I see and hear about a random EV that has X range in 20 degree (Celsius) weather, steady speed of 110 km/h, but Y range (significant difference) if it’s 130 km/h. Even more of a difference if it’s 0 degrees.
If it needs to pull a trailer with 500kg it loses, i don’t know, 25% of the range?
There are probably other examples. I’m not talking these specific examples, i just mean in general.
Nobody ever talks about that when it comes to cars that run on gas or diesel, i assume because it doesnt affect them as much. Why?
In: Engineering
It affects gas and diesel the exact same way, but if even the worst case conditions leave you with a range of 600km on one tank and the ability to fill up in less than a minute pretty much anywhere, you’re less concerned about range and more concerned about efficiency (miles/gallon, l/100km) in a financial sense.
Tldr: electric car – can I travel 700km? Diesel car – how much will it cost to travel 700km?
The biggest reason is that current battery technology relies on chemical reactions, and the efficiency of these reactions decreases with temperature. At lower temperatures, you can’t get as much power out of a battery.
Another reason is that electric vehicles use the battery for heating. In a gas engine, the heat used to keep the occupants warm is waste heat created by the engine so no additional power is required. But battery operated cars use electrical resistance heating which takes power.
Batteries don’t like cold. It affects the internal chemistry making them less efficient.
As for towing, my petrol driven car’s range drops from ~800km with just me and a passenger to <500km when towing a trailer with a load.
Most (all?) chemical reactions are affected by temperature. This also affects batteries (where a chemical process creates electricity), but also the combustion process in a gasoline engine requires a certain temperature – and let’s not mention Diesel engines, which won’t even start if they are cold.
The difference is that a gasoline engine gets hot when it runs, and thus already creates ideal conditions by itself. A battery will also warm up when used, but much, much less and it takes a lot longer, so it remains much longer in a sub-optimal state.
That’s why some electric cars have battery heating – but of course that again requires electricity that is then missing from your range that you can drive…
>Nobody ever talks about that when it comes to cars that run on gas or diesel, i assume because it doesnt affect them as much. Why?
They do, all the time. They just talk about fuel consumption, not range. And it “matters” less because filling up a gas tank costs money, not time.
If I drive 130km/h vs 100km/h in my gas car it does take about 30-40% more gas. It just means that I have to stop sooner to fill the gas tank.
If I drive my EV 130km/h instead of 100km/h it means that I might need to stop to charge…it’s just “more noticeable” than costing 30% more in gas to get to the same place.
Same thing for towing. When I had a camper, It would coust me 50% more gas, but filing up a gas tank takes 5 minutes vs 30-40 to charge an EV.
For most things it does affect gas/diesel cars the exact same way but for those cars nobody cares about range on a single tank, when you hear about it it is usually in the context of cosumption like liter per 100km. If you look up liter per 100km for a car it will have a disclamier somewhere that should say you at what speed and so on.
The one diffrence for EVs is cold temps because the heater in an EV is an electric heater that takes extra energy in a gas car the heat is just taken from the engine because the engine produces the heat anyway so you dont spend any more fuel on it.
While others seem to have the right idea, I think they’re missing the main reason behind the variation to EV ranges. EVs are just more efficient but have way less energy to work with.
A gas engine is at most 30% efficient. And a gallon of gas has a lot of energy in it! So a whole tank of fuel, with a hideously inefficient engine, has a ton of room to hide variations. Gas cars take a mileage penalty in the winter but it’s hard to notice over an entire tank of gas.
An EV has much less energy to work with but the engine is much much more efficnet. My crappy Ford EV has a battery that only holds as much energy as a gallon of gas but can drive me 80 miles. Any slight wind penalty, or temp/battery penalty, will be felt because the engine is using the energy about as well as it can.
Internal combustion engines(ICE) are terribly inefficient, often wasting 60% of the fuel energy to heat waste.
Modern electric vehicles are very efficient, most are 95% efficient or more.
So when its cold outside and we need to siphon off some energy to heat the cabin, there is tons available from from an ICE but with the EV we need to just waste battery power creating heat to warm the cabin.
When it’s hot outside and we need to run an AC compressor, the inefficient ICE engine, already spinning it rotating mass, doesn’t really mind spinning the AC compressor too, but on the EV again we are sucking down battery range to run the compressor.
This is also why we see only a moderate drop in fuel efficiency from ICE when towing or hauling heavy loads, but with EVs we see huge losses in range when towing. We’re essentially only paying 40% for the added weight with ICE, but paying nearly 100% for the added weight with an EV. Because of their respective efficiencies.
The other factor is that to maintain the EV battery’s performance and longevity, it needs to be operated at a specific temperature, typically around room temperature. This means we’re also using the AC and electric heaters to heat/cool the battery to room temperature.
Variation with driving conditions can also be pretty significant with ICE vehicles, but we usually talk about it as fuel economy (mpg or liter/100km) instead of range.
The main reasons we talk about it more with EVs are:
– worse refueling (charging) infrastructure – there are fewer chargers than gas pumps
– longer refueling (charging) time – charging takes longer than pumping gas
– less capability to tack more range on (both in vehicle design and in aftermarket options) – batteries take more space and weigh more than gas, so we can’t just throw more on or carry a gas can for more range.
– harder to fix if you run out – ICE vehicles can just bring a gas can, EVs need a tow or a long while charging
Speed and weight will affect gasoline/diesel the same way it does EVs, it’s just less noticeable because you can fill up a chemically driven car much faster than an EV.
Temperature affects EVs more significantly, ironically, because they are much more efficient than gas/diesel engines. Both engines and batteries work best at a certain (elevated) temperature. Cold starting gas/diesel engines have atrocious fuel economy, but because most of the burning fuel is lost as waste heat, even in cold weather, they quickly warm up and are able to maintain that temperature through waste heat of the fuel. Therefore the engine can stay warm without affecting the gas mileage too much.
Batteries also need to be warmed up but since they are so efficient, they don’t have much waste heat to use, so they have to use energy from the battery to heat itself, which reduces the range of the car.
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