The 40KWH Battery Topic

golfcart said:

danrjones said:

So we have three 2018's with various mileage (you didn't say yours but I'll guess its not the same) and all three are showing similar SOH.
91.8%, 93.14% and 93.71%

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I'm currently at only 11000 miles. The car sat on the lot for over a year (presumably at a high SOC) before I leased it.

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Exactly the same as me, and it sat around at a very hot dealer location and I've been using it in a very hot location. I've got 3090 or so as of this AM, so a lot less miles. So two examples of low mileage and three examples of higher mileage and almost exactly the same battery stat.


92.23% SOH @ 25185 miles / Cool (?) Climate (WA)
93.71% SOH @ 11000 miles / Moderate (?) Climate (VA)
93.14% SOH @ 3090 miles / Hot Climate (CA)
91.80% SOH @ 2843 miles / Cool (?) Climate (NY)
93.07% SOH @ 19807 miles / Mild Climate (CA)

Another data point, Built & bought in Sept 2018, currently 19,807 miles with a SOH of 93.07% Garaged & driven in the 93422 zip code if you want to look up weather.

Typically keep the pack between 30-80% & have done 5 QC session in the last 4 months but those are 1/day(week rly) & only are adding about 40-50% charge. My pack is almost never above half on the temp bar & basically only after a very hot day or 2-3 of those QC sessions

DougWantsALeaf said:

My wager is the BMS is managing down the pack to give it the best chance to stay at or above 70% at the 8 year mark (or 100K miles). I wonder if pulling it down a bit quicker than natural decay helps preserve the battery a bit better.

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A decay rate of 0.4 A-hrs per month over 8 years ends up at 67% capacity, so that is a very good bet.

Could be that the rate is higher when the pack is new and then levels off somewhat as time passes to squeak in above 70% at the 8 yr finish line.

Worrying about GIDs or Health or SOH or any other of these artificial made-up values is just numerical mathturbation. The only number that matters is Capacity in A-Hrs.

Worrying about GIDs or Health or SOH or any other of these artificial made-up values is just numerical mathturbation. The only number that matters is Capacity in A-Hrs.

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All of these numbers are provided by the BMS, so they are all subject to questioning. Until 2016 at least, the SOH has been a reliable indicator of pack capacity. That may still be the case...or not.

LeftieBiker said:

Worrying about GIDs or Health or SOH or any other of these artificial made-up values is just numerical mathturbation. The only number that matters is Capacity in A-Hrs.

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All of these numbers are provided by the BMS, so they are all subject to questioning. Until 2016 at least, the SOH has been a reliable indicator of pack capacity. That may still be the case...or not.

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Point well taken. Until someone loses a bar and has a leafspy report to go with it we will not really know, or unless someone thinks they have definitively lost real range.

LeftieBiker said:

Worrying about GIDs or Health or SOH or any other of these artificial made-up values is just numerical mathturbation. The only number that matters is Capacity in A-Hrs.

Click to expand...

All of these numbers are provided by the BMS, so they are all subject to questioning. Until 2016 at least, the SOH has been a reliable indicator of pack capacity. That may still be the case...or not.

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I track both SOH% and Ahr, if you look at the table of values I post you'll notice that they change by exactly the same percentage each time I record them. I think that this shows 100% SOH = 115.44 Ahr and that SOH is just likely a percentage of the remaining Ahr relative to that 115.44 value. So take your pick which one you want to report, I don't think it matters...

As to the accuracy of these values, I can't vouch for that.

That's essentially my point as well. All LeafSpy values come from the BMS. We have no precise way, other than less than precise charge capacity and range tests, to absolutely verify the values.

I agree that ahr is a truer measure of capacity "changes" so knowing where the pack started is paramount since no two are created equally, yada yada...

But charge capacity can be measured by GIDs (as long as setting isn't changed) and kwh available at full charge. Both also require knowing new pack parameters.

But unlike my previous 3 LEAFs, the SOH is actually being VERY accurate to what the ahr is stating. I don't have any recent full charge stats to use but if going by last one back from July/August for Dungeness Spit hike, I had 35.6 kwh from 38.3 when new or 92.95%

I was at 92.55% at the time. Now, the full charge capacity is somewhat derived since I never got consistent figures so its an average based on full charge SOC of 97.7% which is the norm (I had one charge at 99.2% :shock: )

Using ahr, I ended with 106.47 ahr from a start of 115.05 ahr or 92.54%

So the only question is Hx which was hovering around 114 for me but has risen slowly over the past month or so cresting 117?

nlspace said:

DougWantsALeaf said:

My wager is the BMS is managing down the pack to give it the best chance to stay at or above 70% at the 8 year mark (or 100K miles). I wonder if pulling it down a bit quicker than natural decay helps preserve the battery a bit better.

