Phoenix Range Test Results, September 15, 2012

My Nissan Leaf Forum

Help Support My Nissan Leaf Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
kolmstead said:
drees wrote:

There's only two things that might cause one car to turtle at 350V and another to turtle at 290V.

1. A software problem. No further explanation needed here.
2. At least one cell-pair with significantly lower capacity than the rest - one cell-pair hit the low-voltage limit and the BMS shut the party down. Should be easy to check with a Consult by taking this car down near turtle.
-----

If we know the voltage at which a battery with all good cell pairs goes to turtle, then anyone with Gary's SOCmeter can run to turtle and check pack voltage. If it's significantly higher than normal, you have one or more bad cell pairs, which would be a warranty issue.

Or that the pack is out of balance. Need to charge and not drive right away, at least occasionally.
 
kolmstead said:
drees wrote:

There's only two things that might cause one car to turtle at 350V and another to turtle at 290V.

1. A software problem. No further explanation needed here.
2. At least one cell-pair with significantly lower capacity than the rest - one cell-pair hit the low-voltage limit and the BMS shut the party down. Should be easy to check with a Consult by taking this car down near turtle.
-----

To me, this could be the most exciting news from the Tempe test. If we do have one or two cell pairs failing, all it will take to demonstrate this is to run the car down to VLBW or better still, turtle, and have the dealer perform a cell pair voltage check. But it is crucial that the car not be charged before this is done. My experience has been that the first thing the dealer does with a low SOC car is charge it up. My car, which turtled on the way to the dealer in January, was up to 70% SOC before they did cpvc.

If we know the voltage at which a battery with all good cell pairs goes to turtle, then anyone with Gary's SOCmeter can run to turtle and check pack voltage. If it's significantly higher than normal, you have one or more bad cell pairs, which would be a warranty issue.

-Karl

We did this on one of our 362 battery tests that were done (one of 2 cell tests). I drove the car into the dealership, hit VLBW as I was pulling in to the service drive. This was also a day when some engineers, techs, and middle managers were in town back in July, and I think there were there to observe the test. The variance was 23 mV. I think the acceptable tolerance is 50 mV.
 
azdre said:
We did this on one of our 362 battery tests that were done (one of 2 cell tests). I drove the car into the dealership, hit VLBW as I was pulling in to the service drive. This was also a day when some engineers, techs, and middle managers were in town back in July, and I think there were there to observe the test. The variance was 23 mV. I think the acceptable tolerance is 50 mV.
Thanks for that data point!

Perhaps at that time your pack was degraded but no cells were failing or perhaps the dealer did not do the test properly. If they charged the car before the test, that could cause the result they reported. The Nissan LEAF battery is top-balanced, which means that if there is a difference in the capacity of the cells, it will not show up near the top of the range but it will show up near the bottom. (The test procedure specifies discharging the pack before the test, but that doesn't mean they always do it properly.)

BTW, what was the voltage of your battery at turtle in the recent test?
 
There's only two things that might cause one car to turtle at 350V and another to turtle at 290V.

1. A software problem. No further explanation needed here.
2. At least one cell-pair with significantly lower capacity than the rest - one cell-pair hit the low-voltage limit and the BMS shut the party down. Should be easy to check with a Consult by taking this car down near turtle.


I'm not sure why people are connecting voltage with capacity.

I can show you a pack that has 400V but won't get you down the block, and one that has 290V and will drive for 100 miles.

Who told you the BMS shuts the party down when one cell pair hit a low voltage limit? How do you know the whole pack doesn't have a much higher internal resistance and just has a higher open circuit voltage? Is the voltage we get from the BMS correct? Is it calculated? Does it compensate for temperature drift? Did you see the BMS code? Do you know what it's doing?

And I'm saying "you" as in everyone.


I'm getting tired of all these theoretical and speculative discussions. Batteries are not an exact science. Calculating open circuit voltage and coulomb counting is not easy. There are more variables than you can ever imagine. Nobody knows anything. Things are much more complex than everyone thinks they are. There are a few people on here that know this...and they are the quietest.

I can't believe how much time people waste arguing stuff they have no clue about.
 
turbo2ltr said:
Who told you the BMS shuts the party down when one cell pair hit a low voltage limit?
I think Phil did, but perhaps I am remembering incorrectly. Let's just say that the car measures it, so let's hope that's what it does.
turbo2ltr said:
How do you know the whole pack doesn't have a much higher internal resistance and just has a higher open circuit voltage?
That's another possibility. It might explain the fact that Azdre's car did not fail the CELL VOLTAGE LOSS INSPECTION.
turbo2ltr said:
Is the voltage we get from the BMS correct?
Yes. Phil has verified that it is within about 0.5 volts of a calibrated high-accuracy Fluke voltmeter each time he has measured it, including once this week. He also stated that the high-voltage voltmeter in the LEAF cross-checks itself against the low-voltage meters and the car throws codes if there is disagreement.
turbo2ltr said:
Is it calculated? Does it compensate for temperature drift? Did you see the BMS code? Do you know what it's doing?
It might do all of those things, but the number coming out through the meter apparently matches absolute voltage very well.
 
