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"Mileage" on long trips in "cold" weather

Well, I've Volkerized, and can't find anything resembling an answer to the question I'm about to ask, and further, unfortunately, since there are about 5 threads involving cold weather, I'm not sure which to post in, so I figured I'd just start another one. This is a question that might be best answered by someone in a country like Norway who has had his/her Model S for a while.

It is clear that in cold weather, your energy usage is increased, as measured by Wh/mi, probably because of some combination of loss of efficiency when the battery is cold, energy required to heat the battery, and energy one might be using to heat the cabin and/or the seats. When I drive the car now, here, during the few days when the temperature starts off at or near freezing, my energy consumption is greatly increased _on my roughly 7 mile trip to work_. The normal pattern is when temperatures are more temperate is that when the first 10th of a mile ticks off after charging, it says I've used anywhere between 500 and 1200 watt hours / mile (probably because it is counting energy used while charging and sitting there since it first started charging), and then as I drive, the average since charging drops until it winds up somewhere usually below 300 Wh/mi. In cold weather, over the 7 mile drive to work, it seems to stabilize around 400 Wh/mi.

So my question is (I suppose I could do an experiment this Saturday morning if it is cold), what happens after you drive for a while. Does use of the battery generate excess heat which warms the battery and once it is warm, it stays warm without using more energy to heat it than it normally would, and maybe less energy to cool the battery, so that if I went on a long trip, once the initial burst in energy use was done, aside from seat or cabin heat, I would not use much more energy than normal?

I'm thinking of the because I'm going on a 300 mile trip next week and want to know what to plan for. Anyone on Norway? Northern Minnesota?

(I might start it up early in the morning, drive the 40 miles or so to a Supercharger, charge it again to start it's average Wh/mi over again, and then drive back to see what things are like on the return trip.)

Depends. Preheating the battery and cabin will cost you significant energy. Using heated seats and a high cabin temperature also make a noticeable impact. Once you are on the road and the battery is fully heated and the cabin temperature is stable, power use will stabilize. From my observations, plan for at least a 15% extra consumption on your normal driving range. So if you charge to 268 range on max charge, you're probably looking at not much over 200 actual miles vs. 245 or so actual miles in summer temps (assuming ~65mph average speed here). If you have the latest firmware and the car is plugged in (even 110v), you can preheat the car and battery with the 110v outlet without costing you battery power.
Cheers from MN.

No, thxdude,
apart from the cabin heating and defroster, I cannot really see that there is a higher consumption after the first 5-6 miles.
As I said before, I drove 125 miles in darkness in temperatures in the 40's for 125 miles, average speed 56 mph, using 237 Wh/mile in Sweden.

Now it is colder, but I cannot ascertain any meaningful higher consumption, after those first 5-6 miles. When driving normally, I get an average of 275 Wh/mile, and that includes the heating-up periods. My usual trip is about 30 miles.

The S continues to use more energy in cold weather no matter how far you drive. The battery remains exposed and must be heated. I range charged yesterday (P85+) and drove 190 miles @ 55-65, used 395 kwh average, compared to about 290 in temperate weather, and arrived with zero miles left. That's pretty standard effect of cold weather driving. Temp was 36 when we left, 30 (F) on arrival. Kwh use was fairly flat the entire trip.

I have now done my experiment, and to some extent, relieved my range anxiety. I am traveling this Thursday morning from Chapel Hill NC to Augusta GA, over 300 miles, in my S85. It has been around 30-35 degrees here in the morning, and on my 7 mile trip to work, my Wh/mi has averaged over 400.

So this morning (29 degrees at 6:15 AM), I drove to the Burlington Supercharger, about 35 miles mostly at 65 MPH on cruise control on I-40. After the car warmed up some, maybe 15-20 miles, the wh/mile seemed to reduce to the low 300s. I charged about 35 miles at the Burlington Supercharger (mostly to reset the average since last charge in the trip odometer window), and headed back home. On that trip, on cruise control at 65 MPH, wh/mi averaged about 295, with outside temperatures between 32 and 36 degrees. I don't think that is noticeably worse than it would be at warmer temperatures, on a relatively level interstate, at 65 MPH. Maybe a little worse, but not much at all.

