Chaotic Range Readings from 40 kWh 2018 SV

Hi!

I've had a 2018 Leaf SV for a couple months. For the first 2000 miles or so that I had it, I seldom used more than ~70 miles range before recharging, but I did notice on two occasions after longer drives that I got home with a lot less capacity remaining than I expected.

A couple weeks ago I forgot to charge at night, and during my commute to work the range started dropping precipitously when it passed 60% (or so), to the point that I wasn't sure I'd make it into work. Fortunately the rapid decline leveled off, and I got to work where I could charge.

After recharging, I spent that evening trying to reproduce the problem. Which turned out to be easy. I video'd this, and uploaded a portion of the video (below). There was a rapid decline to this point, but the real fun starts about 0:30 in. Note the ideal driving conditions (mid 70s, flat road, motor stays in the "eco" zone). The battery percent jumps all over but rapidly trends downward. Over the 8 minute video it starts at 39% and ends at 23%. I took a screenshot of Leafspy which appears to be showing one cell that has a lower voltage than the rest https://imgur.com/a/cCLHNm5

https://youtu.be/o9wprF0Wry0

I took the car to the dealer for repair, and they returned it saying they couldn't fix anything because there are no codes being thrown. On the drive to work the next day I recorded a video (below), showing more or less the same behavior, but dropping from 48% to 25% over 8 minutes. I took the car to the dealer again, and again they said nothing was wrong, and that I shouldn't bring the car back to them.

https://www.youtube.com/watch?v=b3z2BWc63LI

While I've not tried to drive the car until I get stranded, by my best estimates my 150 mile Leaf will get perhaps 100 miles range on a full charge.

Does anyone have suggestions for next steps? Is there any way to "prove" to the dealer that there is a problem? The other Nissan dealer in town is quite a jaunt away, but I may have to visit them next. I've started pondering a lemon-law claim but that seems like a huge hassle, and I really just want my car fixed...

Thanks for any suggestions!

My 2018 Leaf behaves that way sometimes, although not quite as drastic. The guess-o-meter is significantly off, usually.

I just drove to the Oregon Coast today and at around 40% remaining, the % started dropping rapidly. It’s important to note that this occurred during descent!! I should have been gaining miles using the e-pedal, not losing miles. As a approached 10 miles from the Chademo charger in Lincoln City, I started gaining a significant amount of miles, but not % of battery.

As a rule of thumb, I estimate a loss of 1% per mile, and this method has never left me stranded.

If there is a problem, it's likely a bad cell or two - marginally bad, not enough to throw a code yet. There have been a significant number or 40kwh packs with this issue. What is the build date on the driver's side door sill?

LeftieBiker said:

What is the build date on the driver's side door sill?

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My build date is 03/18

Tortoisehead77 said:

LeftieBiker said:

What is the build date on the driver's side door sill?

Click to expand...

My build date is 03/18

Click to expand...

Same month as mine, IIRC. Most of the bad cells have been in earlier builds, but I seem to recall at least one from March.

Looking at your LeafSpy pix you have a bad cell.

Yep. I didn't see a link to a LeafSpy shot.

LeftieBiker said:

Yep. I didn't see a link to a LeafSpy shot.

Click to expand...

igxqrrl said:

I took a screenshot of Leafspy which appears to be showing one cell that has a lower voltage than the rest https://imgur.com/a/cCLHNm5

Click to expand...

I haven't watched the video but yes, that's bad. It shouldn't be like that when the car's nearly full.

Have the dealer run a CVLI test. It will fail. NO way there should be 200+ mV imbalance when the car's nearly full.

On the 40 battery, at what points does the car take a few percent and hide it in reserve?

On the 62 at different points between 80 and 35% it slowly hides about 8-9% of available capacity making the car appear to lose range faster then it does on Leaf spy.

DougWantsALeaf said:

On the 40 battery, at what points does the car take a few percent and hide it in reserve?

Click to expand...

That could be what’s happening to mine. I start to panic as I lose % rapidly when the battery first drops below 40%. But, I think I make some of that back under 20%. By the time I got to the charging station at the Coast today I had 13% left. But, I didn’t think I would make it because at 30% charge it was dropping rapidly. It was dropping fast even though I was on the west side of the coast range, which is generally more downhill (elevation loss) as you go further west.

cwerdna said:

LeftieBiker said:

Yep. I didn't see a link to a LeafSpy shot.

Click to expand...

igxqrrl said:

I took a screenshot of Leafspy which appears to be showing one cell that has a lower voltage than the rest https://imgur.com/a/cCLHNm5

Click to expand...

I haven't watched the video but yes, that's bad. It shouldn't be like that when the car's nearly full.

Have the dealer run a CVLI test. It will fail. NO way there should be 200+ mV imbalance when the car's nearly full.

Click to expand...

Thanks for this -- that's my belief as well. I showed that picture to the dealer and he seemed completely non-plussed by it. He said the correct way to test the battery is to run it down to about 10%, and then test it. He said when they did that, it tested correctly (or within spec at least).