RegGuheert said:
BTW, what was the voltage of your battery at turtle in the recent test?

Before you guys get too excited about the partial information I gave, two of the cars did not hit turtle (that was my command decision as the last cars were arriving, and we'd already damaged 4 during tows). Not all the drivers got the final voltage, because the Gidmeters were set on Gid # or %.

Here's the list:

LEAF --- CapBars- miles-M/kWh-Volts ---GOM
Red429 --- 10 --- 71.8 - 4.3 - ----------74
Blue494 ---- 8 --- 59.3 - 3.7 - ----------56
Blue534 --- 10 --- 75.7* - --- - 315.5----74 (ECO=84) (*Data edit 75.7 for typo)
White530 -- 10 --- 69.7 - 4.0 - ----------73
White272 -- 10 --- 66.1 - 4.4 - ----------68
Red500 ---- 9 ----73.3*- 4.4 - -342.5*---66 (*No turtle; 2 miles >VLB: Added 4 miles)
White626 --12 ----73.5 - 4.3 - -317.5----73 (CapBars were 10, reset 12, now 11)
Blue842 ---12 ----79.6 - 4.1 - --------- 76
Silver679-- 10 ----71.8 - 4.2 - -303.5--- 75 (18.2 miles after LBW)
Blue917--- 10 ----72.5 - 4.1 - -310.5 ---67
Black782-- 12 ----76.6 - 3.9 - -295.0 ---88ECO (Out4.0/In3.8; LBW 6.9, VLB 6.5)
Blue744 ---9 -----72.3*- 4.4 - -352.0*-- 63 (*No Turtle; 1 mile after VLB; added 5 miles)
 
turbo2ltr said:
How do you know the whole pack doesn't have a much higher internal resistance and just has a higher open circuit voltage?
An increase in internal resistance doesn't change voltage at rest. It will result in a decrease in voltage under load and an increase in voltage when charging.

TonyWilliams said:
Before you guys get too excited about the partial information I gave, two of the cars did not hit turtle (that was my command decision as the last cars were arriving, and we'd already damaged 4 during tows). Not all the drivers got the final voltage, because the Gidmeters were set on Gid # or %.
The cars who did not hit turtle should have their results removed. If you want to show the data that was obtained, it should be with a huge * that those cars did not go to turtle and their results have been adjusted. Adding some arbitrary distance to their results is misleading at best unless you've performed a study on these low-capacity cars that conclusively shows the distance a car with the same number of bars will travel between VLBW and turtle.

If you were basing your earlier comments of 60 volt difference between cars at turtle by including these cars, then that's completely misleading since voltage of the pack starts dropping rapidly after VLBW is reached.
 
drees said:
turbo2ltr said:
How do you know the whole pack doesn't have a much higher internal resistance and just has a higher open circuit voltage?
An increase in internal resistance doesn't change voltage at rest. It will result in a decrease in voltage under load and an increase in voltage when charging.
I'm pretty sure you are both saying the same thing. (I was about to write what you wrote, drees, but then I reread what turbo2ltr said and I saw it can be interpreted pretty much the same way.)
 
drees said:
The cars who did not hit turtle should have their results removed. If you want to show the data that was obtained, it should be with a huge * that those cars did not go to turtle and their results have been adjusted. Adding some arbitrary distance to their results is misleading at best unless you've performed a study on these low-capacity cars that conclusively shows the distance a car with the same number of bars will travel between VLBW and turtle.

If you were basing your earlier comments of 60 volt difference between cars at turtle by including these cars, then that's completely misleading since voltage of the pack starts dropping rapidly after VLBW is reached.

+1 incomplete data should be clearly marked or kept in a separate table. I'm not a big fan of any of this extra data from instrumentation not in the car from the factory. Charge it until it stop by itself, and then drive it until it stops by itself. How far did it go and how did it do compared to the instrumentation we have in the car.

The instrumentation that was brought along for measuring Gid voltage and such is great to see if we can find some pattern leading us to why this is happening, but all we really know right now is that it is happening and Nissan has been in denial up to now. Sounds like they may be changing their position, and I look forward to their response "soon".
 
Tony... school me here... on the surface it seems like the GOM did a fairly good job? What is the take-away from your view.

Thanks

TonyWilliams said:
RegGuheert said:
BTW, what was the voltage of your battery at turtle in the recent test?

