Winter Range and Charging

[Fredneck]

Do you understand the HVAC is constantly pulling in fresh cold air that needs heating.

You didn't quote, so I can't tell who you are replying to.

The HVAC doesn't heat air that isn't being moved. I turn off the fan if I don't need cabin heat.

If the pack falls into the high 40s we can see reduced regen, but that doesn't mean the pack is heated, still affects consumption since we aren't recapturing that energy.

Sorry, I'm not following. What energy aren't you recapturing??? Do you mean the energy the regen isn't recovering? Unless the temps drop near freezing I find the regen still works enough that unless I get caught by a yellow light I still get enough regen that I don't have to hit the brakes. In reality that's where the lost energy goes, needing to use the brakes, not the lower amount of regen.

How long have you been driving a Tesla?
Winter consumption for my car will show in the 500s with some preheating, have had the 5 mile average spike over 800 if I forget to preheat, my commute is little under 7 miles each way. Based on that you would think I have no chance to make the Way Claire supercharger 180miles away with my P85 that only charges to 242 miles when cold. Reality is that once the cabin is warm consumption falls back much closer to normal and in low single digits the 180miles is no problem.
Tires also require a fall top up as pressure falls due to temp.

I assume you are talking about the energy spike that shows up in the first couple of miles when starting out. I've never figured out what causes that. I see it regardless of temperature, so I don't think it is a cold battery thing.

 

[Fredneck]

You have to stop too frequently at the abundance of Superchargers, but then you say there aren't enough Superchargers. Which is it? I'm still working on the couple of 250+ mile gaps on routes near me. I would be glad to be able to stop every couple of hours to make it across these areas.

Sorry, I don't understand your question. Let me restate the issue.

The car has a range of 300 miles. There are chargers every 100 miles, give or take. You have to charge every 200 miles in the warm months because you can't depend on the car to give up every last kWh to reach the charger at 300 miles. So that extended range doesn't accomplish much.

In the winter it is even worse. While the car would easily make 200 miles in warmer weather, in cold weather it has a hard time reaching the charger at 200 miles, so you have to stop every 100 miles. Not even two hours of driving on a highway coupled with better part of an hour charging.

This is why we need more Superchargers, a LOT more. I think there should be a charging station about every 25 miles on the highway. People who use Quartzsite, AZ would likely agree with me.

I can't do anything about the paucity of chargers in areas of the country where EVs are least suitable in the winter. I don't know if that is why Tesla builds fewer charging stations, or if it is simple demand. I would assume there aren't as many Teslas sold in your neck of the woods as other locations. Heck, I think North Dakota got it's first Supercharger a few months ago.

Building out the charging network is a problem for all the EV makers. That is going to cost a lot. If they leave it as a demand based growth, it will be slow and as a result slow the introduction of EVs in general. Even though most people don't need chargers other than at home, that's not how they are used to thinking.

 

[SSedan]

I charged the car yesterday afternoon soon as I got home from work, was topped off to 80% before dinner. Commute is short so regen was still limited when I got home.
Car parked outside overnight currently 27f out and I set the car to 90% so it would warm the pack without cabin heating. 13hours sitting in mid-high 20s and it was 5 minutes in before the 20amps being pulled at 241volt registered a single mile per hour charging. Few more minutes later and 32amps is only giving the car 9miles.
Turned on cabin heat at 66f and two bars of seat heat and charge rate dropped to 4miles 32amps at 241volts and essentially all the pack is seeing is 120volts 12amps charge rate. Heaters are very power hungry and we have less control of them than you think.
I also thought the X had a second heater/AC due to the greater volume in back. Can anyone confirm? This could make it even higher use.

May be some drain for friction warming of wheel bearing grease. Cold also increases internal resistance of the pack which will waste energy as heat without the heater even being active.

If I don't preheat my S once below freezing I can see my average consumption settle in the low 500s for my average 7mile trips.
Preheating doesn't save power but stops the consumption from showing up on the dash. I have seen spikes over 800.
Cold weather swills power, adapt.

 

[ajdelange]

The 3 row X's have a second evaporator than the two row ones but I don't know about a second heater. The cabin isn't any bigger so more heating or cooling isn't required. It's a question of getting the heat (or cold) back to the third row. The fact that Tesla runs a refrigerant line rather than an air duct for the cooling suggests that an air duct isn't practical. One might reason, therfore, that there is a second heater back there but as there is no additional demand for heat that that second heater combined with the front heater share the same load.

No, pre heating doesn't save power but that power comes from the mains and not the battery so that pre-heating on shore power preserves range to the extent it can. On short trips you won't see much benefit but on short trips it doesn't matter.

 

[SSedan]

I should have been clear on my thought of the X having extra HVAC due to volume. I was comparing the extra volume to the S it is based on. With the extra volume I would hope it has more heating capacity.

 

[David99]

It is pretty well known that winter temperatures hit EVs pretty hard when it comes to range. It's not clear to me how much it impacts charging. I'm not talking about charging currents since level 2 charging at home never rises to a point that it is limited really. I'm talking about how much charging is needed to drive the same miles in winter temps.

