And your speculation that charging just short of 100% is essentially harmless doesn't jibe with what is known about lithium batteries. With the optimal storage charge somewhere close to 20%, charging to 98% instead of 100% isn't likely to be the solution.
2016-2017 model year 30 kWh bar losers and capacity losses
- Thread starter cwerdna
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DaveinOlyWA
Well-known member
GrowingTuna said:
Thanks for the input but not mentioning the dealership by name is CRIMINAL! They should be avoided at all costs! Your pack should have read 82.34 ahr. That 100% means nothing. I have LEAF over a year old with 26,000 miles on it with ahr as low as the mid 79's, Hx as low as 95.35% and still 100% SOH...
And yes heat is a killer but the worst is heat, high SOC and Time. Heat you can't change but the rest you can. Don't charge up unless you can do it quickly and drive immediately. IOW; you are better off to QC in the middle of noon day Sun if you are driving right away.
Lets play two scenarios; In both the parking lot temps are say 100º which should be typical for you. Both cars are at 30% SOC and you need a minimum of 70% to get home.
Scenario one; You have workplace charging and as luck would have it; you have a slot from 2 PM to 5 PM that covers the last 3 hours of your work day and its 6 KW level 2 charging. After the charge session is over, you have added a few degrees above ambient to your battery pack but it charges to 90%. This is one of the issues with workplace charging. In most cases, flexibility is not always a given.
Scenario two; you stop and QC a few miles away after work for 20 mins. Your pack finishes 15º above ambient and you charge to the same 90% SOC.
In Scenario one despite being a cooler charge, you still expose your car for a several hours at higher SOC. What is too high? Well, that is temp based and when its warm "some" level of degradation will happen all the time. So its a given that 60% is better than 70%, etc.
In Scenario two despite much hotter batteries, you exposure is now no more than what? Half the charge time plus maybe 20 mins of drive time and you are back below 70% SOC.
Get the picture? But that is only half the story. Its my (much disputed) claim that "hot" is no more than the 80's if the SOC is high enough. Again; how high is that? Good question but was unable to gather enough data to make anything other than a guess so if filling in very large gaps
100% SOC (per car or 97.7% SOC if you prefer) the significant start at 80º so best practice is use buffer. Don't do it over 70º Unless you plan to drive off immediately. For some; that may mean not charging to full at home all Summer long. How crazy is that?
Well, it is pretty crazy and for 6 months; that is EXACTLY WHAT I DID. and drove the car 26,100.2 miles in 365 days at the same time
Remember; the numbers provided are just guesses based on a very randomized data provided by this forum and others. so the "80º" or the "70º" has only casual comments to back it. Comments from here.
GrowingTuna
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Of course, but if I'm only QC to 80%, would this be such a cause for concern? It's my understanding that the damage from high SOC comes when you are charging the battery to full or nearly so. Heat compounds the damage, as well as time sitting at such a high charge. If leaving my car at 80% charge overnight is a concern, that's news to me.
As an aside -- I have noticed that my 30 kWh pack seems to cool much, much slower than the 24 kWh packs were reported to. I've seen others mention this as well. It seems as though when I QC during the day with ambient temps 80+, the pack will never cool down even if I'm driving it around. Only way to cool the pack is wait for the temps to drop at night.
Regarding the aHr -- is 80.6 after a few months on the lot really that egregious? Hx was 96.39 as well when the car was picked up. Honestly hadn't given it much thought, especially given how poor degradation others are reporting. Especially given that the aHr bounces around. Are most people getting cars off the lot with an Ahr of 82+?
arnis
Well-known member
GrowingTuna said:
Correct. Trying to peppy the battery makes almost no difference in terms of Rapid Unscheduled Degradation.
L1; L2; L3 - doesn't matter. Few hours 10 degrees hotter due to QC session - doesn't matter.
No. This only has a cycle degradation. This is hardly a 1-2% per year (that is what my Leaf does mostly).
Damage happen not due to charging, but due to cells being charged.
50% charged is better than 60%, is better than 70%, is better than 80%. And anything above that is already charted territory.
When you got your Leaf, BMS did not recalculate SOH, Hx values. It requires considerable discharges for BMS to notice capacity.