Before you guys get too excited about the partial information I gave, two of the cars did not hit turtle (that was my command decision as the last cars were arriving, and we'd already damaged 4 during tows). Not all the drivers got the final voltage, because the Gidmeters were set on Gid # or %.

Here's the list:

LEAF --- CapBars- miles-M/kWh-Volts ---GOM
Red429 --- 10 --- 71.8 - 4.3 - ----------74
Blue494 ---- 8 --- 59.3 - 3.7 - ----------56
Blue534 --- 10 --- 75.7* - --- - 315.5----74 (ECO=84) (*Data edit 75.7 for typo)
White530 -- 10 --- 69.7 - 4.0 - ----------73
White272 -- 10 --- 66.1 - 4.4 - ----------68
Red500 ---- 9 ----73.3*- 4.4 - -342.5*---66 (*No turtle; 2 miles >VLB: Added 4 miles)
White626 --12 ----73.5 - 4.3 - -317.5----73 (CapBars were 10, reset 12, now 11)
Blue842 ---12 ----79.6 - 4.1 - --------- 76
Silver679-- 10 ----71.8 - 4.2 - -303.5--- 75 (18.2 miles after LBW)
Blue917--- 10 ----72.5 - 4.1 - -310.5 ---67
Black782-- 12 ----76.6 - 3.9 - -295.0 ---88ECO (Out4.0/In3.8; LBW 6.9, VLB 6.5)
Blue744 ---9 -----72.3*- 4.4 - -352.0*-- 63 (*No Turtle; 1 mile after VLB; added 5 miles)
 
mdh said:
Tony... school me here... on the surface it seems like the GOM did a fairly good job? What is the take-away from your view.

Level terrain, constant speed... yes, the GOM handles that well, as we already know. I'm surprised at how well in this controlled demonstration.

But, if we had cars that had been operated up hills, or driving fast, when we took that first GOM reading, it would not be so good.

So, one win for GOM.
 
TonyWilliams said:
Here's the list:

LEAF --- CapBars- miles-M/kWh-Volts ---GOM
Red429 --- 10 --- 71.8 - 4.3 - ----------74
Blue494 ---- 8 --- 59.3 - 3.7 - ----------56
Blue534 --- 10 --- 75.7* - --- - 315.5----74 (ECO=84) (*Data edit 75.7 for typo)
White530 -- 10 --- 69.7 - 4.0 - ----------73
White272 -- 10 --- 66.1 - 4.4 - ----------68
Red500 ---- 9 ----73.3*- 4.4 - -342.5*---66 (*No turtle; 2 miles >VLB: Added 4 miles)
White626 --12 ----73.5 - 4.3 - -317.5----73 (CapBars were 10, reset 12, now 11)
Blue842 ---12 ----79.6 - 4.1 - --------- 76
Silver679-- 10 ----71.8 - 4.2 - -303.5--- 75 (18.2 miles after LBW)
Blue917--- 10 ----72.5 - 4.1 - -310.5 ---67
Black782-- 12 ----76.6 - 3.9 - -295.0 ---88ECO (Out4.0/In3.8; LBW 6.9, VLB 6.5)
Blue744 ---9 -----72.3*- 4.4 - -352.0*-- 63 (*No Turtle; 1 mile after VLB; added 5 miles)

Notably the 8 bar car also had the lowest M/kWH, any idea why that is? If we extrapolate to e.g. 4.2 M/kWh, which is the mean for the other cars, it would have gone 67.3 miles, which makes it less of an outlier in terms of range as it appears. This would also lower the overall correlation of observed range with e.g. capacity bars or gids.

Given the variation in (reported) efficiency, one should actually consider the quotient of actual range (lets assume that these values are comparable, i.e. every car was indeed driven to turtle) of range measured divided by efficiency.

The you would get the following list
[Car] [Apparent capacity (=range/efficiency)] [normalized capacity = (apparent cp- <apparent cp>)/std(apparent cp)
Red429 16.7 -0.43
Blue494 16.0 -0.94
Blue534 18.0 0.57
White530 17.4 0.12
White272 15.0 -1.70
Red500 16.7 -0.46
White626 17.0 -0.13
Blue842 19.4 1.63
Silver679 17.1 -0.13
Blue917 17.7 0.31
Black782 19.6 1.8
Blue744 16.4 -0.63
-----------------
mean 17.3 std 1.3

So all tested cars (with this small sample size), fall within 2 standard deviations of the sample mean, so technically, no outliers there. If we now had results for supposedly healthy new batteries (e.g (e.g. for at least 12 (ideally 30 or so) brand new leafs) under the same conditions, we could actually tell which of the tested cars had significant degradation. If we assume that 19.6 apparent capacity (Black782) is representative of the mean for a healthy battery, and we have the same variation as in our sample of 11 bad cars then we have


Red429 -2.59
Blue494 -3.18
Blue534 -1.42
White530 -1.95
White272 -4.07
Red500 -2.63
White626 -2.24
Blue842 -0.20
Silver679 -2.24
Blue917 -1.72
Blue744 -2.83

Which shows that 7 out of these 11 are below 2 std, i.e. are significantly degraded with respect to Black782.
Right now it actually appears that white272 is the worst case (despite a mere 2 bar loss).

