Advice before purchase - weak cell? - Leaf 40kwh -2019

My Nissan Leaf Forum

Help Support My Nissan Leaf Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

ccmm

Member
Joined
Jan 28, 2024
Messages
15
Hi,
I went to Nissan dealer today for a drive of a 2019, 90000km, 87% soh Nissan leaf.

I used leafspy during my drive.

When I arrived, it was connected to chademo (dc) and car was displaying that charge was at 6kw. First thing I find strange. Sales person couldn't give me any answer. Photo enclosed. Soc was 80%. Battery temp around 40°C and outside temperature close to 0°C. Could that be issue of the car or some limitations set up in charging stations? (Sales guy could not tell me).



Then during my drive test, I checked battery cells. Right after unplugging it, cells seems to be quite balanced with low cells voltage difference.

While driving normally, cells voltage difference remained below 50mv. But when accelerating stronger, difference went up to around 70mv...so I took it to highway and accelerated foot to the floor, several times. Cell voltage difference went up to 115mv. Also cell 1 dropped to around 3.4v. but maybe this is in the norm?

This MV differences were only during acceleration, when cruising, it was balanced.

Is it normal behavior during strong acceleration in winter? Any risk that some weak cell could prevent me from using the car in the next few years? I plan to keep it at least 3 years with maximum 60kms of drive per day, no highway or really not often.

Thanks
 

Attachments

  • IMG_20250111_142355.jpg
    IMG_20250111_142355.jpg
    2.4 MB
  • Screenshot_2025-01-11-14-32-39-701_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-32-39-701_com.Turbo3.Leaf_Spy_Pro.jpg
    544.6 KB
  • Screenshot_2025-01-11-14-27-18-377_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-27-18-377_com.Turbo3.Leaf_Spy_Pro.jpg
    363.9 KB
  • Screenshot_2025-01-11-14-36-12-055_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-36-12-055_com.Turbo3.Leaf_Spy_Pro.jpg
    359.1 KB
  • Screenshot_2025-01-11-14-33-31-069_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-33-31-069_com.Turbo3.Leaf_Spy_Pro.jpg
    496.3 KB
  • Screenshot_2025-01-11-14-37-16-152_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-37-16-152_com.Turbo3.Leaf_Spy_Pro.jpg
    498.8 KB
  • Screenshot_2025-01-11-14-39-30-916_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-39-30-916_com.Turbo3.Leaf_Spy_Pro.jpg
    493.5 KB
  • Screenshot_2025-01-11-14-42-22-935_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-42-22-935_com.Turbo3.Leaf_Spy_Pro.jpg
    530.2 KB
  • Screenshot_2025-01-11-14-44-02-932_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-44-02-932_com.Turbo3.Leaf_Spy_Pro.jpg
    478.9 KB
  • Screenshot_2025-01-11-14-39-30-916_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-11-14-39-30-916_com.Turbo3.Leaf_Spy_Pro.jpg
    493.5 KB
Last edited:
Looks like cells 41-44 are outliers on the high side--maybe they were replaced and the pack SOH was reset?

Definitely some weak cells that show under load, so good test to make sure you know what you are getting. Those weak cells will be the limiters on your driving range.

There are too many inconsistent variables to know how long it would work for you. Take it for a full range drive and check cells at low SOC.
 
I concur with NLspace. I would bet a few cells were replaced.
115mv while not ideal, is not something I'd be too concerned with, I'm more concerned that the low cells are right next to the replaced ones. Are they the next to go?
could give many more miles/years or could have more cell problems in a week, just no way to tell
 
Thanks for your responses. Much appreciated. According to Nissan, it has been bought brand new by the owner to whom they bought it back. One owner, full service and yearly maintenance at nissan, no damage or incident. They showed me the invoices and there was nothing mentioning any cell replacement, but they could have hidden it to me. They propose 12 month full warranty on this car but I will not take the risk. I wanted to go EV to replace my almost dead Renault modus and avoid maintenance of petrol engines and time spent at garage, this particular leaf is maybe not a candidate.
Thanks
 
Hi everyone,
Still trying to find leaf 40 at decent price with soh around 80/90% and good condition.

I found another one. Nconecta, 2020, 125000kms. No warranty, It is sold by owner directly. He uses it everyday to go to work and slowly charge it twice per day (home and office) 5 days per week. Freeway mainly (a little bit more than 100km per day at 130km/h. Consumption +20kwh per 100 kms.

I could drive it around 15kms today. Still concerned with the cells dégradation and balancing as it shows similar results as the previous leafspy captures I shared, althought curve drawn by cell balance is different.

Cells voltage seem also lower than the previous one I tested (at higher soc and equivalent soh, don't know if this normal).

So if anyone had advice to give whether this battery pack seems healthy or not. Not searching the perfect car, just usable for 100km max per day, over the next 3 to 5 years.

Sounds like for 9500 euros, this one and the previous I shared are the best I can get, but if battery fails after 2 years, that will just be waste of money (no way to replace cells here, unless under Nissan warranty)

At rest or driving slowly, cell voltage difference looks ok, but pedal to the floor, difference instantly drop. Don't know if this this normal behavior of pack or if I should pass.

