LeSving wrote:
Another issue is the time it takes to heat it up. At -20, with no electric pre-heater, you can forget to travel in any comfort the first 1/2 hour at least. On my newest electric car the heater is excellent, within a minute or two, and the heat is coming en mass. But that also use lots of battery power. Cars sold in Norway typically have:Pre heater, electric or fuel (Webasto)
Electrically heated seats
Electrically heated wind shield, rear window and side mirrors
Electrically heated driving wheel.
Electrically boosted heater for the compartment (depending on size)
I feel you exaggerate. My diesel burner also has an electric cabin pre-heater, so you have warm air from the vents the moment you turn the key. First half hour? Come on, be sensible. The coolant temp gauge is at normal (~88 deg C) within 5 minutes – the thermostat keeps the radiator closed off while it heats up. Also have the electric screens, seats, etc. and with no perceptible effect on the range because the electricity to run them comes from the alternator.
I don’t do business at -20, but -5 is not uncommon. A internal combustion engine will still heat its cooling circuit to 88 deg C quite easily whatever the outside temperature, and a few litres of liquid piped through at heat exchanger at that temperature is enough to comfortably heat the cabin of any car-sized vehicle.
I feel you exaggerate also on the (perceived lack of) range limitations. You might be happy to plan stops for charging on a 200km trip, but I contend that most people would not be – that is only 1.5 – 2hrs driving which I think most people would prefer to at least have the option to do non-stop. Yes most of my trips are 15-30 minutes, but I value greatly the ability to drive non-stop or at least without fuelling for many hours if the situation requires it. In practice, on a long trip, somewhere around 4 hours is likely to be the point which I stop because I want a rest from driving.
The argument that range of EVs is not much of an issue is like saying that you could remove the 60 litre fuel tank from the average car and replace it with a 20 litre tank and people would hardly notice or care. That is demonstrably not the case.
You do not comment on the overall cost, I see!
It takes a few tens of horsepower for any car to cruise on a road, so one would expect there to be a few tens of kilowatts of heating available from the engine. I would be surprised if that is not enough to keep any car cosy, even at -20. Is there a reason only a small proportion of that heat can be used?
That’s a really good Q.
If I was the designer I would dump any generated heat really fast, because resistance of copper goes up with temperature, which is exactly what you don’t want. Same with heat from the semiconductors, but there the trend is to minimise losses to start with.
And in the summer you don’t want the heat anyway, so one would need servo controlled ducting to route it to the two different places. That already exists in most modern cars. However I suspect it is “low grade heat” i.e. a small delta-t (so not suitable for warming up the cabin) because you don’t want to run any part of the system at say +90C, which is what my VW engine water jacket runs at.
I used to own a Tesla, I became all to familiar with how to reboot the software.
@neil what happened? If the Tesla software crashes, that’s a bit of a worry for a “self driving” car 
johnh wrote:
Car 2 will be a 2-3 year old Golf or similar. While an e-Golf would be fine for the mission, once again the extra cost rules it out.
How fädo you get extra costs for an e-Golf? In Germany at least, there are generous subsidies on electric vehicles, so there is no overall price difference to an ICE car.
MedEwok wrote:
In Germany at least, there are generous subsidies on electric vehicles, so there is no overall price difference to an ICE car.
Subsidies on a used car purchase?
Peter wrote:
If I was the designer I would dump any generated heat really fast, because resistance of copper goes up with temperature, which is exactly what you don’t want.
Designer of what? Not sure I follow.
Surely the designer of a heating/cooling system on an ICE-powered car just builds a simple controllable circuit that dumps heat either to various cabin vents via the heat exchanger or to atmosphere via the radiator, in varying proportions depending on the demand from the climate control system?
Designer of the electronics driving the motor(s).
What I am getting at is that the heat being dissipated may be too low grade to be usable for space heating.
But somebody will know how this is actually done in electric cars. It will be on google I did a quick search and could not find any suggestion that motor or electronics heat is being used. Instead, they do the obvious things: the battery powers an electric compressor for the aircon (and in some cases this is configured as a reversible heat pump so you get heat from the same hardware) and heat dissipated by the battery can be used in the cabin too. But most heating is done with a simple resistance heater which just wastes the battery capacity.
kwlf wrote:
It takes a few tens of horsepower for any car to cruise on a road, so one would expect there to be a few tens of kilowatts of heating available from the engine. I would be surprised if that is not enough to keep any car cosy, even at -20. Is there a reason only a small proportion of that heat can be used?
The assertion from @LeSving surprises me also.
I contend that the average modern (petrol or diesel engined) car can easily keep its cabin toasty warm using heat from the engine cooling system alone, even at -20 outside.
I don’t know what the cabin heater on my car gives at maximum output (or if a number is even published) but if you turn it to max it can make the cabin uncomfortably warm in well under a minute. I would say at least 3-5kW, probably more. It’s like having a central heating radiator designed for a large room placed in a very small room. If you want the same sort of heat output in an EV it means serious battery usage.
Graham wrote:
Ah – I thought @kwlf was getting at the heat from an ICE rather than an electric motor.
I was.
Electric motors tend to be 90%+ efficient so you might only get a few kilowatts of waste heat from them, and they may be in the wrong place for extracting the heat easily. You might get some useful heat from the battery packs. I don’t know.
I could imagine that an ICE car manufacturer might calculate that it is easier to burn fuel to turn the alternator to heat some cheap nichrome wire, than it would be to arrange to extract the waste heat from the engine. It would affect fuel consumption, but perhaps not in a way that would show up in the test figures.
