2016-2017 model year 30 kWh bar losers and capacity losses

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Sagebrush said:
LeafSpy is only as good as the data the LEAF supplies. I'm going retro on this whole business of evaluating battery health. A charge to full (either 80% or 100%) followed by a 50 mile drive will give a remaining SoC that can probably be relied on. The 50 mile drive will have to standardized .
This standardized requirement is probably not true, since the car reports trip miles/kWh

If meters are noted at the outset, so that
miles/kWh is reset;
Initial SoC is noted;
initial odometer is noted.

And then a nice long drive of 50+ miles is undertaken,
kWh consumption is trip_miles divided by miles/kWh. An ~ +/- 1% error is introduced by having only one significant digit
SoC use is initial Soc less final SoC
Total battery capacity is kWh_consumption divided by SoC_use

I tried this just now by charging up to 79% SoC and then driving 65 miles
My problem is that LEAF reported 10% SoC remaining while LeafSpy reported 19% remaining
LEAF may be relying on GIDs to calculate remaining SoC, while LeafSpy may be (??) relying of Ah*V measurements
I'll try a couple more long trips followed by charges to look for changes and hopefully get the GID and SoC meters aligned.
 
Scaramanga said:
I don't know (okay I doubt) that the battery had just improved miraculously, it's likely just fat fingered instrumentation
You are correct - it's just the BMS that is adjusting it's view. Lithium batteries don't magically recover any capacity by cycling. If your previous normal driving routine only had you driving a handful of miles here and there, how often were you recharging? With that kind of driving pattern, waiting until you're below 50% or more to recharge is going to be better for the battery, and could also convince the BMS to keep a more optimistic outlook on the state of it as well.
 
SageBrush said:
The 50 mile drive will have to standardized

That's the problem for most! I totally ignore Leaf's SOC & GOM and rely totally on LeafDD's remaining Ahs,
i.e. 'my standard' range is 2.2 miles/Ahr less 'my standard' minimum remaining Ahrs. For me, LeafDD reduces
"range anxiety" somewhat. Without it, driving the Leaf would be unpleasant.

Note: LeafDD is a battery data monitoring device like LeafSpy with less analytics which is always connected.
 
lorenfb said:
SageBrush said:
The 50 mile drive will have to standardized

That's the problem for most! I totally ignore Leaf's SOC & GOM and rely totally on LeafSpy's remaining Ahs,
i.e. 'my standard' range is 2.2 miles/Ahr less 'my standard' minimum remaining Ahrs.
I'd like to understand this, if you don't mind.

Am I wrong in thinking that the Ahr number is derived from directly measured data like battery voltage, and perhaps past coulomb counting and initial battery parameters ?
 
SageBrush said:
lorenfb said:
SageBrush said:
The 50 mile drive will have to standardized

That's the problem for most! I totally ignore Leaf's SOC & GOM and rely totally on LeafSpy's remaining Ahs,
i.e. 'my standard' range is 2.2 miles/Ahr less 'my standard' minimum remaining Ahrs.
I'd like to understand this, if you don't mind.

Am I wrong in thinking that the Ahr number is derived from directly measured data like battery voltage, and perhaps past coulomb counting and initial battery parameters ?

Partially, but not a function of battery voltage or other initial battery parameters other than the delta coulombs
(the amps-sec). Over the last 45 months (52K miles), monitoring Ahrs loss (60 to 51 now, 12 bars) has been reliable
in determining expected range.
 
drees said:
Scaramanga said:
I don't know (okay I doubt) that the battery had just improved miraculously, it's likely just fat fingered instrumentation
You are correct - it's just the BMS that is adjusting it's view. Lithium batteries don't magically recover any capacity by cycling. If your previous normal driving routine only had you driving a handful of miles here and there, how often were you recharging? With that kind of driving pattern, waiting until you're below 50% or more to recharge is going to be better for the battery, and could also convince the BMS to keep a more optimistic outlook on the state of it as well.

