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

Sat Aug 12, 2017 9:36 am

Sagebrush wrote: 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.
Last edited by SageBrush on Sun Aug 13, 2017 12:14 pm, edited 1 time in total.
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

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DaveEV
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Location: San Diego

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

Sat Aug 12, 2017 10:34 am

Scaramanga wrote: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.

lorenfb
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Leaf Number: 416635
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Re: 2016-2017 model year 30 kWh bar losers and capacity losses

Sat Aug 12, 2017 10:52 am

SageBrush wrote: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.
Last edited by lorenfb on Sat Aug 12, 2017 11:06 am, edited 1 time in total.
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 10.3K miles, SOH 109Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F

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

Sat Aug 12, 2017 11:02 am

lorenfb wrote:
SageBrush wrote: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 ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

lorenfb
Posts: 2487
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

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

Sat Aug 12, 2017 11:21 am

SageBrush wrote:
lorenfb wrote:
SageBrush wrote: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.
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 10.3K miles, SOH 109Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F

DaveinOlyWA
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Delivery Date: 16 Nov 2019
Leaf Number: 319862
Location: Olympia, WA
Contact: Website

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

Sat Aug 12, 2017 11:21 am

drees wrote:
Scaramanga wrote: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?
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 16,686 mi, 91.51% SOH
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

lorenfb
Posts: 2487
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Location: SoCal

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

Sat Aug 12, 2017 11:46 am

drees wrote: 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.
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 10.3K miles, SOH 109Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F

DaveinOlyWA
Posts: 15429
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 16 Nov 2019
Leaf Number: 319862
Location: Olympia, WA
Contact: Website

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

Sat Aug 12, 2017 12:18 pm

lorenfb wrote:
drees wrote: 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...
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 16,686 mi, 91.51% SOH
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

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DaveEV
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Location: San Diego

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

Sat Aug 12, 2017 2:26 pm

DaveinOlyWA wrote: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.

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

Sat Aug 12, 2017 6:17 pm

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
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

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