why worry? Well, in this example, the original battery they were using had only 108 watt hours of capacity. So, every-time they drive home and turn it off at night (or dark because of winter time), they were leaving the battery at a reduced SOC every-time. If the Leaf was ideally keeping this 12V battery at 100% SOC that would mean this light feature is leaving the battery at 108 - 12 = 96 watt hours so, 96 / 108 = 0.89 or 89% SOC. I would state that in my testing, the Leaf doesn't leave the 12V battery in a 100% SOC, but closer to the +80% SOC range, so in this example, their 12V battery was probably starting at (0.8 x 108) = 86.4 watt hours and then drain 12 for something closer to 86.4 - 12 = 74.4 watt hours or 69% SOC every night, provided they were not using the EVSE to charge it. To their credit, they were aware they should not leave the Leaf at 100% SOC all the time unless they were going to drive it soon after, so it's not always plugged in for charging after every night drive.

What is the point of all the math then? Basically, I suspect this feature they were using was a contributing factor to the capacity damage of this 12V FLA battery over time. When the battery was brand new, sure 516 watt hours with some small 12 watt hour drain isn't going to make much of a dent. But...as the battery ages and the capacity starts to shrink, this small drain becomes a bigger impact on the battery. I believe, eventually to the point where it hastens the battery demise towards the end. For a 12V FLA anyway. But that's just a theory, a Leaf theory!

 

[cornbinder89]

Interesting, and likely goes a long way in explaining the vast difference in why we have people reporting different battery life.
I live like your relative, not quite as far to town, but well away. My outbuildings have LED flood lights on the barn and garage. 12 watt floods on a photo cell dusk to dawn. Total wattage is less than one light that were on the farmstead when I moved in.
My garage is a building by itself, exposed on all sides, so gets cold.
In the old days it would 175 watt or higher HPS etc.