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Ingineer
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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 11:40 am

(Repost from the Voltage measurement discussion)

The biggest problem with the Leaf's Instrumentation/BMS (in my opinion) is the use of the Hall-effect current sensor. These are not very accurate for coulomb counting and subject to accuracy degrading effects, such as centerline drift, effects of the earths magnetic field, temperature, etc. The inaccuracy of this is why "some gids are more equal than others". Nissan compensates for this inaccuracy by applying corrections to the SoC by sampling voltage and using it formulas that also take into account the temperature, internal resistance, aging, etc. This is why you can gain/lose SoC suddenly sometimes after power cycling. It will apply changes all at once if the car is power cycled, but if in use, it will apply a correction in the form of a drift which appears as faster/slower SoC counting than real energy out/in.

I was able to meet with the Nissan engineers from Japan last December, including the battery system engineer (I had a one-on-one with him). Their explanation for why we have no direct SoC display in the car was basically that they were afraid to show it and have these corrections occasionally make it "jump" which would "confuse the customer". The Battery Systems Engineer told me that cost was the reason they used the Hall-Effect current counter rather than a more-accurate galvanic shunt.

It's looking like there is some degradation in these hot-climate packs, but it appears that the BMS (LBC) is not dealing with it properly, and not only indicating incorrect loss figures, but also possibly not allowing for full use (charging) of the packs real capacity.

Keep in mind, Nissan did a lot of testing, but the bulk of it is accelerated life tests, which attempt to simulate a much longer real-world use scenario. Unfortunately sometimes there is no substitute for real-world life testing, and it sounds like there are some unexpected results that the BMS software is not equipped to deal with.

Also remember that large automakers, especially Japanese ones, are very methodical about changing things, and it takes a long time to properly implement a fix. If that fix involves software in a critical system, (the LBC for example) it will take many hours of testing before they will even consider releasing it. I believe they will fix this, but it will be done on their terms which means it will take some time before we see a solution.

-Phil
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DaveinOlyWA
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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 12:03 pm

i agree that all data collected should be released. as end users, we all have "something" to contribute especially ones who have monitoring equipment of some sort.

The GOM bases its info on what the LEAF gives it and GIDs are part of that equation.

the GIDs are highly dependent upon several things i am guessing which can include ambient heat, battery pack temps, age, cycles, speed of charge, etc.

it seems that if you run your TBs to 9-10 (still in the white mind you) you probably have permanent reduction in capacity even if your pack is a week old and that reduction is not readily apparent since GIDs are so variable that immediate changes will not be seen.

the tests were great but its different drivers, different driving conditions, different traffic, different everything.

routes were changed based on GID reading. turns missed, etc. so we need to determine an error margin for the data we have. despite all this there are things that can not be ignored

** forget what the car tells you. your own personal experience with the car will tell even a novice much more

** all cars exhibited more range than the charge capacity bars said they had.

** some readings were glaringly wrong putting less "stock" into the disappearing" bar phenomena as being permanent

on my LEAF, i have decided that range testing is not a good thing and i fully believe that anything above turtle has neglible long term effects on pack longevity. there is no doubt a curve near turtle to consider and my personal thing is putting it at 15 GID. no data on this. just an arbitrary # about half way. for those of you who dispute this with NO EVIDENCE whatsoever, let me explain why i feel this way. ALL auto manufacturers provide warnings waaay in advance of a low fuel condition. this is nothing more. its like the "blinking" bar on my Prius. when it starts to blink and its Summer time, i know i need to get gas in the next 100 miles...

the other thing is speed. i found that driving 60 mph (odometer which i am guessing means its really 58) i am getting an estimated 88 mph. this is essentially sea level. average attitude here is 50-250 feet for about 80% of the areas i drive. occasionally i might go higher but only to crest the hill and go right back down.

for you guys, your speedometer reading being what 64? (62 GPS) means that people driving 79 miles who think they have loss? i think your loss is neglible as well it should since both cars are relatively new

without testing on a track (should have asked Nissan to borrow their test track. probably not that busy on the weekend) where speed can be kept constant, no stops, no cross traffic, no on ramps, etc. the distance variation can easily cover the variances we see here.

on the GID readings. ya know from the middle of July to last weekend, i was convinced i had lost 5% of my range. not unhappy or anything. i had to go back and check my "diary" but that is way more than i expected to have at this point.

but lately i am testing at 1% loss. so i have a 4% swing in GID count. so even with a single car it really is a crap shoot getting hard specific data. now i know why Nissan needed a week. so do i!

charge completed today at 3:05 AM, checked it 6:30 AM. GID count 271. yesterday, it was 278. pack "should" be balanced. this is 5th day in a row charging to 100%.

