ydnas7 said:
At the end of the day, Nissan knew very well how the cells/battery performed in the lab, and in test fleets, but didn't know how humans would use the car in the rest of the world. such is life.
I think they knew all of these things, including how humans would use the cars. But I think Nissan had a major disconnect between *accelerated* lab and vehicle testing and how that translates into the customer experience. Specifically, cycling tests *only* tell of total battery losses in a regime that is dominated by constant (or nearly) cycling. Unfortunately, such testing does not provide insight into what proportion of the capacity loss is due to the cycling and how much is simply due to the battery aging (calendar losses).
I believe that the marketing department as Nissan incorrectly assumed that ALL the losses were associated with driving the vehicle and that the capacity loss at the number of miles achieved at the track in Arizona would be the worst case situation, regardless of how little the customer drove the car. In fact, I suspect many assumed driving fewer miles would give the best battery life, even though the reality is that those of us who drive the fewest miles will likely get the smallest number of miles out of our batteries, even if we get more years out of them. I believe it was a case of them not knowing what they didn't know: that in the customer application these batteries would lose more capacity when NOT being driven than they did while being driven.
ydnas7 said:
As it stands, from a global perspective 5 years to 80% and 10 years to 70% still seems pretty good.
Not from where I sit, for a variety of reasons:
- I suspect that the median capacity remaining in 2011/2012 LEAFs after five years of ownership will be below 80%, perhaps significantly. Time will tell, although only Nissan is likely to learn the answer.
- Even Nissan LEAFs which lose less than 20% of their capacity during their first five years are likely to lose way more than half as much during their second five years. As I have pointed out many times, the published literature indicates long-term calendar losses do NOT slow down with time and sometimes they accelerate. The data we have on the LEAF does not indicate that our batteries are any different. Cycling losses typically do slow over time, so I expect there *might* be some slowing with time. Again, time will tell. In this case, we WILL learn this answer.
- Nissan LEAF sales are not evenly distributed in the various geographic regions. Significantly, many LEAFs are located in California, Arizona and Texas. The fact that Stoaty in CA is at three years with low miles and has 18% battery degradation tells me that the typical customer in the largest market for the Nissan LEAF is going to go WAY beyond the capacity loss that Nissan projected in our owners manuals.
- Many statements by Nissan marketing indicated that these were "expect-to-have" numbers rather than average or median numbers. While that is not what was printed in the owners manuals, the spoken words were often expressed in this fashion.
What I am wondering now is how much of the technological and marketing deficiencies with the LEAF have been addresses if/when the promised "hot battery" is released. Specifically, I wonder the following:
- Do the improvements to the battery help with calendar life, with cycling life, or both?
- If there are improvements to calendar life, have the factors which cause linear calendar losses been reduced to the point where they will not dominate calendar losses until much later in the battery's life? (To me, this is the key point that ALL EV batteries must address, regardless of chemistry and/or use of a TMS. But the battery industry still mainly discusses cycling life of emerging technologies.)
- How much of an improvement in capacity fade will a high-mileage customer in a cool climate achieve with the new battery technology?
- How much of an improvement in capacity fade will a low-mileage customer in a hot climate achieve with the new battery technology?
Unfortunately Nissan has chosen to provide no guidance on any of these topics and it seems their customers are again on their own to learn these things without any clear guidance.