I know regen has some impact, but that should be fairly minimal unless you do a lot of stop and go driving. If the driving is mostly at highway speeds and conditions, 50 to 70 mph and no stop and go, what is the source of the reduced range? Is it that more energy is needed to travel the same miles because of the motor, tires or something else in the driveline? Is it that the battery becomes less efficient in returning the energy that was stored in it? Does the capacity of the battery drop so you can't get as many kWh into it in the first place? Does the battery not receive current as efficiently so it takes more energy to charge it up?

Inquiring minds want to know.

Batteries are more efficient at warmer temperatures. There are more losses when using a cold battery. Small but worth noting. As other mentioned, heating the cabin takes a lot of energy that is available 'for free' on a gas car. Thus we see it as loss of range in an EV. Cold temps make many mechanical parts less efficient. Rolling resistance is higher at cold temps as well wen roads are wet or snowy. Cold air causes more drag. Reduced regen captures less energy back when the battery is cold. All things combined just add up in the winter. The largest factors are cabin heating and battery heating. What helps is turning on the cabin heater from your app before you use the car (while it is connected to a charger). This will use shore power to warm with the battery and cabin so it's not lost from the battery. Also, time the charging over night so it is finishing close to when you leave in the morning. Charging warms up the battery (charging losses causes heat in the battery) so you have a warmer battery in the morning without spending extra energy.

 

[Big Earl]

The 3 row X's have a second evaporator than the two row ones but I don't know about a second heater. The cabin isn't any bigger so more heating or cooling isn't required. It's a question of getting the heat (or cold) back to the third row. The fact that Tesla runs a refrigerant line rather than an air duct for the cooling suggests that an air duct isn't practical. One might reason, therfore, that there is a second heater back there but as there is no additional demand for heat that that second heater combined with the front heater share the same load.

No, pre heating doesn't save power but that power comes from the mains and not the battery so that pre-heating on shore power preserves range to the extent it can. On short trips you won't see much benefit but on short trips it doesn't matter.

The rear heater in the Model X is about 2,500 Watts.

 

[Fredneck]

I should have been clear on my thought of the X having extra HVAC due to volume. I was comparing the extra volume to the S it is based on. With the extra volume I would hope it has more heating capacity.

I can tell you the X has issues with heat. I guess if I turned on the heat in the back rows it would help, but every time the car turns the air inside doesn't turn as much and you get an apparent rotation of air which carries a cold draft from the back to the front. I've also felt this when going up and down hills which are a much smaller rotation.

Yeah, it's pretty clear that Teslas are designed in California.

 

[Fredneck]

Batteries are more efficient at warmer temperatures. There are more losses when using a cold battery. Small but worth noting. As other mentioned, heating the cabin takes a lot of energy that is available 'for free' on a gas car. Thus we see it as loss of range in an EV. Cold temps make many mechanical parts less efficient. Rolling resistance is higher at cold temps as well wen roads are wet or snowy. Cold air causes more drag. Reduced regen captures less energy back when the battery is cold. All things combined just add up in the winter. The largest factors are cabin heating and battery heating. What helps is turning on the cabin heater from your app before you use the car (while it is connected to a charger). This will use shore power to warm with the battery and cabin so it's not lost from the battery. Also, time the charging over night so it is finishing close to when you leave in the morning. Charging warms up the battery (charging losses causes heat in the battery) so you have a warmer battery in the morning without spending extra energy.

I looked up the density of air on cars and the change in density is about 10% between a hot summer day and freezing. So if that actually was a dominate effect I should see that in ICE vehicles as well as EVs. I drove the same pickup for 20 years and never saw a 10% variation in mileage unless there was something clearly different like having a kayak on the roof.

I found an equation that related air density to wind resistance and it was linear with density while being proportional to the square of the speed. I did see an effect from speed. If I drove at 70 or above I would lose about 10% compared to 60. I liked getting my 20 mpg, so I was not a popular driver on the highway. lol

 

[ajdelange]

I looked up the density of air on cars and the change in density is about 10% between a hot summer day and freezing. So if that actually was a dominate effect I should see that in ICE vehicles as well as EVs.

The drag force on a car with coefficient of drag Cd and cross sectional area A traveling at speed v through air at density rho is

F = Cd*A*rho*v^2

If the car travels distance x then F*x units of energy must be expended to overcome this drag but the energy consumed per unit distance traveled to overcome air drag is just F. If the temperature changes enough to increase the air density by 10% then the Wh/mi allocated to drag goes up by 10%.

I drove the same pickup for 20 years and never saw a 10% variation in mileage unless there was something clearly different like having a kayak on the roof.

You saw in your ICE vehicle exactly what you see in your BEV. It is simply that air resistance to motion isn't the only sink for energy. There are things like rolling resistance, gearbox friction and bearing friction that have to be overcome too. At least initially gearbox friction will be higher at low temperature as the oil will be stiff until it warms. And, at least initially, tire rolling resistance will be high until the tire warms. But, of course, in cold air and on a cold road surface the tires aren't going to warm as much as they would on balmy spring and hot summer days so rolling resistance will be higher in cold weather.