Still, since we compute a quotient of two very noisy variables, the error on these values is actually going to be quite high. Also, the sample size is really small....What we really need are ~ 30 new cars tested on the same track.
 
TonyWilliams said:
mdh said:
Tony... school me here... on the surface it seems like the GOM did a fairly good job? What is the take-away from your view.

Level terrain, constant speed... yes, the GOM handles that well, as we already know. I'm surprised at how well in this controlled demonstration.

But, if we had cars that had been operated up hills, or driving fast, when we took that first GOM reading, it would not be so good.

So, one win for GOM.
Yes, it's interesting, thank you for pointing it out! I drove Blue744 last Saturday. The GOM indicated 63, and the Leaf went 66.3 miles to the low battery warning, which means that it still had some life left in it. Not a huge aberration, but it's significant nonetheless.

The GOM was showing 47 miles on a full charge the next day (lifted from Randy's blog). It's still pretty inconsistent, but perhaps less so in the degraded cars we have seen? I've noticed that the GOM overestimates the range by about 20 to 30% on a full charge, but this was before the software update (NTB12-015).

ON6s5m
1
 
drees said:
If you were basing your earlier comments of 60 volt difference between cars at turtle by including these cars, then that's completely misleading since voltage of the pack starts dropping rapidly after VLBW is reached.

Yes, of course. From the voltage knee at VLB and 350v-ish, it power dives to 300-ish volts. I didn't make the 60 volt statement while knowing that those cars didn't reach turtle. So, part of the reason I preferred to get all the data organized before spewing it. So, I take the 60 volt spread comment back!!!!

Those two cars that didn't hit turtle can be dropped from consideration, but it's not necessary. We know how far some of the cars went from VLB to turtle (Black782 went 6.5 miles, Blue494 6.7 miles) and for the purpose of a demonstration, the adjustments I made are reasonable.

Plus, they are annotated. The extremes, which was what I was most concerned with, went 59 and 79 miles. I now have access to a new dealer car, and I think it will go 84.
 
surfingslovak said:
TonyWilliams said:
mdh said:
Tony... school me here... on the surface it seems like the GOM did a fairly good job? What is the take-away from your view.

Level terrain, constant speed... yes, the GOM handles that well, as we already know. I'm surprised at how well in this controlled demonstration.

But, if we had cars that had been operated up hills, or driving fast, when we took that first GOM reading, it would not be so good.

So, one win for GOM.
Yes, it's interesting, thank you for pointing it out! I drove Blue744 last Saturday. The GOM indicated 63, and the Leaf went 66.3 miles to the low battery warning, which means that it still had some life left in it. Not a huge aberration, but it's significant nonetheless.

The GOM was showing 47 miles on a full charge the next day (lifted from Randy's blog). It's still pretty inconsistent, but perhaps less so in the degraded cars we have seen? I've noticed that the GOM overestimates the range by about 20 to 30% padding on a full charge, but this was before the software update (NTB12-015).

Another note is that any of the GOM data taken in ECO mode are still WAY off. The GOM is expecting savings from limiting the climate control, and we turned it off. So, GOM does OK with a softball pitch in ideal conditions, but can't even figure out ECO considerations (it should adjust for climate control on or off).
 
palmermd said:
+1 incomplete data should be clearly marked or kept in a separate table. I'm not a big fan of any of this extra data from instrumentation not in the car from the factory. Charge it until it stop by itself, and then drive it until it stops by itself. How far did it go and how did it do compared to the instrumentation we have in the car.

It's marked now with *, and with notes. We did exactly what you suggested, otherwise. Charged car, drove to loss of power (turtle), with two marked exceptions. We measured the distance.

You don't have to look at other data!
 
TonyWilliams said:
palmermd said:
+1 incomplete data should be clearly marked or kept in a separate table. I'm not a big fan of any of this extra data from instrumentation not in the car from the factory. Charge it until it stop by itself, and then drive it until it stops by itself. How far did it go and how did it do compared to the instrumentation we have in the car.

It's marked now with *, and with notes. We did exactly what you suggested, otherwise. Charged car, drove to loss of power (turtle), with two marked exceptions. We measured the distance.

You don't have to look at other data!

I did not, and I suggest others don't as well for the purpose of the test. The extra data gathering is great for other reasons, and I'm glad you were able to gather it. Thank you so much for all your effort in this Tony.
 
Back
Top