So my inference is that once the battery has warmed up, just using it to drive in weather no colder than about 30 degrees, appears to keep it warm enough to give me about the same mileage I'd get anyway, or at worse, only slightly worse. The longest leg of this trip is going to be about 140 miles (I'm charging part-way there at a nice Tesla owner's house), so it is hard to see how if I range charge to 265 I could possibly run out.

@"I charged about 35 miles at the Burlington Supercharger "

You made a five minute stop at a supercharger?

Re: making a quote with @"". I spend too much time on objective-c, I guess.

@redacted

I did charge, not for 5 minutes, but for about 15 minutes. Mostly just to reset the watt hour / mile since last charge (which I could have done in a minute) but I figured that as long as I was there, I might as well charge back to my standard charge of 200 miles. The charging was at slightly under 480 volts and slightly under 120 amps.

On a 190 mile drive from MN to WI, at 15-20 deg F last winter (made the trip 4 times, each time similar temp, road conditions, incl packed snow/dry roads and snow tires) I routinely used 225 range miles (ie 84% of expected range miles. This was driving very conservatively, usu 55mph. At the end of the trip. A warning would come on telling me that the battery was cold and the car should be plugged in. So, the battery continues to need warming on these very cold trips - probably different at 35 deg. My rule of thumb for subzero days is to plan to drive less than 70-75% of rated range, to allow for the unexpected and have a comfort zone.

Has anyone driven in real cold weather (-20C i.e. -4F). How bad does it get? Or even -30C i.e. -22F? That's about the bottom that happens around here and that I might drive in. I know that below -30C Tesla requires you to plug the car in and for sure not to keep it below that temp for >24h. I guess if it gets below -30C I'll just have to make a trip or smth to make sure the battery warms up for at least a short while every day :) But I'd be curious to know what the range is in REAL cold weather, not the soft cold weather of 0C that you're talking about here :)

Sorry, my basis is on 70mph, sub 30F weather. There is a noticeable impact when the cabin heater is continually running. The heating of the battery pack minimal until you get under 40F. Yes, once you get going it should be stable. My main point is to not 265 rated range on the meter when it's 20F outside and expect to drive 260 miles when you need to heat the pack, heat the cabin, drive faster than 55. In this case, you're going to be lucky to exceed 200 miles.

Wow, this is great information for me as I live in Colorado where sub-freezing is the standard winter temperature. Less than 200 miles max range when below freezing is good to plan on. And I still want to know if plugging in when bitterly cold will warm the battery pack without heating the cabin...

@hamer

Good point. After several miles of driving in the cold the energy consumption goes down dramatically. I sometimes forget that there are people that have really short commutes and they may not observe this phenomenon.

Seat heaters use less power than the cabin heat, but that doesn't help the cold feet.

My commute is about 12.5 mi through a few towns on back roads. After experiencing a significant increase in wh/mi with temps in the 30's, I've tried a few different things. By far the greatest increase in wh usage is the cabin heat. Even with pre-heating, the increase is substantial. If I only use the seat heater after pre-heating, I get similar usage to the warmer weather. I won't be continuing that, I don't like cold toes.
Driving with the cabin heat on, off the highways, is akin to idling at stops with an ICE.

For distance, just make sure the cabin is good and warm before unplugging.

hamer;
at worse worst

Does it ever get colder there? Now that you've got these baselines, comparisons would be interesting. You seem to have all contingencies covered, as long as you can make that "friendly" stop. Otherwise, maybe a much slower finish to the drive would suffice.

Is there another stop on the Augusta run? Else the 140mi. leg can't possibly be the longest, as it still leaves 160+ out of your "over 300 mile" run.


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