Rapid charge loss

[cwerdna]

In LeafSpy pro, does anyone know what is considered a bad mV difference between max and min? I get 97mV difference at 86% SOC

That sounds way too high for that high an SoC. I wouldn't even expect that down at 40% SoC.

IIRC, when my '13 is at rest (no extra sag from acceleration) sitting in READY mode and say at above 40% SoC, I don't think I've seen my max mV difference be more than 20ish or 30ish mV.

I could see it getting above 100 mV if you were really low (at or below VLBW, the 2nd warning). I've mentioned what Turbo3 told me numerous times like at https://mynissanleaf.com/viewtopic.php?p=516652#p516652.

I have yet to run my current Leaf super low to observe it on Leaf Spy and it's actually hardly driven at all now.

However, I noticed you mentioned you got a cell replacement. That might be the source of the high imbalance now, if one cell/module is much higher than the others. https://www.mynissanleaf.com/viewtopic.php?p=458196#p458196 and a few posts before it were after Biggiejohn got a module replaced.

 

[DaveinOlyWA]

In LeafSpy pro, does anyone know what is considered a bad mV difference between max and min? I get 97mV difference at 86% SOC

Bad

 

[Jerther]

Hi! Sorry to bring that old topic back up. It's one of the first results on Google for this problem, which I had just this morning.

I drive a 2018 SL LEAF since may this year. So 4 months. I love it, but this morning I had the sudden charge drop on the highway and I had one heck of a panic attack. Seeing the charge drop from 20% to 0% in one minute with all the warnings and sounds in the middle of nowhere is no fun.

So I had pretty much the same thing happened to me as the OP: 75MPH, heater ON, outside temp 5C, going up a hill. State of charge started climbing once I got to the top of the hill and for a minute or so, until it got to 18%. I could safely get to work, no problem. I took a screenshot of the battery graph in leafspy.

After reading this thread, one question remains: is this by design, or is it a problem with the battery that's worth an argument with a dealer?

 

[MikeinPA]

Here is what i think. The LS screenshot looks like good--even excellent-- balance for cells at around 3.50 volts. These are older cells, with higher resistance, and there will be some fade at 75 mph and going up hill. You are pulling a lot of amps and the voltage is going to sag, especially for a cold battery at the lower end of SOC. As it sagged down to 3.3 volts or lower, the car thinks the battery is near empty. Warnings are given.

Ideally you could just look at LS while going up the hill, or collect a log file--but some people worry about having aftermarket products hooked up to the can bus especially at highway condition. What you are trying to observe is the percent charge diving and then springing back almost instantly one the pedal is lifted. Is this a resistance heater as well? Anyway, very much doubt Nissan would see this as a defect, just normal aging.

 

[DaveinOlyWA]

You have a weak cell and it appears by your LS screenshot, you will only see it when the car is under a heavy load. I am surprised you aren't throwing codes...

 

[MikeinPA]

You have a weak cell and it appears by your LS screenshot, you will only see it when the car is under a heavy load. I am surprised you aren't throwing codes...

Could be this as well. Need to watch LS under load. And report back please.

 

[Jerther]

Thanks for the replies! I really appreciate it

I had another run this morning. Similar outdoors conditions, but this time I went only 65mph, and started at 80% charge. No problem.

I understand the batteries on these EVs operate pretty much like ordinary drill batteries. When near empty, they still hold plenty of juice but ask too much and they collapse. Like a previous user said here in this thread, if this is by design on an EV, I would think the electronics on an EV was smart enough to detect that condition and show a proper message instead of throwing panic inducing alarms and beeps.

I have no DTCs. I had one once, but it was for the front camera being unplugged. It was the only code the dealer caught in the last recall, and I fixed it.

I'll take a screenshot of the cells under heavy load. Do the SOC and temperature matter?

EDIT: I think I understand the situation, if it is caused by a bad cell. The car somehow reports the remaining charge according to the cell with the lowest charge, and if one is bad and does not hold charge as much as the others, that cell drops sooner compared to the other cells, and the dashboard suddenly goes crazy. So to prove this I would have to take a screenshot during the worst conditions: cold, somewhat low charge, heavy load. It's scary though! Is it safe, as long as the car does not enter turtle mode?

 

[Jerther]

Here's what I've been able to capture at lower SOC (maybe not low enough, but that's what I've got for now.) We haven't had any cold weather since my original message, and the weather was actually quite nice on the day I took the screenshots.

1- On highway, pedal to the floor, 75 mph
2- same thing as 1, but some time later
3- At destination, fully stopped.

No code, no suddent drop of SOC or anything. Winter's gonna come sooner or later, so I'll have plenty of opportunities to take screenshots while the car plays tricks on me, if needed.

 

[LeftieBiker]

Alas, Nissan will only accept error codes (DTCs), not LeafSpy information of any sort, in determining if there is a problem that the warranty covers..

 

[DaveinOlyWA]

Thanks for the replies! I really appreciate it

I had another run this morning. Similar outdoors conditions, but this time I went only 65mph, and started at 80% charge. No problem.