individual cells do not recover capacity but one cell can prevent the rest of the cells from being charged to their optimum level if not properly balanced. This is likely a partial explanation of what we are seeing. Makes me think maybe an increase in the balancing current might be applicable? But that creates more heat which could be counterproductive?
 
drees said:
Lithium batteries don't magically recover any capacity by cycling. If your previous normal driving routine only had you driving a handful of miles here and there, how often were you recharging? With that kind of driving pattern, waiting until you're below 50% or more to recharge is going to be better for the battery, and could also convince the BMS to keep a more optimistic outlook on the state of it as well.

Right, it's all unreliable theories. The only meaningful and useful battery data are Ahrs, i.e. just like for a lead
acid battery measuring its load current. All lithium batteries, e.g. PCs, are rated in Ahrs and watts, with Ahrs
declining over use & time. So monitoring Ahrs over time is a useful measure of a remaining life of any battery.
 
lorenfb said:
drees said:
Lithium batteries don't magically recover any capacity by cycling. If your previous normal driving routine only had you driving a handful of miles here and there, how often were you recharging? With that kind of driving pattern, waiting until you're below 50% or more to recharge is going to be better for the battery, and could also convince the BMS to keep a more optimistic outlook on the state of it as well.

Right, it's all unreliable theories. The only meaningful and useful battery data are Ahrs, i.e. just like for a lead
acid battery measuring its load current. All lithium batteries, e.g. PCs, are rated in Ahrs and watts, with Ahrs
declining over use & time. So monitoring Ahrs over time is a useful measure of a remaining life of any battery.

no matter what you use, you are hamstrung by Nissan instrumentation. This is the weakness of any measurement. LEAF Spy only reads what the car tells it. So how the ahr is determined is not by measurement but by calculation and its accuracy is anyone's guess.

I see Nissan not wanting to spend a ton of money on this since its the long term trend that only needs to be approximate that tells the story.

It would be nice to have super accurate info that would allow us to better evaluate the true effects our driving or charging habits may have but...
 
DaveinOlyWA said:
individual cells do not recover capacity but one cell can prevent the rest of the cells from being charged to their optimum level if not properly balanced. This is likely a partial explanation of what we are seeing. Makes me think maybe an increase in the balancing current might be applicable? But that creates more heat which could be counterproductive?
You are putting way too much credit in the effects of overall pack balance on the BMS readings and usable capacity of the pack.

Unless there's something wrong with your pack, cell-imbalance won't contribute more than a few miles of range deficit. So even if the BMS is right, given that 1 AHr with a nominal 365V is about 1.5 miles of range, seeing SOH go from 91% to 100% on a 30 kWh car on a 82-83 AHr pack or a change of 7-8 AHr, that's a 10+ mile loss of range.

Let's also assume you see a worse than average 20 mV cell-voltage difference fully charged instead of a 10 mV voltage difference. Also realize that the cell with the low voltages, also have to have the lowest overall capacity. But a 10 mV voltage difference is only a couple percent at most of overall cell capacity, so only a few miles difference in total range at most. You'd have to see imbalance approaching 50 mV or more (about 5% capacity) to see noticable loss of usable capacity due to cell imbalance.
 
lorenfb said:
Partially, but not a function of battery voltage or other initial battery parameters other than the delta coulombs
(the amps-sec).
Please correct whatever is wrong below:

The car has an amp-meter with a granularity of one second
It keep track of the integrated Amp-seconds since the last charge

...
And then ?
How are partial charges handled ?

I'm afraid I don't understand this business, AT ALL
 
SageBrush said:
lorenfb said:
Partially, but not a function of battery voltage or other initial battery parameters other than the delta coulombs
(the amps-sec).
Please correct whatever is wrong below:

The car has an amp-meter with a granularity of one second
It keep track of the integrated Amp-seconds since the last charge

...
And then ?
How are partial charges handled ?

