Advice on Cell Balancing

[aneesh84]

I am planning to buy this car 2018 40kwh. The battery was changed 3 years ago 130000 kms ago. On checking with leafspy cell voltage difference was about 50 mv and went to 70 mv at times while driving. Is this a sign of bad cells or something that will get fixed by cell balancing ?

 

[LeftieBiker]

Welcome. 50 mv isn't a huge difference. Look at the number at a low state of charge to see if any cells are going bad. If it stays near 50 then you are ok. I don't know how much variance is normal while driving; hopefully someone else will answer that.

 

[Stanton]

If you can figure out a way to post the cell-pair graph (from LS), then we can respond; right now there is no link.
Also would be good to post a screen shot at both high and low SOC.

 

[LeftieBiker]

I was able with Firefox to right click on "Image" and open it in a new tab.

 

[GerryAZ]

How many miles (or km) on the car? There are some unusual numbers in the LEAF Spy data shown in the screenshot. The AHr value of 655.36 does not make sense and the SOH of 83.77% is low. 50 mV difference between highest and lowest cell pair is not bad, but I question the validity of that number given the obviously incorrect AHr value. I doubt that a 2018 has had the battery changed unless it had defective cells.

 

[knightmb]

I am planning to buy this car 2018 40kwh. The battery was changed 3 years ago 130000 kms ago. On checking with leafspy cell voltage difference was about 50 mv and went to 70 mv at times while driving. Is this a sign of bad cells or something that will get fixed by cell balancing ?

Re-link imaged to help with topic.

 

[Stanton]

I have a theory on why is AHr (and other) settings don't make sense.
He said the "battery was changed": if it was an upgrade from 24kWh->40kWh, then you need to select some "custom" settings in LeafSpy to get the correct values (I know this because I have to do it). However, we don't know the car history until he confirms.
Regardless, it does look like that pack could use a good "top balance" session (or two) before deciding if any of those (low) cells are problematic.

 

[aneesh84]

How many miles (or km) on the car? There are some unusual numbers in the LEAF Spy data shown in the screenshot. The AHr value of 655.36 does not make sense and the SOH of 83.77% is low. 50 mV difference between highest and lowest cell pair is not bad, but I question the validity of that number given the obviously incorrect AHr value. I doubt that a 2018 has had the battery changed unless it had defective cells.

The problem was that I was new to using Leafspy and by default the setting was for 24 Kwh battery pack while the car was 40 Kwh. The car has done 360000 kms, but the seller said that Nissan had changed the original battery at 130000kms under warranty.