Stories from the cold snap

Winter in CanadaLast month, parts of the US and Canada braced for record-breaking low temperatures as a blast of arctic air blew across North America. Here in Ottawa, the thermometer stayed below -20C for three days in a row, plunging to as low as -28C.

A temperature of -25C is an important threshold for the LEAF batteries because the chemical process that produces electricity will basically freeze at that temperature. To prevent that from happening, the battery pack is surrounded by thermal blankets and electrical heaters to keep it warm. According to the Owner’s Manual, the heaters kick in at -17C, heat up the batteries to -10C, and then turn themselves off until the battery temperature hits -17C again.

The heaters consume about 300 Watts when running, which is not a lot energy compared to what the motor uses (up to 80 kW). If the car is plugged in, the heating energy comes from the grid, but if the car is unplugged, the heaters will use electricity from the battery itself, creating yet another impact on total range if you park outside for long periods of time.

Another important point to keep in mind is that the heaters will only turn themselves on if the batteries are at least 30% charged. What happens if there’s not enough charge? Well, if the battery temperature drops below -25C, a safety mechanism will prevent the car from operating. You will either have to wait for the air temperature to rise again or plug the car in so that it can warm itself up using energy from the grid.

That’s all the theory but how often do the battery heaters run in practice, and how much energy do they use?

I ran a little experiment during the cold snap by leaving the car unplugged during the night and also during the day, and used the data logger from FleetCarma to verify how much energy was effectively used. I also measured the impact on my daily range, simulating the case where I would not able to trickle charge at work.

Parking overnight outside unplugged

Outside Temperature

With the weather forecast calling for very cold temperatures overnight,  I charged the LEAF to 80% (10 bars) and left it parked outside for the night, to see how the battery heaters would work. I also wanted to measure the effect of driving to work in the morning without any pre-heating from the grid, basically the opposite of what I would normally do — a worst case scenario we all try to avoid. The result was quite interesting.

IMG_8910-1Early in the morning, with the temperature just a notch from -28C, I actually caught the LEAF in the act. From inside the house, I could see the bright blue charging status indicator lights blink in a specific pattern, showing that the battery warmer was busy doing its work.

Carwings CarWings indicated that the battery charge had dropped from 10 to 8 bars overnight. More precise data from Fleetcarma showed that the battery warmer ran for 2 hours and 42 minutes, bringing the battery charge from 79.6% down to 67.4% (a 12.2% loss).

Once inside the car, the Dashboarddashboard confirmed the 8 bars of charge. It also showed a single bar of battery temperature. For some reason, the car thermometer showed -23C, almost 5 degrees warmer than the outside temperature. Notice the estimated range of 64 km. That is very optimistic.

Arrived at workIt usually takes me 2 to 3 bars to get to work without any climate control, but at this temperature, with no pre-heating and with the cabin heater on, it took me 5 bars instead. As you can see on the left, I arrived at work with only 3 bars left and estimated range of 21 km. Fleetcarma data showed that the 37 min, 17.15 km trip reduced the battery charge from 67.3% to 39.8%, arriving at half of the original 80% charge I had in the morning. As for that optimistic range of 64 km, in reality it was more like 38 km (with an 80% charge).

Arrived at workWith -25C on the dashboard thermometer, the remaining 21 km of range would be enough to take me back home. However, if I had to spend 8 to 9 hours at work with the car unplugged, the battery warmer would probably kick in during the day again causing the estimated range to drop. Fortunately, I have access to a 120 V outlet at work, which makes a big big difference in winter, so that wasn’t a concern.

So, parking outside unplugged overnight: definitely not a good idea!

Parking outside at work, unplugged

On a different day, I did the exact opposite: parked overnight plugged-in as usual inside the garage, and parked outside the whole day at work unplugged. The battery warmer did not kick in at any time during the night, even though my garage is not heated. Temperatures during the day were not as harsh as during the night, going from -27C at 8am to a high of -22.5C  at 4pm.

Arrived at workI left to work with a full charge (88.7% SOC), drove the same 17 km, arrived with 67% left, or 77 km of estimated range. I parked outside as planned. The battery warmer kicked in 4 hours later and ran for 3 hours and 7 minutes, causing the battery charge to drop from 66.3% to 57.5%, an 8.8% loss.

photoBefore I left work, I pre-heated the cabin remotely, while still unplugged, which took another 1.7% of the charge, down to 55.8% SOC. I arrived home with 37.7% charge, or 26 km of estimated range left.

Total range for the day (with a full charge, without charging at work): 34km driven + 26 km left = 60km.

Conclusion: Parking outside at work is not as bad as parking outside overnight, mainly because hours are shorter and temperatures are usually higher so impact on range is not as critical.

So how much energy does the battery warmer consume?

During the experiment, I was able to measure three battery warming events in total. While that is not enough data to extrapolate a pattern or a formula, this is the summary of what I was able to observe:

  • For temperatures varying between -22C and -28C.
  • Time it took for the battery warmer to kick in: 3.5h to 7.5h
  • Warming time: 2.7h to 5.2h
  • SOC% drop: 8.8% to 16.4%
  • Power consumption: 287W to 421W

15 comments on “Stories from the cold snap

  1. Pingback: Canada’s 1st Nissan LEAF – Stories from the cold snap ! - Time to Electrify

  2. When you are plugged in inside the garage it’s lvl 2? I am curious if just lvl 1 overnight would be enough to keep the battery heater from cutting in…

    • We have a Level 2 (240 V) in the garage but a Level 1 (120 V) is more than enough to keep the battery warmer going. It only needs 300-400W, out of the 1440 W a Level 1 can supply. Also, I’m yet to see the battery warmer kicking in with the Leaf parked inside. My unheated garage is about 10 degrees warmer than outside.