I'm afraid I don't understand this business, AT ALL

Yes, you are correct:

1. The BMS has an integrating "amp-meter" which monitors both positive (charging) and negative (discharging)
and stores that value, e.g. coulombs (Ahrs/3600), flowing in/out of the battery.
2. The BMS was most likely initialized (coded/flashed) with the initial value of Ahrs when the Leaf battery
was installed.
3. Over time as the battery is used/discharged and charged (even small partial charges), the algebraic sum
of the coulombs modifies the battery's initial value, thereby providing the battery's present condition when
fully charged relative to when the battery was new in Ahrs.

Remember, you used the LeafSpy Ahrs to evaluate your potential purchase of your Leaf, i.e. the Ahrs were within
5% of a new 24kWh Leaf. Most on the forum indicated that Leaf would make a good purchase, as you have hopefully
discovered over time.
 
lorenfb said:
1. The BMS has an integrating "amp-meter" which monitors both positive (charging) and negative (discharging)
and stores that value, e.g. coulombs (Ahrs/3600), flowing in/out of the battery.
2. The BMS was most likely initialized (coded/flashed) with the initial value of Ahrs when the Leaf battery
was installed.
3. Over time as the battery is used/discharged and charged (even small partial charges), the algebraic sum
of the coulombs modifies the battery's initial value, thereby providing the battery's present condition when
fully charged relative to when the battery was new in Ahrs.

Remember, you used the LeafSpy Ahrs to evaluate your potential purchase of your Leaf, i.e. the Ahrs were within
5% of a new 24kWh Leaf. Most on the forum indicated that Leaf would make a good purchase, as you have hopefully
discovered over time.
Thanks a lot for the explanation
That coulomb counter presumably accumulates errors over time. What correction mechanisms are applied ?

Our LEAF is fantastic for our uses and was very inexpensive. It has though been losing ~ 1.5% of Ahr capacity according to LeafSpy every month which is sad; but more to the point may not even be true since the car's range does not seem affected by range experience or the car range GOM. I know the caveats regarding GOM, but I mention it because our driving is very predictable, our lifetime miles/kWh is unchanged, and during the summer A/C is used that if anything will increase the car consumption rate yet the GOM continues to report ~ 1.1 miles per percent SoC.

So my interest here is as much to understand battery estimates in general as any specific car issue. I'd like to understand the discrepancies between the different health monitors and find an accurate method. It would also be nice to understand this stuff, so thanks again for that.
 
SageBrush said:
lorenfb said:
1. The BMS has an integrating "amp-meter" which monitors both positive (charging) and negative (discharging)
and stores that value, e.g. coulombs (Ahrs/3600), flowing in/out of the battery.
2. The BMS was most likely initialized (coded/flashed) with the initial value of Ahrs when the Leaf battery
was installed.
3. Over time as the battery is used/discharged and charged (even small partial charges), the algebraic sum
of the coulombs modifies the battery's initial value, thereby providing the battery's present condition when
fully charged relative to when the battery was new in Ahrs.

Remember, you used the LeafSpy Ahrs to evaluate your potential purchase of your Leaf, i.e. the Ahrs were within
5% of a new 24kWh Leaf. Most on the forum indicated that Leaf would make a good purchase, as you have hopefully
discovered over time.
Thanks a lot for the explanation
That coulomb counter presumably accumulates errors over time. What correction mechanisms are applied ?

Our LEAF is fantastic for our uses and was very inexpensive. It has though been losing ~ 1.5% of Ahr capacity according to LeafSpy every month which is sad; but more to the point may not even be true since the car's range does not seem affected by range experience or the car range GOM. I know the caveats regarding GOM, but I mention it because our driving is very predictable, our lifetime miles/kWh is unchanged, and during the summer A/C is used that if anything will increase the car consumption rate yet the GOM continues to report ~ 1.1 miles per percent SoC.

