edatoakrun
Well-known member
While this study was not specifically designed to answer that question, IMO, the data required to largely answer that question is not "missing".GRA said:...What's unfortunately been missing from this test is any comparison to a group of vehicles operating in a temperate climate and undergoing the same cycling, so that we would have some idea of the point at which battery cooling starts to make a big difference...
Look at the capacity loss and average battery temperatures over the seasonal periods marked by 10,000 mile capacity tests:
http://avt.inl.gov/pdf/energystorage/DCFC_Study_FactSheet_EOT.pdf" onclick="window.open(this.href);return false;
There are very high rates of capacity loss at very high battery temperatures, which averaged over 104 F while charging for the DC LEAFs during the April to October 20 k miles driven, resulting in ~62% of the total average capacity loss over 50 k miles occurring during just those 20 k miles.
In contrast, over the only 10k miles driven entirely in the winter (January-March) but still with relatively high average battery temperatures of over 80 F (that's still higher than my warm-climate LEAFs average pack temperature is when it is charged in the early morning in mid-Summer!) the DC LEAFs only experienced ~9% of the total average capacity loss over 50k miles, less than one third of the rate of capacity loss reported from April to October.
What is missing, is data on how much lower capacity loss is at cooler pack temperatures, which almost all LEAFs experience for three-to-twelve months of the year.
It doesn't sound like there was ever any "danger" involved, though it was a test of the LEAF pack under more severe conditions than any LEAF in private use in the USA is likely to ever approach.="GRA"...We also still don't know what the effect of frequent QCing (as advocated by those who want to see QCs spaced every 50 miles along freeways) would be, although we do know that such treatment in an uncooled pack like the LEAF's will boost the battery temp well up into the danger zone.
From the summary, p 12:
http://avt.inl.gov/pdf/energystorage/FastChargeEffects.pdf" onclick="window.open(this.href);return false;...The four BEVs driven in Phoenix, Arizona were faced with a hot climate, and two were fast charged twice as often as recommended by their manufacturer. Despite these conditions, the vehicles were operated without failure for 50 thousand miles. A greater loss in battery capacity was observed for the fast charged vehicles, though the difference compared to the level two charged vehicles was small in comparison to the overall capacity loss...
Most LEAF battery packs spend relatively little time at the very high temperatures (even those that regularly and rationally utilize DC charging) compared with the large amount of time at very high temperatures maintained in this test, which looks to have been the primary cause in reduced pack life, as shown by this study.
Which should not exactly be a surprise, since high ambient temperature was listed first as factors reducing battery life in the disclosure signed by (almost) all of us when we took delivery.
The study suggests little likelihood of rapid capacity loss for LEAFs in most climates, under most driving patterns, and using more rational charging/SOC patterns, which actually spend much or most of their time with pack temperatures below the minimum average temperatures while charging (~ 77 F during Winter) the study LEAFs experienced.