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Not to mention that graph of battery energy density is significantly out of date.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.

[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/

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.

[1]: https://voltaplex.com/media/whitepapers/specification-sheet/...

Not hugely related but VW have sent their electric hill climb car around the ring (6:05)

https://youtu.be/lRHIiJjWhWo

Very very fast although its not a racing car per se

I like the detail that went into your reply, but it would be a lot better (and less downvoted) if you removed the vitrol.

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.

That wasn't the part that I had any complaints about, although it's not the real reason electric cars didn't win: https://news.ycombinator.com/item?id=20182159

Agreed.

I had another comment focused more on the historical state: https://news.ycombinator.com/item?id=20182159

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.

Tires are the largest maintenance cost for cars, so that's absolutely a valid consideration. The rest of the argument is junk though.

You can argue these points and prove mathematical efficiently all you want, in the end, it's about those who control the purse strings.

Right now, that is still 'Big Oil'. They are buried into our politicians pockets like an Alabama tick.

I still think there is a limit in chemical density that cannot be overcome without significantly changing technological principles of current batteries. Maybe hydrogen fuel cells would be a better solution after all if we can find an efficient way to contain it. Easier said than done...

Energy density of hydrogen per litre is few orders of magnitude lower than that of petrol. Really the only saving grace of hydrogen vs batteries is the speed of refueling.

If someone invented a cheap round trip processing method CO2 -> petrol then EV's would have a hard time I suspect

But we would still need batteries to store regenerative braking energy (i.e. it would be a hybrid).

You can use ultra-capacitors. Like Nawa's:

https://newatlas.com/nawa-technologies-carbon-ultra-capacito...

https://newatlas.com/nawa-nanotube-ultracapacitor-production...

Formula E would be a good proving ground for them.

You can have a flywheel for that.

Don't know why you're getting downvotes, this is a thing.

https://www.racecar-engineering.com/articles/f1/williams-f1-...

Here are two such efforts:

https://carbonengineering.com/

https://www.prometheusfuels.com/

I think molten salt (latent heat) batteries could push the boundaries further as researchers continue to design salt mixtures with lower melting points and higher and higher delta_k's (economic considerations of compounds included).

Though for usage in cars would imply some kind of small/portable vacuum storage tanks and a way to put the heat to work (most likely initially through a steam engine and eventually directly to electricity via advanced thermocouples[0])

[0] https://arxiv.org/abs/1308.5935

> Really the only saving grace of hydrogen vs batteries is the speed of refueling.

And range, weight, and (eventually) price. Batteries need to improve in all these areas.

Fuel cell cars are expensive at the moment because they're produced in such low volumes. But Toyota thinks that if they produced FCEVs at scale they could build them cheap:

https://www.thedrive.com/tech/26050/exclusive-toyota-hydroge...

Toyota is the only company pushing hydrogen as a fuel for cars, and it's puzzling why, because they really don't have many advantages, and a ton of disadvantages compared to BEVs.

Everyone else is working on BEVs, including the Chinese.

Hyundai is working on fuel cell cars as well:

https://www.electrive.com/2019/06/05/hyundai-to-sell-their-f...

Am I misreading the gp's cited chart? According to that, it seems like hydrogen is only a factor of around 4x worse in terms of volumetric energy density, and is better than petrol in weight density.

Weight density doesn't help you in a car; these aren't rockets where most of the weight of the vehicle is fuel. In a car, the weight of the fuel is barely noticeable. What's much more important is the size of the tank, and a hydrogen tank takes up a lot of room (to get decent range), and is also quite heavy to contain a pressurized gas that literally leaks out constantly because its molecules are so small.

Weight density is better. Nothing else comes really close. The volumetric missmatch could be right.

And you can always refine it into methane for an even higher density.

Still better than current batteries. You could pump that up if you store it in a liquid state to a level above common fossil fuels. Not saying you don't open a can of worms for implementing it...

Hydrogen in liquid state leaks out of any container that you put it in. 70kg lead bottle stores only 1L of hydrogen and all of it evaporates naturally in 1-2 months through the metal. So no, storage of liquid hydrogen is a terrible idea.

It does diffuse through everything, but there are several research projects in that direction. It is the smallest element and it helps if that bottle is solid, but I still see potential.

