Mottyski82
Posts: 69
Joined: Fri May 17, 2013 2:22 pm
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Leaf Number: 405969
Location: Hinesburg, VT

LEAFspy says Bad Cells?! :(

Fri Aug 15, 2014 9:18 pm

Long time lurker, first time creating a new topic/post.
I allowed my LEAF traction battery pack get super low (never have driven it to such a low a state of charge). I had used LEAFspy (not lite or pro) for the trip which got me down to 10 GIDs (3.6% GIDs). LEAFspy tells me .8 kWh remain when I had parked. The Point of this topic is that in the voltage histogram section, it showed two red lines, (said Bad Cells... #19, #40)!! :( :( Usually cell pair voltages register 9-14 mV diff.) Now, 109mV cell diff. Min: 3.428, Average: 3.503, Max: 3.537.

Batt stats: AHr=65.12, SOH=99%, Hx=99.48, 336.31V

I would post a screenshot or two if I knew how to do so, but alas... I know not how.

Has anyone EVer seen this note in red at the bottom of the Batt stats screen saying Bad Cells? If you have, what does it mean? Do you think these cells; #19 #40 could be replaced under warranty? Yikes!

I'm not fretting about it just yet. I LOVE my LEAF (EV)! Thanks in advance for the comments!! :)

mctom987
Posts: 333
Joined: Wed Jun 25, 2014 6:52 pm
Delivery Date: 29 May 2014
Leaf Number: 332755
Location: San José

Re: LEAFspy says Bad Cells?! :(

Fri Aug 15, 2014 9:47 pm

The red lines are shunts, not bad cells. All the shunt does is stop flow through that cell. Usually it's done because the cell is discharging faster than the others. If you continually see specific cells with an active shunt, it could point to an issue with that module, and it may need to be replaced.

That said, I have a screen shot with 94 active shunts. (:
2014 Green Leaf SL +PP
June: 580.6 mi, 4.7mi/kWh
July: 1443.8mi, 4.8mi/kWh
Aug: 1157.9mi, 5.1mi/kWh

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Nubo
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Re: LEAFspy says Bad Cells?! :(

Fri Aug 15, 2014 10:16 pm

voltage differences between cells will be much more pronounced when they are nearly fully drained.
Last edited by Nubo on Fri Aug 15, 2014 10:38 pm, edited 1 time in total.
I noticed you're still working with polymers.

mctom987
Posts: 333
Joined: Wed Jun 25, 2014 6:52 pm
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Location: San José

Re: LEAFspy says Bad Cells?! :(

Fri Aug 15, 2014 10:23 pm

Nubo wrote:voltage differences between cells will be much more pronounced when they are nearly fully drained. Charge to 100% and give it a few hours plugged in after that, to allow some cell balancing to take place.

Odd, I recalled having a rather high SOC. Looked up my screenshot, and it was 90.7%.

Edit: Image instead of text
Image
2014 Green Leaf SL +PP
June: 580.6 mi, 4.7mi/kWh
July: 1443.8mi, 4.8mi/kWh
Aug: 1157.9mi, 5.1mi/kWh

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gbarry42
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Re: LEAFspy says Bad Cells?! :(

Fri Aug 15, 2014 10:49 pm

If those cells are bad, you will also see a high differential while being charged, and the bad cells will show a higher voltage than any of the others. They'll be the first to reach full charge. You have to check while the charge is in progress.
And there goes the first capacity bar! At 24,000 mi on 9/9/2013.
Second bar at 30,500 mi on 2/7/2015.

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drees
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Re: LEAFspy says Bad Cells?! :(

Sat Aug 16, 2014 12:45 am

mctom987 wrote:Odd, I recalled having a rather high SOC. Looked up my screenshot, and it was 90.7%.

Yeah, seeing nearly all shunts on after a 100% charge is normal. a 16 mV spread between min/max is pretty typical, too when fully charged.

When you can only balance a pack by discharging cells, if you want to bring the voltage up of 1-2 cells that are low, that is your only option.

BTW, if you are wondering about the relatively low SOC (90.7%) despite having just charged to "100%", I saw the same thing recently after QCd the previous day - my SOC registered only 90.1% right after a 100% charge completed.

