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/Up to 1000 charge cycles/ is a big damper on the excitement, for me. Does anyone know if a limitation like that is inherent to the chemistry here or is this something that they could potentially (hopefully, vastly) surpass?
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Indeed. Tesla Model 3 consumes about 50MJ of battery energy per 100 km. Toyota Prius consumes about 4.5 liters of gasoline. That gives roughly 150 MJ. So a electrical car consumes 3 times less or about 33% of energy of one of the best hybrid drivetrain.
Is that fresh out of the factory or after a few years of service? I think a lot of the metrics around hybrids are a bit optimistic. In the same way that official metrics for EV ranges are usually a bit more than is realistic. Hybrids running on battery are about as efficient as an EV. When you enter the highway, they turn into ordinary ICE engines. If you use your prius exclusively for traffic in your neighborhood, y…
I believe this is because the electric motor can handle the torque variation so the engine runs in a more consistent optimized torque band
/Up to 1000 charge cycles/ is a big damper on the excitement, for me. Does anyone know if a limitation like that is inherent to the chemistry here or is this something that they could potentially (hopefully, vastly) surpass?
From the paper: Specifically, for the same average current and voltage window, varying the dynamic discharge profile led to an increase of up to 38% in equivalent full cycles at end of life.
This tracks well with actual real-world data on BEV battery performance in cars with decent battery management.
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Indeed. Tesla Model 3 consumes about 50MJ of battery energy per 100 km. Toyota Prius consumes about 4.5 liters of gasoline. That gives roughly 150 MJ. So a electrical car consumes 3 times less or about 33% of energy of one of the best hybrid drivetrain.
Is that fresh out of the factory or after a few years of service? I think a lot of the metrics around hybrids are a bit optimistic. In the same way that official metrics for EV ranges are usually a bit more than is realistic. Hybrids running on battery are about as efficient as an EV. When you enter the highway, they turn into ordinary ICE engines. If you use your prius exclusively for traffic in your neighborhood, y…
That being said, both the figures mentioned are to me a little bit optimistic.
I don't know about Teslas, but my fuel economy presents itself like this(figures are in litres per 100km):
-City driving: ~5 + ~100ml to bring the engine to working temperature. Checks out to 7 on a 7km drive and falling with distance.
-Highway, so maintaining real 120-140km/h (speed limit around here), 6.3-6.5. Absolute worst was 7.8 during a snowless -20°C night.
-Backroads doing 70-90km/h, average trip speed 50km/h, and here is where I think hybrids shine - 4.0-4.2.
-Hypermiling record: 3.7 as I was steadily rolling at 20-30km/h to a highway onramp a few kilometres away.
Overall fuel economy is nice, but what I like about this car the most is the ease of manoeuvring on the parking lot and very little vibration when the engine is running.
Previous discussion (2016): https://news.ycombinator.com/item?id=12240000
Well. No. Not yet.
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If this comes through it may boost performance to have a turbocharger for better forced air intake. Or with a tank of pure oxygen, have the EV act like it was gasoline engine on nitrous oxide. Somebody should calculate a ballpark figure for the number of grams or kilos of oxygen that would be needed per mile for an average vehicle.
> If this comes through it may boost performance to have a turbocharger for better forced air intake. No it won't. At most, the battery might need a small fan. Turbochargers are needed for regular cars because internal combustion engines just suck.
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Not really. In a fuel cell the reaction products are discarded (the reactants cannot be discarded, as they are needed for the reaction to take place). In a metal-air battery, air from the atmosphere is taken into the battery and the oxygen from it becomes bound to the metal, in a metal oxide. So unlike for a fuel cell, where the vehicle becomes lighter after the fuel is consumed and the reaction products are discarde…
How would an aluminum-ion battery work out as for as theoretical charge per weight or volume? I know that is decades out, of course.
In an aluminum-air battery vs. a lithium-air battery, the mass per electron is, in the most favorable case for lithium, of 17 for aluminum vs. 15 for lithium, which results in an energy per mass for aluminum of around 82% of that of lithium. However lithium forms by oxidation not only Li2O, but also peroxide Li2O2 and superoxide LiO2, which may worsen a lot the energy per mass.
