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Discussion Starter #1
Leaf spy shows a 100-140mv difference in one cell in our 30kw 2017 leaf. This is present whether its at high or low soc, and shows a weak cell warning when its at lower soc. From other threads I understand this isn't a true weak cell as that would only really be apparent at lower soc. The range is less than we would expect and drops unpredictably. It went in for diagnostics yesterday and we got it back today- apparently they cleared a few fault codes (relating to quick charge and gps apparently so unlikely in our mind to make much difference) but they said nothing else wrong with it, despite their own print out showing the same >100mv difference. Apparently this doesn't matter at all to them and and they are only worried about the soh which is in high nineties/has all its 12 bars.

I've read lots of threads on here where different people have had varying success with Nissan regarding cell issues. Unfortunately I'm away and so wasn't involved in the discussion with the dealership and haven't seen the print out that they gave my husband, but after an hour long discussion where he and the dealer disagreed re whether there was an issue he's called Nissan to raise it as an issue as we aren't happy. Although I specifically asked for a CVLI test when I booked it in I don't think they did this- however I'm not sure if this is more helpful for a weak cell rather than one that has a persistent difference as the dealer isnt disputing there is a difference in one cell, but just that it isnt relevant at all? Although at lower soc it drops down below what leafspy counts as weak cell voltage. I've looked at the EVB section of the manual that Layzee mentioned but I cant find if it actually states what the maximum differential should be. It says in there:
If a malfunction (e.g. abnormal voltage) occurs in a Li-ion battery cell, the module which includes the malfunctioning cell must be replaced.
but it doesn't say as far as I can see what they consider an abnormal voltage to be.

Does anyone know if if there is any documentation that states what the cell differential should be and when it should be replaced?
Thanks
Kirsty
 

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Leaf 30kWh, Outlander PHEV
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@Layzee any thoughts?

- Leaf 30 kWh
Sent from mobile phone so please mind the typos
 

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It would be good if you could post lspy screenie, you dont mention what range you are actually getting.
What I did when I had bad cell issue was create a trip log by this i mean map out a route say 60 miles in length start at 100%soc and record every 10 miles what the soc is being displayed both on lspy and dash.
What I found with mine was initially lspy and dash were displaying very nearly the same soc% but once i hit 30 miles the dash % display plummeted while lspy % remained more linear, this is caused by the bms using the lowest cell voltage to calculate remaining range whereas lspy looks at overall % left in battery.
I did the same route twice and the results were identical, for boots and braces I then reveresed the route just to rule out that it was a terrain issue and again same result, range dropped dramatically after 30miles.
for the first 30 miles I used about 11% soc between 30-40 miles it doubled to 22% same again between 40-50miles 22% and the available range just plummeted.
Lspy was showiing 50% soc while dash was showing 21% soc on a 24kWh battery thats a huge loss of range

Nissan are reluctant to do anything unless dtc codes P3180 or P33E6 have been triggered, these will only trigger if you go to start the car and even though you have a charged battery it goes into limited power mode.

If you find the same or similar result take your trip log and lspy screenies with you to nissan and have a chat explaining the unexpected loss in range.
Go with a very low battery (2 bar remaining) and ask them to do a cvli test, as doing their normal battery diagnostics will not show up the error, ask for a copy of the results, then you know they have done it !!
Hopefully if you have a reasonable dealer they will get it sorted for you, they turned mine around in a week.




As it is a 2017 leaf you still have 5 years warranty on the battery so even if they are reluctant to do it now it will get worse and eventually they will have to do it.

I am pretty sure that the manual states a max 30mV differential across the battery
 

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Thinking about it when the dealer said they had carried out cvli test what was the soc of the battery when you collected the car ?
If they had done a cvli test correctly they should have discharged the battery until cell voltage reaches 3.712mV that is part of the requirement for the test, so unless they recharged it when you picked it up it should have been nearly flat ?
 

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Thinking about it when the dealer said they had carried out cvli test what was the soc of the battery when you collected the car ?
If they had done a cvli test correctly they should have discharged the battery until cell voltage reaches 3.712mV that is part of the requirement for the test, so unless they recharged it when you picked it up it should have been nearly flat ?
3.7V is the stable voltage for Li-ion.. Approximately 50% SoC

- Leaf 30 kWh
Sent from mobile phone so please mind the typos
 

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Discussion Starter #7
Thanks

We did do a bit of a log before it went in for diagnostics but this was mid actual journey rather than just to check car out and it wasnt intended for us to share with nissan so its not necessarily easy to follow- we will try and repeat with both readings at same times and with regular drop in 10% SOC rather than slightly erratic
Leaf spy SOCCar SOCDrop in Car SOCMiles between readings car SOC
98.1​
97​
0​
0​
92​
5​
6​
78.3​
(10)
79​
13​
12​
74.2​
(2)
75​
4​
3​
57​
18​
11​
38​
19​
8​
26​
12​
3​
43.9​
(8)
At onset of journey SOC was fairly similar spy vs dash 98.1/97% and again in the middle 74.2/75% but by end it was 43.9/<26%
As you can see (hopefully?!) at the end of the journey the SOC dropped by 19% but we only travelled 8 miles and 12% drop for 3 miles compared to at the begining of the journey it was roughly 1%=1mile

A more recent journey went from 100% to 14% on the dash (so 86% drop) for 51 miles
 

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Discussion Starter #8
The report we got doesnt look like yours- I dont think they did do a CVLI test despite me asking. This is all my husband came home with. We dropped it off with a low charge as we knew it would need that, and it looks from the paperwork like they did one of their tests at a lower charge but they then charged it and re-ran a test (we got a remote charge notification) but the print off we got looks like they ran that at fairly close to full charge and we didnt get the print off from any earlier test.

