I think it's worth making it super easy for everyone to see what NTB11-076a is all about. Here's a
link to the full document. And, here's the pertinent part that is the cause of much debate.
Given the absence any authoritative data from Nissan stating what the
minimum capacity of a
new battery shall be under specific conditions, the best we have is NTB11-076a. Please correct me if there is any more authoritative information from Nissan on this.
Clearly, Nissan has left some room for manufacturing tolerances in this range expectation (+/- 5%, to be exact). Tolerances are a normal part of anything that is mass produced. Keep in mind that these tolerances exist in the battery (its effective capacity), the efficiency of the rest of the power train, and the instrumentation that is used to measure the battery and provide the 4.0 miles/kw data required to use the range chart provide above in NTB11-076a. A 5% tolerance is well within reason for the
cumulative tolerances of all systems that make up the car.
Tony Williams is convinced that by demonstrating a new car
will cover 84 miles at 4.0 miles/kw, this settles the arguments about what the baseline expectation for all cars shall be. However, in the most objective frame of mind, it is statistically insignificant and
proves nothing. I do not doubt that a single car, or set of cars, will be capable of achieving this range.
The crux of all arguments (regardless of bias) is that given a
beginning of life capacity of XX kw/h, the capacity loss after YY time, or ZZ miles, is/isn't excessive. These arguments are less than objective for two very significant reasons:
- First, we MUST establish a statistically significant, new battery capacity baseline and the standard deviation. In absence of this, the best data we have to go with is NTB11-076a. Sadly, we don't know how many sigma Nissan used when they bounded their tolerances for publication.
- Second, we MUST establish what the nominal schedule for capacity degradation is within 2 or 3 sigma allowances. Nissan has given little guidance other than the 2 data points that some are making linear assumptions with and extrapolating upon. But, we simply don't know what to expect without collecting a wide array of data from cars in all regions of the country.
I want to thank Tony and the rest of the crew that performed testing, with especial thanks to the patience/understanding of the members whose cars were damaged in the towing. I would humbly ask that Tony share ALL the data, in one place (as opposed to sprinkled throughout all these many pages) with all the worts and any incompleteness clearly highlighted. It is very understandable that typos and errors will be made -- please correct such mistakes as needed and provide a dated change log showing what/why something is changed.
The next step is to objectively establish a baseline and nominal degradation rates. How can I help with this cause?
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The amount of FUD (fear, uncertainty, doubt) that is generated on this site due to incomplete analysis is just as frustrating as Nissan's seemingly dismissive/non-responsive handling of the situation.
Nissan made it very clear from the beginning that "gradual capacity loss" was not warrantied, yet, we all jumped head first into this pool of uncertainty without any formal definition of the term "gradual" when we bought/leased our cars. Is that Nissan's fault? Partially, yes -- they wrote the ambiguous warranty. We are just as culpable for agreeing the terms were acceptable.
At the rate that many early adopters are using incomplete data to prove a biased point, market forces will require that such ambiguous warranty terms MUST be addressed for future EV programs to be successful. This will be a Good Thing in the long run, but, the short-term outcome is tenuous and we should be prepared for the worst.
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