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

Posted: Sat Aug 12, 2017 10:18 pm
by lorenfb
SageBrush wrote:
lorenfb wrote: 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.

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

Posted: Sun Aug 13, 2017 7:12 am
by SageBrush
lorenfb wrote: 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.

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

Posted: Sun Aug 13, 2017 8:18 am
by DaveinOlyWA
SageBrush wrote:
lorenfb wrote: 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.

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

Posted: Sun Aug 13, 2017 10:14 am
by lorenfb
SageBrush wrote: 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.

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

Posted: Sun Aug 13, 2017 11:08 am
by DaveinOlyWA
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.

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

Posted: Sun Aug 13, 2017 7:36 pm
by cwerdna
https://www.facebook.com/groups/nissan. ... 294298139/ 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.

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

Posted: Mon Aug 14, 2017 4:56 am
by DaveinOlyWA
cwerdna wrote:https://www.facebook.com/groups/nissan. ... 294298139/ 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...

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

Posted: Mon Aug 14, 2017 6:40 am
by SageBrush
cwerdna wrote:https://www.facebook.com/groups/nissan. ... 294298139/ 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 ?

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

Posted: Mon Aug 14, 2017 9:15 am
by SageBrush
lorenfb wrote: 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 ?

Image

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

Posted: Mon Aug 14, 2017 8:04 pm
by cwerdna
DaveinOlyWA wrote:
cwerdna wrote:https://www.facebook.com/groups/nissan. ... 294298139/ 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. ... 22R9%22%7D - another 3 bar loser on a '16 SL in Phoenix. Built in 2015.
https://www.facebook.com/groups/nissan. ... 264196342/ - 1 bar gone on a '16 in FL. In a comment further down, he states it was built 2/16 and bought 10/16.