Battery seems to be degrading fast

Bought my 2019 SV new in September of last year. I didn't learn of LeafSpy until November and when I ran the app my SOH was already down to 97.54 after just 2k miles and a couple months time. I have LS set up to send data to a server I run so it logs results automatically in a database. I then have some Excel reporting that charts the data out, you can see below. As of today, at just shy of 5k miles and about 5 months of ownership I'm already down to 93.83. Does this seem pretty accelerated? I never DCFC and I'm religious about not charging past 80% (to the point where I've built hardware and software that shuts off the pilot signal to the EVSE). I only charge to 100% for cell balancing maybe every 3 weeks and always right before a long drive. So I feel like I'm doing everything I can. I live in North Carolina and we haven't even hit the hot weather yet!

Am I worrying over nothing or does this seem like it's going to be a problem? Oddly, it seems wear had stabilized for a few months after a sharp dropoff in the beginning and lately it's been sinking like a stone. As you can see from the chart. No changes in my driving/charging habits. The range guess-o-meter has probably lost about 10 miles of range since new.

Please post a cell balance graph from LeafSpy. Yes, your battery does seem to be losing SOH at an accelerated rate.

As requested... It was never clear to me what all this meant, maybe you can explain.

Each vertical line represents the voltage of a single cell. If one or more of the lines is very much lower (or on rare occasions, higher) than the rest, that would indicate one or more likely bad cells. Yours looks fine.

OK thanks for that, makes sense. So what do we think is going on with my plummeting SOH? It's hard to make projections from this pretty erratic data, but keeping up at this pace the car (or at least the battery) will be in a landfill within a couple years it seems.

The battery warranty will get the battery replaced in a few years if this keeps up. Have you monitored how hot the pack is getting and staying? IIRC, you don't DC fast charge the car, so that isn't it. It's Winter, so there should not be loads of ambient heat... I honestly don't know what's up. You may have a defective battery.

I haven't made a concerted effort to monitor battery temps, I have pulled up the gauge just on the dashboard occasionally and it always seemed to be in the normal range. But I can make an effort to look at that more. But as you say, it's winter time and I never DCFC, always just L2. Once the 95 degree F days hit in a few months I can't imagine what's going to happen!

My understanding of the warranty is they only need to restore the pack to 9 bars, is that correct? I don't think I just get a brand new pack, but I could be wrong. I'm a little nervous about depending on the warranty program, even my dealer told me after the sale Nissan often finds ways to weasel out of honoring the guarantee :roll:

Todd1561 said:

OK thanks for that, makes sense. So what do we think is going on with my plummeting SOH? It's hard to make projections from this pretty erratic data, but keeping up at this pace the car (or at least the battery) will be in a landfill within a couple years it seems.

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The first 5% of capacity loss is usually fairly rapid. Don't panic!
At least yet.

Also, the BMS's estimate of SOH isn't that accurate. Capacity estimation isn't an easy problem, with out lab grade temperature controls and instruments.

Multiple factors can drive the estimate both up and down from the "true" value. LeafSpy reads out the BMS's estimate, there is no magic window on the side of a battery pack saying SOH.

Everyone so far has gotten a new pack.

I don't think that this is a case of the BMS just happening to be estimating on the low side of accurate every single time you measure the SOH. It is true that everyone so far who needed a warranty replacement has gotten a new pack when the issue was capacity loss. A few people with bad cells over the years have just gotten those cells replaced.

Re: the warranty rejections, that's just what my dealer told me as they were trying (unsuccessfully) to get me to buy an add-on warranty from them. Probably just some typical dealer smoke. Thanks for the input, I'll keep tracking it and see how bad it gets. If I wind up having to go the warranty route I'll post back how painful or not that becomes.

