I’ve been gathering performance data from the LEAF since day one, but it took me a while to figure out the best way to compile and analyze the data. The main reason is that the LEAF does not display an exact state of charge for the batteries, but only a rough one-out-of-twelve bars charge level, which is not very precise.
It is possible to purchase an SOC-meter (state of charge meter) that plugs into the LEAF’s internal data port and displays a more accurate read of the battery’s state of charge. But more recently, users at the My Nissan Leaf Forum realized there’s a strong correlation between the charging time display, particularly the one displayed for 120V charging, and the actual SOC values, with the relationship published in this chart. The charging times give you about 50 levels of resolution (from 0:00 to 25:00 in 0:30, or 2%, increments) compared to the 12 bars in the regular battery level gauge. You could also use the 240 V charging time (7 hours from zero to full) but that would provide only 14 levels of resolution.
As an example, if the charging time display says it will take 3.5 hours to charge to 80% using a 120 V charger, it means you have 70% usable energy in the batteries. A 4-hour estimate means 68% charge level, and so on so forth.
So I went through my logs and found 148 trips where I had saved the 120 V charging times before and after each trip, as well as the outside temperature and traveled distance. Most of the trips were from my commute to work (17.1 Km each way), but the average trips were 28 Km each.
For each trip, I calculated the total energy used and estimated how long I could have gone on that trip on a 100% charge. Then I sorted all the estimates by outside temperature and averaged the results for each temperature level. It’s a fairly simplistic method but, given enough samples, it should give us a good picture of the LEAF performance under my driving profile.
Here are the results:
The vertical bars show the estimated range for each temperature. The black line is a linear trendline. Precision is higher between -12C and +12C where 90% of the measurements were made.
Some interesting points to draw from this chart:
- The absolute worst case is 80 Km range on a full charge. This has more to do with use of climate control than with the outside temperature per se.
- The chart shows it is possible to hit the advertised 160 Km of range even on temperatures as low as 5C. This has a lot to do on how efficiently you’re able to drive, even at low outside temperature.
- The linear trend shows a 20 Km loss in range for each 10 degree drop in temperature. In overall terms, a rule of thumb estimate would be:
- 160 Km @ 20C
- 140 Km @ 10C
- 120 Km @ 0C
- 100 Km @ -10C
- 80 Km @ -20C.
- Notice that these results are mostly based on short 28 Km trips, where range is usually not a big concern to the driver. On longer trips, you’re more likely to drive more efficiently and go easy on climate control use in order to conserve energy. For example, early this month I was able to drive 125 Km @ -10C on a full charge.
Finally, these results are fairly similar to the ones provided by Ross Redman, who bought the first i-MiEV in Canada. His results were published on a recent article by CBC, and shamelessly reproduced below.
So what’s the practical impact of this drop in range?
In my particular case, it’s very minimal. My regular commute to work is a 35 Km round trip. The longest regular trip I have to make during the week is 70 Km. The only real difference is that I have to plan a bit more, and eventually “top off ” the charge during the day, in the coldest days, instead of just overnight. For me, that’s a very small adjustment to make, and I’m still able to drive the same 2,000 Km a month at a much lower cost to me and to the environment.