My contention is any time 95 cells have voltage "x", and 1 cell has voltage of "0.9x", there is something wrong.

The trouble of course is getting the dealer to acknowledge that!

Tortoisehead77 said:

My 2018 Leaf behaves that way sometimes, although not quite as drastic. The guess-o-meter is significantly off, usually.

I just drove to the Oregon Coast today and at around 40% remaining, the % started dropping rapidly. It’s important to note that this occurred during descent!! I should have been gaining miles using the e-pedal, not losing miles. As a approached 10 miles from the Chademo charger in Lincoln City, I started gaining a significant amount of miles, but not % of battery.

As a rule of thumb, I estimate a loss of 1% per mile, and this method has never left me stranded.

Click to expand...

I'm in Oregon as well. I've found that when it gets into its "drop quickly" mode, it also "regains quickly" during regen, which is different than the symptom you saw. I actually suspect if I were willing to continue driving at 15%, I'd probably get an additional 40 miles at that point, because clearly there is energy in the battery, just that the computer isn't recognizing it, presumably because of the low voltage in the bad cell.

But this means that, with anything under 30% or so, I can't get in the car and have any idea how much range is remaining. Could be a bunch, could be a little. Kinda like having a new car where the gas gauge is non-functional!

LeftieBiker said:

If there is a problem, it's likely a bad cell or two - marginally bad, not enough to throw a code yet. There have been a significant number or 40kwh packs with this issue. What is the build date on the driver's side door sill?

Click to expand...

Interesting to hear this. I've seen another video on youtube that had a similar pattern. My build date is 04/18. The car did sit on the lot (in hot central-Oregon weather) for a year or so before I bought it, so I've wondered if that caused the problem. Though if so I'd expect more than one cell to be affected.

Flyct said:

Looking at your LeafSpy pix you have a bad cell.

Click to expand...

Out of curiosity (I'm new to Leafspy -- just got it after observing this issue), do you generally expect all the cells to lose voltage at the same rate? After driving for a while, half my cells still show full voltage, and half have dropped significantly. The dropped/full are interleaved (i.e. 1,3,5,...,95 are low, and 2,4,6,..,96 are still full).

I've been wondering if the pack is logically divided into two halves, and the one with the bad cell is not being used because the computer is trying to balance the two halves.

See:
https://imgur.com/a/4mxsRuH




Thanks!

Sorry. I wish I could be of more help. Maybe Googling for site:mynissanleaf.com cvli will turn up something helpful.

https://www.mynissanleaf.com/viewtopic.php?f=30&t=18468 had no luck (I actually know him and have talked to him in person years later). His car ended up with this guy who did succeed in getting his dealer to replace the bad module: https://www.mynissanleaf.com/viewtopic.php?f=9&t=21700. The voltage values will likely be different on 40 kWh Leaf though. But still, the amount of imbalance you were seeing at high SoC is NOT normal.

I've been wondering if the pack is logically divided into two halves, and the one with the bad cell is not being used because the computer is trying to balance the two halves.

Click to expand...

No. The Battery Management System (BMS) uses the lowest cell voltage as the controlling input when it comes to allowable voltage. IOW, when the weakest cell reads low, the BMS assumes that the pack is low. To put it a third way, the pack is only as strong as the weakest cell.

igxqrrl said:

Tortoisehead77 said:

My 2018 Leaf behaves that way sometimes, although not quite as drastic. The guess-o-meter is significantly off, usually.

I just drove to the Oregon Coast today and at around 40% remaining, the % started dropping rapidly. It’s important to note that this occurred during descent!! I should have been gaining miles using the e-pedal, not losing miles. As a approached 10 miles from the Chademo charger in Lincoln City, I started gaining a significant amount of miles, but not % of battery.

As a rule of thumb, I estimate a loss of 1% per mile, and this method has never left me stranded.

Click to expand...

I'm in Oregon as well. I've found that when it gets into its "drop quickly" mode, it also "regains quickly" during regen, which is different than the symptom you saw. I actually suspect if I were willing to continue driving at 15%, I'd probably get an additional 40 miles at that point, because clearly there is energy in the battery, just that the computer isn't recognizing it, presumably because of the low voltage in the bad cell.

But this means that, with anything under 30% or so, I can't get in the car and have any idea how much range is remaining. Could be a bunch, could be a little. Kinda like having a new car where the gas gauge is non-functional!

Click to expand...

This is good to know. Thanks!

I’ve owned 3 Leafs now. A 2015 24 kWh, a 2018 40 kwh and currently a 2019 62 kWh. I’ve never seen LeafSpy voltage spread like yours.

Here’s a screenshot of my 2015 24 kWh Leaf



Here’s the 2028 40 kWh Leaf



And here’s my current 62 kWh Leaf Plus

The 2015 is a 24kwh Leaf. The 30kwh pack was offered beginning in the 2016 model year, IIRC. Or are you referring to the build month?

LeftieBiker said:

The 2015 is a 24kwh Leaf. The 30kwh pack was offered beginning in the 2016 model year, IIRC. Or are you referring to the build month?

Click to expand...

You're correct. I fixed it.