Thanks a lot
 

Attachments

  • IMG_20250118_093934.jpg
    IMG_20250118_093934.jpg
    3.5 MB
  • Screenshot_2025-01-18-09-39-25-739_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-18-09-39-25-739_com.Turbo3.Leaf_Spy_Pro.jpg
    296.2 KB
  • Screenshot_2025-01-18-09-36-49-943_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-18-09-36-49-943_com.Turbo3.Leaf_Spy_Pro.jpg
    510.3 KB
  • Screenshot_2025-01-18-09-36-47-261_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-18-09-36-47-261_com.Turbo3.Leaf_Spy_Pro.jpg
    503.1 KB
  • Screenshot_2025-01-18-09-25-08-559_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-18-09-25-08-559_com.Turbo3.Leaf_Spy_Pro.jpg
    498.9 KB
  • Screenshot_2025-01-18-09-23-23-809_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-18-09-23-23-809_com.Turbo3.Leaf_Spy_Pro.jpg
    508.1 KB
  • Screenshot_2025-01-18-09-19-55-906_com.Turbo3.Leaf_Spy_Pro.jpg
    Screenshot_2025-01-18-09-19-55-906_com.Turbo3.Leaf_Spy_Pro.jpg
    510.3 KB
The Delta V on the pack doesn't seam too bad. L/S tells you what is NOW not what may happen in the future. There are no guaranties with L/S readings. It is what it shows today, and I'd be happy with the Delta V reading today.
Only you can weigh the choices before you. 100Km? likely no problem as it is now, no one can tell what will happen with a vehicle in 3-5 years. Cars have engines and transmission that let-go and no when can predict when that will happen, and EV is no different, different problems but no crystal ball to tell what might happen in years to come..
 
The Delta V on the pack doesn't seam too bad. L/S tells you what is NOW not what may happen in the future. There are no guaranties with L/S readings. It is what it shows today, and I'd be happy with the Delta V reading today.
Only you can weigh the choices before you. 100Km? likely no problem as it is now, no one can tell what will happen with a vehicle in 3-5 years. Cars have engines and transmission that let-go and no when can predict when that will happen, and EV is no different, different problems but no crystal ball to tell what might happen in years to come..
Thanks a lot for this feedback. Indeed, no cristal ball so things could go wrong. But I guess that if at the time of the measure one or several cells look weak regarding mileage and being obvious that cells can only degrade more overtime, some cars can be recommended or not (more or less risk). The first car I shared l/s captures from is still on sale. Can I conclude from your messages that first one could be a risky purchase when second one not particularly? Thanks a lot
 
The Delta V (Mv reading in block numbers on the upper right of the bar chart) is what is key here. It is the mv reading between the highest and lowest cells in the pack.
A healthy battery will have the smallest Delta V , but all batteries will have some variation in the cells.
screenshots of the graph when the battery is underload and below high SOC will show "weak cells" being substantially lower than the rest of the pack.
The 1st car you showed, had the highest and lowest cells right next to each other. This is likely due to low cells that were replaced with much newer cells (giving you the "high" cells) but the ones next to them were lower than adv leading me to suspect they might be starting to weaken also.
A battery pack is only as good as it's weakest cell.
neither of them show a huge Delta V but the 2nd one has more even distribution of the highest and lowest cell.
20mv delta is excellent, 50 is ok and anything below 150 under load is not likely give a symptom (code or sudden loss of power under load)
The Hx and amp/hr readings between the two cars are fairly close together.
My guess is the 1st had a few cells replaced and the 2nd did not (as built pack). Neither are glaring obvious that something is failing, but the one with cells replace and the lowest cells being next to the highest cells, leaves me with more questions than the 2nd one.
If I had to choose, I'd likely take the 2nd one even though it has more miles and slightly more degradation of the pack (as one would expect with more use) because the distribution of the "wear"is more even across the pack.
It is very hard to see the future clearly from what is today. Both may give long life.
 
The Delta V (Mv reading in block numbers on the upper right of the bar chart) is what is key here. It is the mv reading between the highest and lowest cells in the pack.
A healthy battery will have the smallest Delta V , but all batteries will have some variation in the cells.
screenshots of the graph when the battery is underload and below high SOC will show "weak cells" being substantially lower than the rest of the pack.
The 1st car you showed, had the highest and lowest cells right next to each other. This is likely due to low cells that were replaced with much newer cells (giving you the "high" cells) but the ones next to them were lower than adv leading me to suspect they might be starting to weaken also.
A battery pack is only as good as it's weakest cell.
neither of them show a huge Delta V but the 2nd one has more even distribution of the highest and lowest cell.
20mv delta is excellent, 50 is ok and anything below 150 under load is not likely give a symptom (code or sudden loss of power under load)
The Hx and amp/hr readings between the two cars are fairly close together.
My guess is the 1st had a few cells replaced and the 2nd did not (as built pack). Neither are glaring obvious that something is failing, but the one with cells replace and the lowest cells being next to the highest cells, leaves me with more questions than the 2nd one.
If I had to choose, I'd likely take the 2nd one even though it has more miles and slightly more degradation of the pack (as one would expect with more use) because the distribution of the "wear"is more even across the pack.
It is very hard to see the future clearly from what is today. Both may give long life.
Great and I couldnt be more grateful for the time you spent responding me. This is really kind. I will confirm my willing to buy second one to owner at the condition that he allows me another drive but this time with soc between 25 and 40 %. From what I read here and there, MV delta under load can increase at low soc, especially in winter. That would give me better picture of the pack. Thanks a lot 🙂
 
Hi, thanks everyone for your advices.
@hornstudio, I am based in normandie, close to the English channel, in France. Not really hot climate. It's relatively cold this winter (subzero each time I tested the cars).
Couldn't drive again, still waiting response from seller. My only fear is not even range, I guess that with one or two weak cells (if confirmed), range should be enough for my need (wanted to buy a 24 or 30 at first place) but the risk of not being able to use the car at all in the next few years.
 
Last edited:
What is your budget? I have friends in Netherland that sell LEAF but I am sure you find one nearby.
 
Back
Top