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Winter Driving Warning

Firstly I must state that I absolutely love my MS, and this is my first post so seeing other people getting ripped apart in this forum i am hoping everyone will be gentle with me since it is my first time.

Not a complaint really but just a heads up to those who live in cold climes ... I planned a trip from my home up to Lambeau last weekend to try and enjoy what turned out to be a miserable game, and was surprised by the amount of degradation of range experienced in the 20 degree weather. I have made similar length trips in the summer/fall, and even longer without this problem. I had max charged my 85 overnight, ran a few errands first but left with at least a 250 mi range and arrived in the parking lot with 75 mi left. Google maps shows it at a 109 mi trip but that seems long based on how long it took, but even at that I was about 66 mi short. I did drive a little fast (low 70's) but had the heat set on 66 and was just playing AM radio. I was forced to find a charger to make it back post game and using plugshare and driving around a bit found a Tesla labeled charger at AMI, inc on the north side of town - thank you whoever you are! I was then stuck charging it for approx 3 hrs, and decided to try and make it back when the charge hit 129 mi - i assumed if i toned down the speed (60 mph) and set it to powersave i should make it (I think it is really closer to a 90 mi trip). However I only made it down to fabulous Sheboogie WI with the low batt warnings starting and 22 mi of range left, that was a 67 mi trip, again a significant degredation of range on the order of 40 mi. Keep in mind this is pretty much all "freeway" type driving. There was a Kwik Trip with a 120V plug, but in this weather that pretty much only keeps the batt warm. Fortunately my better half was able to fetch me, and i am still not there waiting.

Thankfully the service folks in Villa Park, IL (thanks Laura et al) were kind enough to divert a delivery truck in the area to pick it up and bring it back to me the next day. I think all agreed that level of degradation was not anticipated by anyone, therefore i wasn't just being dumb in my range expectations. The point of this story however, and the tech seemed to agree with me, is that if you are doing just highway driving in cold weather (20 degrees is frankly not even that cold up here in the hinterlands!) the battery seems to be doing double duty of staying warm and moving the car. There is very little regen happening to help the batt along, so if presented with this situation one should plan accorgingly - by my higher math skills based on the above example even somewhere in the vicinity of 65-70% of what the car tells you it can go to be conservative. Not sure if even colder temps would degrade even further? So if i could have a do over i would have just used my wife's hybrid, until they put some superchargers up my way.

It would probably helped a bit if you had selected "Range" mode from the menu. It actually reduced my cold weather battery usage by about 15%.

@Robert has a thread for efficient driving tips for his EU driving as well.

More battery usage is needed to maintain temperature for pack for sub zero weather...

Tesla's online calculator pretty much predicts the range you got on this trip, and strongly suggests that limiting your speed a bit would have made a big difference. See calculator:

http://www.teslamotors.com/goelectric#range

I have said this before (at more length; this is the telegraphed version):

1. Charge up so you have some insurance in terms of rated miles over miles you need to drive, at least 25%. If you have 100 miles to go then charge to at least 125.

2. Put your Energy app up and keep it there. Drive at a speed such that averaged over 30 miles, your projected range is always greater than your rated miles left. Preferably a good cushion more.

3. If you find you're losing that cushion, slow down. As much as it takes to get the projected range back up. If you have to drive the rest of the way home at 40 MPH that's better than running out of charge.

4. After you've gotten used to your car under a variety of conditions so you _know_ what it'll take to go from A to B, you won't have to pay as much attention, but under less than perfectly known conditions, watch it all. Speed eats mileage, especially in cold weather. 70 MPH eats a huge amount more mileage than does 55.

Interesting, AmpedUP. I tested my conditions and my recent mileage was explained, too.

Amazing what reading the provided materials does for your understanding. ;-)

Alright, not sure which way your were coming from but I'm in vikings territory and my husband went to that interesting game. It was much colder then 20 degrees especially when considering that arctic wind we had. That is something to factor in next time (wind and wind chill). You are right about that traveling too fast. Though I have to say, around here if your not going 70 your basically road kill, so it's hard not to speed.
Glad tesla helped you out. (What service!)