I understand the batteries on these EVs operate pretty much like ordinary drill batteries. When near empty, they still hold plenty of juice but ask too much and they collapse. Like a previous user said here in this thread, if this is by design on an EV, I would think the electronics on an EV was smart enough to detect that condition and show a proper message instead of throwing panic inducing alarms and beeps.

I have no DTCs. I had one once, but it was for the front camera being unplugged. It was the only code the dealer caught in the last recall, and I fixed it.

I'll take a screenshot of the cells under heavy load. Do the SOC and temperature matter?

EDIT: I think I understand the situation, if it is caused by a bad cell. The car somehow reports the remaining charge according to the cell with the lowest charge, and if one is bad and does not hold charge as much as the others, that cell drops sooner compared to the other cells, and the dashboard suddenly goes crazy. So to prove this I would have to take a screenshot during the worst conditions: cold, somewhat low charge, heavy load. It's scary though! Is it safe, as long as the car does not enter turtle mode?

Glad to see you found out the real reason because your EV does not work like a drill battery that has 4 cells (or less) Your EV has many cells and the load on each cell is relatively small as long as they are balanced. But the issues you see are triggered by the LBC which monitors voltage and triggers a fault when one cell hits the low voltage parameter.

 

[Stanton]

Here's what I've been able to capture at lower SOC (maybe not low enough, but that's what I've got for now.) We haven't had any cold weather since my original message, and the weather was actually quite nice on the day I took the screenshots.

You definitely have a weak and strong cell...but the delta is not that bad yet. My advice is keep an eye on it as 40 kWh packs are notorious for weak/bad cells/modules (I had a bad module and replaced it--now it contains my strong cell). As mentioned, you won't get any help from Nissan unless it throws DTCs...and that won't happen until you see deltas of hundreds of mV (at which point you will have severe problems at lower SoC).

 

[Jerther]

Okay! So I'll keep an eye on this. At some point I may try to force the DTC while the battery warranty is still on, as I've read in another thread. I understand the weak cell may not be weak enough to throw a code yet.

Thank you very much for your advices everyone

 

[Jerther]

Update: DTCs aren't enough. Here are a few things I wish I knew:

While riding to work today, the SOC went from 40% to --- in like 15 seconds, and then I've had the car suddenly forced into neutral while the dashboard was lit like a christmas tree, leaving me stranded on the side of the road. No amount of off and on again would change anything, so I left it off. I called a towing, but in the 20 minutes it took to arrive, I turned the car back on and to my surprise, all the warnings were gone like nothing ever happened and the SOC was back to 41%. So I took the car to the dealer on its own power and they told me they had to follow a Nissan procedure. It implies the battery being between 40 and 50%, and then taking it for a spin under load. Well, they did, but since the outside temperature went from -5C to +10C, the problem did not occur, and so they had insufficient data.

We agreed that I should take the car in again, with the battery already at about 45%, while the forecast is cold enough.

I'm not sure they'll charge me this time, but I certainly had to pay for the towing. The dealer told me to keep my receipts.

So even though Leaf Spy reports a nice State of Charge, if the car says there's no power, it WILL force itself into neutral at some point. But then if you give it some rest, it'll come back on again just fine. So wait a bit before you call a towing.

To be continued...

 

[DaveinOlyWA]

SOC is the least valuable part of the equation.

Pack balance is the canary here. This event should have triggered a weak cell warning in LS.

 

[Jerther]

It is very valuable for me because the problem won't occur with any significance at SOC over 50%, and I highly doubt Nissan will consider a warning coming from LS...

Anyway, I think a warning to state the obvious is quite irrelevant at that point. I did read the DTCs while I was waiting though. I've never seen so many at once. It looks like the whole car suffered a stroke. Before the event, there were only codes for the TPMS (APM).

 

[DaveinOlyWA]

multiple codes are normal when a failure to start happens. Most only know that a request to start did not provide the expected result to their function.

Just like the "christmas tree" display. No, everything didn't break.

 

[Jerther]

Here's an update. I went to the dealer yet again yesterday since it was -15C outside and I almost got stranded again on a hill at 85% charge. They couldn't replicate the problem but they offered to keep the car and try again early this morning and finally they replicated the problem. They gave my car back and said they'll call me in a few days for the next steps.

I asked how they replicated the problem (so I could understand why it was so hard) and they said they had to accelerate the car from 0 to 80 Km/h to put some load on it. And of course, between 40 and 50% charge. Well it happened to me only on the freeway so...

Anyways, to be continued.

 

[Jerther]

Update: I just hung up with my dealer. They called to tell me they received my new battery, and were almost sorry they couldn't install it before the holidays. Not even two weeks

So I'm getting a new battery! Is there something I could do before and after they make the switch? Something that would be helpful to people here like logs from LeafSpy, screenshots, tests, anything?

Update jan 9th 2024: I got the new pack installed yesterday.