The 62kWh Battery Topic

[DougWantsALeaf]

The newer 2020 Leafs appear to take the full buffer in one go down to 92-93%, vs the incremental reductions seen with the 2018s and 19s. At 93%, you should be around that 56kWh of energy usable, which is what is commonly reported as the usable capacity.

[DaveinOlyWA]

The newer 2020 Leafs appear to take the full buffer in one go down to 92-93%, vs the incremental reductions seen with the 2018s and 19s. At 93%, you should be around that 56kWh of energy usable, which is what is commonly reported as the usable capacity.

So the LEAF Spy stats aren't showing true degradation? Interesting theory. By now, its obvious Nissan is manipulating the numbers for some purpose. I guess we will have to wait a few years before finding out if it worked. I am fairly sure you saw this, but there is a 40 kwher pushing 112,000 miles still 12 bars.

[DougWantsALeaf]

Yes, that's my theory. My guess it is based on amount of time at higher temps, actual capacity, and time since build (maybe miles too). Guessing there is some basic formula it is using on amount of buffer to hold.

My wager as well is that we will see very few bar losses before about 3 years and a few months for the 2018+ cars so that the cars coming off of 3 year lease can be resold at full bars. Guessing as well the BMS is also managing to minimize warranty claims.

It seems to be working. There are an increasing number of 100K plus 2018 Leafs now, and all appear to have full bars.

[Kieran973]

I have two things to report about my SV+ battery -- one which I interpreted to be good news, one bad news.

First, the bad news

I recently took my SV+ on a 290 mile trip from the NYC area to the DC suburbs. The trip down was easy and uneventful. Four days later, the day before I was to drive back to NY, I decided to check out one of the new 100 kW EVGo stations in northern VA (I was staying with family with no charging options other than L1 and wasn't going to get to 100% SOC by the following morning without a DCFC). I charged for about 30 minutes and was impressed to see that until about 60% SOC the SV+ was charging at around 70 kW. This was at about 3 PM. However, the following morning, we left for NY. Ambient temps were in the 50s and 60s and it was raining slightly. The battery temp display on the dash was at the exact mid point when we left. We drove 165 miles, averaging about 68 mph, to an EA station in southern NJ. We charged there for about 40 minutes at around 2 PM. But here's the thing: when we were done charging, the battery temp display had shot up to just one bar shy of the red zone. So why is this bad news? Well, if driving 165 miles in 50ish degree weather and then fast charging for 40 minutes can cook your battery that much, this simply can't be good for the long term battery degradation of this car. Imagine if it had been 85 degrees outside. Imagine if I'd driven closer to 200 miles. Honestly, I've been itching for EVGo to upgrade all their stations to 100 kW (they're allegedly all prewired for 150 kW), but now, I'm not so sure I want that. When I've driven my Leaf+ 160-180 miles in summer weather and then fast charged at a 50 kW EVGo station, the battery temp display has barely gone up. So it seems that there's a big difference in heat accumulation between charging the Leaf+ at 43 kW average for 30-40 minutes vs charging at 68 kW average for 30-40 minutes. Of course, it's possible that the reason my battery took on so much hear during this 70 kW fast charging session was because of the 70 kW fast charging session done 24 hours before. (Normally, on trips like this, I wouldn't fast charge two days in a row.) But if not, and if using 100 kW chargers adds that much heat consistently to the Leaf+ battery, then I'm just going to stick to 50 kW chargers.

Second, the good news

I just passed the 6 month mark on my Leaf+, though the car itself is a full year old since it has an 11/19 build date. (It's a 2019, but I bought it new for a big discount in early May 2020). Here are my Leaf Spy stats. I took a reading on two consecutive days at different SOCs to see what changes if any there would be:

11/3/20:
SOC: 48.8%
AHr: 170.90
SOH: 96.88%
Hx: 108.35%
GIDS: 368 (49.1%)
Remain: 28.5 kWh
Odometer: 5289 miles


11/4/20:
SOC: 81.0%
AHr: 170.90
SOH: 96.88%
Hx: 108.45%
GIDS: 612 (81.6%)
Remain: 47.4 kWh
Odometer: 5303