We have had a cold snap in boston recently and I noticed that my watts/mile have increased dramatically. In the summer my driving habits get a round 300 watts/ mile, yet now doing the same commute in cod weather I am closer to 400. The car doesnt really like the cold

Brit - wind chill has no effect on battery life or any other mechanical device, only living things.

Of course if you are driving into the wind, that definitely affects your range but not because of the wind CHILL.

@ L8MDL

Windchill can affect nonliving things including machines. If you take something warm and set it in the cold, it will typically cool faster if there is wind.

Tesla has a 89 mpg equivalent gas mileage in average temperatures. What is the mpg equilavent in the cold winter months?

@ Smith 1:

"Windchill can affect nonliving things including machines. If you take something warm and set it in the cold, it will typically cool faster if there is wind."

Indeed, but once it gets to the same temp as the surrounding air the wind chill has no further effect. The enhanced speed in cooling requires that the probed area be directly exposed to the movement of air, ie - convection. Conduction of the cold is less of a concern since the batteries are not directly exposed to the cold nor are they in direct contact with the battery pack's shell. (Per my understanding the batteries are immersed in an inert liquid.)

Batteries in the 'S should be much less affected by the cold than are those found in the Leaf, Volt, iMiev and others.

@ AmpedUP - i have indeed read the calculator you mention and copied on your post, but it doesn't even come close to the degradation i experienced. The calculator does not allow you to go below 32 degrees, so perhaps if it is more logarithmic than linear it may get you there, but clearly at the 65 mph and 32 degree setting a prediction of a 243 - 218 mile range (the lower with the heat on but it doesn't specify how high) doesn't even approach my experience. Even on the return trip when i was averaging about 60 mph with the "range" mode on - my range on a full charge would have approximated 160 mi not the 243/218 that is listed. Also, the very experienced Tesla technician who delivered the car back to me (again thanks for the great service), told me there still is a learning curve on this even for Tesla and that degradation i experienced was primarily due to the twin factors of highway driving (only) and the cold.

@ Jewsh, it is important to both read the materials provided, and also helpful to understand its limitations. The fact that it lists 301 as an expected range in any conditions except for extreme tailwinds should clue you in on that. With this post i was simply trying to be helpful to those of us who live in cold weather, not in any way to disparage my MS which i love dearly, so no need to be snarky.

@dimbulb9595. But Jewsh put a winky smiley face after that. Not true snark, more like gentle chiding, and you did ask us to be gentle. :-)

True--snark and winky face are mutually incompatible. You don't per chance have Swedish ancestry? ;)

@ Jewsh

Tesla batteries would still be affected by wind chill. I doubt your assertions about other manufactures batteries, since you have a poor record of accuracy with your previous assertions.

Analogy. And if you put a windbreaker on it might reduce the windchill, but you're still going to be affected by the windchill.

@jtodtman

I think you're right perhaps I was being a little too sensitive, and thanks for the gentle assurances, it feels like one of those nice cuddles just after.

Good post dimbulb9595. People need to be aware of the effects of weather below the 30 degree mark. Living in St. Louis I usually don't see temps that cold. It's good to hear reports so on the few days it does get that cold I know to divide my range in half.

The mid 30's temps we have had recently has my watt/mile in the upper 300's and if I am leaving with a cold battery the watt/mile is in the upper 400's to low 500's for the trip.

I leave my car set on ideal miles and use my watt/mile info more than anything else. If I am seeing an average watt/mile in the 500 range I know I will have half the range.

Heh. Just had a regional dyslexic moment: I read Jgrogan above as saying they just had "a cod snap in Boston". Imagined some sort of Frozen Fish Fest!
__________
There were posts last winter reporting battery chill at hwy speeds. That's a large exposed surface, and every insulation has its limits.

I've had my MS since 4/2013 and I absolutely love it as an around the town commuter car. IMHO electric cars kind of suck for long distance travel. Its way too inconvenient to try to find charging stations and then wait for the charging. At least 95% of my driving is around town so it not a big problem for me. We always take the gasoline car for longer trips. If you only have one vehicle then I wouldn't recommend an EV.

