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Discussion Starter #1
Hi all,

My brother has a 2014 24kwh tekna leaf with only 18k on the clock, he has had it for 4 1/2 years.
Recently, he told me he was seeing eratic % charge drops gong up hills, and eratic % regen back in gong down the hill.

Sounded to me like a rogue cell or 2. Investigated with a leafspy, and over a few weeks monitored things.

What we found was cell 49 on 4.07v with the rest balancing at the top coming to the end of the charge on 4.132v, so cell 49 quite considerably lower, 62mV, plus, showing red with all the rest so bleeding, whilst cell 50 was showing blue taking charge (49 and 50 are the on in the same battery enclosure)

A week later, after trying to force balance by plugging back in a few times after the end of charge... now cell 49 on 4.057 with the rest at the end of charge at 4.13 or so spread 80mv.

2 weeks later, again after trying to force balance its getting worse.... cell 49 4.048v the rest at top end of charge around 4.137... spread 89mv..

So, the spread is widening.

All the while cell 50 (on the same pair as cell 49) is always blue indicating taking charge, whilst ive never so far seen cell 49 on blue when balancing, always red, it is of course blue when charging, but not on balancing at the very top.

So, i`m thinking we have a drain on the cell, and the only connection to that cell is the copper buss rail and the balance tap wire. Have we got a BMS problem?

From my readings taken from my ENV200 via leafspy during driving when i bought the van a cell voltage of 4.04 represents about a 65% state of charge.... so that cell over time has got considerably out of balance to the rest of the pack.

Whats yout thoughts on this folks...

Thanks.
 

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Check it at low soc to see what it is as it is this that will scupper your range 40 - 60mV isnt a great difference tbh mine was a lot worse, I think it was constant at around 90mV @ 100% soc but as the soc dropped down into the 70% area the range really dropped off quickly.
A good indicator is soc% reported by the car and Lspy if they differ massively as the soc% goes down then you have a problem.
Check this thread out:
 

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Discussion Starter #3
Thanks layzee,

did you get it sorted or have you lived with it?

bearing in mind now the car is 6 years old, no doubt Nissan will not offer a fix as its out of the 5 year warranty, but the car has only covered 18k miles.
My 2015 Env200 has done 70k miles and the battery is within 10mv balance, i thibk is SOH is 86%, mine has just lost its first bar at 84%.

Check it at low soc to see what it is as it is this that will scupper your range 40 - 60mV isnt a great difference tbh mine was a lot worse, I think it was constant at around 90mV @ 100% soc but as the soc dropped down into the 70% area the range really dropped off quickly.
A good indicator is soc% reported by the car and Lspy if they differ massively as the soc% goes down then you have a problem.
Check this thread out:
 

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Thanks layzee,

did you get it sorted or have you lived with it?

bearing in mind now the car is 6 years old, no doubt Nissan will not offer a fix as its out of the 5 year warranty, but the car has only covered 18k miles.
My 2015 Env200 has done 70k miles and the battery is within 10mv balance, i thibk is SOH is 86%, mine has just lost its first bar at 84%.
Yes I did get it sorted, but it was a bit of a struggle to get them to do the initial test to prove that a problem existed, it wasnt until I showed them Lspy screenie that they then finally did a cvli test and there it was the proof.
Up until that point no dtc codes had been generated, Ironically the following morning even though fully charged the car would not start and it generated the dtc code.
I was impressed with the service car was gone a week, but unfortunately they did not do a good job of pre charging the new cells, I still have a 60mV delta which has not changed in a year and is highly unlikely too, but the discharge is now much more linear and I get a much better range.
 

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Discussion Starter #5
i will advise my brother to seek a dealers advice, maybe ask nissan UK to help out been as the car has only done 18000 miles. Im not holding out much hope tho.
How long ago did you experience this issue, how much warranty remained for you?

Thanks
 

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Mine was still under warranty so they had to do it my mileage at the time was around 18000 miles.
 

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They replaced 2 modules (4 cells) but they failed to precharge them to the correct level.
There is a specific procedure and calculation to be done to get the precharge voltage level correct, obviously with a 60 mV difference clearly shown on Lspy, they failed maybe their maths was out, the 4 cells they replaced are low, the rest of the cells are within about 10-12mV so had they done the job right it would have been a great battery.
I did speak to them about it but was told by the technician at Lookers (they replaced the cells) that the cells would balance during normal use.
I have tried all sorts to get them to balance but to no avail, the delta has not changed in over a year.
 

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Understand that that battery balancing system can only DISCHARGE cells. It has no ability to charge the low cell. All it does is drains the higher cells at a very low rate, in an effort to bring them down inline with the lower cell. The pack is then charged as normal and all the cells recharged in series.

It certainly sounds like a bad cell, and you will need to get a dealer to perform a CVLI test.
 

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How has this Leaf mostly been charged? It might be worth changing the charge speed eg using 7kw if it only gets granny charged or using granny charging if it's normally 7kw.
 
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