Sudden Turtle Mode in Very Cold Weather

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LeftieBiker said:
alozzy said:
It would be helpful to the community if someone uses LeafSpy, while the car is in turtle mode, to see if there's a large cell imbalance.

There pretty much has to be, unless ALL of the cells are low. Cell voltage is what the BMS uses to assess the battery while driving.

Exactly, that's why I'm curious and would be interested in a definitive answer ;)

Seeing detailed LeafSpy metrics, from these LEAFs that are experiencing unexpected turtle mode events, might help me (and others with older LEAFs) to predict similar events with my own car. Should my LEAF start to exhibit similar symptoms, I would pull the trigger and buy a newer LEAF.
 
I agree that this is needed. I think that what will show is one, two, or several cells that have severe voltage sag that is worsened by cold. Here's a suggestion for LeafSpy Pro: have a mode that takes a "video clip" of the cell histogram over, say, 10 to 30 seconds. A mini movie, if you will, of what is happening with cell voltages. Hopefully it would also include a couple of other parameters like speed and battery temp sensors, to both make it easier to associate the video with what the car is doing, and to establish what kind of battery temp is problematic.
 
Last night think I experienced one of these sudden drop in SOC. My leaf had been left parked outside for ~30 hours in 20F weather on @ 55% SOC at my part-time employer so the car was cold-soaked. My return commute was 30 miles which that route is almost entirely expressway. Normally would expect that drive to consume 25-30% SOC in 20F cold weather so range to make the drive was never in question.

Roughly 1/2 way home I noticed SOC had dropped to mid-30’s % which I thought was odd. Then about 5 miles later the 1st LBW alarm chimed (9% SOC on a 40KWh pack) which cleared with “OK” switch. Then almost immediately it chimed a VLBW warning (4%) and I noticed 1% SOC before I could clear the message. So exited the expressway an exit early on max regeneration and the SOC recovered to 8% almost immediately. SOC held steady while taking back road the last couple miles. This is just bizarre and the 1st sign of any issues with this car.

I’m just wondering if a flaky 12v battery could cause this drop? Mine is still original 3-yr-old and almost 59k miles. Would hate to think a traction battery cell is failing. Leafspy readings have always looked very good on the battery so not an intuitive conclusion.
 
rogersleaf said:
I’m just wondering if a flaky 12v battery could cause this drop? Mine is still original 3-yr-old and almost 59k miles. Would hate to think a traction battery cell is failing. Leafspy readings have always looked very good on the battery so not an intuitive conclusion.
What you describe is a traction battery/weak cell(s) problem. The 12v battery only comes into play when starting/charging the car; once the car is running the 12v bus is powered off of the main (400v) bus.
Having said that, I would have that 3-year old 12v battery checked (and even replaced); it's not worth getting "stuck".
 
And as much as it sucks I have had this happen a bunch as our Leaf ages. When the battery is really cold it is more likely for an individual cell to drop below that "turtle" threshold. I have found taking it easy on the battery when it is really cold helps avoid that. I just wish we could somehow force the battery heater to come on ourselves if we needed to. The other day ours sat outside at my work when it never got above 0F outside, the pack was 4F according to leaf spy and outside was -6F when I left work, just drove normally (without any rapid acceleration) home without an issue.
 
Stanton said:
rogersleaf said:
I’m just wondering if a flaky 12v battery could cause this drop? Mine is still original 3-yr-old and almost 59k miles. Would hate to think a traction battery cell is failing. Leafspy readings have always looked very good on the battery so not an intuitive conclusion.
What you describe is a traction battery/weak cell(s) problem. The 12v battery only comes into play when starting/charging the car; once the car is running the 12v bus is powered off of the main (400v) bus.
That is my guess also
 
Turtle has been coming on somewhat regularly on my '12SL with 8 health bars when the outdoor temps are single digits or colder and parked outside with a battery temp in the single digits to 0F. Doesn't seem to matter much SOC% but probably happens more with a lower SOC. I get basically NO regen bubbles no matter what SOC and even without turtle I'm missing my last 3 power bubbles, when the turtle comes on I miss the last 5 bubbles or only have 4 which truthfully is enough to get around town on 40mph roads. With a full charge, it shows about 30 miles on the GOM mostly due to heater use.
 
That is the same way ours behaves when it is really around 0F. I guess it's good to know it isn't just our Leaf, but once warmed up, it behaves much better.
 
