I wanted to go back and readdress my earlier comments on the blog post by Mr. Larsen. When I first read his post, I got excited because for the first time I saw somebody siding with Nissan who used an actual Nissan document to support their argument. Previous posters were just using antictodal evidence and were theorizing and it was just a mess. I hoped that this blog post, using the document from Nissan would have generated some good discussion.
Instead, because the blogger used an editorial style in his review in which he gave a history with several errors, that also included several, what seemed like, personal attacks on the test participants, what we got was just a bunch of bickering. The conversation seems to have stalled. What I saw in his argument if you strip away all the commentary and just look at his data, was something interesting and I was sure Nissan was going to come to a similar conclusion, and based on the latest comments from Nissan, seems to have come true.
The first thing you come to when going through his report ( http://www.casteyanqui.com/ev/capacity_kerfuffle/index.html" onclick="window.open(this.href);return false; ) is the chart on the right hand side. He generated a chart that shows how much loss a car should have based on Nissans assumptions (12,500 miles per year). If we get to 20% loss in 60 months, that means 0.33% loss per month. This seems like a reasonable assumption and the chart seems reasonable.
Now lets apply this to our test cars. For simplicity sake, I'm going to just use one car. Sorry for picking on you whoever owns this car. You can apply this to more if you like. I'll use a high mileage car B494 at 29,000 miles. According to the chart this car at 29k should still have 91 percent of its capacity left. If you look at the chart in years, it should have (I'm guessing at 18 months...sorry for the guess, but I don't know the date for sure) 94 percent. Now I'm not sure how to weight these two numbers, but even if we use the worst case number, I'm sure that the owner of this car would be satisfied if the car still had 91 percent of its original capacity.
Now this is where the report and the document from Nissan (Technical Bulletin NTB11-076a) get a little messy. We know that this car should have 91% remaining, but 91% of what? I think we can all agree that it should be 91% of whatever capacity it had when it was new. This may vary from car to car, but it should be true that it loses 91% of ITS original, not some arbitrary number. But from the manufacturers point of view they need to pick some number as a baseline from which to test all their cars. So they need to have a number that is near the bottom of the range they produce to be comfortable. This brings us to the table on the TechBulletin. The table on page two describes how much capacity we can expect "on a new vehicle (no battery capacity loss)". They use average energy economy to see how the driver rates in efficiency and then go across the table to see how far you can go. The blogger made an incorrect assumption that the spread on the table is a variance on the driver efficiency (YMMV), but this is incorrect. The table shows consumption at exactly 4.0 m/kWh and gives a range of distances for a new car. Given that the line on the table is for eactly 4.0 then the range of miles relates to the capacity of the battery. This means that the usable battery capacity when new ranges from 76/4=19kWh to 84/4=21kWh. This shows a manufacturing variance of 10% which is quite high. From Nissan's point of view they would base losses off the lower of the two numbers. Do I believe that they have that big a variance in manufacturing? Absolutely not. This document in my opinion (here we go...you can ignore the rest of this sentence if you like) this document is just to allow Nissan technicians to look at a battery and to explain that everything is normal when it clearly is not. You can come up with your own idea as to why there is this spread, but the fact remains that this document exists and it is what Nissan techs are using to determine how much capacity you have lost. It is why so many have had their inspection and the results have come back "normal".
Ok, back to how much capacity is there really. Tony did a great job building the range chart on this site ( http://www.mynissanleaf.com/viewtopic.php?f=31&t=4295" onclick="window.open(this.href);return false; ) The chart was built with emperical data from his original Leaf. There have been hundreds if not thousands of people who have looked at and used this chart, and nobody has come back to say that it is off by 10% when looking at a new vehicle. For myself, the chart is a little bit conservative, but very close to dead on. The chart also correlates very nicely with the the 38mph estimate on page 3 of the Nissan TechBulliten (TB). In fact, it is just a little bit conservative. What does this mean? It means the range chart is a very good tool for estimating range, and it matches Nissan's estimate, and it matches the upper estimate on the chart from page 2, and it matches all other documentation that I have ever seen that a new LEAF has a 24kWh pack that has 21kWh usable capacity. This makes the upper number the number that should be used and the lower number on the table on page 2 should be eliminated, but is there to cover Nissan from capacity loss.
So this means that we should be using the 84 miles to turtle number on the chart on page 2 of the TB. So now we are back to the 91% of 84 miles is what should have been the range of B494. 76.4 miles and it only did 59.3 miles which means it has a loss of 29.4 percent or in other words it has 70.6% of its original capacity which is well below the estimated 91% and it is why the owner of this car is rightly upset.
The other eye opening thing about this document, which I did not pick up earlier is that there is 21% of the total capacity at or below the last/bottom bar on a new car. If you look at the chart on page 2, you can see that it will go 68 miles until it reaches 1 bar remaining, and then go until 84 when it reaches turtle. Clearly this is something I overlooked as it is right there on Tony's chart. I'm not sure how this changes as the pack loses capacity, but I can imagine two ways. The first is that it is still 20% of what you have left, and the other is that it is the same as the original capacity and there is 16 miles on the last bar. If it is the first case, then B494 will get to one bar after driving 47.4 miles, and then will have 11.86 miles on the last bar. If on the other hand the last bar is a fixed capacity then they will reach the last bar in 43.3 miles, and then have 16 miles remaining. Either way this is a big eye opener for me in that this is why the owners are reporting that the car can only go 40 miles at this point. Most people will start to look for a place to stop and plug in once they get to the last bar. Particularly since the car becomes annoying and starts hounding you to do so once you are there.
