Subzero Cold & Electric Cars

[Algr]

TL;DR Summary

Can an L1 charger keep a car warm enough to prevent people stuck in traffic from freezing?

So there is lots of news this year about electric car owners getting stuck in the cold. There was a highway where people were stuck for hours. Emergency services could deliver gasoline to trapped cars, but electric vehicles had to be abandoned at the side of the road. Commentators are calling this winter the death of the electric car.

All highways already have electric lighting. Could this be tapped into by installing ordinary AC outlets for cars to tap into in emergencies? That sounds to me like a low cost short term solution to the problem. In the US, home outlets provide 1500 watts. Not enough for meaningful charging. (Even overnight they are suboptimal, but not useless.) But could an L1 charger keep a car warm enough to prevent people stuck in traffic from freezing?

I didn't know that there are people who apparently can't charge at home and rely entirely on superchargers. Even an L1 neighborhood network for street parking would be a big step up over nothing, and would be far cheaper to install than fast chargers with payment services. (I'm assuming that like streetlamps, these would be free to use, and paid for with road taxes, or a national subsidy.)

 

[berkeman]

Interesting idea...

 

[Bystander]

TL;DR Summary: Can an L1 charger keep a car warm enough to prevent people stuck in traffic from freezing?

But could an L1 charger keep a car warm enough to prevent people stuck in traffic from freezing?

Nope.

 

[Algr]

Nope.

Really? Not even with blankets, and heated seats as the only use of power?

 

[Baluncore]

Make sure you have a life jacket, when you go out in a boat.
If you travel by car in winter, carry a sleeping bag and thermal underwear.

 

[Algr]

When are humans ever prepared?

 

[Frabjous]

I am reminded of the old Jaguar joke. You need two, one for home and one for the repair shop. Or in this case, one to abandon in the cold.

 

[Vanadium 50]

Nope.

Why do you say that?

On 120 V I can warm my car's cabin before I drive it. To be fair, it may be subzero outside but not in my garage. But it's still cold.

 

[Vanadium 50]

I see one practical matter. L1 charging is 12 amps. A HPS lamp is more like 6. So, not only would you need to turn the lights off at night, you could only use every other post. That limits you to around 10 cats per mile in the cities (and zero in the countryside!).

 

[Bystander]

Why do you say that?

The news story; drivers/passengers had to be rescued. Might have been misreported, but not worth my while/time.... When do people drive around in their garages?

 

[Baluncore]

I am reminded of the old Jaguar joke. You need two, one for home and one for the repair shop.

With the Mini, you also needed two. One for each foot.

 

[Algr]

Nope.

I'm really tempted to test this by sitting in my car with a space heater. I know cars can't be as well insulated as a house, but the space that needs to be warmed is tiny, and many new cars have heat pumps that would generate even more heat than a space heater at a given wattage. Alas, the really cold weather appears to be over for now.

If I can get my car interior to 80° in 20° weather, would the 60° difference hold for colder weather? Would the car be 40° when it was -20° outside?

I see one practical matter. L1 charging is 12 amps. A HPS lamp is more like 6. So, not only would you need to turn the lights off at night, you could only use every other post. That limits you to around 10 cats per mile in the cities (and zero in the countryside!).

Well yes, you'd have to deliver more power to the highway lighting grid. But somehow I doubt that cut the wires so thin that they wouldn't have any extra capacity. And it is less power then the same cars would be drawing if they were at home on L2 chargers.

 

[Vanadium 50]

If I can get my car interior to 80° in 20° weather, would the 60° difference hold for colder weather? Would the car be 40° when it was -20° outside?

No.

 

[Algr]

No.

Why?

 

[Vanadium 50]

Why is 2+2 not equal to 5?

 

[Averagesupernova]

I think the whole news story which I have not read is more than likely politically motivated.
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Couple of points:
If you drive around with an electric car in the winter with a low battery that can't run the heat for more than a little while you can expect the same thing as you could expect driving around with a mostly empty tank of gasoline. You deserve what you get.
-
People may not have a way to fast charge at home. Too bad, so sad. I don't drive my vehicle into my garage on an empty tank of gas either.
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Electric cars will have some growing pains. It should be the owners responsibility to see to they can keep them running the same way it should be their responsibility to keep up payments, etc. I haven't ever bought a vehicle that I cannot afford to keep on the road due to insurance, fuel mileage, payments, etc. No different. If I decide to cheap-out and plug my car in at my parents house, friends, work, anyplace I don't pay for electricity and charge slowly and drive around with an almost dead battery most of the time because of this I guess I can expect less than stellar results. I suspect this happens regularly.

