Myth Busters needs to look at this.
Assuming, of course, the EV stated out fully charged. Someone towards the end of a trip may wind up in a jam like that with a low charge to start. Of course, I’d expect that to be only a small portion of the stranded, not most of the EV’s.
But that consideration applies equally to the ICE cars. They may have a full tank or nearly empty.
I guess I am arguing against a widespread belief (not necessarily held by you) that being trapped in a snowstorm or extended traffic jam is a particular problem for EVs, and this being held out as a reason not to buy an EV. Whereas in fact the opposite is true - for a given “percentage full” an EV almost certainly has better stamina than a fossil fuel car; even a car with 10% or 20% battery charge can probably sit out even an extremely long wait.
One other consideration I haven’t mentioned (because I don’t know the answer): how well does an ICE cope with idling continuously for many hours?
In Ireland there is an emergency mobile charge option for EVs.
Mobile Electric Car Charging | Emergency Charging | theAA
However the most practical option in a given situation may be to bring the car to a nearby public charger.
The recommended technique is to only run the engine 10-15 minutes out of an hour to preserve fuel but keep the car movable.
One bonus for an EV stuck for hours is no risk of a carbon monoxide leak killing the occupants.
In the garage, too. House power go out? Pile into your Tesla, enable “camp mode” and sleep in comfort. Should last upwards of a week if you only use it at night.
All the while grumbling over not getting the transfer switch installed to run the essentials off my generator…
I disagree. You are leaving out several factors:
- Cars are poorly insulated compared to houses
- You also have to keep the battety warm.
- Resistive heat takes a lot of energy.
- A car has a lot more surface area to cabin space, leading to more heat loss pe4 sq ft of space than a house.
Car and Driver measured a 122 Wh per mile difference in a Tesla model 3 betwwn heat off and heat on max with seat warmers. That’s 35% more energy. And it was only 38F when tthey did the test, not -30. So bettery heating would have been much less.
Cabin heaters in electric cars run between 2kW and 7kW. A 7kW heater will drain a Tesla standard range battery in 7 hours. I think the Tesla heater is smaller, though. Maybe 3kW? So let’s take a 54 kWh battery at half charrge, and say we can run it down to 10% in an emergency, so we have 21.6 kWh left. A 7 kW heater will drain that in three hours. A 3 kW heater will drain it in 7 hours.
Of course, you might have a vehicle with a much bigger battery and a heat pump, which will be much better. But that’s not everyone. There are a lot of EVs out there with small batteries and resistive heating. They could easily run out of juice heating a cabin for a few hours in -30 weather.
No one is saying that an ancient Leaf with a half charge is going to be great in the cold. But then, neither is some tiny compact gas car with a few gallons left in the tank.
A Model 3 with a heat pump only uses about 750 watts with an outside temp of 3 C, inside 21 C. Without the heat pump, 2.2 kW. Sure, that’ll get worse as temps go down further. But it’s not going to leave you with just a few hours of heating, at least not without assumptions so pessimistic that they can’t be applied to gas cars as well.
Some of your assumptions are ridiculous, anyhow. Why would you only run down to 10% in an emergency? It’s an emergency–you run it down to 0%, just as you’d run a gas car down to empty.
The prospect of getting stranded for hours at -30 in my '09 Fit with a quarter tank of gas is pretty much terrifying. At idle at those temperatures the heater will pull the engine temp below operating temperature.
This is why sane people do their best to avoid long road trips during extreme cold snaps, and if they do have to travel have contingency plans in place.
Here’s a guy who slept in a Model 3 with a heat pump at -3C (video) (article). Bottom line, with temperatures from -3C and dropping to -8C he used 10.2kWh with the inside temperature set to 21C for 7.5 hours.
While the battery is still warm the heat pump is more efficient at moving heat from the battery to the cabin. As the battery gets colder, the heat pump has to work harder, and so draws more power heating the cabin.
So, with a battery at 50%, your still looking at a day or so of heat. More if you lower the inside temperature to 13C or so. Not comfortable, but certainly survivable if you have a winter coat and stuff.
My Model 3 has the resistive heater, and it can pull up to 6.4kW or so. Much less efficient, but it’s not going to need to run at full blast the entire time, either.
Recently, the car had sat and was completely cold, and then I had to drive 3 miles in a snow storm. I used 2.72kWh for the trip. Normally that trip is about 1.24kWh. The temperature outside was 7F (-14C) and inside the car was 80F (27C), because I needed to keep the windows clear.
From my experience, in my car, it does well in very cold temperatures because pre-heating is wonderful. No need to wait for the engine to warm up to start getting heat, either.
If you want to push an EV to it’s absolute limits in cold temperatures, then you’re going to reach a failure point. That may be a different failure point than in a gas car. If all you want to do is commute 30 km to work when it’s -15C in the morning, no problem.
