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

Mon Nov 13, 2017 11:58 pm

lorenfb wrote:After about 10 years (2500 cycles) the difference in degradation between the 100-40% and the 85-25% SOCs is only about 3%,
or about .30% per year. Now should a Leaf owner overly focus on what charging cycle is optimum to minimize degradation
or on what factors related to battery heat should be of more concern, e.g. excessive QC on a hot day?

A rapid cycle test where you go through 2500 cycles in 7 months is NOT the same as your typical usage cycle where you will leave the battery sitting at 100% for extended periods of time, not to mention at temperatures much greater than 20C.

Both of those factors will make the difference significantly larger in real life.
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jhm614
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Re: 2016-2017 model year 30 kWh bar losers and capacity losses

Tue Nov 14, 2017 7:20 am

LTLFTcomposite wrote:As for routine daily charging it gets plugged in when it comes home in the evening.

This is the one piece I would recommend you that you alter - the battery is getting hit with a double-whammy. It is charging while it is still hot (probably) and sitting for multiple hours at 100% while still hot from charging (probably). I would recommend using the 'end charge' timer, so charging completes 30 minutes before leaving in the mornings. Of course, you may want to wait until after the warranty replacement to make the change.

Unfortunately, I don't have a big data set on this. I am just basing it on a single anecdotal point - my own experiences with the 24kWh battery. I followed your current method with my first battery and cooked it in about 27 months. For my replacement battery (with the original chemistry), I charged using the 'end timer', so charging happens from 1 a.m. to 5 a.m. My second battery lasted almost twice as long as the first. Of course, the 30kWh battery may be nothing like the 24kWh battery but your charging pattern is exactly like mine was and you are getting very similar degradation results.
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Re: 2016-2017 model year 30 kWh bar losers and capacity losses

Tue Nov 14, 2017 9:44 am

drees wrote:A rapid cycle test where you go through 2500 cycles in 7 months is NOT the same as your typical usage cycle where you will leave the battery sitting at 100% for extended periods of time, not to mention at temperatures much greater than 20C.


Where was that stated as NOT being a problem, i.e. 100% for extended periods of time? The issue being debated is related to charging
to 100% and not using the battery for a short period of time prior to driving.

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

Tue Nov 14, 2017 9:47 am

jhm614 wrote:Unfortunately, I don't have a big data set on this. I am just basing it on a single anecdotal point - my own experiences with the 24kWh battery. I followed your current method with my first battery and cooked it in about 27 months. For my replacement battery (with the original chemistry), I charged using the 'end timer', so charging happens from 1 a.m. to 5 a.m. My second battery lasted almost twice as long as the first. Of course, the 30kWh battery may be nothing like the 24kWh battery but your charging pattern is exactly like mine was and you are getting very similar degradation results.


Yes, I totally agree, i.e. use the timer to offset charging from the last drive if possible.

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

Tue Nov 14, 2017 9:52 am

johnlocke wrote:
Oils4AsphaultOnly wrote:
lorenfb wrote:
Further analysis of the linked graphic of degradation based on a generic Li ion battery for typical charging cycles used

Image

After about 10 years (2500 cycles) the difference in degradation between the 100-40% and the 85-25% SOCs is only about 3%,
or about .30% per year. Now should a Leaf owner overly focus on what charging cycle is optimum to minimize degradation
or on what factors related to battery heat should be of more concern, e.g. excessive QC on a hot day?


20C == 68F

Combine that chart with Table 3, and you'll see it's all downhill from there as the temp increases to the equivalent of our region. Also, I would go through 2500 cycles (that chart is charting partial charge cycles, not full charge cycles) in just 5 years (more frequent charges as the capacity degrades). Lastly, you chose a data point that looked to be an anomaly. @ 2200 cycles, the difference was actually 4% for a 60% DoD. It's actually 5% difference if looking at the 50% DoD lines. Since we know a shallower DoD cycle is better for battery life, the [Edit:] less severe degradation must be attributable to the lower SOC that the battery is charged to. So revising the calculations for 2200 cycles, 50% DoD, and 5 year span, that's 1% (@ 68F peak temp) per year due to simply charging to a lower SoC.

BUT all of that misses the forest for the trees! The red, black, and dark blue lines ALL have worse battery health (regardless of the DoD charge cycle) than even the heaviest DoD cycle (green line @ 60%) which only charged to 85%.

For practical purposes, some of us would like to extend the life of the battery where we can (limiting the battery temp during charging isn't within my control in my use cases, and potentially others as well).

In light of this, and the fact that you don't have data to claim otherwise, it is a disservice to claim that charging to 100% is no worse than charging to 90% as long someone uses the car right away. For commuters that can't control where they park or when they charge (during the day), the SoC they leave at absolutely makes a difference.

