Tesla is rumored to start production of 40700-size Li-Ion cells for their battery packs in the near term.
One of those would be extremely similar in size to 3x18650, while offering roughly twice the capacity, and a significant safety benefit (no possibility of cell mismatch).
Bright times ahead!
40 mm diameter…. Well well well, that’s just perfect for flashlights… 
If it can really offer twice the capacity then that’d be amazing. Would be great for smaller lights like the MF01S.
Where did you hear this rumor? Can’t find anything online.
Yeah, when I google
tesla 40700
I don't get any relevant hits.
Have not heard that rumor before, but I won’t say it’s not true.
Before the model 3 was introduced, Tesla used 18650 cells. Up to 8,000+ per car.
But they realised there are formats with a higher energy density per cm³.
Initially they went for the 20700 strategy, a lot of battery manufacturers joined that.
These seems to have become the new standard cell for E-bycicles.
But prior to the launch of the model 3, Elon Musk himself (?) made a last calculation.
Not just in view of the energy-density, but also in view of the cooling properties needed.
And ultimately he choose the 21700 format, starting with model 3.
Surpassing the much loved 26650 format, which never was a champion in energy density.
I think it is highly improbable the new 21700 strategy is abandoned shortly after it’s introduction.
Unless ……. Panasonic & Co came up with an altogether different chemistry and better cooling.
4070 is mentioned here:
A youtube video claimed that it was started by tesmanian.com, but I can’t find anything on there. The exact wording was ’ increase cell diameter to 1.57” ’.
EDIT: found it - Tesla Next-Gen Battery With Maxwell Tech & Patents
On the cooling side, the new cells are supposed to have significantly lower internal resistance due to a new electrode manufacturing process, and so would need less cooling.
There is no talk about abandoning the partnership with Panasonic. If tesla wants to scale up production of the current model 3, new model Y, soon to come semi truck and cyber truck as well as the stationary storage division per plan they need to increase their battery supply by orders of magnitude. Since that kind of supply doesn’t exist, they are attempting to start their own production in addition to what they can source from Panasonic, Samsung SDI, LG chem and CATL.
makes sense, fewer cells, simpler wiring, simpler bms, lower cost. increased reliability,
Oboy. Back to the long, heavy flashlight.
I bet M@g sues over the form factor.
https://www.teslarati.com/tesla-battery-day-doomsday-legacy-carmakers-electric/
Well, at least it explains Teslas recent insane stock movement where it went from overpriced at $300 a share to EXTREMELY overpriced at $900 a share (currently $741 a share still valuing the company significantly more than Ford and GM). Beyond electric cars, capable scaled up storage batteries could and likely would be used by everyone in the world to store wind and solar power in an attempt to move away from carbon sources.
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mag will not fit 40mm cell, D tube id is a bit less than 35mm,. boring out is also not an option, due to o ring seats,
Unless we are all moving to 4D Maglites and BLF GT as EDC, this will not survive in our EDC life
I did. :innocent:
our edc’s are safe, 18650\350 are still around
Great, another reason to buy more lights. 
40700 cell has 3.6x the volume of a 21700 so could have approximately 3.6x4.8Ah=17.3Ah.
If they exist, these cells will not be going to the consumer market. It’s possible, but not guaranteed that other manufacturers will copy the form factor.
So don’t worry for now 
An SP36 with a 40700?! YES PLEASE!!
Which is more than 4*18650 and close to 4*21700.
If this cells shows up, the current pop can lights will quickly become obsolete.
And now we wait until Elon Musk googles to discover this thread, and he’ll be like hey 40700… why not? And this is how we get what we want! 