Not from me. I posed the question because I don’t know the answer and was curious. Combination of the thread about the traffic jam in Virginia, and the cold temps here at home (currently -32 C) got me wondering.
My Model 3 has the electric heat, not the heat pump. (older. )
In -20°C (below Zero F) I find it will take 2 to 3 km range for each km travelled - in stop and go city
commute averaging (with traffic lights) 15mph I use up to 4km per km. In highway travel, much less, maybe 1.5 to 2. Part of that is cabin and seat heat- remember heat is per minute not per km. The slower you go, the worse it is. At freeze temp (32°F or 0°C I would get about 1.5 to 1 on highway driving.
Also note, cold batteries don’t recharge well, so regen for braking is not as useful - which adds to energy used as it is not recovered.
Does this bother me? No. The basic fact is that I “fill up the tank” every night. I rarely use the high-speed level 3 superchargers.
Charge? At 40A 240V (Level 2 charger) so about 10kW, I add 58km/hr (which is about 35mi/hr.)
So for a stranded motorist, a tow truck with a level 2 charger10kW might sit there for half an hour giving the car the juice to go 17mi, which should get them to the next charger - or else they were really screwed, it wasn’t just a case of a few miles short of target. Meanwhile, Biden’s infrastructure bill is promising to put fast level 3 chargers all over the map, which should help things.
When high speed (level 3) chargers are everywhere, i can see a dedicated charger truck with a higher end generator (or maybe all tow trucks will have them) giving you 450V; a charge of 250kW is possible, but 100kW to 150kW is more likely.
For now, towing is simplest and less demanding of the tow operator’s time - when time is valuable.
An important point for I95 mess is that to charge a battery, it has to be warm. So your supercharger or tow truck may spend up to 15 minutes of that charge current heating the battery before it can charge at full speed in cooler weather after a prolonged stop. (If you just arrived at a supercharger station, odds are your battery was warm from travelling - and Tesla’s will “pre-condition” the battery when the computer knows from your trip planner that you are approaching the next charge station.
I need to also point out - I can preheat the car and the battery while plugged into house charger, if necessary, to both make it comfortable and help with regen. I can use the phone app to start cabin heat remotely wherever it’s parked, but the main advantage of electric heat is “instant on”; so even if I don’t preheat the car, it start blowing hot air in seconds. (Not like my BMW which can take minutes to get warm) I understand the newer Model 3 has steering wheel heat. I miss having that feature.
I don’t know about EV batteries, but a lot of batteries suffer damage if drained too much/entirely. Now, genuine life or death kill the car, right? But if you can avoid that you might avoid a costly repair bill.
I’d be shocked if any modern EV allowed you to damage the battery by running it down. It would be a serious safety issue since batteries damaged in this way have unpredicable behavior–like catching on fire. I can’t speak for other EVs, but Teslas at least can run down to 0%, then go another 10-20 miles in a degraded mode. Even when you go through that buffer, the battery should not have taken any damage. Only if you fail to charge it in a reasonable time from there would there be damage–due to the natural self-discharge of batteries, even when the car is off it’ll be draining the battery slowly.
There are some reports of older Teslas being bricked in this way. Some owners would leave their cars unplugged for months at a time, only to find that the batteries were fried when they came back. Sucks for the owners, but it’s not really different from a gas car. You can’t just leave it parked somewhere for an indefinite period with no maintenance and expect it to come through unscathed.
Indicated zero and a real actual no joules left to be had state are very different things in modern EVs. Manufacturers are known to tweak the software to change the indicated state of charge as they optimise their cars. Zero is nothing more than the “please don’t run the battery down past this state, it will hurt its lifetime” number. The real zero is not what the car tells you. Same for 100% as well.
However, no doubt, really cold temperatures do not play well with lithium batteries. Same for really hot, although not quite as badly. Living anywhere where a car breakdown is life threatening makes for a different view on cars. Here in Oz it isn’t quite as horrendous. A 50 C day is capable of killing you if you are stupid, but a -30 C day will kill you even if you are smart. Here it is the temperatures and the distances that will kill you.
This scenario posits that charging stations only have two plugs. Do you know of such small stations? I suppose some may exist somewhere. I’m only familiar with the Tesla network and those seem to have a minimum of 4 stalls, and I think those are older ones in more remote parts of the country. But the stations going across the Prairie Provinces have a minimum of 6 and those along I-94 in ND and MT all seem to have 8.
At the other end of the spectrum of station sizes, there’s some along I-5 between LA and SF that have dozens, as many as 95 at Kettleman City.
What I’ve seen of the inside of car doors is a lot of open space. I wonder if it would make sense to insulate the doors and roof of a car
The problem with car doors is that the space needed to accept a window winding down is huge, and makes any other use of the space difficult at best.
No doubt, better insulation is not unreasonable. But the glass area involved in a modern car makes this a difficult problem. When Tesla are trying to sell you a near full size glass roof, performance in the cold doesn’t seem high on their agenda.