Spring can’t come fast enough. But do have to admit the little leaf is running fool in the snow with Michelin x-ice, and managed 0F commutes this year that were totally impossible with my ‘14.
 
alozzy said:
It would be helpful to the community if someone uses LeafSpy, while the car is in turtle mode, to see if there's a large cell imbalance.
My own event a couple nights ago didn't completely turtle, but was heading on that trajectory pretty quick. Today was another near-0F commute with high teens on the return trip. I ran leafspy this time while driving to see if it would act up again today (it did not) and to watch cell balance and actual battery temps.

Think I'm seeing the problem now... Battery temps today were relatively low (3 segments on dash) and showing in the low-to-mid 30F's on leafspy, SOC was under 40%. The cell balance becomes very unbalanced (say in 50+ mV range) if the car is pulling higher power loads such as @ 3KW to heater and pulling a grade at expressway speeds. Under those conditions, certain cell pairs (#50 or 51, and a few adjacent cells) basically drop off the bottom of the leafspy voltage graph. Once the battery temps warmed slightly (@ 4 segments & in 40F's on leafspy) or the load dropped, the cell balance leveled out and looked very normal. In hindsight, the events from a couple night ago was along the same pattern. The SOC cratered when pulling a substantial long expressway grade and then recovered when I headed for the exit.
 
It looks like my initial reply was incomplete. There is a third possibility, and it now seems likeliest: a cold-soaked battery with cells so close to the low voltage cutoff that they reach it without the motor being under much more load - they just can't provide power as well as they normally would, and slowly lose ground, so to speak.
 
I had the same thought about proving a battery defect while watching this happen. Doubt this throws any fault codes and would be difficult to reproduce at this point in the battery warranty life. I do still have 41K miles of warranty so who knows.

This behaves a lot like the battery decay in my old iPhone SE. If the phone was in a pocket and outside in Winter cold, sometimes the SOC would abruptly crater. If rebooted the phone, the SOC would recover some but relatively obvious it wasn't happy. Then Apple stepped in and said my battery was starting to fail.
 
I've had the same sudden drop in SoC, turtle mode and power limited when driving on the highway at lower temps. This winter it happens every time I drive on the highway with even a slight sustained uphill grade when the battery temp is 4 bars or less. I've had it happen with SoC ranging from 30%-60% and battery pack temps as warm as 48F. We've been going back and forth with the local Nissan service department, Nissan engineering and Nissan consumer affairs for a few months now. No resolution yet. We haven't gotten any DTCs yet when this happens. The car has been completely unusable for highway driving when the battery temp is 3 bars or less, unless it's flat enough to allow the battery to warm up before there's any uphill grade.

This morning the Nissan techs hooked up a diagnostic computer to the OBD2 and sent me off on a drive to try to catch the problem and get the data. I had about 40% SoC and a battery pack temp of 38F. It dropped SoC, turtled and went into power limited after a couple miles on the highway with a slight sustained uphill. I limped back to the dealership and the tech pulled the data to send off to Nissan engineering. They didn't find any DTCs related to the problem. Now we need to see what the Nissan engineers say. My service guys are acknowledging that the car is failing to perform basic functions and is creating unsafe situations, so they're continuing to fight for us. But we'll have to see how far they can get with what they have for information. Also, the tech seems pretty motivated to determine a course of action because he's dealing with 4 other Leafs with the same problem. Once spring comes, I guess we put it all off until next winter or we loose another SoH bar, from 9 to 8.

It's been pretty warm here in norther UT this past week but it's supposed to get cold again next week. So I'm going to try to get it to generate some DTCs when the battery pack temp is lower. I will also try to catch it with a screen record video on Leaf Spy.

The car is a 2017 with around 56k miles SoH is at 9 bars/72.48%.
 
LeftieBiker said:
Do you think that you could find out whether the other 4 Leafs with this issue are also 30kwh?

I think he did say they were 16's and 17's, but I will ask again next time we talk. He did say that there was one other car this winter (not one of the other 4) with a 30kw battery that was having similar issues but it lost another SoH bar down to 8. They replaced it with a 40kW battery. He's hoping my car does the same. But at 72.48% SOH, it probably won't happen for several months. We've lost 3 SoH bars over the past 2.5 years. He said he hadn't seen the issue prior to this winter, then a rash of them (6 I suppose) came in this winter. 5 of those are unresolved. He's hoping these morning test drives with the diagnostic computer will give him a formula for repeating and resolving the outstanding cases.
 
4 temp bars :D I could only wish, often this winter when I get in mine there have been NO temp bars :( 0F or colder and generally a pack temp of 0 or single digits :eek:
 
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