Why is this good news? My understanding is that more than any other factor (miles driven, number of QC's, ambient temps, frequency of time spent at 100% SOC, etc), the biggest driver of measurable SOH reduction in the Leaf during year one is simply time. And my Leaf+ is a year old and has apparently only lost 3.12% of capacity in its first year. Yes, this isn't the whole story, and perhaps those who know more about the implications of my GIDS, Hx, and AHr readings could chime in. And yes, while the car is 12 months old, I've only owned it for 6 months. But my sense is that the dealer neglected this battery in the usual Nissan dealer ways for the first six months of this car's life (one small example: I begged them not to charge it to 100% when I picked it up, and it was at 100% when I picked it up). And yet, SOH reduction is only 3.12%. I'm not sure why. I've definitely been driving less -- in non-pandemic times, the car would have had closer to 9,000 miles on it by now. And I've been pretty meticulous about keeping it as close to 50% SOC as possible. (For example, my wife takes it to work now, and we cycle it between 55% - 45% SOC most of the time, or 60% - 40% SOC when we get "lazy"). But I've taken it on several long distance trips to VA, MA, and NH, fast charging for 30-45 minutes on each trip leg (almost always on 50 kW chargers). During one of these trips, the car was in VA for 3 weeks during the summer where it lived outside at ambient temps in the 80s and 90s all the time. The car's also black and it's not always possible to park it in the shade. Anyway, I'm encouraged by this --- I was expecting a 6-7% drop in SOH after one year. Because if I really did only lose 3.12% this year, and if the biggest drop in SOH is during the first year, then annual SOH loss going forward may even settle down to around 2%, which I would consider pretty respectable.

[DaveinOlyWA]

I have two things to report about my SV+ battery -- one which I interpreted to be good news, one bad news.

First, the bad news

I recently took my SV+ on a 290 mile trip from the NYC area to the DC suburbs. The trip down was easy and uneventful. Four days later, the day before I was to drive back to NY, I decided to check out one of the new 100 kW EVGo stations in northern VA (I was staying with family with no charging options other than L1 and wasn't going to get to 100% SOC by the following morning with DCFC). I charged for about 30 minutes and was impressed to see that until about 60% SOC the SV+ was charging at around 70 kW. This was at about 3 PM. However, the following morning, we left for NY. Ambient temps were in the 50s and 60s and it was raining slightly. The battery temp display on the dash was at the exact midpoint when we left. We drove 165 miles, averaging about 68 mph, to an EA station in southern NJ. We charged here for about 40 minutes at around 2 PM and when we were done, the battery temp display was just one bar shy of the red zone. So why is this bad news? Well, if driving 165 miles in 50ish degree weather and then fast charging for 40 minutes can cook your battery that much, that simply can't be good for the long term battery degradation. Imagine if it had been 85 degrees outside. Imagine if I'd driven closer to 200 miles. Honestly, I've been itching for EVGo to upgrade all their stations to 100 kW (they're allegedly all prewired for 150 kW), but now, I'm not so sure. When I've driven 160-180 miles in summer weather and then fast charged at a 50 kW EVGo station, the battery temp display has barely gone up. So it seems that there's a big difference in heat build-up between charging at 43 kW average for 30-40 minutes and charging at 68 kW average for 30-40 minutes. Perhaps the high heat build up during the 70 kW southern NJ EA charge was influenced by the 70 kW northern VA EVGo fast charge 24 hours before, and normally on trips like this, I wouldn't fast charge two days in a row. But still, if using 100 kW chargers adds that much heat to the battery, I'm just going to stick to 50 kW chargers.

Second, the good news

I just passed the 6 month mark on my Leaf Plus, though the car itself is a full year old since it has an 11/19 build date. It's a 2019, but I bought it new for a big discount in early May 2020. Here are my Leaf Spy stats. I took a reading on two consecutive days at different SOCs to see what changes if any there would be:

11/3/20:
SOC: 48.8%
AHr: 170,90
SOH: 96.88%
Hx: 108.35%
GIDS: 368 (49.1%)
Remain: 28.5 kWh
Odometer: 5289 miles


11/4/20:
SOC: 81.0%
AHr: 170.90
SOH: 96.88%
Hx: 108.45%
GIDS: 612 (81.6%)
Remain: 47.4 kWh
Odometer: 5303