In the parent article, they have succeeded to produce mostly Li2O, but even so their batteries have still produced some amounts of peroxide and superoxide during deep discharges.
So the energy per mass for aluminum-air batteries could be up to 80% to 85% of that of lithium-air batteries.
Most other oxidants besides the oxygen from air are heavier, which would reduce the advantage of lithium vs. aluminum (because the oxidant mass would be a greater fraction of the battery mass), so aluminum-ion batteries, if possible, could have an energy per mass very close to that of lithium-ion batteries.
On the other hand, aluminum metal and aluminum oxides are much denser than lithium metal and lithium oxides, so aluminum batteries could have much better energy per volume than lithium batteries. Unfortunately, until now the problems caused by aluminum as a cathode material have not been solved.
I'm a bit excited but also a bit tired of hearing about all these batteries. I just want someone to wake me up when we have a commercially available 1kwh+/kg with decent durability, decent price, and good safety. Maybe this is a good idea for an ammoseek website but for batteries that can send alerts. I'm honestly surprised a quick search didn't turn one up.
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A lithium-air battery (in general all metal-air batteries) is likely to have lower efficiencies for a complete cycle than other lithium-based batteries, perhaps not much above 80%, if not even less. The lower efficiency is caused by one of the reactants being a gas, which causes certain thermodynamic constraints. A fuel cell with hydrocarbons would have a slightly better efficiency than the best mobile thermal engine…
> The claim from the parent article is wrong and it is based on an incorrect method for computing the ideal energy per mass ratio for lithium-air batteries. Can you elaborate for laypersons such as myself?
That claim is based on dividing the stored energy by the mass of lithium, which is incorrect.
The product of the reaction, i.e. lithium oxide, is stored in the battery, so a lithium-air battery can never be lighter than the lithium oxide.
Because the mass of lithium oxide is what counts, the energy per mass of pure lithium, which is indeed not much less than for gasoline, must be divided by a factor that varies between 2.14 and 5.57, depending on the construction of the lithium-air battery.
The best value of 2.14 is when the discharged battery contains only Li2O. The worst value of 5.57 is when the discharged battery contains only lithium superoxide, LiO2.
In the parent article, they claim that their discharged battery contains mostly Li2O, with only small quantities of peroxide Li2O2 and superoxide LiO2, but the exact amounts of peroxide and superoxide have not been measured.
So when computing correctly the energy per mass ratio, for lithium-air batteries it is limited to a value less than half of that for hydrocarbons. In practice batteries need a lot of materials besides the active reactants, so the achievable energy per mass ratio will be several times lower.
The advantage of hydrocarbons, regardless whether they are used in living cells, thermal engines or fuel cells, is that their reaction products are eliminated into the atmosphere, so their mass does not matter. The energy per mass for carbon atoms in hydrocarbons and for lithium atoms in lithium metal is approximately the same, but with lithium it is impossible to neglect the mass of the oxidant, like with carbon, because the reaction products cannot be dumped outside.
So for any battery except for fuel cells, what counts is the sum of the masses of the reactants, e.g. lithium + oxygen in the best case, or e.g. zinc + manganese in the cheap non-rechargeable batteries. It is wrong to compute the minimum mass of a battery by using only the mass of one of the reactants, like in the parent article, instead of both masses.
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That's a comparable rating to the NMC Lithium cells used in an electric car, yet an EV can typically get > 200,000 miles from their cells. A charge cycle is defined as 0% -> 100% -> 0%. If you never do that, you get a lot more effective charge cycles. Edit: That's not the full explanation. 300 miles of range for a typical EV * 1000 cycle rating gives 300,000 mile rating. You likely charge a lot more than 1000 times o…
To add on to that, battery "lifetime" is typically defined as 80% of original capacity. So after 1000 full cycles, you still have 80% capacity left!
I don’t have exact numbers.. based on graphs I’ve seen I would guess that if the original cycle life was 1000 cycles you may have another 500 cycles until the battery is actually unusable. But it probably depends a lot on the specific chemistry and how the car is used.