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Comment by cbmuser | Hacker News Reader

Yes, but their energy density has hardly changed and every gasoline tank beats your average LiIon battery by a factor of 10:

> https://en.wikipedia.org/wiki/Energy_density#In_chemical_rea...

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Don’t forget to account for the differences in engine and drivetrain efficiency. a gasoline engine gets way less of the gasoline's energy to the wheels. The engines of today are 30-40% efficient iirc, and then you lose more in the tranmission, differentials, etc. Electric motors are ~80-96% efficient and there is less transmission losses involved after that too.

also energy density of cells and packs continues to improve and has improved a lot since 1991

Additionally, electric engines and drive-trains are much lighter. You don't need a gearbox, compressor and many other components. This makes up for some of the extra weight of the battery.

Source?

One source on recent energy density improvements:

https://cleantechnica.com/2020/02/19/bloombergnef-lithium-io...

A source on electric motor efficiency: https://insideevs.com/news/348504/tesla-improves-motor-effic...

A source on internal combustion engine efficiency: https://en.wikipedia.org/wiki/Engine_efficiency#Internal_com...

As to the drivetrain losses through transmissions and differentials, I have only my own experience from working on cars, dynos (measuring the power to the wheels), and racing. It depends on drivetrain layout. front engine front wheel drive has fewer losses than front engine rear wheel drive, all wheel drive usually worst of all. You lose another 5-15% depending.

Probably you will also find this video interesting, which goes into depth on the full lifecycle of different fuels and the overall efficiencies:

https://www.youtube.com/watch?v=0d0MPg7DxbY

Besides what the other guy posted, see how far you can drive per unit of energy.

A gas car getting 26 mpg -> 26 miles from 33.41 kWh of energy -> 1285 Wh/mi

A Tesla Model 3 getting 353 miles from a 75 kWh battery -> 212 Wh/mi

That's a 6x advantage.

I don't think that's fair - the energy density has been improving largely how everything else in the world does, incrementally, step by step. It's unfair to expect a magic overnight revolution.

https://cleantechnica.com/2020/02/19/bloombergnef-lithium-io...

Lithium-ion is something of an everyday miracle. I'm older and I remember previous rechargeable battery technologies and they were just terrible. Also, Gas and tiny portable batteries have nearly nothing in common. You're not going to be able to fit an ICE into my iphone. What's with the weird comparisons? I don't see how they are helpful. Its like when we talk about hate crimes or civilians killed in war, and other people bring out unrelated stats about car accidents or cancer. This is a common thing on the internet that almost no one questions. Its weird and frankly a dishonest rhetorical trick.

>You're not going to be able to fit an ICE into my iphone.

Someone please send this comment to Colin Furze.

To be fair to op, lithium ion batteries are used in cars so it's not like the comparison is totally unwarranted. Energy density is one of the key factors in the viability of electric transportation so it makes sense why op would bring it up

Energy density is a meaningless measure for cars. $ per mile isn't. If you have a heavier battery, you just need a bit more of it to drive the same amount of miles. It just boils down to cost in the end. You can also trade weight for mileage and have less battery. That lowers the cost and improves the mileage. Apparently Tesla has pushed internal cost per kwh of storage below 100$ now. That price is going to drop further.

But lets look at actual mileage at two roughly comparable cars (same vendor and brand):

Mustang Mach E 88kwh/300 mile EPA range. Or about 3.4 mile per kwh.

2021 Ford Mustang Mach 1 does 5.6 gallons per 100 miles (with the 8 cylinder engine). Or about 18 miles per gallon.

https://www.fueleconomy.gov/feg/noframes/43610.shtml

These are just official numbers, take them with a grain of salt. Also, both cars have a couple of variants obviously. Particularly the petrol mileage is likely to get a lot worse over the lifetime of the car as the engine wears out. This is less of a thing with EVs. And you probably have to drive the petrol Mustang like a nun to actually get 5.6 gallons per 100 miles. Likewise EVs have different mileage depending on driving style, temperature, etc. Lets just say they are both a little bit worse typically.

But they are nice numbers to work with and they are based on real world efficiency rather than archaic notions of potential energy, energy density, etc.

