Bad Cell in Leaf Spy: What to do about it?

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gmikol

Well-known member
Joined
Dec 5, 2013
Messages
110
Location
WA State
So I saw something unusual on Leaf Spy this afternoon as I'm pulling into my driveway:



What, exactly does the "Bad Cells" mean? Is this something I should have the dealer look at? I don't charge to 100% all that often, but it's had 3 or 4 100% charges in the last month or so, including one last night...so it should be well-balanced.

17 GIDs left at this point, and battery temps in the upper 70's.

I don't expect the dealer to necessarily know anything about Leaf Spy, so what should I tell the dealer? My 12-month battery check is not until January. Is it OK to wait on this?

Thanks--

G
 
ElectricEddy said:
Any DTC's ?
No...didn't think to check that. I forget that Leaf Spy can read those. I'll check it tomorrow AM. Will re-charging clear the DTC's (fi any)?

Turbo3 is using some criteria to decide the bad cell. What criteria, and what is that based on?

--G
 
Detailed explanation and discussion at http://www.mynissanleaf.com/viewtopic.php?f=9&t=17676&p=383401&hilit=+cvli#p383401" onclick="window.open(this.href);return false;.

Service manual says test is for when customer complains of range loss.
But most dealers will not run the test unless the customer pays for it.

Unclear whether dealer will then replace the modules that have bad cells and whether Nissan would cover that under warranty.

I have yet to read any posts saying anyone has confronted Nissan on it.
 
Thanks, @TimLee -- I hadn't found that thread in my search.

From what I've found, it seems like the dealer won't do anything about it unless you're showing the P33E6 error code. There also seems to be some question as to what the formula for calculating the Judgment Value really is.

It's useful as an indicator, though. A couple of days later, I looked at the battery stats while it was charging (I think it was around 50-60% at the time), and cell # 28 wasn't any higher or lower than the others. I also checked DTC's, and there were none reported for the HV pack.

Next time I get the pack down below VLBW, I'll take a look again, just to see if it is still acting funny, or if it was a transient issue. Don't know when that will be, though. It doesn't get down that low very often, with charging available at both ends of a 22-mile one-way commute.

--G
 
The formula can be found in the 2011 April version of the Leaf Service Manual on page EVB-67.

If there are any other formulas please post them and where you got them from.

The only formula I know about is Judgement = Avg - (max - avg)*1.5 and the min voltage must first be below 3.713 volts. The Leaf must be parked. So you don't make this measurement while the battery is under load.

For this example the numbers are min=3.645, avg=3.673, max=3.690. Filling in the formula gives:

3.673 - (3.690 - 3.673) *1.5 = 3.673 - (0.017)*1.5 = 3.673 - 0.0255 = 3.6475

Because the minimum cell is 3.645 we know at least one cell is judged as bad.

It is possible that after heavy use the battery needs some time to stabilize. So if you leave the battery sit for a few hours and it still reports a bad cell it would have more significance.

You should definitely keep an eye on cell #28.
 
I saw that, and the scans of the relevant pages from the manual.

I can't find the reference now, but I thought I had also seen a formula that used 2.0 as the factor instead of 1.5

That formula is also not in the 2013 ev powertrain manual. Apparently the consult tool calculates the value now, so the tech doesn't have to rely on a formula. No way of knowing whether it has changed for 2013 and beyond.

I was parked, but I had literally just pulled into the driveway after about 35 miles of mixed city & highway driving.

I'll definitely keep an eye on things going forward.

--G
 
After doing my regular commute today, which I logged entirely in Leaf Spy Pro, on the 'battery cells' page I was given a note that I had 4 weak cells. The delta was 40 mV. Dash SOC 15%, 44 GIDs and 3.3 kWh remaining. http://kootenayevfamily.ca/img_1350/

This surprised me, as I haven't seen this message before (although I've only had the app for a few months, and have only fully logged several trips).

A few hours later, my wife took the car to the grocery store, and arrived home with 8 GIDs - I ran it down to turtle at 6 GIDs, then took a screenshot of the 'battery cells' page again - no weak cells anymore, despite the delta of 374 mV! http://kootenayevfamily.ca/img_1357/

Running the numbers through the formula up thread shows that my minimum exceeded the calculated value, so I guess that's why they didn't show up?

Anyways, my SOH has generally been quite high for how old my car is, the mileage and the reasonably hot summers, so I'm not really complaining, and will keep a watch out for more of the same. I can't help wonder though if it is somehow related to the other item I've noticed with 'clunking' sounds from my battery pack and odds 'burning' smells! :shock:

http://www.mynissanleaf.com/viewtopic.php?f=30&t=19883
 
Turbo3 said:
The formula can be found in the 2011 April version of the Leaf Service Manual on page EVB-67.

If there are any other formulas please post them and where you got them from.

The only formula I know about is Judgement = Avg - (max - avg)*1.5 and the min voltage must first be below 3.713 volts. The Leaf must be parked. So you don't make this measurement while the battery is under load.

For this example the numbers are min=3.645, avg=3.673, max=3.690. Filling in the formula gives:

3.673 - (3.690 - 3.673) *1.5 = 3.673 - (0.017)*1.5 = 3.673 - 0.0255 = 3.6475

Because the minimum cell is 3.645 we know at least one cell is judged as bad.

