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Comment by hughrr | Hacker News Reader

The thing that gets me with the success stories is the issue with risks and planning for success only.

When you’re driving in the colder parts of Europe it’s generally advisable to keep your tank at least 50% full all the time. If the shit hits the fan, like it did for me in Switzerland once, and you’re stranded for 4 hours due to a crash out of your control, your car becomes a fairly important life support system until the road is cleared. There is no recovery option when there are a few hundred cars in the same shit.

So you’re 3 miles from a supercharger with 15% battery left and your car is a frozen brick in under an hour. You can’t deliver more fuel to it and your efficient route plan is a liability and there’s a queue of bricked EVs waiting for flatbed recovery.

I’m not criticising the concept but the current execution and the perception of it.

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> So you’re 3 miles from a supercharger with 15% battery left and your car is a frozen brick in under an hour. You can’t deliver more fuel to it and your efficient route plan is a liability and there’s a queue of bricked EVs waiting for flatbed recovery.

There are a few things to consider.

First up, if you want to optimize for energy efficiency then the best option in an EV is to carry a blanket and rely on the seat heaters as much as possible.

Consider this scenario with a long range model 3. 80kwh, 15% means you have 12kWh available (Let's drop that to 8 due to cold weather). The seat heater consumes 500W at low power. That gives you 16/people hours of heat.

But let's say you just run the HVAC straight. You've still got 1 hour of heat (assuming it's using the 6kw restive heater. More if you are using the heat pump).

In any event, the approach to "I'm in an EV and stuck in traffic" is exactly the same as if you were in an ICE with low fuel. Shut things off. Wait until you are freezing, turn it on again. Ration your fuel/energy until you are unstuck.

To get to your charging destination in this scenario, you need roughly .9kwh of energy (300wh / mile, which is on the high end) or about 2% of your battery.

This is good practical advice for how to maximize EV energy use in an emergency.

That said, these vehicles are clearly not made for a long haul cold weather existence. Can they be made to work for occasional use with some planning and prayer? Sure. But these stories and the counter-claims leave no doubt that people who park cars in -30F and do 300 mile one-way trips through mountain passes and deserted highways should stick to ICE vehicles. If you're doing some variant of this with regularity (say 0F and occasional 150mile trips), you should probably do the same for safety reasons, even though EV will probably be fine for all but the rarest disaster.

Regardless of ICE or EV, people doing this kind of driving are well-advised to prepare for having a non-functional vehicle. It's always best to stay with the vehicle if it's habitable and if rescue is what you can count on, but having cold-weather gear, food, shelter, means to create/use external heat sources, and ability to "hike out" are some basic rules of the cold road that even 'tourists' should abide by. If you're doing remote winter driving, basically also pack for winter backpacking. This in addition to road flares, small shovel, tow strap, etc. to support the vehicle. It's less necessary now than it was in, say, the eighties when vehicles were far less reliable, but it's still practical advice: be prepared.

> That said, these vehicles are clearly not made for a long haul cold weather existence. Can they be made to work for occasional use with some planning and prayer? Sure. But these stories and the counter-claims leave no doubt that people who park cars in -30F and do 300 mile one-way trips through mountain passes and deserted highways should stick to ICE vehicles.

I'm guessing this is hyperbole, but really, this is a scenario that does not exist pretty much anywhere outside of Alaska and Russia. And even still, you'd probably be shocked (heh) at how many fast EV chargers present in these locations.

Every year, the situation with EV chargers has gotten better, by a lot. Consider the fact that John Day OR has a fast charger [1].

There aren't many places in the continental US more than 100 miles from a fast charger. Very little prayer is needed, though a bit of planning is nice. It's hard to find a location that you can't comfortably reach with an EV that has 300+ miles of range.

[1] https://www.plugshare.com/location/304770

Canada has high latitudes as well. Only part hyperbole, which is why I make the statement that even if you're doing only 0F and 150m, the same prep is a good idea. Really any drive where, in the event of your vehicle breaking down exposure would be life threatening (Alps, Rockies, Cascades, you name it), you should prepare accordingly whether EV or ICE. Having climate control in your vehicle should not be your primary contingency in the event that forward movement ceases.

Considering EV's lose range based on temps, that charging stations are still sparse in hostile environments, that a passers-by can't siphon out fuel for you (I know an ICE can jump start a Tesla, but not sure how practical it is to charge a Tesla from an ICE), ICE engines are still a better bet if you're in such conditions.

Car and Driver did a test using an older Model 3 with a resistive heater (the newer models use a much more efficient heat pump), and found that it used around 2.2% an hour to keep the cabin warm.

https://www.caranddriver.com/news/a38807463/tesla-model-3-cl...

In your example with 15% left, you'll use ~9% battery while in traffic for 4 hours keeping the heat and car on, leaving 6% to get to the next charger. At ~300wh/mile you'll arrive with ~4-5% left. There's also buffer under 0%, but it's not guaranteed.

4-5% is not a comfortable number to be at, but I think it's acceptable in a worst case scenario like this. That being said I would definitely turn down the heat, and drive slower for the next few miles (and check for alternate chargers) to minimize power usage.

Man, the heat pump hvacs are impressive :). My 2018 model LR 3 has a resistance heater and a heat pump heater is the one thing I really wish I had.

I really wonder how a heat pump can achieve so much efficiency gain. Heat of electric resistance is about 99% energy efficient: almost all energy is converted into heat, nothing else.

It can be that efficient when set to some point that would cook you. For low human temperatures that we call comfortable, it is not so efficient.

What is the electrical energy converted into at lower temperatures if not heat?

It just goes back to the battery to complete the circuit. Heat is created by resistance and if the energy going through the heater isn’t being resisted enough, there is no heat, just wasted energy. Most of these heaters regulate temperature by turning off/on/off and it’s the coming up to full resistance that is when the energy is “wasted” and doing it at human temperatures is a lot of off/on cycles. Also, it’s worth pointing out that not 100% of the energy is converted to heat, or you’d have a gigaton bomb instead of a heater.

A resistive heater directly converts electricity to heat, whereas a heat pump instead moves heat, from the outside to inside of your car. The heat your car gains is reflected by the heat the outside loses. In that way, they can be 300-400% “efficient”, because we do not care about the outside air around the car getting a little bit colder.

> whereas a heat pump instead moves heat, from the outside to inside of your car.

I completely forgot that the energy of the outside air is used, that explains it of course.

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