You're still missing the big point of that chart. After 5000 cycles under the most strenuous conditions, you would still have 78% of the capacity! 5000 cycles represents at least 14 years of operation. Short cycling the battery is better for the battery but even cycling between 25% and 85% only adds about 10% to the capacity at 5000 cycles. Leaf batteries fail within five or six years Not fifteen. Charging habits are not the problem.


Well put! An agreement for all maybe near.

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

Tue Nov 14, 2017 10:57 am

jhm614 wrote:
LTLFTcomposite wrote:As for routine daily charging it gets plugged in when it comes home in the evening.

This is the one piece I would recommend you that you alter - the battery is getting hit with a double-whammy. It is charging while it is still hot (probably) and sitting for multiple hours at 100% while still hot from charging (probably). I would recommend using the 'end charge' timer, so charging completes 30 minutes before leaving in the mornings. Of course, you may want to wait until after the warranty replacement to make the change.

Unfortunately, I don't have a big data set on this. I am just basing it on a single anecdotal point - my own experiences with the 24kWh battery. I followed your current method with my first battery and cooked it in about 27 months. For my replacement battery (with the original chemistry), I charged using the 'end timer', so charging happens from 1 a.m. to 5 a.m. My second battery lasted almost twice as long as the first. Of course, the 30kWh battery may be nothing like the 24kWh battery but your charging pattern is exactly like mine was and you are getting very similar degradation results.



your charging is how it should be done but it does not help the people in places where the overnight low temps are in the mid 80's or even 90's. LEAF chemistry simply does not tolerate sitting at high SOC and "warm" temps. The sucky part is its becoming pretty apparent that it doesn't have to be all that warm or all that long a time.
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 (build 10/2016)"low water marks" 26,100.2 miles.363GID Ahr 79.55Hx95.35%kwh28.1QCs227,L2's 237
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Re: 2016-2017 model year 30 kWh bar losers and capacity losses

Tue Nov 14, 2017 12:50 pm

jhm614 wrote:
LTLFTcomposite wrote:As for routine daily charging it gets plugged in when it comes home in the evening.

This is the one piece I would recommend you that you alter - the battery is getting hit with a double-whammy. It is charging while it is still hot (probably) and sitting for multiple hours at 100% while still hot from charging (probably). I would recommend using the 'end charge' timer, so charging completes 30 minutes before leaving in the mornings. Of course, you may want to wait until after the warranty replacement to make the change.

Unfortunately, I don't have a big data set on this. I am just basing it on a single anecdotal point - my own experiences with the 24kWh battery. I followed your current method with my first battery and cooked it in about 27 months. For my replacement battery (with the original chemistry), I charged using the 'end timer', so charging happens from 1 a.m. to 5 a.m. My second battery lasted almost twice as long as the first. Of course, the 30kWh battery may be nothing like the 24kWh battery but your charging pattern is exactly like mine was and you are getting very similar degradation results.


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

Tue Nov 14, 2017 1:45 pm

EVs need to be engineered to handle the use case of the car being plugged in when it returns to its primary garaging location in the evening. Period. We plugged the Volt in every evening when it came home and it worked fine for three years until we turned it in.

I used the charging end time on our 2012 LEAF and the benefit was bupkis; the battery was shot by the end of the lease. At some point you get to that snipe-hunt aha moment that these things are just crap and all these silver bullets to prolong battery life are a waste of time. That said, with an eight year warranty if Nissan wants to throw a new battery in every couple years do we really care?
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Re: 2016-2017 model year 30 kWh bar losers and capacity losses

Tue Nov 14, 2017 2:29 pm

LTLFTcomposite wrote: That said, with an eight year warranty if Nissan wants to throw a new battery in every couple years do we really care?
Of course we care. Otherwise consumers have to adjust their range estimates of the battery when new down by 40% or so to account for degradation before the warranty kicks in. And that is before the Winter-time correction.

You are confused about the plugging in routine. No problem plugging in when you get home; the smart behavior is to delay charging until a cooler time for all the routine days when the next use is the next day.

It is easy to say what "should" be engineered to accommodate any and all morons, but the car cost then increases.
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Re: 2016-2017 model year 30 kWh bar losers and capacity losses

Tue Nov 14, 2017 3:10 pm

SageBrush wrote:You are confused about the plugging in routine. No problem plugging in when you get home; the smart behavior is to delay charging until a cooler time for all the routine days when the next use is the next day.


This drives me crazy. Wouldn't a simple software/firmware update allow for better control of the battery charging? Instead of all of these smart chargers, why can't the embedded software/UI in the car accommodate the same functions that OpenEVSE, Juicebox, etc all do?

The above is more of a rhetorical question. I know it's possible and I know that Nissan made design decisions to only provide the functionality they did...but it still doesn't make it ok :-)
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