BMS calculates battery capacity looking at the voltage while counting how much juice has been used/added. Above 50% charge
state voltage is pretty constant. Therefore no good capacity valuation can be done.
When you got your vehicle, it was already degraded. BMS just didn't know that. Until you showed it to BMS.
If it wasn't a lease, I would return the vehicle immediately. Because it was not stored according to manufacturer's recommendations.
Though now you know what will happen with your vehicle, if you charge it to 100%. Add around 1-2% extra degradation due battery cycling to that two digit number and you get expected degradation when used and immediately charged to 100% when not.
PS: 100% on a Leaf is around 4.14V. 100% on a Tesla is 4.2V. Tesla's 100% selection defaults back to 90% after some period.
Nissan knows that their battery is s*it in heat. They don't even allow higher SOC to begin with.
We, (you guys in hot climates), can only voluntarily go lower.
BS. You don't need to have extensive analysis of banana yoghurt shelf life if you have that analysis for cherry yoghurt just to estimate
how long will it last in a fridge and how long next to keyboard and mouse :lol:
Definition of speculation is "the forming of a theory or conjecture without firm evidence." We have evidence that milk products spoil faster at room temperature compared to fridge. We have evidence that Leafy flavor spoils faster than Musky flavor.
There are joghurts that do not spoil, but our version definitely does spoil.
Suggesting keeping joghurts in the fridges is transparently sensible. Suggestion to charge to lower SOC also.
Flavor plays a role at the rate. Not on the direction of capacity slip.
What is on the other hand speculation, is that keeping Leaf's cells at 3.0V will degrade them faster, compared to, lets say 3.1V.
DaveinOlyWA
Well-known member
GrowingTuna said:
Its temperature dependent. The only thing I see as certain is that the danger temperature range is not as high as we want it to be.
But the key is getting away from "As long as the SOC is XX or less, I am ok" especially temperatures are not considered.
But back to the basics. Can't change temperature and the car is there for a specific purpose. That purpose overrides everything else. Its my take that if you can get away with charging to 60% then do that especially when its hot. The "magic 80% SOC" quite simply failed us but to what degree is a mystery due to vastly different charging habits.
To put it another, simpler way: pack temperatures of 6 bars or higher are to be avoided if possible, regardless of SOC. Heat all by itself is a problem.
jbuntz
Well-known member
80Ah is pretty good compared to my 2016 that was about 72Ah at delivery.GrowingTuna said:
GrowingTuna
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arnis said:
Aha -- I hadn't considered that. So it's very likely that degredation was substantially worse than the BMS was reporting. Still, this seems to be within the typical levels of capacity loss we've seen reported.
I leased the vehicle; I did my homework before getting the car and assumed degredation would be an issue. I wonder how worried Nissan is about this. Seems like this was a terrible pack to offer an 8 year warranty against degredation loss. And if the cooling issues with the 30kWh pack are (at least in part) due to the increased density as I've seen suggested quite often, it makes me wonder if this problem will be even worse in the 40 kWh pack. :shock:
arnis said:
You appear to have a limited ability to structure a rational analogy. Maybe try using a coherent thinking process if it's possible,
e.g. like you may have learned in a middle school logic class.
Surely you've done a full research on the effects of charging to 100% versus a lower value as it relates to degradation for the Leaf's battery,
and have corroborative data since you're so resolute. And how about a real controlled study as for charging to 90% versus 100% over time,
and not your guessing or someone's anecdotal "experience". Again, please fully quantify the degradation delta, i.e. additional loss
in SOH per year. Additionally, please reference and fully annotate your research sources and concussions specific to the Leaf's battery
as it relates to and supports "your theories". Furthermore, data relative to the Leaf's battery versus Tesla's battery is the concern
on this forum, either in tabular or graphical form would be ideal.
Oils4AsphaultOnly
Well-known member
lorenfb said:
How about you stop preaching your sermon and respond to my figure 6 from the battery university? http://mynissanleaf.com/viewtopic.php?f=30&t=23606&start=520#p510669
That's a controlled study showing that cycling the battery from 100% SOC down to 50% is worse than cycling from 75% down to 25%. Instead of ignoring it, why don't you provide a fully detailed study backing your claim?
Save your breath for another debate.Oils4AsphaultOnly said:
Lorenfb is going to tell you that the formulation in the Nissan battery is different and the results may not apply.
