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Figure 1: My Tesla Model 3 in 8” of new snow in the morning. Brighton Ski Resort in Utah. December 26, 2021. Photo by Fritz Hasler/CleanTechnica.

Autonomous Vehicles

Driving Your Electric Car in Winter — Range & Tesla FSD Tips in Heavy Snow, Freezing Rain, -20℉

Curious about driving an electric car in very cold weather and bad/snowy road conditions? Let me provide some answers and perspective.

Note: From the time I arrived at 7:00 a.m. until leaving at 11:00 a.m., Brighton received over 8” of fresh snow. Dual motors (four-wheel drive) and all-season tires were no match for this situation. My Tesla Model 3 was high centered in the deep snow. All four wheels would spin, but the car wouldn’t budge. Plastic pads under the front wheels and a strong push from the parking lot attendants got me moving, and momentum got me out of the lot by the skin on my teeth. However, driving up and down the canyon on snow-covered roads was not a problem.

Note: Recently, a Washington Post EV hatchet job and couple of rebuttals on CleanTechnica have addressed some aspects of winter driving in electric cars. I am covering other aspects here. To start with, I’m going to discuss using Tesla Full-Self Driving in such conditions.

Preparing Your Snow-Covered Model 3 for “Full Self Driving” (FSD) Beta

So, your car looks like mine in Figure 1, what do you need to do to let it drive automatically on clear roads?

First, I brush as much snow off the car as I can wearing my ski gloves or with a broom or a brush. You don’t want your headlights or taillights covered. You don’t want the snow on your hood to blow up and blind you. You don’t want the snow on top of your car to blow off and blind the driver behind you.

Second, you make sure that none of the cameras are covered with snow. On the Tesla Model 3, there is a flush-mounted forward-looking camera behind your windshield right in front of the mirror. There are two flush mounted forward-looking cameras on each side pillar at the vertical midpoint of the windows behind a pane of glass. There are two rearward-looking cameras on protruding trim just in front of the doors. There is also a backup camera just above the license plate. You need to rub the backup camera with a wet finger to remove a thin coat of slime that often covers it, but you can usually just brush off the other cameras. If you have been covered with mud from a passing vehicle, you may need to wipe off the cameras with a wet rag.

Will your car drive automatically on partially or fully snow-covered roads? FSD Beta follows the road surprisingly well on partially snow-covered roads. Looking at the graphics, it interprets the piles of snow left by the snow plows properly as the sides of the roads. I am afraid to trust FSD Beta on fully snow-covered roads because it doesn’t know if am going to slide out on a sharp turn. It would work to set the maximum speed to 15 mph, but the cars behind me wouldn’t appreciate that.

So, you are driving along a partially snow-covered Interstate highway and a passing car sprays you with snow and mud. You are likely to get a warning that FSD is impaired or unavailable because one or more cameras is occluded. I assume you Florida drivers observe the same thing in a heavy rainstorm. [Editor’s note: Yes, or sometimes bright sunlight in the morning (or I presume evening). —Zach Shahan] Also, even Autosteer will stop functioning when your windshield wipers are operating at level 2 or above.

What Happens to Your Range with Winter Driving?

Figure 2: My wife Mary. My Tesla Model 3 in 4” of fresh snow. Snow Canyon State Park in Saint George, Utah. January 26, 2021. Photo by Fritz Hasler/CleanTechnica.

I thought the main range reducer with winter driving would be the loss of energy from the battery. When skiing in -2℉ or colder weather at Brighton, my cell phone goes dead in less than 60 minutes. Your EV battery will fare better, but you get the point — it will lose power. Furthermore, with my old Nissan Leaf, we would seldom run the heater in winter because we would lose 20% of our range. Newer Model 3s have heat pumps which are more efficient. If you are worried about range, your heated seats and warm clothes will require much less energy than the air heater.

However, there are other factors as well: Cold air is denser, so air resistance will be greater. But the biggies are snow-covered roads and, worse, mushy snow or slush on the road. The final possible problem would be a headwind. Google your current wind speed and the wind speed at your next charger or destination. If you have a headwind of 20 mph or greater, it will significantly reduce your range. Your solution in all these cases is to stop at an earlier charger, and if this is not possible, slow down. Each 10 mph you are able to slow down will significantly increase your range. Turn on your flashers if you are more than 15 mph below the speed limit. One time, when I had a 50 mph headwind, the only solution was to draft 15–20 feet behind a big truck. This is not safe, but running out of charge and being stranded on the road or reducing your speed to 10 mph on the Interstate would be even more dangerous.

Bottom Line: Take all these winter driving factors into account if you don’t have ample range for a given leg of your trip.

Washington Post Article on Winter Traffic Jams in EVs

A recent article in the Washington Post described a huge traffic jam in Virginia where drivers had to spend the whole night on a blocked freeway in freezing weather. The Post posed the question: How would these drivers have fared if all who were trapped in their cars for an entire night in freezing weather were driving electric cars? It’s a good question! However, any gasmobiles running low on gas would face the same problems. The important thing is to be prepared.

There were also recent articles about tourists in Pakistan who thought it would be cool to see some real winter weather in the mountains. At least 22 of them died when they were trapped in a traffic jam by heavy snow.

Picture the worst case situation: You are driving your Tesla EV and have enough charge to reach the next Supercharger, but not much more. You are living in the far north — Canada, Northern Minnesota, or Wisconsin, for example — where the temperature is -20℉  and the road is blocked by cars and trucks stalled in heavy snow not very far from your exit. There is a solution: A prudent driver would plan for such a possibility and have a way to keep warm, a few granola bars, and something to drink for each passenger in order to survive such a situation.

Obviously, Florida and Virginia drivers would only need to take precautions during a cold snap, but in the far north, a driver would be wise to plan carefully for such a possibility. For the -20℉ worst-case scenario, a down coat, insulated ski pants, a mummy sleeping bag and a reflective emergency bivy for each passenger would be prudent. You can get a compact 0℉ mummy bag at Recreation Outlet in American Fork and Salt Lake City, Utah, for $90. REI in SLC carries emergency bivys for $17. Snow boots would also be helpful if you could walk a short distance to safety. This may be an unlikely event, but if it does happen, these things could be the difference between life and death. If you have more than one set, you might also be able to save the life of another driver.

With the right clothes and equipment, you could be sleeping peacefully listening to your favorite music on Tesla’s fantastic sound system until you are rescued rather than freezing to death.

Consider that the most likely situations where this might happen would be freezing rain or heavy snow. Both conditions can be avoided by listening to the weather forecast. In the case of heavy snow (or freezing rain), don’t go out!

 
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Arthur Frederick (Fritz) Hasler, PhD, former leader of NASA Goddard Space Flight Center Scientific Visualization & Analysis Laboratory (creator of this iconic image), and avid CleanTechnica reader. Also: Research Meteorologist (Emeritus) at NASA GSFC, Adjunct Professor at Viterbo University On-Line Studies, PSIA L2 Certified Alpine Ski Instructor at Brighton Utah Ski School.

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