Click to expand...

A decay rate of 0.4 A-hrs per month over 8 years ends up at 67% capacity, so that is a very good bet.

Could be that the rate is higher when the pack is new and then levels off somewhat as time passes to squeak in above 70% at the 8 yr finish line.

Worrying about GIDs or Health or SOH or any other of these artificial made-up values is just numerical mathturbation. The only number that matters is Capacity in A-Hrs.

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Yes, as is the case with any type of battery. It's as simple as that.

This might be a dumb question but how exactly does the car know its own A-Hrs capacity?

I mean without actually charging up to a true 100%, which it doesn't let you do, or emptying to a 0% state, which it also doesn't let you do?

Do they have a high and low voltage benchmark in between 100% and 0% that it then uses to estimate the A-Hrs between those two voltage benchmarks, and uses that to estimate the full capacity? Because as we have all seen it looks like their is an algorithm to artificially lower your capacity every day or two and then "catch-up" about every 3 months.

danrjones said:

... how exactly does the car know its own A-Hrs capacity?

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Within the Battery Junction Box located inside the Pack there is a bi-directional Current Sensor. This sensor constantly measures all current going into or out of the pack such as occurs during charging or driving.

The Lithium Battery Controller (LBC) records this measurement at a really high speed such that it can perform calculations and report the average current value to the Vehicle Control Module (VCM) over the CAN buss at about 100 times a second.

The 24 kWh pack has 96 pairs of 30 A-Hr cells, so the nominal capacity is 60 A-Hr; multiply this by 3600 seconds/Hr to put it in terms of electron charge as 216,000 Coulombs in a full pair [1 Amp is 1 Coulomb per second]. Use the corresponding cell data for the 40 or 62 kWh packs to get those.

So by measuring the current over time they are essentially counting the number of electrons. And by keeping a running tally the LBC knows how full the pack is (i.e. the capacity) at any given time.

danrjones said:

This might be a dumb question but how exactly does the car know its own A-Hrs capacity?

I mean without actually charging up to a true 100%, which it doesn't let you do, or emptying to a 0% state, which it also doesn't let you do?

Do they have a high and low voltage benchmark in between 100% and 0% that it then uses to estimate the A-Hrs between those two voltage benchmarks, and uses that to estimate the full capacity? Because as we have all seen it looks like their is an algorithm to artificially lower your capacity every day or two and then "catch-up" about every 3 months.

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The LEAF does have a meter to track it but there is still some estimation going on. If you have LEAF Spy, you will see the ahr on the cell voltage screen and that is the theoretical maximum. There is another screen that shows you the current ahr. Supposedly at full charge, these two numbers will match. I have never seen that. I think you have to have all cells perfectly balanced for that to happen which is all but impossible.

Final 40 kwh stats. Some good, some not so good but one thing was very clear; it was cheap to operate!

https://daveinolywa.blogspot.com/2019/11/november-2019-drive-report-another.html

I just did a Leaf Spy reading after (roughly) 6 months of ownership on my 2019 SV. The results are not encouraging. It would seem I've already lost 5% capacity.

Purchase date: 4/30/19. Build date: 02/2019.

Leaf Spy Reading: 11/23/19
Odometer: 10,448

AHr: 109.77
SOH: 95.09%
Hx: 112.95%
GIDS: 387
SOC: 79.7% (dash says 81%)
Remain: 30.0 kWh


My daily charge is to 60%. My wife and I do use the Leaf as much as possible - we use it for about 85% of our driving (17,000 miles a year projected) and only use our Honda CRV for about 15% of our driving (3,000 miles a year projected). And I did take the Leaf on several medium range road trips this summer and fall - NYC to Boston and back 4 times, NYC to D.C. and back once - during which I obviously QC'd, but I never drove more than 200 miles in one day and never QC'd more than twice in one day. So I'm hoping that this apparent 5% capacity loss in 6-7 months time can be explained by Leaf Spy's supposed 3% margin of error. Otherwise, unless there's a serious drop off in the degradation rate, I'm on track for 10% capacity loss in the first year.

I do, however, still love this car.

I was at about 4% loss after 6 months, but the BMS stopped updating for the Winter, and when it did resume in the Spring the total loss was only a bit under 5% - for the year.

