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The author makes quite some big claims without any evidence, including that "Energy density in these batteries is quickly reaching its theoretical limit". This

by davedx 5y ago

The author makes quite some big claims without any evidence, including that "Energy density in these batteries is quickly reaching its theoretical limit". This is misleading bordering on false. Companies like Enovix [1] and Sila Nano have commercialized pure silicon anode batteries for small devices with energy densities greater than the current generation of Li-Ion with graphite/silicon anodes. A whole host of companies are attacking the "battery energy density" problem from all sorts of angles (including Tesla - no mention of 4680 cells in the article, because that would undermine its premise). There is no law of physics saying "350 Wh/kg is the absolute upper limit". [1] https://assets.website-files.com/6023ee57b22bf2f0c312206d/611fc38d49e8a40bc05fee2c_Value%20of%20Energy%20Density_White%20Paper_0820.pdf https://assets.website-files.com/6023ee57b22bf2f0c312206d/61...

whatever1 5y ago
We can cite hundreds maybe thousands of references of experimental high density batteries introduced last 30 years. No luck getting them to large scale production.
staplung 5y ago
My understanding is that the 4680 cell doesn't have any better energy density than what Tesla is currently using (the 2170). Yes, it has 5x the energy of the 2170 but it's also 5.5x bigger in volume. In essence, the energy density of the cell has gone down, not up. The battery as a whole could still go up because bigger cells mean less weight in the steal casing, better packing efficiencies and the tabless-ness of the 4680 should allow more efficient thermals. I'm assuming that the claimed 16% improvement in range would come from that. The big improvement of the 4680 is the power (and manufacturing costs), not the energy. In any case, it's sort of a moot point if Tesla won't sell these batteries/cells to anyone else. Anyway, my take on the article was that the practicality of the electric airplane basically comes down to battery tech. If someone produces a dramatically better battery I assume that putting it into an airplane will be straightforward. So if you want to build an electric airplane what you should really be building is a better battery.
- genewitch 5y ago
  Why is everyone using 4 digits for batteries that are labelled as 5 digits? 18650 are 18650, not 1865 even if it makes more sense that way. I wonder why the nomenclature changed?
- davedx 5y ago
  Yeah, you're right - the 4680 is a bigger battery, but my point is battery technology is being pushed on multiple fronts by a host of companies, some of whom have everything at stake to stay competitive. Also agree that battery tech is what matters. I'm following the space closely. I also made this tool to play with the variables if you're interested: https://redskyforge.com/electric-aircraft/ https://redskyforge.com/electric-aircraft/

by davedx 5y ago

whatever1 5y ago

We can cite hundreds maybe thousands of references of experimental high density batteries introduced last 30 years. No luck getting them to large scale production.

staplung 5y ago

My understanding is that the 4680 cell doesn't have any better energy density than what Tesla is currently using (the 2170). Yes, it has 5x the energy of the 2170 but it's also 5.5x bigger in volume. In essence, the energy density of the cell has gone down, not up. The battery as a whole could still go up because bigger cells mean less weight in the steal casing, better packing efficiencies and the tabless-ness of the 4680 should allow more efficient thermals. I'm assuming that the claimed 16% improvement in range would come from that. The big improvement of the 4680 is the power (and manufacturing costs), not the energy. In any case, it's sort of a moot point if Tesla won't sell these batteries/cells to anyone else. Anyway, my take on the article was that the practicality of the electric airplane basically comes down to battery tech. If someone produces a dramatically better battery I assume that putting it into an airplane will be straightforward. So if you want to build an electric airplane what you should really be building is a better battery.

genewitch 5y ago
Why is everyone using 4 digits for batteries that are labelled as 5 digits? 18650 are 18650, not 1865 even if it makes more sense that way. I wonder why the nomenclature changed?
davedx 5y ago
Yeah, you're right - the 4680 is a bigger battery, but my point is battery technology is being pushed on multiple fronts by a host of companies, some of whom have everything at stake to stay competitive. Also agree that battery tech is what matters. I'm following the space closely. I also made this tool to play with the variables if you're interested: https://redskyforge.com/electric-aircraft/ https://redskyforge.com/electric-aircraft/