Flame Suit On!!

Smith - If the air temperature is above freezing and the wind chill is below freezing, a pond of water will NOT freeze. The temperature of an inanimate object cannot go lower than the air temperature despite wind chill temps. A battery reacts to ONLY air temperature, not wind. If it did react to wind chill, don't you think your Tesla battery would freeze up when traveling 80 mph in 10 degree weather (a -21 degree wind chill)? Guess what? It won't. And neither will your 12 volt battery. Here's a primer from NOAA for you:
http://www.crh.noaa.gov/ddc/?n=windchill

@Amps2go - It's not inconvenient to use a Tesla Supercharger, and you can add a large number of miles very quickly. I agree that in many parts of the country, long distance travel in an EV is still not practical. As the Supercharger network grows, there will be many places where the Tesla is the ideal car for both local and long-distance driving.

Where are you trying to go, Dr. Cobert? You live right on the recently completed west coast corridor and will probably have a route to the east coast via I90 in the not-too-distant future. I'm biding my time a long way from any current SC, but look forward to using my P85+ as a long distance cruiser. To each his/her own, but what the heck?

Jewsh wrote:
"Indeed, but once it gets to the same temp as the surrounding air the wind chill has no further effect."

I think you will find that this is also the case for living things. :p

@L8MDL
You are correct that an inanimate object will not drop to a lower temperature than the air temperature despite wind chill temps. However, you are forgetting that the car is using energy to actively maintain a temperature that is higher than ambient. The stronger the wind, the greater transfer of heat away from the car and therefore the more energy required to keep the batteries nice and cozy.

The wind chill "temperature" is what it will feel like to a person, though the temperature will not actually be any lower. The reason the temperature feels lower is because the wind is constantly replacing the air in contact with our skin (that our body just warmed up) with cold air. This makes our bodies work harder to keep warm, just like the cars battery management system.

@Bighorn-
There are currently only 2 superchargers in the entire state of WA. I could do a trip to Portland or Vancouver but that's about it. No easy charge if I go east on I-90, SR 2, SR 20 .... Also nothing on Olympic peninsula or Oregon Coast. When I'm traveling, I don't want to have even the slightest worry about where I'm going to fuel up. Also waiting for 25 min is not something that I want to do when I'm trying to get somewhere. There are gas stations just about everywhere currently. It takes less than 5 min to fuel up a gas car. The future will be much better for EV's but that's probably several years or decades away.

Bent - incorrect. If the air temperature is 0 and the wind is blowing 20mph, your Tesla battery will be 0. Your body, on the other hand, will be -22 and you will suffer frost bite in about 15-20 minutes.

Pbendo - agreed, but the machine suffers no effect from the wind CHILL temperature. It will suffer from wind RESISTANCE, but that is a different discussion.

@L8MDL

Sorry, but wrong again. If the temperature is 0, nothing (human or inanimate object) well achieve a temperature lower than 0.

The human will feel like the temperature is lower because the heat will be removed from his/her body at a more rapid pace by the moving air.

"Wind Chill" is merely a way to relate the rate of temperature change to the feel/perception of the temperature. The actual temperature does not change due to wind alone.

@L8MDL

Sorry but wrong again - slow down- you are making mistakes faster than I can correct them.

When the air is colder than the battery pack, the speed of the wind will increase the transfer of heat between the cold air and the warm pack and therefore require the car to spend more energy to keep the pack warm.

This is why we blow on hot food before putting it in our mouths. Our breathe is warmer than the ambient air, yet it still cools the food because air in motion will transfer more heat from the food to the air.

But you are right on one point, wind resistance is a different discussion.

I had a similar experience today as well, I drove 184km and lost 141km of range and we were only at 0c(32degrees). This is a concern for me because this is a three time a week trip for me, 184km is only one way. Sure driving slower is part of the answer but not if it adds 40-50 mins of extra driving time to my day.


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