Sudden Turtle Mode in Very Cold Weather

[alozzy]

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.

[LeftieBiker]

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.

[binks]

I will try and use leaf spy if it happens again but I also agree its probably some bad cells

[rogersleaf]

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.

[Stanton]

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".

[BrockWI]

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.

[SageBrush]

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

[jjeff]

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.

[BrockWI]

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.

[rogersleaf]

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.