 

[Baluncore]

It was surprising to me how many people bought a car, then run it out of fuel the next day.
With a tank full of "hope", like Pandora, they find that even the hope has escaped.

I wonder if that now happens to EV drivers, or have range estimators stepped up in accuracy, and give more dire warnings.

 

[Rive]

All highways already have electric lighting. Could this be tapped into by installing ordinary AC outlets for cars to tap into in emergencies?

What's the distance between lamp posts, and how many cars will be on that distance?
Each with 1500W, on extender... Laid out on the snow... Waiting for the snow-plowers to cut them all...

.... I would rather suggest emergency stoves for EV-s.

 

[Tom.G]

If I can get my car interior to 80° in 20° weather, would the 60° difference hold for colder weather? Would the car be 40° when it was -20° outside?

No.

I would disagree with that negative answer.

Here in the USA we rate thermal insulation effectiveness as 'R' value; the R being the Thermal Resistance. An R of 1 indicates that heat flow thru a surface is:
1 BTU/Hr/SqFt/°F.
BTU = 3.41Watts
Hr = time in Hours
SqFt = area inSquare feet (0.093 Square Meters)
°F = temperature difference across the barrier in Degrees Fahrenheit (0.56°C)

Please notice that the thermal flow is directly dependent on the temperature differential.

I know, we are weird here in the US. Much of the rest of the world uses Thermal Conductance (K), Watts(W), Degrees Kelvin, Area (SqMeters).

It always comes down to the fact that heat flow rate is dependent on area, temperature difference, and material characteristics. That is just like an electrical circuit: ΔTemperature ≡ Voltage; Energy ≡ Current; R ≡ Resistance

One confounding factor is that air speed does contribute to additional thermal transfer. That is because in still air their is a semi-stagnant air film at the surfaces that contributes to the thermal resistance. With added air flow, this semi-stagnant air film is continually removed, exposing the surface to the ambient temperature.

As an example, my 4-door car has a bit over 31 SqFt of glass. Just because I happen to remember that ordinary window glass has R= 1.1, I'll use that. Lets take the temperature difference of 60° that @Algr asked about.

Re-arranging the definition of R-value above we get:
(Area x ΔT)/R = BTU
(31 x 60)/1.1 == 1860/1.1 == 1691BTU/Hr == 5766W ≈ 5.8kW to keep the car at 80°F with an outdoor temperature of 20°F.

Of course there will be heat loss thru the rest of the car body, not just the glass. Working in our favor though is that the people in the car are also generating heat.

End Rant.
Tom

 

[Baluncore]

Of course there will be heat loss thru the rest of the car body, not just the glass. Working in our favor though is that the people in the car are also generating heat.

If you can cover the car with snow, that will insulate the car from the wind, and from the -40° clear sky at night.
Drink water, and eat more sugar to maintain your internal body temperature.

 

[Algr]

I think the whole news story which I have not read is more than likely politically motivated.

Yes. I came here so I could bring informed replies to such discussions. The comments sections on those videos tend to be echo chambers. Naysayers will grasp any half-baked idea to create "unsolvable" problems. An EV connected to an L1 charger for a few hours is guaranteed to start and not need towing. Your typical ICE car today, does not offer such a guarantee, unless also plugged in with a heater.

I would disagree with that negative answer.

Here in the USA we rate thermal insulation effectiveness as 'R' value; the R being the Thermal Resistance. An R of 1 indicates that heat flow thru a surface is:
1 BTU/Hr/SqFt/°F.
BTU = 3.41Watts
Hr = time in Hours
SqFt = area inSquare feet (0.093 Square Meters)
°F = temperature difference across the barrier in Degrees Fahrenheit (0.56°C)

Please notice that the thermal flow is directly dependent on the temperature differential.

Thank you! This is very useful.

What's the distance between lamp posts, and how many cars will be on that distance?
Each with 1500W, on extender... Laid out on the snow... Waiting for the snow-plowers to cut them all...

If you ever have traffic suck on the freeway for hours you have a systemic problem that has nothing to do with how the cars are powered. It will be a long time before there are that many EVs on the road. By then, it will be realistic to have plugs every 20 feet (in the city), or inductive charging in the roads so that cars can charge while moving, or maximize the work-from-home movement.