tomsax said:
I've written up some results from the data collected for the Plug In America LEAF Battery Survey.
[...]
The full report with more detail, information on capacity loss in different climates, analysis of factors other than mileage and climate on battery capacity, and how to interpret Nissan's battery report is available here:
http://www.pluginamerica.org/surveys/batteries/leaf/Leaf-Battery-Survey.pdf" onclick="window.open(this.href);return false;
[...]
Hi Tom, all:
I read through the report (and did participate, though my initial participation was only after a little driving). A few initial thoughts:
- Thanks for doing this. I think there is an effort made to make this survey and report (and I'm thinking there will be subsequent reports and discussions) one that is useful, including to professionals who are decision-makers with respect to the Leaf. The most important point I think is that this survey and report(s) was/is/are what is needed - a good shot at straight-forward unbiased thoughtful collection of information and analysis of it.
It seems to have been referenced explicitly in the Andy Palmer Battery-Warranty note issued two days ago, so that supports the idea of it serving in a useful way to all concerned. I also think in general the idea is that in the face of a hot-button issue or issues, it can be very useful to have a party which meticulously provides really useful cool-headed data to all concerned.
- Sorry for the hassle from me about whether we drivers can log back in and repeat the survey without fear of accidentally creating a second database entry. As you mentioned, the answer is given here:
http://www.pluginamerica.org/surveys/batteries/leaf/faq.php
...How to Update a Report
Just submit a new report. I'll match it up with your previous reports. I use the country, model year and VIN sequence number to uniquely identify vehicles, so it's really important that you enter your correct VIN number.
...
- These statements in the conclusions, among others, seem worth noting:
Conclusions
Of 240 LEAFs reported in the survey, with a median of 11,600 miles driven, 90.8% are still showing all 12 capacity bars, meaning they are within 15% of nominal full capacity. Subjectively, 76.3% of owners believe they have lost no more than a few miles of range.
Of the data collected and analyzed thus far in the Plug In America LEAF Battery Survey, by far the strongest indicator of premature battery capacity loss is the owner’s local climate conditions, specifically cars that have lost enough capacity to be visible on the car’s dashboard capacity display are nearly all in hot-weather climates.
Not every car in a hot climate is seeing battery capacity degradation, and this study does not yet have enough information to determine what fraction of cars are affected....
- I was a bit confused as to this statement also in the conclusions:
...The Battery Information Sheet that LEAF owners are supposed to receive when they have their annual service done has potentially significant educational potential. If presented and explained by a knowledgeable technician, this report can serve as a method to educate owners on best practices for maintaining the health and capacity of their battery pack. Although the effect of doing well on the report is apparently too small to be measured by this survey, Plug In America recommends that LEAF owners be aware of the issues and follow them as much as is convenient in their use of the vehicle by avoiding habits that have little benefit to the owner and potentially contribute to battery pack degradation.
The reason I was confused is that, from reading the report, and from participating in discussions in this forum, it looks like there is some question as to whether following all the recommendations for battery care (as gone through on the report card) really helps _quite_ as much as Nissan seems to think. Specifically as to fast charging:
Does keeping fast charges to a minimum really help that much (aside from possible tie-ins with thermal management esp. in hot climates)?
....The graph below shows the odometer and number of quick charge sessions reported for each vehicle, with vehicles grouped according to their capacity bars. The graph shows that many of the cars that have lost capacity reported no use of quick charging, and a broad scattering of significant use of quick charging in cars with significant miles driven without losing any capacity bars....
The report also mentions:
...Nissan originally recommended no more than one quick charge per day, but in later revisions to the LEAF Owners Manual, removed that statement....
Seemingly countering this, in the Q&A accompanying Andy Palmer's announcement, it was reiterated or re-affirmed:
Q. How does the frequency of fast charging affect the rate of capacity loss? Are there other factors that influence the rate of capacity loss?
A. Quick charging the vehicle more than one time a day will affect and may hasten the rate of battery capacity loss. Other factors that will affect and may hasten the rate of capacity loss include, but are not limited to: (1) Sustained high battery temperatures (caused, for example, by exposure to very high ambient temperatures or extending highway driving with multiple quick charges); (2) Sustained high battery state of charge (caused, for example, by frequently charging to 100% state of charge and/or leaving the battery above 80% state of charge for long periods of time); and (3) Higher than estimated annual mileage accumulation (such as more than 12,500 miles per year).
On the issue of trying to charge past 80% unless it is anticipated that it will be used and necessary, I'm wondering if it's a more complicated matter of "if you always use up more than 20% charge within a few hours of topping up, then maybe it doesn't matter", or maybe you're fine?
- I was upset about Andy's "moving of the bar" (in my view) in his interview with Chelsea a few months ago so that all of a sudden Arizona residents faced a norm of 7,500 miles per year in the comparison discussions of battery degradation. This isn't mentioned in the battery report although this point is:
In October, 2012, Andy Palmer, executive vice president of Nissan stated that the
battery degradation norm was set using the LA4 driving cycle and 12,500 miles per year, yielding an average battery capacity level of 80% at 5 years and 70% at 10 years.
I suppose if the 7,500 mile comment was not mentioned in the report, then maybe it wasn't strictly relevant, and maybe Nissan has "moved on" in some way from an argument which in my view was specious, but I am just wondering where things are as to that 7,500 statement (even for drivers with a 12,000 miles per year lease?), especially since the 12,500 miles per year statement is mentioned so prominently at the begi- nning.
- Can any data be presented and examined versus other numbers, as to average number of miles per day or week or month or year? Much or all of the report seemed to focus on total miles per car, but many cars and drivers will differ in average miles per day.
- I have to go back and look at trying to integrate car wings data next time I fill things out.
- I'm assuming that temperature for a given zip code are the highest average monthly temp listed at the link given here:
http://www.melissadata.com/lookups/ZipWeather.asp
These numbers seem about right, but when I click into daily, something seems wrong (way too consistent/static). Maybe they are a trailing average?
I find myself thinking often about altitude above sea level. This is, I'm thinking, subsumed within the highest average temp numbers, but is on my mind in part because in my case it is a differentiating point between myself and the Phoenix and Tucson drivers, and so explains why things are a bit cooler here, on average. Altitude is mentioned in the report as a side note in understanding why a zip code may not cover the whole story in the case of an individual car. I have no clear question or statement here other than it might be an idea in recording zip code on a record also to record corresponding altitude information.
- I also find myself wondering as to the long-term impacts of charging at 110-120 as versus 220/240. Was this included as part of the data, or maybe it is buried somewhere in Carwings data?