Looks like 5-7% loss in first 12-15 months is quite the norm. The real question is what happens after that. I lost LESS than one percent from month 15 to month 21. This covered all Summer and several stints of battery baking. The car has moved on (probably didn't like me abusing her ) and I have a new pack to tortue. I am expecting the same; higher degradation rates initially, settling down in a year or so.

Being a larger pack with the associated easier cycling should make a difference but I am expecting the difference to be small so I will predict 5% after a year. We have 50 weeks and 5 days to wait to find out

LeftieBiker said:

I was at about 4% loss after 6 months, but the BMS stopped updating for the Winter, and when it did resume in the Spring the total loss was only a bit under 5% - for the year.

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DaveinOlyWA said:

Looks like 5-7% loss in first 12-15 months is quite the norm. The real question is what happens after that. I lost LESS than one percent from month 15 to month 21. This covered all Summer and several stints of battery baking. The car has moved on (probably didn't like me abusing her ) and I have a new pack to tortue. I am expecting the same; higher degradation rates initially, settling down in a year or so.

Being a larger pack with the associated easier cycling should make a difference but I am expecting the difference to be small so I will predict 5% after a year. We have 50 weeks and 5 days to wait to find out

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All good points. If after 2 years, I could stay above 90% SOH, then settle down into a sub 4% average annual capacity loss rate, that wouldn't be too bad....

I should be coming up any day now on my next "big" update; however, if as others suggest BMS stops in the winter, maybe not. My SOH has been stuck for awhile now - although the HX is climbing rapidly. I find that odd. My HX had started downward this fall/winter until I did a single fast charge a few weeks back, then it has climbed steadily. I have filtered out any data where I had more than two readings - ie, got rid of any in between data, that were triplets or more.



Date SOH AMPHr Hx
05/03/2019 97.63 112.70 97.50
05/06/2019 97.62 112.69 97.94
05/07/2019 97.61 112.68 98.03
05/10/2019 97.60 112.67 98.39
05/13/2019 97.59 112.66 98.55
05/15/2019 97.58 112.65 98.73
05/19/2019 97.57 112.63 98.84
05/27/2019 97.55 112.61 99.27
06/01/2019 97.53 112.59 99.61
06/04/2019 97.50 112.55 100.12
06/11/2019 97.44 112.48 101.03
06/12/2019 97.43 112.47 101.25
06/13/2019 97.42 112.46 101.25
06/14/2019 96.49 111.39 101.58
06/15/2019 96.28 111.15 101.58
06/16/2019 95.64 110.41 101.67
06/17/2019 95.42 110.15 101.82
06/19/2019 95.40 110.13 102.15
06/20/2019 95.38 110.11 102.25
07/15/2019 95.19 109.89 103.22
07/24/2019 95.10 109.78 104.04
08/11/2019 94.90 109.55 104.95
08/30/2019 94.73 109.36 106.05
09/05/2019 94.68 109.30 106.27
09/10/2019 94.65 109.26 106.45
09/11/2019 94.64 109.25 106.48
09/12/2019 94.50 109.09 106.47
09/13/2019 93.73 108.20 106.48
09/14/2019 93.30 107.71 106.45
09/15/2019 93.29 107.69 106.45
09/17/2019 93.28 107.68 106.42
09/19/2019 93.27 107.67 106.41
09/23/2019 93.25 107.65 106.25
09/29/2019 93.23 107.62 106.50
10/16/2019 93.19 107.58 105.56
10/21/2019 93.19 107.58 105.34
10/23/2019 93.18 107.57 105.20
10/27/2019 93.16 107.54 105.15
11/05/2019 93.16 107.54 105.08
11/11/2019 93.15 107.53 104.88
11/14/2019 93.14 107.52 104.83
11/15/2019 93.14 107.52 105.07
11/18/2019 93.13 107.51 105.37
11/20/2019 93.12 107.50 105.52
12/05/2019 93.12 107.50 106.04

Interesting to see many 40 kWh batteries are hovering around 92 - 93 SOH. Mine is sitting at 93.3 SOH after 11,800 miles and just under 12 months service life.

jdcbomb said:

Interesting to see many 40 kWh batteries are hovering around 92 - 93 SOH. Mine is sitting at 93.3 SOH after 11,800 miles and just under 12 months service life.

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Yes, and it seems to be almost irregardless of mileage. Granted we have a small sample size here.
I need to check but I think my Odometer is around 3300 miles. I'll check at lunch.