New 40kwh battery on 2018 SL, sudden charge drop at low load

[Jerther]

Deleted. Forum did some trick on me.

 

[Jerther]

@knightmb So all in all, when it's below freezing, charge on arrival when the battery is warm. Else, try to limit charge up to 80%. Charge up to 100% just before leaving and only if necessary.

It would be nice to know at what motor power those voltages were so all over the place.

It was "WoT" and the power meter in the car dashboard was full. That's all I can say :/

I would say, that this pack is not new but refurbished from used battery cells.

Could be!! The dealer gave me some pictures. I've got a sticker on the battery, and the TechLine order. The part # is 295B0-5SL4ARE. I've seen it listed as remanufactured but also sometimes as new. So I'm not sure.

Here's the photo of the battery sticker:

 

[Lucky]

And also, man that's expensive

Yes, in my country Slovenia last price for the new pack was around 17.000€ at the dealer.

When the cells in a battery pack are mixed from used ones, they each have their own "personality" because of their different history. This also shows in their ESR value (simply internal resistance). They could have the same capacity, but they won't have the same resistance. So under load their voltage drop will be different. Higher the internal resistance, deeper the drop. So the weakest cell will eventually trigger turtle mode, or in worst case power off, because LBC will kick the protection in. Otherwise it would damage the cell and this could be unsafe.
Try charging it and testing under load again. I wonder what Leaf Spy will show.
It would be nice to know the battery current, this way approximate ESR could be calculated.

 

[Jerther]

So it's been a few weeks now and many full charge cycles. The soc is stable when the battery temperature is above 5-10c, even at low soc like 10-15. Yesterday I went to the dealer again after experiencing sudden soc drop from 49 to 40 on the highway while it was -15c outside. They convinced me to leave them the car for them to diagnose the battery. (The Sentra is nice to drive, nicer than the Qashqai, but nowhere near the leaf )

Here's a leaf spy capture while I was accelerating. Battery temperature is quite low. I know enough to say that I cannot trust this battery under 50% on cold days. To be continued.

 

[Stanton]

So it's been a few weeks now and many full charge cycles. The soc is stable when the battery temperature is above 5-10c, even at low soc like 10-15. Yesterday I went to the dealer again after experiencing sudden soc drop from 49 to 40 on the highway while it was -15c outside. They convinced me to leave them the car for them to diagnose the battery.

I've seen worse (much worse).
To be honest, almost any battery will have trouble at such low temps; not sure I would go to the trouble of replacing any cells/modules if you don't have these problems above "freezing".

 

[Jerther]

That's what I'm starting to think too but this is no 10 year old battery, it's supposed to be brand new (or remanufactured at least). That would mean all brand new EVs have this problem, and it's ok? No, I don't believe so. Nobody here would have EVs if that were the case, right?

not sure I would go to the trouble of replacing any cells/modules if you don't have these problems above "freezing".

In Florida no, obviously! But here, where winter is a big deal, I certainly would because else I would have to deal with severe range anxiety, 6 months a year. In fact I've been for the last 4 months and It's exhausting.

TL;DR: bit of exasperated rant.

Winter is almost over but I'm not sure I'll go through another one with 80km effective range, sometimes having to quick charge for an hour+, ruining evening plans... You see the 3 quick charges on the screenshots? These were because at 40% the battery wouldn't let me accelerate normally from traffic lights. And at -10c it takes an hour at 20$/h to go from 40% to 70%. My wife is terrorized of driving this car farther than the next corner. No, really, that's absolutely not fun. I love the leaf but these 3 quick charges made me miss my Suzuki for a moment, and it saddens me a great deal. So yeah, I'd gladly go ahead and replace these cells.

This battery is not as bad as the previous one: at least I don't get stranded! But "good enough, sometimes" won't cut it for the most expensive car I've ever bought The dealer, who's been really really nice to me, will call me back today so we'll see.

 

[Jerther]

So they called me back. They had an engineer visiting and the asked him to test all cells and they're fine. Also they asked me how many % loss I observed, to which I answered 10, but from their test drives (0 to 80km/h), the sudden drop was in the order of 1% and this is not abnormal at -10c (ambient, not battery), but on the verge to be. And with their results, I agree with their conclusion.

This is all part of the battery warranty, and they'll keep the case open. They asked me to let them know should anything worse happens.

So I think I'll put the battery to the test, and see if it will collapse like the previous battery did. I didn't want to get stranded again so I was careful not to put too much load, but at this point I guess I have two choices: find the battery's limit and see if it's acceptable, or live in fear If the battery drops no more than 10%, reliably, I can live with that. It's the 50% down to "SERVICE EV" that scared the *** out of me.

 

[Jerther]

It got down to -20c earlier this week. It was the perfect time for a torture test!

Here's a leafspy screenshot from when I started my trip to work. Notice the battery is at about -10c:

50km and 35 minutes later, I took a video while climbing a long hill. THAT hill, where I got stranded once. By that time the battery temperature got up to between 0 and 3c. (Taking a video while driving, at high speed, was a bit dangerous and also is illegal so I hope it's the only time I do this... There was no traffic so it was relatively safe.)

https://photos.app.goo.gl/smSqpcVbjUp6b9Ni7

Finally, here's leafspy when I got to work, which is another 20km away from the hill. By that time, the battery had warmed up and I could accelerate with all the power I wanted, no problem.




So I understand this test is not casual driving. Well, not usual casual driving Still, that's a 33% drop!!! Anyway I just need to know, is this expected from a new battery under these conditions? Do all new LEAFs do that? Do all other new EVs do that (Tesla, Hyundai, Toyota, GM, Ford...)? Am I being excessively aware and people just don't notice?