i think my saving grace in all this?? my total 7 TB time being less than one hour
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 deceased. 29,413 miles. 2018 S40; 15,000 miles, 478 GIDs, 37.0 kwh 109.81 Ahr , SOH 94.61, Hx 120.15
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Pipcecil
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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 12:49 pm

based upon the results, there is still a good correlation between all the data. Yes, as anyone who does repeated test there is always that one or two outliers that come back with unfathomable results (and there ALWAYS IS), but when you fit a line into the data, you still get a good correlated result: less bars = less range. It would be different if 8 bar car was to the top with some tens, etc., but it didn't, minus your main outlier source. As a Texas leaf, I can easily vouch of the maximum numbers achieved is almost perfectly ideal situation. My A/C runs between .5-1.5 kw/h usage, usually closder to the 1.5. At 4 miles/kWh you could easily argue the total trip used 5 "miles" in range (a good estimate based upon real-life A/C usage). Take off more mileage for not going below LBW, to be conservative, maybe 5 miles (it may be more closer to 10). So those ranges are 10-15 miles higher than normal average driver. The 8 bar car would probably be expected to have 45-49 miles of real driving range on a highway. That is a significant reduction from the 84, hell thats a significant reduction from EPA's 73.

I do believe after look at the results that the BMS and the battery gauge could be faulty in some way and mis-reporting. But, seeing how the range mileage calculator is so off on many occasions, I don't find it difficult to believe this software is indeed "all over the place" as well. BUT, even with the fault meters, there is STILL range problems.

Since Blink has started charging for their use, I tried to make a round trip (at 100%) to and from work as i did last year - usually arriving at home with 3-4 bars left in range. I can no longer do that without hitting LBW or VLBW. So I am forced to charge at work, costing me $2 a day or ~$40 a month. So, I am directly being affected, pocketbook wise. I feel sad for those that can no longer make it to and from work anymore that may have to purchase an entirely new car.
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TonyWilliams
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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 1:17 pm

kolmstead wrote:
thankyouOB wrote:i looked at the data.
the range does not seem all that bad for these cars, considering that they are supposed to be paradigms of troubled Leafs.

what do we conclude from this?



That for freeway driving, with A/C on and going no lower than LBW, the 4-bar car has maybe 45 miles of range.

-Karl


The four bar car on a cold, 32F/0C winter Phoenix day, and the heater going, might not go 45 miles....

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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 3:22 pm

RegGuheert wrote:
drees wrote:But still doesn't explain the wonder-car Blue534. Really want to know what makes that car tick. :)
Me, too! Unfortunately that VIN does not appear to be in the Wiki, so the identity of the owner is a true mystery. I don't know if LEAFfan (our range leader) participated in the test or not, but I've been wondering if he was the driver of Blue534!


Blue534 is not on this forum.

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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 4:05 pm

WetEV wrote:Note that while the battery isn't warrantied, the rest of the car is. That would include the instrumentation. Understand?

Nissan might be as puzzled about parts of this as the rest of us are.


Great angle. For everybody who wants to unload their car, just go to the dealer every week complaining of "instrument problems" and use Andy's no bad battery statement as proof that your instrument is bad.

When not fixed after 3 visits, Lemon Law it. Never mention battery capacity.

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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 4:11 pm

One correction has been pointed out to me!

Blue534 went 75.7 miles, not 79.7.

I will post all the recorded data in a few days. I wanted attention focused on the specific issue of range, and just introducing Gid count in the results has had the expected result of losing focus on the core issue; the consumer has a car that lost significant range in a car with already extremely limited range.

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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 4:16 pm

Thanks to Tony and the whole test team for doing this. It's nice to have a coordinated range comparison under similar conditions, rather than anecdotal stories from owners about range loss.

And, don't let the arm-chair quarterbacks get you down. It's easy to criticize, but much harder to execute a test like this.
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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 5:08 pm

Surprise! Nissan was telling the truth about the poor instruments. Am I the only one that thinks the primary focus should be on Nissan fixing this before they tackle battery degradation?

Also, I for one wouldn't mind seeing the miles/kWh posted as a good faith effort to preserve the integrity of the test results. All data recorded should be disclosed.
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palmermd
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Re: Phoenix Range Test Results, September 15, 2012

Wed Sep 19, 2012 5:16 pm

kubel wrote:Surprise! Nissan was telling the truth about the poor instruments. Am I the only one that thinks the primary focus should be on Nissan fixing this before they tackle battery degradation?

Also, I for one wouldn't mind seeing the miles/kWh posted as a good faith effort to preserve the integrity of the test results. All data recorded should be disclosed.



I agree, but also remember that the data is not meaningful given that we proved they have an instrumentation problem. The real data point that was made is that the car does not travel as far as it should during controlled conditions. That is the only real meaningful data point we need. Everything else (gids, volts, amps, miles/kWh, etc...) is just distracting from the point of the test.

At the end of the day, we proved that both the owners and Nissan are correct. The LEAF has a big problem with instrumentation, and it also has a problem with early capacity loss. Neither of these was a big surprise, but we now have some controlled test results that prove it.
Michael

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