This is an incredibly myopic take masquerading as "first principles". First, you're flat wrong on the differences between gas and batteries, especially for cars. Second, you need an actual reason energy density is the fundamental metric- cars aren't rockets and weight isn't the end-all.
It's impossible to neglect the efficiency here. Car-scale combustion engines have a real world efficiency of around ten percent compared to electric. A gallon of E10 contains 34.9 kWh and randomly picking a Toyota Avalon you'll get a real world 17 mpg with that[1], which works out to 16.4 mpge.
Compare that to real world measurements of a Tesla Model 3, a car that is MUCH more powerful and heavier, but gets 147.4 mpge[2]. The Avalon gets 11% as many miles per unit of energy stored. E10 is equivalent to 1.32 kWh/kg (4.8 MJ/kg).
Not to mention that graph of battery energy density is significantly out of date. Normal li-ion, is at 300 Wh/kg (1.1 MJ/kg) and li-sulfur is commercially available at 500 Wh/kg[3] (1.8 MJ/kg). Even Tesla's batteries are above 250 Wh/kg.
So the bottom line is the difference is ~5x right now. Is that enough to matter? 15.5 gallons of gas (standard fuel tank) weighs 44 kg, or 2.7% the total weight of the Avalon. The full capacity in batteries at 250 Wh/kg would weigh 232.32 kg, or 11.4% more. As much as 2 people + luggage. That's a totally irrelevant increase in weight; luxury or performance cars in a given class can weigh DOUBLE the lightest cars in the same class.
The energy density of batteries is a red herring for all vehicles except cargo/tanker ships and long-distance airplanes. It's completely irrelevant for vehicles. The charging speed is arguably minorly important but by FAR the most important things are the upfront and lifetime cost. That is related to energy density... the energy density of the power plant's fuel, not the battery. And again, it's incredibly naive to assume the weight is the major factor in cost.
It seems like you responded only to the gravimetric density part of the chart and not the volumetric part of the chart.
For performance cars, weight is absolutely a factor. (I'm not aware of any performance cars that weigh twice as much as their competition.)
(I do think it is fair to ignore the financial energy density and assume that a century of progress would have addressed substantial fraction of that gap.)
> It seems like you responded only to the gravimetric density part of the chart and not the volumetric part of the chart.
Gravimetric (specific energy, Wh/kg or MJ/kg) energy is generally more relevant than volumetric (energy density, Wh/l or MJ/l), because batteries are about twice the density of gasoline. Weight is also more valuable than volume in most vehicles, and a battery system already takes up hardly any more than a full combustion system. For example most electric vehicles now have a front trunk just to use up the newly available space.
> For performance cars, weight is absolutely a factor. (I'm not aware of any performance cars that weigh twice as much as their competition.)
Sure, but again this is an 11% weight difference, and range matters least on a performance car. A 918 weighs 25% more than an Agera RS. If you want to talk about power density, an electric battery will beat a gas engine to absolute shreds.
> If you want to talk about power density, an electric battery will beat a gas engine to absolute shreds.
Most (all?) production electric cars struggle to do a full power complete lap of Nürburgring Nordschleife without heat-related issues. They're amazing at the Stoplight Grand Prix (and I enjoy my cheap LEAF daily), but struggle as racecars.
>> I'm not aware of any performance cars that weigh twice as much as their competition.
> Sure, but again this is an 11% weight difference
I was just responding to a previous post claiming that "performance cars in a given class can weigh DOUBLE the lightest cars in the same class", nothing more. If you claim the span is much less than double, then I agree.
> Most (all?) production electric cars struggle to do a full power complete lap of Nürburgring Nordschleife without heat-related issues. They're amazing at the Stoplight Grand Prix (and I enjoy my cheap LEAF daily), but struggle as racecars.
No, they just don't make electric race cars. There is not yet sufficient demand. Properly cooled electric batteries make as much power as f1 engines without breaking a sweat.
Sony VTC5a cells[1] are 85% efficient at their full rated power, and can sustain that continuously for their full capacity. They do 2.4 kW/kg without a gas tank, exhaust, turbos, or intake. Their ten second burst current is double that, 4.8 kW/kg. That puts it at the same level or higher than current f1 engines, which run less than 2000 km.
If you count the weight of ancillaries as you should, electric batteries come out way ahead, particularly the most powerful ones.
> I was just responding to a previous post claiming that "performance cars in a given class can weigh DOUBLE the lightest cars in the same class", nothing more. If you claim the span is much less than double, then I agree.
I was referring to the A-F market segments when I said class, not saying that performance have a weight range that large. Performance or luxury cars can weigh twice as much as a lightweight car of the same rough size.
It would also be nice if they responded to my actual point. Which was the state of technology over a hundred years ago. Using bad lead acid batteries vs poor efficiency petrol engines. The petrol was just way ahead at the time.
The tl;dr is that market forces led to early electric cars being slow and expensive- they were luxury vehicles primarily targeted at women, because they didn't have to be manually started. The cost was about equal before the model T, and speed could have been equal without any design compromises. The cost of fuel was also about equal.
The main reasons they weren't adopted was the lack of charging at home and secondarily the lack of good speed control. Not a big issue at low power, but once you can hit 40+ mph it's cumbersome and dangerous to be throwing switches to accelerate.