  3. Thanks for the update Ricardo, good info. During our cold snap (ice) cars were not starting. No problem for my Prius as it doesn’t have a starter and I would imagine the leaf doesn’t have one either, another advantage Canadians are probably not unaware of.

    Does the Leaf have good fording through snow? What’s the highest snow depth you’ve traversed?

    • Hi Rick. The Leaf doesn’t have a starter either. Our Corolla does and needed a new 12V battery to get it through this winter.

      I found that the Leaf gets through the slush very well compared to the other cars I had, probably because of the extra weight of the batteries and the traction control. I almost got stuck in the snow once when I slid out of a curve and ended up on the shoulder covered with packed snow. I don’t know how deep the snow was but I could feel it hitting the floor underneath. I was able to keep the car under control and used the little momentum I had, and the traction control, to keep the car going, ever so slowly, without getting into a full stop. You could tell the wheels were just rolling without spinning, and the yellow traction control light on the dashboard was blinking like crazy. I was able to bring the car back to the road very slowly, with a big sigh of relief at the end.

  4. Yuhhhhh. Comin’ at ya from Saskatchewan where the current temperature is -35 AND I also drive a Corolla with a freshly charged battery. Obviously always a good idea to have a strong battery under the hood come Canadian winters eh boys!? ANYWAYS, yes, every year at first snow fall I take my car in for service at a local dealers (Capital Ford Lincoln) “quick lane”. They test all my gadgets and doo-dadds and make sure the olllll Corolla is in good running shape before things get ugly outside. I’m not sure what they do to my Battery, but I have never ever had a problem with it, and I work shift work over night, so during the week, it doesn’t even get plugged in over night! Take a look. You guys do anything to prep your vehicles for -800?

  5. Hi Ricardo, just found your blog…great info! I just bought a 2015 Leaf here in Richmond Hill 2 weeks ago primarly for my wife to go to work. I also work at IBM Canada at our Markham HQ. I wonder how many ibmers have EV…Two questions:

    1. Do you find that you really need the level 2 charging to keep a level of convenience? I don’t have one, using only the 120v in my garage, but thinking about it.

    2. How did you get your office location to adopt a EV parking spot? I don’t think one exists at 3600 steeles.

    • Hi Ernie,

      Congrats on your 2015 Leaf! I only know one other IBMer here in Ottawa driving an EV. He drives a modified Ninja Kawazaki motorcycle!

      The need for a level 2 depends on your typical daily drive. My commute is 35 km but it’s not uncommon for me to drive 100 or 150 km in one day, so I definitely need a Level 2 (240 V) charging station at home to fully charge overnight. On the other hand, my wife drives less than 50 km/day so she always gets a full charge on her Volt every night on a Level 1 (120 V). She doesn’t need a Level 2.

      As for the EV parking spot at work, it required a few tries until I found the right person to ask. We can chat about it on SameTime.



  6. Thanks very much for your blog. I read it all before deciding to buy my Leaf here in Ottawa. I just got it last week and I’m really enjoying it. 🙂 🙂 (I do need to get my level 2 charger though.)

    One question: How is your battery holding out after 3+ years? How many bars of strength does it have now? And how many kms are you up to now? Thanks for any info on this.

    • Hey Stephen. Congrats for your Leaf! Sounds like you’re hooked now. I can tell you there’s no way back. LOL

      I haven’t updated the blog in a long time. Sorry about that. I still have 12 bars of capacity after 73,000+ km and almost four winters. Battery capacity is at 86.4% as reported by Leaf Stat. Degradation seems to be slowing down though. I only lost 1.6% since I first started measuring it more than a year ago. I hope it stays this way.

      Overall, the car is still doing great. I haven’t had any problems since the 3-year full warranty expired in the summer so I’m crossing my fingers. I recently changed summer timers for the first time. And we traded our Corolla for a used Volt so we have two EVs in the family now. Like I told you, there’s no way back. 🙂


  7. Hey Mr. Leaf, I’m using your picture of the car thermometer and maybe the battery on Montreal Rampage ( as part of a fear and loathing news column. I hope that is okay. Let me know if it isn’t and I’ll take them down.

    • Hi Rachel. Most of the pictures on the blog are mine but not *all* of them. Not sure which ones you’re referring to exactly. Send me the links of each picture and I’ll let you know. If they’re mine you’re free to use them.

  8. Hi there. I just found your post after Googling Leaf Winter Range. It was a very enlightening read. I’m hoping to make the leap to an EV in the next few years. The Leaf is my current car of choice but I’m excited to see the crop of “entry-level” electrics coming from other automakers. Anyway, just wanted to thank you for sharing your experience!

  9. Hi there. I just found your post after Googling Leaf Winter Range. It was a very enlightening read. I’m hoping to make the leap to an EV in the next few years. The Leaf is my current car of choice but I’m excited to see the crop of “entry-level” electrics coming from other automakers. Anyway, just wanted to thank you for sharing your experience!

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