Back to the OPs question - IIRC LeafSpy can apply the formula for detecting cells that are low enough voltage compared to the rest that may qualify for replacement. This is only possible at low SOC. But that said, a 109 mV diff at 10 GIDs actually sounds pretty good. Last time I got my battery that low (3.9%) my diff was 333 mV. Even at 7.0% it was 222 mV.
'11 LEAF SL Powered By 3.24 kW Enphase Solar PV

Mottyski82
Posts: 69
Joined: Fri May 17, 2013 2:22 pm
Delivery Date: 06 Apr 2013
Leaf Number: 405969
Location: Hinesburg, VT

Re: LEAFspy says Bad Cells?! :(

Sat Aug 16, 2014 6:23 am

Thanks all for the great feedback so far! As it happens, I was expecting to QC last night @ the local Nissan dealership, only to find out that the thermostat filter was clogged and the CHADeMO was not operating because of the thermostat error. So anyway, cord to the level 2 which is a couple of parking spaces away was long enough to reach to the QC space, and so I ended up being able to balance the pack with a full charge... So maybe I was better off allowing for the 100% charge overnight.
I did come back to the car at about 63% SOC and took a reading with LEAFspy, and then again of course @ 8am when the cells had been balanced. It seems that the "Bad Cells" were probably just at the point where the battery management stuff shut down those cells to prevent over-discharge, because when I took the readings while charging and fully charged, the #19 and #40 cells did not seem to be much higher voltage than the others. During the charge check, the voltages of all the cells were dancing around like ripples on water, no cells were (REALLY) spiking high, and others seemed very similar to the ones in question. I will keep an eye on those warnings though, and probably track which cells are registering as "Bad Cells" on LEAFspy. If the fellow who created/produced LEAFspy is reading this, I sure would like to know his take on what "Bad Cells" is supposed to mean / what that was for in his mind...

Thanks again everyone! :)

mctom987
Posts: 333
Joined: Wed Jun 25, 2014 6:52 pm
Delivery Date: 29 May 2014
Leaf Number: 332755
Location: San José

Re: LEAFspy says Bad Cells?! :(

Sat Aug 16, 2014 9:55 am

No problem. Thanks for making the font big and easy to read.
2014 Green Leaf SL +PP
June: 580.6 mi, 4.7mi/kWh
July: 1443.8mi, 4.8mi/kWh
Aug: 1157.9mi, 5.1mi/kWh

TimLee
Posts: 2811
Joined: Thu Jan 20, 2011 9:40 am
Delivery Date: 17 May 2011
Leaf Number: 2026
Location: Chattanooga, TN

Re: LEAFspy says Bad Cells?! :(

Sat Aug 16, 2014 1:59 pm

Mottyski82 wrote:... The Point of this topic is that in the voltage histogram section, it showed two red lines, (said Bad Cells... #19, #40)!! :( :( Usually cell pair voltages register 9-14 mV diff.) Now, 109mV cell diff. Min: 3.428, Average: 3.503, Max: 3.537.

Batt stats: AHr=65.12, SOH=99%, Hx=99.48, 336.31V
...
Has anyone EVer seen this note in red at the bottom of the Batt stats screen saying Bad Cells? If you have, what does it mean? Do you think these cells; #19 #40 could be replaced under warranty? Yikes!
...

Yes.
Jim had asked in the main thread for people to report if bad cells were detected.
Test is the Cell Voltage Loss Inspection (CVLI).
See viewtopic.php?f=44&t=12789&p=308501&hilit=cvli#p308501, pages 268 to 270 of 2011 manual.
I took time to run heater long enough to get down to voltage level couple weeks back. Took a long ways past LBW.
Had planned to report but didn't find time to review logs and graph the bad cells voltages yet.
I had eight showing bad at VLBW.
# were increasing as battery voltage went lower.
Might have been 12 to fourteen if I went to Turtle.

I'm not sure what Nissan response will be on replacing the cells. The test is for review of battery condition when fault codes are not present. And does say to replace modules containing cells that don't pass the criteria.

For me eight out of 96 is a lot. I will have to check the cell #s versus module location. But could be 6 to 8 out of the 48 modules.

Tim Lee
Chattanooga, TN

Man. Date: 03/10/11, VIN # 2026
Delivered 05-17-2011
Blue Ocean, 2011 SL-eTec

TimLee
Posts: 2811
Joined: Thu Jan 20, 2011 9:40 am
Delivery Date: 17 May 2011
Leaf Number: 2026
Location: Chattanooga, TN

Re: LEAFspy says Bad Cells?! :(

Sat Aug 16, 2014 2:05 pm

If you search MNL for CVLI there are about five pages of posts on the subject.
Some say the test is only done when there is a certain error code.
But the manual says "performed to identify cells that the cell voltage is on the decrease (although not judged as malfunction in DTC) and this may lead to a malfunction, if left stand."

Tim Lee
Chattanooga, TN

Man. Date: 03/10/11, VIN # 2026
Delivered 05-17-2011
Blue Ocean, 2011 SL-eTec

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