Good points, if you recall I evaluated a small but geographically dispersed sample three months ago. I used Gid counts, because none of these folks have lost any capacity bars at the time. While I realize that Gids do not equal permanent degradation, they do represent a capacity reading, and I hope that if nothing else they can be used as a proxy for capacity degradation. That said, the sample showed very clear correlation to average ambient at the place of residence (around 70%) and weak correlation to vehicle age and miles driven. This was suprising, since it was previosly believed that cycling losses, and by extension mileage, will play a pivotal role.edatoakrun wrote:And clearly, there is a correlation of capacity bar loss with both time and miles driven, whatever adjective you use to describe it.
If bar loss was not correlated to these factors, and an entirely random event, then the entire field of your graph would have equal distribution.
Both of these factors might be expected show far greater correlations in cooler climates. Even more so, if they are restated as time from delivery, and number of charge cycles. But in Phoenix, both of these individual factors are themselves probably reflecting (in varying amounts) a much "strong"(er) correlation, to exposure to high battery temperatures.
When I saw how much larger the dependence on ambient temperature was when compared to the other two factors, I rang my private alarm bell, and let a few people know about it. Unfortunately, they did not see or want to believe the significance of the data they were looking at. It was difficult to argue otherwise given the sample size and the type of data used (Gids).
I would not be at all surprised to see stronger correlation to mileage than my original sample implied, if you restricted yourself to a particular locale (hot or cold), just like what Stoaty's plot showed. This is my personal opinion, but I do not believe that what we see in Phoenix is in any way abnormal, we are just seeing it sooner due to elevated ambient temps. It seems to be accepted practice to cycle batteries in a temperature controlled chamber to accelerate aging and get test results sooner than it would take at normal room temperature.