Last year, I posted my first Range vs. Temperature report after the first winter with our Leaf. As the temperature dropped, you could clearly see a trend going down in terms of range, from about 140 Km in the summer, to 80 Km in the winter. We had a fairly mild winter for Canadian standards that year, and I happened to be away on vacation during the coldest days. As a result, I only had a few trips under very low temperatures and the lowest I was able to record was “only” -22C (-8F), and without enough trips to create a good average.
The second issue was that I didn’t know the car very well and I used the cabin heater a lot. As a result, I ended up not having enough data to show how much effect cabin heating would have on range. So the drop in estimated range was fairly significant as you can see below.
Last winter, I decided to make an experiment to test my hypothesis that cabin heating, not outside temperature, is the main factor affecting range in the winter. As the temperature dropped in January, I decided to take one for the team and drive with minimal cabin heating as much as possible, relying mostly on the heated seats, heated steering wheel and a good winter jacket. I also pre-heated the car before each trip, trying to simulate what I would normally do on a long trip. Pre-heating the car means charging for 20 to 30 mins before each trip and also pre-heating the cabin for at least 15 minutes while still plugged in. This procedure heats up the coolant used by the heating system, using grid power instead of battery power.
The estimated range is based on 120 V charging times. I didn’t use the FleetCarma data because I wanted to compare the results with the original baseline from the first winter, which I created before having the data logger.
With all that in place, I got the following results:
By comparing the two charts side-by-side, you can clearly see that I was able to consistently get at least 100 Km of an estimated range and bring the trend line to a flat line, regardless of the outside temperature.
These results confirmed my expectations but I still find it quite impressive. It is as if the battery didn’t care about the outside temperature as long as its own internal temperature was fine. The fact that you’re either charging or driving the car maintains a flow of electrons in and out of the battery which is enough to generate enough heat to keep the battery chemistry warm. The real challenge is how to keep yourself warm, and any passengers you might have.
I only had two trips recorded with temperatures below -23C, but I had to use the cabin heater in both occasions (freezing to death has its limit). One trip was at -25C (94 km range) and the other at -27C (74 km range). For the latter, the thermometer outside the house actually said -29C but I used the car thermometer as a more consistent reference. I added these two data points to the graph below to illustrate that the flatness of the curve breaks down, closer to last year’s trend, the moment you turn on the heater.
One thing these results show is that the cabin heater in the 2011 model is very inefficient. There is hope the 2013 will perform better but it is yet to be tested under the deep freeze (some people expect the performance to be the same when the temperature falls below -10 C).
Some LEAF owners have been successful in installing an internal ceramic heater in the cabin that performs much better than the regular heater. It is also possible to carry a separate 12 V to power that ceramic heater. With such auxiliary heating system in place, I would be very confident that the Leaf could drive 100 km in one charge in the winter regardless of the outside temperature.
With winter quickly approaching, we’ve been getting a lot of questions about how the Leaf performs under deep freezing temperatures. Our Leaf already has two Ottawa winters under its belt and we’re getting ready for its third one without a lot of concerns since we pretty much know exactly what the car can and cannot do. So this is how I can summarize our experience with Leaf in the winter so far.
- Range definitely drops but how much it drops mainly depends on how much you use the cabin heater, not necessarily on the outside temperature.
- If you heat up the cabin like a furnace and drive like there is no tomorrow, your typical 140 km range can easily drop all the way down to 60 km or even less. But if you manage to keep your cabin cool, drive conservatively, and use some of the techniques described below, you can still drive 100 km under fairly low temperatures.
- With a short commute like mine (17 to 29 km each way), winter range is rarely a concern. However, if I need to run some errands in the evening, I do need to top off the charge during supper. To me, that’s main difference between summer and winter. In the summer, I rarely need to charge during the day.
- During the weekends, most of our driving is spread out during the course of the day, with many opportunities to recharge at home. For longer than usual winter drives, we take our range extender (my wife’s car).
- Heavy snow fall increases rolling resistance, and heavy freezing rain requires you to run the windshield defrost most of the time. I find these two conditions actually worse than a bone chilling but sunny day.
- There are several techniques you can use to minimize the use of the cabin heater. It is essential to pre-heat the car before you leave, using grid power, and take advantage of the heated seats and heated steering wheels, and keep your winter jacket on.
- The 2013 model has a more efficient cabin heater that is expected to perform better than the one that I have, but its performance is yet to be tested under very low temperatures.
- Range concerns aside, the Leaf is the most comfortable car I’ve ever had in the winter. The extra weight from the batteries and the traction control system make it very safe to drive under heavy snow and slush conditions. It doesn’t have any problem “starting” in the cold, or that heavy and sluggish feeling of a gas car in the winter.
- Finally, being able to charge at work, even from a regular 120 V outlet, makes a huge difference during the winter, for three main reasons:
- All the energy I spend driving to work is easily recovered during the work hours, so any concern about range only starts after 5 PM.
- Charging at work keeps the battery warm during the day, improving the car performance during the drive back home.
- I’m able to continue to charge to 80%, at home and at work, which increases the longevity of the battery pack. Without it, I would probably need to charge to 100% at home every night.
I hope this helps anyone considering buying a Leaf but is still concerned about driving it in the winter.