Abnormal cell voltages on 2016 sv with 40kwh pack (replaced by nissan)

[osi]

So I just bought a new leaf with a 40kwh pack, and have noticed with leafspy that 4 cells seem to be .05v higher than all the other cells. This doesn't seem normal, I've been driving around 2015 for over a year and haven't seen anything like it. Could it be like this because the bms believes those cells have less capacity than the rest? i don't think this battery has been even near turtle mode yet. I've reset leafspys data on my phone and it still shows this, leafspy also seems to want to auto select a 60kwh pack instead of 40 for some reason. The car still has plenty of capacity warranty left, so I'm not too worried about it being defective but I'd like to figure out why it's doing this, also would like to know if other 30kwh-40kwh swaps experienced this. If I remember correctly, the 2018 leafs charge to 4.2v, while 1st gen leafs only charge to 4.1v, it seems related to that.

First image is around 90%, second one it's 55 miles later at 55%

http://imgur.com/a/YK6mTzc

 

[LeftieBiker]

Usually, bad cells are identified by their low voltages, while recently replaced cells show up as higher. In the latter case, it tends to slowly improve. Maybe the new pack had a couple of bad cells, and they were replaced...?

 

[osi]

Usually, bad cells are identified by their low voltages, while recently replaced cells show up as higher. In the latter case, it tends to slowly improve. Maybe the new pack had a couple of bad cells, and they were replaced...?

maybe, but would that explain why 4 cells are charged near 4.2v? in the first photo they were around 4.15v, and the car was at 90% charge, so they must of been higher. Im worried those cells will degrade quicker than the rest because they're being charged higher, i'd imagine every time i use regen they're getting more stress than the others, especially at high soc. its worrisome that the BMS is allowing for the difference in voltage. the battery has been driven on for about 900 miles, pretty sure its never been taken close to vlbw. Could it be leafspy/my phone acting up?

 

[osi]

I'm beginning to think that this is a REFURBISHED 40kwh pack, where 4 cells have degraded and were replaced, assuming the car it was taken from got a fresh battery.. I still haven't had a chance to range test it on the highway, but in the city with moderate ac and getting in and out a lot, Ive been able to get around 120 miles. SOH has already decreased to 98.16%

 

[LeftieBiker]

Nissan's battery warranty has always (and still, AFAIK) allows for refurbished packs as replacements. Since the car it's in is used, and was a 30kwh Leaf, I wouldn't get too upset if the new pack has a few new cells. I don't think that you have to worry about them degrading significantly faster, so if the range is what it should be, I'd try to be happy that this is a 40kwh Leaf, rather than upset that it may have a refurbished pack. How much did you pay for the car?

 

[GerryAZ]

As LeftieBiker said, don't worry about the cell voltage differences as long as the car performs OK and range meets your needs. I have been driving Leafs since 2011 and using Leaf Spy since it became available. The replacement battery in the 2011 was always well balanced until the car was totaled and the 2015 was well balanced until a few weak cells started showing up well beyond the 5-year, 60,000-mile capacity warranty. The 2019 has higher cell voltages at full charge and more variation between cells than the previous cars. Therefore, the newer batteries are definitely different. I was concerned at first because of the higher voltages at full charge and a few cells that appeared weak based upon the Leaf Spy cell voltage displays both at full charge and when deeply discharged. I eventually accepted the variation and just drive/charge the car as needed since the cell voltage variation does not seem to impact range and the battery is under warranty if there are any problems in the future.

 

[osi]

I knew it was a gamble going into this. im not upset, more just concerned about the battery and what its doing. i also think that maybe the shunts on those cells don't work, but i would assume the car would throw errors at that point, idk. I paid around 13k for it. I know in the owners manual they state the warranty only has to return the car to 9 bars of capacity, but from what i've seen in pretty much every degradation case is they just swap in a fresh pack, usually they only refurbish a pack if a cell has gone bad. I find it interesting that this leaf potentially has a refurbished 40kwh pack, while it seems other 30kwh replacements by Nissan get a new 40kwh pack. it must be luck of the draw if that's the case, oh well it must have at least 30kwh of range so i cant complain.