First off, your comment is mainly about current technologies. That misses the entire point of my comment. They were working in the lead-acid regime. Calling my graphs out of date is moot (even when you consider that 500Wh/kg is only a slight bump in my [0] link). I do think EV will win in the end, but that that statement has nothing to do with what my original comment was about. Also current gasoline engines are more than 25% efficient, not 10. But that's beside the point.
So if you're going to attack me, attack me on my points. Don't create a false comparison. Petrol had more than 10% efficiency from the get go. 10% of 50MJ/kg is much larger than 100% of 0.18MJ/kg (upper end of Lead-acid). You'd have to have an engine under 0.1% efficiency for EV to be able to compete in the beginning. (You'd have to have that upper end of lead-acid) This is all my comment was about. The state of technology and manufacturing (both!) over a hundred years ago. I was responding to "We could have had electric cards from the beginning" not "We can have electric cars now". If I said the latter then I understand your visceral, but I didn't.
Yeah, things are different now. Those 1.8MJ/kg engines at 100% (we'll round up) are able to start competing with 25% of 50MJ/kg(12.5MJ/kg), but there's still a way to go. That's why a Camry and Model 3 have similar weights and the Camry gets twice the range. But yeah, things are looking much better for the EV's now because there are other factors that matter like torque, space, and we don't need to often go more than 200 mi. But most of these factors are, for the average user, less important and so don't matter as much. Especially in the beginning where electric vehicles were struggling to drive between cities.
I look forward to the future of EV, but that doesn't discredit the history. And that doesn't make lack of technology a myopic take. Reality is just that a petrol vehicle getting 100 miles range is easier than an electric and requires less advanced technology and manufacturing techniques. But technology and manufacturing has progressed A LOT in the last hundred years.
Will charging speed really only be of minor importance? How do you charge your vehicle if you live in an apartment building? And if you can't do that and charging at a station takes more than 3-5 minutes then you cut out a huge part of the populace.
> Will charging speed really only be of minor importance? How do you charge your vehicle if you live in an apartment building? And if you can't do that and charging at a station takes more than 3-5 minutes then you cut out a huge part of the populace.
Yeah, that's what I'm saying. If you have to leave your home to charge, the time is relatively unimportant. Sub 3-5 minutes is a big deal because you can do it on the way home from work, but you could also accomplish that with a battery swap or even a small top-off block you keep indoors. I could have phrased it better by saying that charge speed is arguably a major issue, but only if there is no way to solve the distribution problem.
Until then it's pretty low value- 10 minutes doesn't have much benefit over 30 minutes since you have to plan around it. If you're stopping for ten minutes, you may as well eat or run errands, and then it might as well be 30 minutes.
If it's 30+ minutes you need to do it while you run errands or something, so it may as well be an hour. You'll only ever notice on the few days you drive for hundreds of miles at once. If it's over an hour, it might as well be 6+ hours, because you'll only ever do it overnight.
For mass adoption you need chargers at most parking spots. Since cars spend almost all their time parked, charging time really is not all that important.
adding mass increase the costs of tires (ongoing) wheels, shocks and other suspension bits that have to be stronger and bigger to support the mass, and it increases wear on roads too. so energy density does affect upfront costs and lifetime costs.
Again, an 11% increase. It's tiny. My point is that it's vastly outweighed by other effects, not that it literally does not exist.
I'm making the case that treating the specific energy/energy density of batteries as the end-all, be-all is foolish. I am not arguing that it is nonexistant, just not relevant.
Sure, but if you're going to go that direction with your argument you need to account for the environmental damage caused by burning fossil fuels inefficiently in motor vehicles.
It's impossible to neglect the efficiency here. Car-scale combustion engines have a real world efficiency of around ten percent compared to electric. A gallon of E10 contains 34.9 kWh and randomly picking a Toyota Avalon you'll get a real world 17 mpg with that[1], which works out to 16.4 mpge.
Compare that to real world measurements of a Tesla Model 3, a car that is MUCH more powerful and heavier, but gets 147.4 mpge[2]. The Avalon gets 11% as many miles per unit of energy stored. E10 is equivalent to 1.32 kWh/kg (4.8 MJ/kg).
Not to mention that graph of battery energy density is significantly out of date. Normal li-ion, is at 300 Wh/kg (1.1 MJ/kg) and li-sulfur is commercially available at 500 Wh/kg[3] (1.8 MJ/kg). Even Tesla's batteries are above 250 Wh/kg.
So the bottom line is the difference is ~5x right now. Is that enough to matter? 15.5 gallons of gas (standard fuel tank) weighs 44 kg, or 2.7% the total weight of the Avalon. The full capacity in batteries at 250 Wh/kg would weigh 232.32 kg, or 11.4% more. As much as 2 people + luggage. That's a totally irrelevant increase in weight; luxury or performance cars in a given class can weigh DOUBLE the lightest cars in the same class.
The energy density of batteries is a red herring for all vehicles except cargo/tanker ships and long-distance airplanes. It's completely irrelevant for vehicles. The charging speed is arguably minorly important but by FAR the most important things are the upfront and lifetime cost. That is related to energy density... the energy density of the power plant's fuel, not the battery. And again, it's incredibly naive to assume the weight is the major factor in cost.
[1]: https://www.fueleconomy.gov/mpg/MPG.do?action=mpgData&vehicl...
[2]: https://www.fueleconomy.gov/mpg/MPG.do?action=mpgData&vehicl...
[3]: https://sionpower.com/