So my interest here is as much to understand battery estimates in general as any specific car issue. I'd like to understand the discrepancies between the different health monitors and find an accurate method. It would also be nice to understand this stuff, so thanks again for that.

Charging!

Go back in this thread (I know its hard because of the "tennis conversation" ) but what is still true after all the claims, disclaimers and disputes?

Doing a full charge and balance will give you a more correct picture of where your battery is. It does not add capacity, it only gives you a better picture of your battery's condition.
 
SageBrush said:
Thanks a lot for the explanation
That coulomb counter presumably accumulates errors over time. What correction mechanisms are applied ?

Right, nothing is perfect. Having not designed/coded/disassembled the BMS ECU, I can't really address the issue of
accumulated errors, but most likely Nissan has minimized that issue. Other numerics, e.g. Hx, that rely on multiple
data have compounding error issues. Ahrs data error only results from the accuracy of the current monitoring
electronics, and that is somewhat minimized by the charging/discharging errors offseting.

So, the only Leaf battery data I concern myself with is Ahrs and battery output impedance (both LeafDD & LeafSpy
calculate), another measure of battery condition over time like with any battery type.
 
The reality is no one measurement is gospel or even close for that matter and it really doesn't have to be. A basic understanding of what they are combined with monitoring over time and how they are affected by driving habits are more than sufficient.
 
https://www.facebook.com/groups/nissan.leaf.owners.group/permalink/1591060294298139/ is a report of a 3 bar loser on a 30 kWh car. Post says location is Chandler, AZ, states car is 1.5 years old and shows 14,099 miles on the odo.
 
cwerdna said:
https://www.facebook.com/groups/nissan.leaf.owners.group/permalink/1591060294298139/ is a report of a 3 bar loser on a 30 kWh car. Post says location is Chandler, AZ, states car is 1.5 years old and shows 14,099 miles on the odo.

that is 3 new reports in one weekend...
 
cwerdna said:
https://www.facebook.com/groups/nissan.leaf.owners.group/permalink/1591060294298139/ is a report of a 3 bar loser on a 30 kWh car. Post says location is Chandler, AZ, states car is 1.5 years old and shows 14,099 miles on the odo.
Does the report say how much capacity was lost at 3 bars ?
 
lorenfb said:
So, the only Leaf battery data I concern myself with is Ahrs and battery output impedance (both LeafDD & LeafSpy
calculate), another measure of battery condition over time like with any battery type.
I'd like to hear your opinion:

LeafSpy gives me Ahr and Voltage numbers at the top of my cell voltage histogram. I presume the Ahr is extrapolated out to a full battery, while the voltage appears to be average cell voltage * 96. So e.g from the photo below 384.11*58.15/1000 = 22.33 kWh

If I charge to 100% and calculate the Ahrs*voltage, would that be an accurate kWh capacity of the battery ? I'm inclined to say no because the voltage decreases as the energy is consumed. But lets say that I knew the average battery voltage from 0 - 100% SoC. Could I then calculate an accurate usable kWh capacity ?

uc
 
DaveinOlyWA said:
cwerdna said:
https://www.facebook.com/groups/nissan.leaf.owners.group/permalink/1591060294298139/ is a report of a 3 bar loser on a 30 kWh car. Post says location is Chandler, AZ, states car is 1.5 years old and shows 14,099 miles on the odo.

that is 3 new reports in one weekend...
I hope these below aren't dupes. Both of these were posted Monday, 8/14/17.

https://www.facebook.com/groups/nissan.leaf.owners.group/permalink/1591060294298139/?comment_id=1591482800922555&comment_tracking=%7B%22tn%22%3A%22R9%22%7D - another 3 bar loser on a '16 SL in Phoenix. Built in 2015.
https://www.facebook.com/groups/nissan.leaf.owners.group/permalink/1592078264196342/ - 1 bar gone on a '16 in FL. In a comment further down, he states it was built 2/16 and bought 10/16.
 
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