Why is this good news? My understanding is that more than any other factor (miles driven, number of QC's, ambient temps, frequency of time spent at 100% SOC, etc), the biggest driver of measurable SOH reduction in the Leaf is simply time. And my Leaf+ is a year old and has apparently only lost 3.12% of capacity in its first year. Yes, this isn't the whole story, and perhaps those who know more about the implications of my GIDS, Hx, and AHr readings could chime in. And yes, while the car is 12 months old, I've only owned it for 6 months. But my sense is that the dealer neglected this battery in the usual Nissan dealer ways for the first six months of this car's life (one small example: I begged them not to charge it to 100% when I picked it up, and it was at 100% when I picked it up). And yet, SOH reduction is only 3.12%. I'm not sure why. I've definitely been driving less -- in non-pandemic times, the car would have had closer to 9,000 miles on it by now. And I've been pretty meticulous about keeping it at close to 50% SOC as possible. (For example, my wife takes it to work now, and we cycle it between 55% - 45% SOC most of the time, or 60% - 40% SOC when we get "lazy"). But I've taken it on several long distance trips to VA, MA, and NH, fast charging for 30-45 minutes on each trip leg. During one of these trips, the car was in VA for 3 weeks during the summer where it lived outside at ambient temps in the 80s and 90s all the time. The car's also black and it's not always possible to park it in the shade. Anyway, I'm encouraged by this --- I was expecting a 6-7% drop in SOH after one year. Because if I really did only lose 3.12% this year, and if the biggest drop in SOH is during the first year, then annual SOH loss going forward may be around 2%, which I would consider pretty reasonable.

You are like 5, 10th? LEAF I've seen with a higher SOH that spent time on the lot. Actually could be more since so many 2019's were sold this Summer. I am guessing you will drop down to about 93ish % before your degradation rate slows way down. Pro tip; if you want to know your LEAF's birthday, record your LEAF Spy stats every day this month. Guessing you will lose 1% more or less but the day it starts its drop is likely the day your car was made.

Mine was built 10/19 and my car's Birthday was Oct 23. How accurate is that? Who knows but I say its probably real close if not dead on.

[DougWantsALeaf]

Ok, my theory here is that the algorithm for the extra buffer the battery keeps is based off of build date and as the car ages it keeps less of a buffer to keep a flat line of available capacity (or in other words SOH).

So when a car sits for 9 months or more, that buffer requirement starts coming down before the car is ever really used, allowing SoH to stay high.

Or maybe Leaf batteries just do better when aged first.

[DougWantsALeaf]

Well.... the bms giveth and it taketh away. This quarterly dropped me about .8% down to 93.93%, taking back what it gave last quarter. I have been DC charging this quarter vs. Prior using my nctc... I wonder if the DC count plays into the algorithm.

[GerryAZ]

Personally, I don't believe the LBC (Lithium Battery Controller or BMS for Battery Management System) is hiding or reserving any capacity on purpose. I believe it just calculates and stores (and Leaf Spy reads) capacity information based upon the periodic measurements it makes as the car is used. It does clearly update its capacity information four times per year (about every 90 days). My car was parked at my office while I was out of town for almost a month so my mileage the past 90 days was less than average and the periodic update happened while it was parked. I parked it in the morning on 9/29 at 21,777 miles with the following statistics: AHr=166.72; SOH=94.51%; Hx=101.93%; V=359.43; Gids=445; and highest battery temperature was 95.4 F. I returned in the evening on 10/27 to the following statistics: AHr=166.17; SOH=94.20%; Hx=101.93%; V=359.01; Gids=427; and highest battery temperature was 62.4 F. AHr and SOH have continued their gradual downward trend as I have been driving since my return. Here are the statistics for my periodic full discharge tests:

LEAF 2019 Battery Information 2.jpg

As you can see, present AHr is 94.85% of original, SOH=94.84% of original, Gids=96.85% of original, and latest charging energy from wall is 95.07% of first full discharge test after 22,049 miles and 15 months of use.

[DaveinOlyWA]

Well.... the bms giveth and it taketh away. This quarterly dropped me about .8% down to 93.93%, taking back what it gave last quarter. I have been DC charging this quarter vs. Prior using my nctc... I wonder if the DC count plays into the algorithm.

I doubt it. If I were to speculate, I would say the BMS analyzes our driving needs and tailors the pack to fit. If you drove less, it restricts more of the pack (SOH goes down) to increase longevity since the additional range is not needed. I know that sounds crazy but having the capacity go up is just as crazy so who is the craziest? Me or Nissan? Or is it simply planning for the future?

[DougWantsALeaf]

Actually one more observation. I didnt charge to 100% even once this past quarter, where I had the quarter before. I am wondering if like Tesla you need to charge to 100% every now and then to calibrate the pack.