It is possible that after heavy use the battery needs some time to stabilize. So if you leave the battery sit for a few hours and it still reports a bad cell it would have more significance.

You should definitely keep an eye on cell #28.

Does the service manual specify the SOC at which voltage measurements should be taken? Leaf Spy routinely flags at least 5 cells on my pack as bad around VLBW and below, no DTCs. I usually see this after pulling into garage, so it is possible this doesn't occur after the car sits for some time, need to verify. In any case I suspect it is not an actionable situation.
 
achewt said:
After doing my regular commute today, which I logged entirely in Leaf Spy Pro, on the 'battery cells' page I was given a note that I had 4 weak cells. The delta was 40 mV. Dash SOC 15%, 44 GIDs and 3.3 kWh remaining. http://kootenayevfamily.ca/img_1350/

This surprised me, as I haven't seen this message before (although I've only had the app for a few months, and have only fully logged several trips).

A few hours later, my wife took the car to the grocery store, and arrived home with 8 GIDs - I ran it down to turtle at 6 GIDs, then took a screenshot of the 'battery cells' page again - no weak cells anymore, despite the delta of 374 mV! http://kootenayevfamily.ca/img_1357/

Running the numbers through the formula up thread shows that my minimum exceeded the calculated value, so I guess that's why they didn't show up?

Anyways, my SOH has generally been quite high for how old my car is, the mileage and the reasonably hot summers, so I'm not really complaining, and will keep a watch out for more of the same. I can't help wonder though if it is somehow related to the other item I've noticed with 'clunking' sounds from my battery pack and odds 'burning' smells! :shock:

http://www.mynissanleaf.com/viewtopic.php?f=30&t=19883
It would appear that Nissan's formula they originally used has trouble if the cells are well matched at the lower voltages when there is little difference between min and max values. This may be why Nissan dropped this formula from their later Service Manuals.

In additional to the minimum voltage to run the test it looks like there should be a minimum delta as well. So if your cells are well balanced the test is not run. In your case the weak message when the cells have a delta of only 40 mv can be ignored.

I am working on the next release and will probably add a 200 mv delta requirement before I give any weak cell messages.
 
Turbo3, thanks for your input, much appreciated! And double (or triple, or more even!) for your work on Leaf Spy. Well worth the money. Make sure you cash in on your efforts now, since when we are all driving around in 300+ mile Leafs we won't need this type of software anymore.

Cheers.
 
My LEAF gets 3 years old soon - in april 2016.
Only 19k km run. But sometimes, while driving, I see Cell #49 is weak - but not often. Most times it says: ALL CELLS ARE OK.

When the car is standing still over night and shunt order is right, it looks like one line - all cells.

http://www.bilder-upload.eu/show.php?file=dce7a7-1451762132.jpg

SOH was 90% when i got the leaf (an old man was using it, no QC CHAdeMO done before, only L1/L2 charging at home), no high speed.
Now SOH is 93% and i did a few QC already. Many often, i am driving a 160 km trip - with one QC at half of the way.

At home only charging with 10A ICCB - 2.2 kW :)

http://www.bilder-upload.eu/show.php?file=0b4d72-1451762189.jpg

Leaf has warranty until april 2018 on battery ... do i need to do some action because of this cell or is it ok?!
 
Normally i charge to 80% but when i need the car the next days he gehts balanced to 100% always.
Ohne when using CHAdeMO QC he is not always balanced - but that is because the leaf stops charging at 91-98%...

BUT today - after driving 100 km (was on a trip the whole day with -0,6 °C Temperature of Cells :eek: in the morning) the SOH went from 93% to 94% (Hui...). I got the car in august with 90% SOH. The pre owner was never charging with CHAdeMO (!) and always charged to 80% he said. The car is nearly 3 years old. 19,5 k km run.

http://fs5.directupload.net/images/160103/kkvruuw2.jpg

But: Usable kWh is 19,1 kWh - a few days ago (not as cold as today with up to -7 °C!) it was 19,4 kWh (with 93% SOH).
 
When I first got to low voltage required for CVLI about two years ago it showed about eight bad cells early on when min to max delta was small.

By the time delta got above something like 65mV none showed bad.

As pack has gotten older and lost three capacity bars and now always charge to 100% and deep cycle a lot more, only one or two cells show "bad" and it is for a very brief time.
 
It appears to me that the Cell Voltage data that the car has available to read
is sometimes from two different scans of the cells, part when the cells were
loaded (all at a lower voltage) and the other part when the cells were unloaded,
or possibly even during Regen (so the cells were at a higher voltage).

Thus, it might be important to let the car sit for a little while, or perhaps
operate at a constant load for a while, so that this split-scan data is not
a possible cause of the apparent two "different" clumps of data.
 
garygid said:
It appears to me that the Cell Voltage data that the car has available to read
is sometimes from two different scans of the cells, part when the cells were
loaded (all at a lower voltage) and the other part when the cells were unloaded,
or possibly even during Regen (so the cells were at a higher voltage).

Thus, it might be important to let the car sit for a little while, or perhaps
operate at a constant load for a while, so that this split-scan data is not
a possible cause of the apparent two "different" clumps of data.
The original cell loss calculation was done with the Leaf in park so it is not under load.

It takes the BMS almost a second to scan all 96 cell voltages. It is done with a serial link running at 19,200 baud.
 
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