Besides in-vehicle storage being completely infeasible for many reasons, how exactly do you propose to safely allow consumers to refill a tank with liquid hydrogen? They use it for rockets sometimes, but it's handled very carefully by highly trained technicians under very controlled conditions and the fueling procedure is nothing like a stop at your local gas station.

isn't it still much better than batteries?

Dont you forget something- hydrogen if hydrolizes takes place in situa - aka directly below a windpower or solar-plant, has the lowest conversion loss right there.. Also storage can be improved by now chemically - meaning you bind it to a https://en.wikipedia.org/wiki/Hydrogen_storage#Liquid_organi...

and reduce that to a nearly solid material with extremly high energy density. Its okay to be a tesla fanboi, its not okay to propagate ancient technological "insights".

To me, there's not so much difference between batteries and fuel cells - one stores the redox reaction components outside the electrode/electrolyte setup, that's all. The advantage of hydrogen in this setup is the ability to pull oxygen from the air and then dump the reaction product.

Depending on the process of extracting hydrogen, it could also be more environmental friendly overall. I don't know much about the battery life cycle, but I image there to be "casualties".

I know there are many, many problems to solve for fuel cells and if you are scared of some burning batteries, this solution probably doesn't provide much consolation.

>Another reason: Even today the energy density of batteries is SUBSTANTIALLY smaller than that of fossil fuels.

That's irrelevant. The thing people keep forgetting with fossil fuels is that most of that energy is being wasted to just produce heat. With an EV, 95-98% of the battery's energy is being used for propulsion (unless you turn on a heater of course).

In short, you're comparing apples to oranges.

It's not irrelevant. The high water mark for Li-Ion efficiency is 0.875 MJ/kg[1] (in practice e.g. a Tesla seems to be 0.7 MJ/kg). For petrol that's 46.4.

Now, let's adjust that for the efficiency of the power train. Let's give the electric car 100% (in practice it's 95-97%). Production ICE engines are around 20%. That gives us 46.4 x 0.20 = 9.28 MJ/kg.

That's a 10.6x difference in favor of petrol if we take the optimistic 0.875 number. The most fuel-efficient cars sold today consume around 5L/100km. A liter of petrol is 0.78 kg. A 1000 km of range is the probably holy grail for an electric car.

A a car powered by petrol needs to carry 39 kg of fuel at the start of a trip for that range. That'll be at best ~390 kg for the Tesla at its theoretical limits, which isn't counting overhead weight associated with the battery pack, and unlike a petrol-powered car the weight doesn't reduce as you go through the trip (a significant hurdle for e.g. electrically powered airplanes).

Of course the power train of an electric car is lighter than on the ICE-power vehicle, but the ICE still wins, and all of this is before we get to the battery needing much more volume than petrol, although as the Tesla shows you can win back some space by placing it in the floor, which isn't a realistic option for ICE.

None of this means electric cars aren't viable, but the weight and volume differences for the same MJ are inherent, and aren't going to go away.

1. https://en.wikipedia.org/wiki/Energy_density

You're comparing solely based on the weight of the energy storage medium (fuel/batteries). Two problems here: 1) ICE cars have big, heavy engines to burn that fuel and produce mechanical power, whereas BEVs have much smaller motors, so there's a big weight advantage for the BEV. (I see you addressed this, but you're also missing the volume savings with electric motors; gas engines take up a ton of space with all the associated plumbing and systems). 2) In gas cars, the fuel isn't really a big component of the vehicle's weight, which is why Tesla is able to add another 500-1000 lbs of batteries and not have too much trouble with that. That's basically like adding 3-4 adult Americans. Gas cars do not get significantly better fuel economy with empty fuel tanks.

As for airplanes, this discussion is about cars, not airplanes, where things are really different. Power-to-weight-ratio is far more important with aircraft since they have to fight gravity constantly. Aircraft will surely be the last bastion of fossil fuel usage because of this.

But electric vehicles weigh more than gas equivalents. A Model 3 (standard) is 3552lbs. I found that a Camry is similar in weight (3572lbs; similar weights for the Leaf and Volt). But if we compare the range the Model 3 has 220 mi while the Camry has 352/512 (city/highway). We can pretty conservatively say that Camry is going to get approximately twice the range for the same weight. And extra 500lbs on the Tesla only gets you another 100 miles.