Sorry I'm asking a lot of questions. I do have many. One day I'll get this sorted and I'll be the one who's answering questions for people around me when they finally get EVs. I'm really eager for that day

Another test I need to do is to let the car out on a very cold night, at 40% soc, then drive it in the morning. Last time I did that (by accident), I couldn't accelerate from stop to 50 km/h without getting a 10% sudden drop. But that was a week after I got the new battery and before I had fully charged it at least once.

 

[Jerther]

Well even when the battery is warmed up, under 40% the SoC gets all over the place. 0-80 km/h is always fine. I get problems under sustained load.

Here's leafspy when soc had suddenly dropped 10%



I can't believe this would be normal.

 

[Snakebitten]

Does 3.106V (average) = 36.7% SOC? I mean in reality vs what LeafSpy declared?

 

[Jerther]

At that point the dashboard was showing something around 15%, down from about 25.

 

[knightmb]

I would comment that at this point, it looks as though the pack either needs more balancing through a deep discharge and recharge or the pack is not really brand new and has a mix of old and new cells that is throwing off things internally for the BMS. Unfortunately, the latter means annoying behavior like this for the owner.

 

[Jerther]

@knightmb Thank you for your input, I appreciate it. I truly do. I remember that procedure you explained earlier. It's a bit involving but I'll try it if I have to.

 

[Jerther]

My Nissan dealer called me back yesterday for a follow up. I said I experienced more collapses but also that I highly doubt they could replicate a battery collapse on this battery with their parameters (0-80kph), but they insisted on doing more testing during today's cold snap (-16c) and I accepted. I also gave them my video.

(The Nissan Rogue 2021 is nice. More reactive than the previous Sentra and Qashquai )

So they called back again this morning, and lo and behold, they could replicate a battery collapse. I have no idea how they've managed that but wow! Anyway they've submitted their captured data to Nissan and they're waiting on a reply. They should also comment on the video I made.

Man this story does not want to end! To be continued soon!

 

[cornbinder89]

My Nissan dealer called me back yesterday for a follow up. I said I experienced more collapses but also that I highly doubt they could replicate a battery collapse on this battery with their parameters (0-80kph), but they insisted on doing more testing during today's cold snap (-16c) and I accepted. I also gave them my video.

(The Nissan Rogue 2021 is nice. More reactive than the previous Sentra and Qashquai )

So they called back again this morning, and lo and behold, they could replicate a battery collapse. I have no idea how they've managed that but wow! Anyway they've submitted their captured data to Nissan and they're waiting on a reply. They should also comment on the video I made.

Man this story does not want to end! To be continued soon!

Great news that they can document it, bad news that Nissan "rebuilt" packs are junk. Hope a new pack is in your future soon.

 

[Jerther]

Here's the news: Nissan acknowledges there's something wrong, but they asked, and get this @knightmb, that I do three complete 100% to <10% discharge cycles, and charge only on L2, and then try to replicate the problem again. Haha, nice They were kind of surprised I was already aware of the procedure

They were also nice enough to offer to do it for me, but I'm not driving the Rogue anymore than I need to. Plus I'll get to document this as much as I want.

I'll obviously post back here whenever I can.

 

[knightmb]

I probably have enough screenshots to write a (how to) for this, that might be better than to keep copy/pasting my same response in every topic it comes up. The only downside is that it won't fix any actual battery issues, but it's a good starting point to troubleshoot issues such as this when the cells can't be balanced by regular driving habits. Thanks for keeping us up to date on everything, it is very helpful for the rest of us.

 

[Jerther]

I'm really glad I can help too

By the way, does the battery temperature matter in this calibration? I can either take my time and do it when it's convenient, or do it in one go while it's still cold outside but if I do this the battery might not have enough time to completely cool down.

 

[knightmb]

I'm really glad I can help too

By the way, does the battery temperature matter in this calibration? I can either take my time and do it when it's convenient, or do it in one go while it's still cold outside but if I do this the battery might not have enough time to completely cool down.

It does in the sense that a cold battery won't be charged to the same level as a warm battery. So if a brand new 40 kWh Leaf battery is able to have 39 kWh of energy put into it at room temperature, this is going to be reduced when the battery is colder via the BMS tracking power in and power out, etc. I don't know the exact amount since I don't know what lab specs the Nissan cells are rated for, but the BMS probably has all of that programmed into it and most of our observations about it here seem to confirm that. More on the order of 1 or 2 kWh difference, but with so many variables to track (cell temperature, voltage, resistance, etc.) that is better left to the BMS to do the heavy lifting on that math.

 

[cornbinder89]

Here's the news: Nissan acknowledges there's something wrong, but they asked, and get this @knightmb, that I do three complete 100% to <10% discharge cycles, and charge only on L2, and then try to replicate the problem again. Haha, nice They were kind of surprised I was already aware of the procedure

They were also nice enough to offer to do it for me, but I'm not driving the Rogue anymore than I need to. Plus I'll get to document this as much as I want.

I'll obviously post back here whenever I can.

Correct me if I'm wrong, but all this about discharge- recharge is to get the BMS to map the battery more accurately, and will have ZERO effect on a bad cell or cells that are unable to keep up with the rest of the pack and cause the car to turtle or brick on the side of the road.
If you are diagnosing a real world problem like the car not being able to handle high draws (going up hill at speed) it is more or less useless to make the BMS more accurate.
If you are the dealer and need to justify saying there is nothing wrong, then getting an accurate read may be to their advantage. The gray area is when the battery is on the edge of being degraded enough to qualify for replacement, then an accurate BMS read could enter into it.
With that said, the OP is having the 1st problem not the 2nd. Afterall, the whole purpose of the BMS is to charge all cells to equalization and to shut down before a problem turns to a thermal run-away.