I appreciate I have longer on the battery warranty but if it can barely do 50 miles despite having their 'full 12 bars' I'm not happy to wait until it gets under 9 bars for them to do anything. Unfortunately the dealer wasnt especially helpful, said they have fixed two fault codes (as per pic) and that there isnt any other problem - so waiting now for head office to get back to us.
 

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Discussion Starter #9
After re-reading the OP you should have something like the attached if they did a cvli test and gave you a copy
Thank you- thats really helpful- I'll print that out when I convince them to take it back for the CVLI test so I can see if the paperwork they give me after is similar
 

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The most interesting bit of the report is the last one (194651) there is enough info there to do the calculations to work out the "Cell Voltage Loss Judgement Value".
First you divide total battery voltage by 96 = 4.109
Identify min and max cell voltage, min = 4.000 max = 4.124
Then "A" take max cell voltage from avg cell voltage 4.124 - 4.109 = 0.015
Then "B" take Avg cell voltage from min cell voltage 4.109 - 4.000 = 0.109
Which voltage is larger A or B
in your case B is greater

The solution in this case is replace the module including the cell of the minimum cell voltage, which by the looks of it is cell 75, it also looks like the max "cell voltage divergence" is 40mV not 30mV as I mantioned earlier.
The above calcs are taken from EVB P33E6 under dtc/circuit diagnosis in teccie manual.

attached is the chart I used for trip logging.

I think you have a good case, the fact that the dealer said a 100mV delta makes no difference just goes to prove that they dont know much about how the leaf works.
When I went to my dealer it was the first case they had come across and they didnt really know what to do or how to do it, so i left a copy of the page from the teccie manual on the seat for them, initially they only did the standard annual battery diagnostics which came back 5 stars all the way, I like you had all 12 bars and a good soh, when they came back and said it was fine I questioned it showed them leafspy and my trip logs, they then ran the cvli test which showed the bad cells.
127960


The day after they ran the cvli I went to start the car and the above happened that is when the dtc error codes get generated.

Keep us updated on your progress
 

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Discussion Starter #11
Thanks thats really helpful- unfortunately missed call from Nissan to discuss it this afternoon so will have to wait to call them back.
I drove it down to turtle mode this evening to see whether it would trigger any codes, cant seem to get it to trigger the dtc codes P3180 or P33E6.
Leaf spy showed 20% SOC remaining when in turtle mode and a 620mv difference
 

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If that aint a bad cell ill eat my leaf, they have to replace that under the warranty, unexpected loss in range covers that, if your local dealer wont do it go to another if you have one nearby and try again.
Have you been assigned a case manager yet ? if so he/she wont take any notice of leafspy but should arrange with a dealer to have diagnostics done.
when I had the problem I drove it like i stole it, rapid charged and took it down to turtle to try to stress the cell as much as possible.

Good luck and please keep the updates coming
 

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Thanks, am I right in thinking that although taking it down to turtle multiple times is generally bad for the battery because its basing that on the lowest cell the rest of the battery isnt actually going to be stressed in the same way- since without that cell it would still be at 20% ish? So although it may encourage the weak cell to fail quicker I wont be doing permanent damage to the rest of the battery?
 

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Thanks, am I right in thinking that although taking it down to turtle multiple times is generally bad for the battery because its basing that on the lowest cell the rest of the battery isnt actually going to be stressed in the same way- since without that cell it would still be at 20% ish? So although it may encourage the weak cell to fail quicker I wont be doing permanent damage to the rest of the battery?
Based on Voltage shown I'd agree.. Any impact will be on the cell with severe degradation and not the whole pack

- Leaf 30 kWh
Sent from mobile phone so please mind the typos
 

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Thanks, am I right in thinking that although taking it down to turtle multiple times is generally bad for the battery because its basing that on the lowest cell the rest of the battery isnt actually going to be stressed in the same way- since without that cell it would still be at 20% ish? So although it may encourage the weak cell to fail quicker I wont be doing permanent damage to the rest of the battery?
Yep spot on !
 

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Discussion Starter #16
Just dropped it off for dealer to look at it tomorrow (long wait for a slot with courtesy car!), no fault codes at all so far so have a feeling we might be in for a fight but I printed off the CVLI instructions (although it does say in the manual to be done if set fault codes so will see what they say) and will double check tomorow that they are definitely doing it.
 

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good luck lets hope you have a result dont forget a full copy of the result for your records ;-)
 

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Update:
Dealer called within half a day of us dropping it off to say it had gone to Gateshead. At this point according to Nissan EV app they hadnt discharge the battery past the 25% that we had dropped it off with so I dont know if they even did the CVLI test. The person who told me it was going to Gateshead couldnt even tell me if they had found a fault or if they couldn't find a fault and so were sending it to them for further investigation. However as I suspected they needed to change the cell and knew that would need to be at Gatehead I was relieved and didn't question them further.

We got the car back today, very minimal communication/documentation from local dealer and none from Gateshead (although I notice an email address on the one bit of paper we did get so am planning to ask them for more details). Since they havent given me any documentation really I dont know exactly what they found/what the CVLI test showed but can only assume it showed them what we expected which was we had a faulty cell as they apparently changed module 19.
This is screenshot taken after it was collected, clearly much less of a drop than previous (detected initally at 119mv but worsened subsquently) but thats taken at a relatively high SOC so difficult to know what it will be like at lower charge. It doesnt look to be fully balanced- now the cells either side are a little low too- I assume these are the three cells in module 19. I think 30mV is still at the top of what the gap should be? Will I guess need a few charges and a bit of a test drive to see how its going.
 

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Sad that you are getting so little in the way of explanation. Ideally you need to give it a full 100% charge to give it the chance to balance the battery, then a deep discharge taking LEAFSpy readings at both points.
Fingers crossed!
 
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