Just to give an idea of what to expect I averaged about 301 Wh/mi last winter and about 294 last summer - only a couple percent difference. I'll note again that Stats shows about 7% change for the X fleet.

I did see an effect from speed. If I drove at 70 or above I would lose about 10% compared to 60. I liked getting my 20 mpg, so I was not a popular driver on the highway. lol

70 vs. 60 represents a 17% change in speed but increases drag by 36%. Even though drag represents only part of energy consumption an increase in it of 36% is going to be visible in the overall consumption.

 

[Big Earl]

I can tell you the X has issues with heat. I guess if I turned on the heat in the back rows it would help, but every time the car turns the air inside doesn't turn as much and you get an apparent rotation of air which carries a cold draft from the back to the front. I've also felt this when going up and down hills which are a much smaller rotation.

Yeah, it's pretty clear that Teslas are designed in California.

The S and X are particularly bad about that. They've fixed the problem in the Model 3. Running the rear heat in the X will help.

 

[jrennie]

Cold midwest winter.
Model 3 long range.
Could I drive 90 miles, leave car in airport parking without charging, return in 5 days, heat car after landing to remove snow and warm up and drive 90 miles back home?

 

[Saghost]

Cold midwest winter.
Model 3 long range.
Could I drive 90 miles, leave car in airport parking without charging, return in 5 days, heat car after landing to remove snow and warm up and drive 90 miles back home?

Should be doable. You’d properly need to turn Sentry mode off, though.

 

[Big Earl]

Cold midwest winter.
Model 3 long range.
Could I drive 90 miles, leave car in airport parking without charging, return in 5 days, heat car after landing to remove snow and warm up and drive 90 miles back home?

That might be cutting it close, depending on temperature and weather. If it's snowing, I don't think you'll make it. Note that this is the Model X forum - you might want to post your question somewhere in the Model 3 forum.

 

[jrennie]

That might be cutting it close, depending on temperature and weather. If it's snowing, I don't think you'll make it. Note that this is the Model X forum - you might want to post your question somewhere in the Model 3 forum.

Thanks

 

[Fredneck]

The drag force on a car with coefficient of drag Cd and cross sectional area A traveling at speed v through air at density rho is

F = Cd*A*rho*v^2

If the car travels distance x then F*x units of energy must be expended to overcome this drag but the energy consumed per unit distance traveled to overcome air drag is just F. If the temperature changes enough to increase the air density by 10% then the Wh/mi allocated to drag goes up by 10%.


You saw in your ICE vehicle exactly what you see in your BEV. It is simply that air resistance to motion isn't the only sink for energy. There are things like rolling resistance, gearbox friction and bearing friction that have to be overcome too. At least initially gearbox friction will be higher at low temperature as the oil will be stiff until it warms. And, at least initially, tire rolling resistance will be high until the tire warms. But, of course, in cold air and on a cold road surface the tires aren't going to warm as much as they would on balmy spring and hot summer days so rolling resistance will be higher in cold weather.

Just to give an idea of what to expect I averaged about 301 Wh/mi last winter and about 294 last summer - only a couple percent difference. I'll note again that Stats shows about 7% change for the X fleet.


70 vs. 60 represents a 17% change in speed but increases drag by 36%. Even though drag represents only part of energy consumption an increase in it of 36% is going to be visible in the overall consumption.

Like I said, other than driving at a different speed or tying kayaks on the roof, I never saw more than a ±10% deviation in fuel economy (and that was a rare thing, not dependent on weather, winter or anything else, normally within a 10% window). It is great to talk about theoretical equations, but the proof of the pudding is in the eating. There are many, many aspects of fuel economy which are not part of the air resistance equation.

 

[Fredneck]

The S and X are particularly bad about that. They've fixed the problem in the Model 3. Running the rear heat in the X will help.

How was this "fixed" in the model 3? Is this another example of Tesla having to learn lessons the other car makers have learned a long time ago?

 

[Fredneck]

The rear heater in the Model X is about 2,500 Watts.

Can I ask where you got that number? I like to be able to verify numbers if I'm going to cite them to others. How about the front heater in the X? Is that 5 kW like others say? And the battery heater, I've seen 5 kW and 6 kW?

 

[Big Earl]

Can I ask where you got that number? I like to be able to verify numbers if I'm going to cite them to others. How about the front heater in the X? Is that 5 kW like others say? And the battery heater, I've seen 5 kW and 6 kW?

Testing a vehicle and monitoring energy consumption while hooked up to shore power on a JuiceBox Pro 40.

Front heater is 6 kW and is variable output. Battery heater is about 5 kW (labeled as 6 kW) and is not variable output from what I can tell. More information about battery heater consumption is available in other threads - I haven't spent much time testing it.

 

[Big Earl]

How was this "fixed" in the model 3? Is this another example of Tesla having to learn lessons the other car makers have learned a long time ago?

Better insulation in the doors and dash, improved HVAC design, larger ducts to the floor vents and different control algorithms.