With these numbers, 1 gallon is roughly the equivalent of a bit over 5kwh when it comes to mileage in a gas guzzler like the Mustang. Cost for that from a super charger depends on a few factors. Likewise for a gallon of fuel (e.g. taxes). On a super charger at 28cents per kwh, it's like filling your tank for about 1.40$ per gallon , which would be a pretty good gas price that most of the world has not seen in a few decades. A super charger is probably the most expensive place to get your electricity. So, you might do better if you have cheap nightly grid rates or rooftop solar. There are lots of ways to get that number down. But 1.4$ per gallon equivalent is a lot cheaper than petrol. About 2x depending which state you live. Closer to 3x in some states. EVs are a bit heavier than petrol cars of course. But not 10x. Nowhere close to that. Maybe 1.5x or so. Half the energy cost per mile at the price of 50% extra weight is not a bad choice.

That's the reason people are switching to electric. It's just cheaper. It gets better when you also consider maintenance cost. It gets better still when battery and vehicle prices continue to drop. Purchase price of EVs is currently still slightly higher than the equivalent petrol car. But not for very long apparently.

Your mileage may vary but nowhere near 10x. More like 0.5x.

Energy density on mass is not entirely meaningless. A heavier car requires larger tires. That makes the tires a more expensive continuing cost, and creates more particulate pollution. A heavier car also requires larger brakes and pads (though electric cars can offset this with regen). A heavier car also puts more wear onto the roads. A heavier car also makes the car slower at a given horsepower, and have worse handling characteristics.

So metrics like energy per kg, energy per volume, and energy per $ can all be relevant.

In theory yes. In practice, the mach e handles very nicely compared to the mach 1. You'd not buy the latter in favor of the former for it's raw performance as the mach e is simply faster. Brake pads last longer because of regenerative breaking (i.e. you hardly use your brakes at all). Tire wear on a mustang is something to be mindful of. But then doing donuts seems to be a thing with these cars. Ridiculous torque has a price. You see the same pattern with other EVs and increasingly high performance electrical sports cars breaking all sorts of records.

Energy per kg is relevant when weight matters. For example in electrical planes. In cars, $ per mile is the one to focus on. Of course that continues to improve as energy density improves so they are somewhat linked.

Range matters. My current Volvo V40 can, at highway speeds, go for 1100km on a full tank of diesel.

There is no electric car at a similar price that can go farther than 500km, in practice I'd be shocked if it went more than 400km.

I'd want range to be at least 80% of that of the diesel before I switch.

How often do you drive 880km in one go?

You've got to remember that with an EV, you start every day with a full 'tank'*

(* as long as you've got somewhere to plug it in overnight, which is a problem in some places, granted)

Not often, but we're not going to buy 2 separate cars, 1 for regular trips and one for road trips.

Range anxiety is a thing, especially since the "failure mode" is really bad. Super chargers are really rare compared to gas stations and if you run out of battery, with regular charging it takes 10 hours to charge.

Maybe 880km is too much, but for sure I'd want 60% (so 660km) + something extra, maybe 50-80km, to not feel anxious when driving long distance.

Plus overnight charging is unfortunately still a problem.

I personally think that for me (and I guess many others), the next generation of EVs or maybe the facelift for the current generation should be really close to what I want. By next generation I mean that many EVs are/will be launched soon (so 2020/2021/2022), in the car world a generation is usually around 7-9 years (so 2027-2031), and a facelift is done usually mid-cycle (so probably 2025-2026).

I've found re-charging on long journeys to be ok although it helps to have a plan A and a plan B and for best results you combine charging with lunch or something. But I do live in Europe where distances are shorter and chargers are more plentiful

Most people do most of their charging at home. Our off peak cost at night is 5 cents per kWh. Much, much cheaper than superchargers.

>Our off peak cost at night is 5 cents per kWh.

Must be nice. Triple that in California (where most EVs are).

I on purpose focused on super chargers to drive the point home. 15 cents is still a lot cheaper than super charger prices. You can drive that down further by e.g. using solar power. That high price is an excellent incentive to invest in roof top solar.

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