Thermodynamics says that unwanted chemical reactions are going to proceed at faster rates as the temperature and SoC increases so your data is qualitatively correct and applicable, but the nitty gritty details of how much are uncertain.
So you are both right, but for different reasons.
hyperionmark
Well-known member
Yet another thread ruined by people getting so worked up about being right. And we wonder why we have all sorts of issues in this country when even a thread about batteries has us insulting each other. Has to be a better way.
ironmanco
Well-known member
hyperionmark said:
Another point to make here is that the biggest impact we can have on battery issues for the Leaf is to educate ourselves on best practices for charging, storage and driving. Unless we plan on joining the engineering team or filing suit against Nissan, it would seem that an extraordinary deep dive into the 30kWh battery would not be very beneficial. From a purely interest and educational aspect there may be some merit, but when it comes right down to it, I would imagine that the typical Leaf driver wants to know best practices for battery longevity. Granted, this is driven from the deeper understanding of how the battery operates, but using anecdotal, correlative and transitive data and experience seems like a great start rather than waiting for definitive data based on the death of a couple hundred thousand 30kWh batteries.
The poster on this called it "surge driving," IIRC, so you could try searching for that. Last thing I remember seeing, he reported something like "my numbers are in free-fall, and no amount of surge driving will bring them back," so it sounded like the "increase" in SOH was temporary, based on gaming the algorithm with a lot of high-throttle/high-regen cycling, and that eventually the calculation caught up with him and started to decline to the "true" SOH.ironmanco said:
DaveinOlyWA
Well-known member
Oils4AsphaultOnly said:
all this would be easier if Battery U would create experiments based on their own observations.
A single degradation chart run at a single temperature range puts us exactly where we started from giving us info we already knew.
Oils4AsphaultOnly said:
From your reference:
That's the generic basics. We really don't know the actual battery cell voltage characteristics in the Leaf's battery and how the BMS is
programmed to control/limit the cell charging voltage, and thereby avoiding potential degradation.
As expected, the battery chemistry affects the cell voltage and where 100% SOC occurs, which implies that avoiding true 100% SOC
can be avoided by how the BMS is designed. So a BMS may report 100% SOC for a Li ion EV application, but actually not fully charging
the battery to what might be actual 100% SOC, thereby compromising a few miles of range but protecting the Li ion battery. It's likely
that this maybe the case for the Leaf. So without actual battery cell test data from the Leaf, and not applied generic data, it's speculation
to conclude anything meaningful about SOC charging for the Leaf and its effect on degradation.
Oils4AsphaultOnly
Well-known member
lorenfb said:
That's not quite true.
At 363 GID's (when I still had it), the pack voltage read 395.13, which gives us a cell voltage of 4.116, At my most recently balanced full charge (348 GID's), the pack voltage read 395.44, giving a cell votage of 4.119.
So that's the max that the BMS is set to charge the cells to. That's pretty close to the voltage characteristics of the batteries used by battery university, making their data-set pretty applicable.
You once claimed to have data proving that a high SOC didn't affect battery life, but I don't recall seeing it. Would you mind pointing me to it?
Oils4AsphaultOnly said:
Right, but the Leaf's 100% SOC voltage still maybe below where the actual problematic charging voltage occurs resulting in significant
degradation, e.g. 10%.
Oils4AsphaultOnly said:
I've never stated nor implied that I had any actual data. I've always argued that actual Leaf battery cell characteristics/data were lacking to
conclude or recommend any optimum charging mode.
ironmanco
Well-known member
lorenfb said:
Maybe not "optimum" but I think there is PLENTY of data and experience to recommend best practices for charging. Are we really shooting for the optimum or at least some basic methodology better than willly-nilly charging?
In other words, it is worth waiting around for complete and definitive testing that will guide us in an absolute approach to charging as compared to applying some general guidelines for charging based on what we currently know/understand?
Just because I don't know if something is completely and absolutely the right approach doesn't mean I won't at least try it. The most important part of that logic is if I apply some of these basic battery maint guidelines would actually be more detrimental vs. beneficial? if your answer to that is no, then I would think that they're worth following.
To extend this logic - just because I don't know the absolute impact of leading a sedentary lifestyle doesn't mean I wait around being sedentary until proven otherwise
