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A look at the new Tesla cells

11493 Views 124 Replies 14 Participants Last post by  Kevin Sharpe
2170 cells replaces 18650 standard at the Gigafactory.

Doubtful they will be available to DIY community, though. The big boys will probably contract full production.
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There is a lot of outdated and incorrect information in that report and video.
3000mA vs 6000mA electrical charge ??
97cc volume capacity ??
What is all that about ?
21700s and 20700s have been available in various forms for a while in portable toolpacks, and even commercial Ebike packs ( Panasonic released in 2015).
Also available individually/loose via reputable retailers.
Samsungs 21700-30T is rated for 30 amp continuous discharge, 50 A burst. (Lygte tested)
Teslas cell will most likely again be a compromise of more capacity, longer cycle life, but without the extreme power ability.
 

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Discussion Starter · #3 ·
There is a lot of outdated and incorrect information in that report and video.
3000mA vs 6000mA electrical charge ??
97cc volume capacity ??
What is all that about ?
As I read it, the extra volume was minimal while the energy captured was almost doubled by tweaking both the production process and some of the materials. It isn't just about the form factor.

21700s and 20700s have been available in various forms for a while in portable toolpacks, and even commercial Ebike packs ( Panasonic released in 2015).
The article said 2170 more than once, which was confusing because of the missing zero on the end, but I believe you are correct that the form factor has been out there previously. However, those are NOT the same batteries as Teslas. Tesla is doing something proprietary with their Gigafactory batteries to get that energy density.

Teslas cell will most likely again be a compromise of more capacity, longer cycle life, but without the extreme power ability.
When you have a 100Kwh pack in a car, you don't need tremendous C rates to operate the motor at peak power, so that would make sense. On the other hand, until we get all the numbers reported on their proprietary formulation it may be premature to speculate that they sacrificed power density for greater energy density - they may have managed to get both.
 

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??? Did you read the script or watch the video ?
That article , mostly transcribed from the included video is based on old info and put together by someone who doesnt know what they are talking about.
What is a charge capacity of 3000mA or how do you get a a cell volume of 97 cc from a 21700 ? (Its 24.2cc)
And "tested at 5750- 6000mA output ???.....is not 6Ah capacity, its just BS !!
There is nothing extra special in Teslas 21700, its just a larger format of their existing cells, possibly with a different Cathode for good cycle life, .
It is 50% bigger by volume, but not in energy capacity with 4.75 Ah.
 

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Discussion Starter · #5 ·
First and foremost, I am not here to make excuses for bad writing.

So I watched both stupid videos and I agree the dumb narrator was clearly pulling some stuff out of his nether regions. The numbers that seem to be "hard" are these:


  • Larger form-factor (1.333x volume, not 1.5x) somehow helps facilitate cheaper production and also somehow factors into stuffing more energy into a pack. Good.
  • Musk (his voice) and his associate on tape claim a 10-15% improvement in energy density due specifically to chemistry changes (whether from anode, cathode, or electrolyte changes not specified). Since 18,650 is specified as 250wh/kg, that would put the new cells between 275-287.5wh/kg for JUST the chemistry.
  • They also claim cost advantages for the larger cell, and an ability to pack more in with more battery and less structural supporting materials. This in turn implies a synergy of factors giving the final pack a higher energy density than just chemistry changes alone would provide, and at lower cost. In other words, the final installed pack might have, say, a 30% energy density than the old pack. If the old pack was 300 miles, that would be nearly a 100 mile improvement in range for similar price. Pretty good.
  • The numbers for 3,000mA and 5,750-6,000mA are probably meant to mean maximum usable discharge rate. If you get double the discharge rate from 1.33x the volume, that implies substantially improved energy density. Also good.

I don't see anything in these multiple incremental improvements to be derisive about other than the poor reporting.
 

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Sorry but...
21700 is 45% more volume than 18650.
Energy Capacity of the 21700 would need to be 5Ah+ to even have the same energy density. But these new cells have been reported to be 4.75 Ah.
Im sure you are aware that Teslas most recent 18650 cell , in their largest 100kWh pack, has to supply 6-7C (20A) for short periods (Ludicrous mode) and can continuously supply 10 amps.
 

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Discussion Starter · #14 ·
Really? Didn't tesla open their patents? Also, what you are saying could be true for these new cells, but in past they've used regular panasonic 18650be cells and they are available to anyone.
Well that's a fair question, and they did stop pursuing patents. I suppose that if Sanyo doesn't disclose use of a patent on the cell we can't know. On the other hand, if Tesla's chemistry is fairly new it seems pretty unlikely others are using it already - changing the guts of a battery requires some expensive changes to the assembly line and to the vendors from whom they source materials (and who would be the vendor creating Tesla-clone anodes and cathodes?) - so they might not want to pay for that unless they believe that the improvement is worth the cost of the switch over.
 

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If Tesla have any "Secret Sauce" to build into their new cells, they have been uncharacteristicly shy of even hinting about it ?
(Remember this is the guy who has said he is going to put people on Mars in the near future :eek:)
Also, since they use large capacity packs (40kWh+), Tesla will likely focus on capacity, safety, and cycle life factors, rather than any major step forward in output or charge rate, so a 3-4C rate discharge is fine for them.
However, if someone is thinking of using Tesla cells in a low capacity pack (<20kWh), then those cells may not be the best choice.
 

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Discussion Starter · #16 ·
If Tesla have any "Secret Sauce" to build into their new cells, they have been uncharacteristicly shy of even hinting about it ?
I was going by the video, in which Musk plainly said there were changes in the chemistry which helped increase the energy density. Not being psychic, I can't tell you whether he was being honest.... ;)

(Remember this is the guy who has said he is going to put people on Mars in the near future :eek:)
lol, define "near future?" You never know, he may do it...

Also, since they use large capacity packs (40kWh+), Tesla will likely focus on capacity, safety, and cycle life factors, rather than any major step forward in output or charge rate, so a 3-4C rate discharge is fine for them.
I would hope so...

However, if someone is thinking of using Tesla cells in a low capacity pack (<20kWh), then those cells may not be the best choice.
Absolutely agree -without spec sheets we can't know if they are "better" for a given application.
 

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With 50+% more volume in the new cell, it ought to be possible to get over 5Ah capacity in. But i am willing to bet they have not reached that figure.
Eventually, someone will get hold of a few cells to reveal all. ;)
 

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The only people interested in extreme power output are the RC hobbyists, and one of a kind applications. EVs have too many cells in parallel that cell power output is not an issue at all.
Not strictly true..dependig on the definition of "extreme"..
Cordless power tools put huge loads on the batterys, (previously 18650s, but now switching to The 20700 and 21700 cells).. With 15-20C not uncommon.
Ecigs and high power flashlights also demand high currents from small single cell , packs.
Even tesla push their cells beyond normal limits when they pull 1500 amps from a 74p cell group !
 
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