So while the gp to this comment and my original comment focus on the weight and density of the storage media this is one of the largest factors. What the graphs I linked to show is that basically the weight for gasoline is not a major part of the vehicle weight. But on the other hand, for electric vehicles it is a significant weight.

The point I was making with my original comment wasn't that electric vehicles won't win (I think they will) but rather that it is a ridiculous notion that they would have won from the beginning. These new batteries take extremely complex engineering to achieve. And only because of these new batteries are they starting to win. If we go back to when everything was made from steel then your electric car is also going to gain more weight. Even from the get go petrol vehicles had longer ranges. My comment (and a lot of people are missing this) was not about NOW it was about the past. I want to stress that it has nothing to do with current tech. It has to do with what technologies they had available to them. Also how impressive the work is that has been done to create these new generations of batteries (and is still being put in). Petrol won because it was the easiest route. But EV is winning because it is superior (with the advancements and the path that it is on).

1) Guilty as charged. It's far from an apples to apples comparison, but if you compare like-to-like models of EVs and similar ICE vehicles you get the same story everywhere. Around 1/2 to 1/3 the range of the ICE vehicle, and 20-25% heavier.

E.g. the Chevy Sonic[1] & Bolt[2] are equivalent EV/ICE vehicles. They weigh 1300 & 1600 kg respectively, have the same cargo volume, but ranges of ~750 km (most pessimistic) & ~380 km (most optimistic).

So that's the like-to-like comparison. We can see that all things added up these vehicles are heavier and have much less range.

2) These volume savings are overstated and if anything work in the favor of ICEs, not EVs.

Look at a cutaway of the Chevy Bolt[3] or other reasonably priced EV like the Hyundai Ioniq or BMW i3[4]. Yes you get relatively more cargo volume in a Tesla Model S compared to other Sedans, but at that point you're paying tens of thousands for a luxury vehicle whose gimmick is things like the frunk. If you drop the same money on an ICE that optimizes for cargo space you'll come out way ahead.

3) A Tesla Model S's 85 kWh battery pack is 540 kg. If that's 3-4 adult Americans they've gotten a bit fatter on average since I last checked :)

In any case, that gets you a 420 km range, which tells you something about how heavy the car would be and how little space would be left for anything else if they were aiming for ICE-like range.

4) "Gas cars do not get significantly better fuel economy with empty fuel tanks": Yeah exactly. The point is that EVs inherently do not share this benefit.

5) Yeah we're talking about cars, but the point of bringing electric airplanes into it is to show how electric vehicles are weight and volume limited in an area where everything is done to bright the weight down, whereas someone might (wrongly) argue that for cars the weight doesn't matter that much.

1. https://media.chevrolet.com/media/us/en/chevrolet/vehicles/s...

2. https://media.chevrolet.com/media/us/en/chevrolet/vehicles/b...

3. http://www.boronextrication.com/2016/04/03/2017-chevrolet-bo...

4. https://www.autoblog.com/photos/bmw-i3-ev-cutaway/

And then there's the cost of the fuel. Electric car fuel is currently about 1/5 of the cost of gasoline and dropping. In addition, the cost of maintaining and electric is also much less than an ICE car so in terms of dollars per mile driven electrics are way cheaper. And that's where ICE really takes the head shot.

That heat is not wasted if you live in a place that has seasons. I’d like to see EVs with a petrol burning heating system that could provide cabin and battery heat during winter. Many gas stations sell untaxed kerosene that I think could be used because it’s for heating, not motor fuel.

Even with heat being wasted, the energy density is so high that it still outpaces batteries by a significant margin. For example... try making a battery powered 747 airliner... you can't because the weight is too high.

I'm surprised many people missed this. That 10% of 50MJ/kg is still more than 100% of 1.8MJ/kg (current advanced batteries) and substantially more than 100% of 0.18MJ/kg (lead acid). Which my comment was about manufacturing and technology over a hundred years ago. My comment was focused on the latter comparison and not the former (which was just a side note). I guess everyone latched onto my side comment.