Unfortunately, it seems I'm right about the battery warranty. This text is straight from the 2019 Nissan warranty booklet :/

https://www.nissanusa.com/content/d...af/2019/2019-Nissan-LEAF-warranty-booklet.pdf

This warranty covers any repairs needed to return battery capacity to a level of nine remaining segments on the vehicle’s battery capacity level gauge. If possible, the lithiumion battery components will be repaired or replaced, and the original lithium-ion battery will be returned to the vehicle. If necessary, the lithium-ion battery will be replaced with a new, remanufactured or factory reconditioned lithium-ion battery. Any repair or replacement made under this Lithium-Ion Battery Capacity Coverage may not return your lithium-ion battery to an “as new” condition with all 12 battery capacity segments, but it will provide the vehicle with a capacity level of nine segments or more on the battery capacity level gauge.

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LeftieBiker said:

I don't think that this is a case of the BMS just happening to be estimating on the low side of accurate every single time you measure the SOH.

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It isn't possible to know. Driving habits change SOH estimate. As do charging habits. But both don't have a quick impact on real SOH.

Todd1561 said:

Unfortunately, it seems I'm right about the battery warranty. This text is straight from the 2019 Nissan warranty booklet :/

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Sure. But so far as I know only new packs have been used for replacement packs. Some packs with a bad cell or two had just those cells replaced.

Nissan is promising less than Nissan has delivered in the past on battery warranty.

WetEV said:

Nissan is promising less than Nissan has delivered in the past on battery warranty.

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That's great to hear, I always put more weight on real world experience anyway.

Todd1561 said:

WetEV said:

Nissan is promising less than Nissan has delivered in the past on battery warranty.

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That's great to hear, I always put more weight on real world experience anyway.

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Also, think about it - if they repair it just to the minimum and you still have 4 years left on your warranty, then they would have to do it again, and again.
As far as I read it, the warranty doesn't stop after the first repair.

BTW, I'm at 91.73% on a 2018 that I bought new abut 9 months ago.

The main reason that they don't replace cells for degradation claims is that the cells tend to degrade evenly. IOW they'd have to replace many or most of them just to get back to 9 bars. And yes, then they might have to do it again.

Todd1561 said:

I haven't made a concerted effort to monitor battery temps, I have pulled up the gauge just on the dashboard occasionally and it always seemed to be in the normal range. But I can make an effort to look at that more. But as you say, it's winter time and I never DCFC, always just L2. Once the 95 degree F days hit in a few months I can't imagine what's going to happen!

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Problematic battery temperatures not only result from ambient temperatures. You did mention DCFC, but internal battery heat is also
caused by the traction motor. At speeds greater than 60 MPH (flat terrain - 40kWhr Leaf) will start to raise the battery temperature even
when the ambient at 70 - 75F. Obviously even greater battery heat results from climbing long grades at speeds less than 60MPH.
It's less of a problem with the 60kWhr Leaf, i.e. bigger battery - less internal battery resistance.

About once a month we drive an hour of highway around 68 MPH (and then back), I guess that’s not helping. Pretty lame Nissan still hasn’t included battery temp management. Had I understood this important difference I highly doubt I would have bought a Leaf. Likely a Bolt or sprung the extra for a Tesla. I buy cars for the long haul, the Leaf just doesn’t seem to be built with that kind of buyer in mind. Combine this with them raising the cost of replacement batteries and it doesn’t seem like Nissan is too concerned with environmental impact of their cars. Which is the main reason I bought it to pair with my solar array.

Live and learn I suppose.

Driving at 68MPH in cool weather isn't overheating your battery. You have an unusual, at present unknown problem with it. I would suggest watching the temp bar screen anyway, as it's not impossible that you have a defect in manufacturing that is causing the battery to get hot for no external reason. That will at least let us rule that out.

Sounds good, I’ll keep the temp gauge up especially on my next long interstate drive to the in-laws. I did notice that after I got back from my last trip was the last time I saw a substantial drop in SOH. Hey if nothing else, this car will be a decent excuse for me not to see my in-laws so often!

Thanks everyone for chiming in providing their experience and knowledge.