Also ty gerryaz for your input, i'll try not to worry about it so much and just drive it

 

[osi]

the car absolutely refused to go into turtle mode, i drove it at least 15 miles past the last bar disappearing, lowest voltage in leaf spy was around 2.75, i gave up at that point because i was worried about damaging the battery... is this normal? leafspy showed 0gids and 0kwh remaining for several miles, i drove around 35 mph with ac blasting, i was expecting to hit turtle mode quite early but it just kept going and going... Im convinced either leafspy is malfunctioning or the car is, could be wrong tho. the images linked are from a 150 mile trip starting at 98%, with about 10 minutes of 20kw DCFC because i was worried i wouldn't make it when i was at 20%/100 miles in, probably can get around 130 at most on a charge here in the summer with ac. the second image shows the lowest i took the car... nearly 500mv of difference seems like a lot, and 2.75v seems really low. i thought turtle mode always happened before or at 3v?


https://imgur.com/a/ahZeCMa

 

[GerryAZ]

This is a screen shot of the last discharge test on my 2019. The individual cell cutoff voltage is lower on the 2019 than the two previous cars and the difference between highest and lowest cell voltages is also higher (especially when the battery is deeply discharged). I have done 4 full discharge tests on the 2019 and my experience is that the turtle and shutdown levels are not as consistent as the previous cars.

I just noticed that the SOC % on your Leaf Spy screen shots is not correct so you may want to check all of your Leaf Spy settings.

 

[osi]

Screenshot_2020-05-10-03-51-51.pngThis is a screen shot of the last discharge test on my 2019. The individual cell cutoff voltage is lower on the 2019 than the two previous cars and the difference between highest and lowest cell voltages is also higher (especially when the battery is deeply discharged). I have done 4 full discharge tests on the 2019 and my experience is that the turtle and shutdown levels are not as consistent as the previous cars.

I just noticed that the SOC % on your Leaf Spy screen shots is not correct so you may want to check all of your Leaf Spy settings.

Ah, thank you for sharing that, much less worried now. i was probably extremely close to hitting turtle mode then, im quite surprised that the cutoff voltage is lower. everything i read about leaf batteries has indicated it's higher, i guess its a bit harder to find good info on 2018 and newer leafs.
Leafspy gets wonky with 40kwh packs put into 30kwh leafs by nissan, the app always auto selects 60kwh as the battery size, and the SOC and AHr is off, other than that the gids, kwh, soh all seems accurate. i've cleared the app data and stuff but it doesn't seem to help.

 

[GerryAZ]

The low voltage cutoff is lower and the high voltage cutoff is higher (at least for the 62 kWh battery) compared with 2011 and 2015. That is why I said earlier not to worry too much because I suspect the 40 kWh battery limits are similar.

 

[GaleHawkins]

I'm beginning to think that this is a REFURBISHED 40kwh pack, where 4 cells have degraded and were replaced, assuming the car it was taken from got a fresh battery.. I still haven't had a chance to range test it on the highway, but in the city with moderate ac and getting in and out a lot, Ive been able to get around 120 miles. SOH has already decreased to 98.16%

With a SOH decreased to 98.16% would indicate a new 40 kWh pack was put in the car from my experience. Our new 40kWa pack SOH was at 99.87% when installed in our 2016 Leaf SL and after 8 months/13K miles SOH was at 96.08% last Saturday when it T-Boned a mini van that lost the race with a red light.

After about 10 charges to 100% my mV difference ranges from 2-4 mV with 3 being the norm in our case at 100% SOC.

I expect your battery pack is new. Our old 30 kWa pack dropped to 8 bars after 24K miles/40 months of use. I hoping the 40 kWa battery will still be fine when the car makes it to 100K miles. My rate of declined since I started recharging from 70% to 100% has dropped by about 50% but I do not know why. Normally it declines about .01% daily where driven 100 miles or parked for 24 hours.

 

[cwerdna]

What's kWa?