I also do expect a 5500mAh cell which is a nominal 20Wh. That would result in using a third of the cells they use today to make a pack, reducing pack complexity and manufacturing costs. There's so much opportunity for improvement, good days are upon us.
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FlatSix911
Porsche 918 Hybrid
Given the new cells are ~47% larger by volume, and assuming the 2nd gen chemistry cells with the silicon anodes were ~3300mAh, then just the volume increase alone would render a ~4850mAh cell. It would take another 13% increase in density due to chemistry changes/packaging efficiency to hit 5500mAh... that doesn't seem terribly unreasonable.
With most things staying the same, the lower number of cells to achieve the same capacity will also result in lower building costs and *higher reliability* of the pack (less friction bonded fuses and links). This is a big question mark with the initial 21700 cells since they will not have a reliability rating and history like previous 18650 cells. Then again they might be a lot better. Only time will tell.
To get to 20 Wh per cell requires a 75% increase in active materials.
The volume increase 18650 to 21-70 is 46.6% increase.
The weight increase is likely to be 56% to 75 grams
The cell casing, if the thickness does not change, will decrease from about 3.8% to 3.3% at the larger size.
If the active materials (cathode, anode, etc) are half the weight (50%) of the cell, that will need to increase to 56% in the larger cell to achieve a 75% energy increase.
If the active material is 62.5%, it will need to increase to 70% for a 75% energy increase.
If the active material is 75% by weight, it will need to increase 84% for a 75% energy increase.
I.E., the active material portion of the cells is increasing 6% to 9% by weight using these examples. Surely, this can be done by rolling a thicker layer of cathode and anode. As the battery size and range of the car has increased, the rate at which the ions move in and out of the cathode and anode slows down as the load is shared by more cells.
Tesla has shown its vehicles have more than enough acceleration and thus power/torgue/electron flow. Surely, Tesla is optimising its cells for energy density. It already uses NCA cathodes for this purpose.
So has anyone heard of an energy capacity figure for the Panasonic/Tesla 2170s? In all the discussion at the January dog-and-pony show at the Gigafactory, that didn't seem to come out . . .
Here is the article from the normally Tesla shorter Tilson about the gigafactory presentation and how it changed his mind about Tesla.
Tesla - Tilson Compares To Amazon And Netflix But Won't Buy Or Short
Lots of pictures about the battery in the article.
Tesla - Tilson Compares To Amazon And Netflix But Won't Buy Or Short
Lots of pictures about the battery in the article.
NeverFollow
Active Member
1. Does anyone know the root problem of the LG cells used for the Samsung Note 8 smartphone fiasco ?
2. Does anyone know who makes the cells used for the Faraday Future FF 91 and how they compare with the Panasonic 18650 or 21700?
2. Does anyone know who makes the cells used for the Faraday Future FF 91 and how they compare with the Panasonic 18650 or 21700?
This is the best public information I've seen on 2016/2017 cells: http://www.emove360.com/wp-content/...Report-ver-3-presentation-for-conferences.pdf
Tesla 2170 Battery Cells: Greater Power At Comparable Cost
Rumors only, but the claim here is that Panasonic support about double the discharge rate of the current 18650s. Perhaps this will allow higher C-rate charging as well. Still no amp-hour information other than speculation that's the cells are about 5ah.
Rumors only, but the claim here is that Panasonic support about double the discharge rate of the current 18650s. Perhaps this will allow higher C-rate charging as well. Still no amp-hour information other than speculation that's the cells are about 5ah.
Samsung SDI and LG Chemicals to Mass-Produce 2nd Generation Cylindrical Batteries for Electric Vehicles
Their claim is that the Tesla/Panasonic cell is only 4500mAh. This contradicts Musk on highest energy density, and the claim seems thinly sourced. We will hopefully hear an official number soon...
Well, we now know the Tesla/Panasonic cells, assuming they are nominally 3.6 volt, are rated at 5.0Ah, or have 18Wh each. This is only a small improvement on the current 18650s when you take the volume increase of the new cells into account. The pack for the long-range M3 has 4,416 of them, and is nominally 79-80 kWh, with something like 75kWh usable. The standard pack is about 53.5kWh, with 2,976 cells, and a usable capacity (probably) of around 50 kWh. Efficiency on the M3 is very good to get the 220 mile EPA range. This strongly suggests that these cells in a MS/MX will not give a substantial increase from the 100kWh currently available from 18650s. Given that, I would expect the 18650 packs to continue until we see a more substantial update of the MS/MX models.
I may have used an high cell weight in that last calculation: 75g. I see other 21700 cells can be as light as 67g, a weight which would put the energy density at about 270wh/kg, better than current Panasonic 18650s, but not by a lot.
JRP3
Hyperactive Member
Are you suggesting that Tesla built the cells for higher C rating, sacrificing some capacity density, or that the larger format on it's own would provide higher C rating? (Because the latter would not be accurate).
G
Generally, obtaining higher C-rating in a cell requires lower energy density, as the cell designer has to provide more area for conductivity at the expense of reactive material. I was suggesting that Tesla/Panasonic may have gone with a lower impedance, higher C-rating cell at the expense of some energy capacity. Low impedance also has advantages in avoiding pack heating under high-draw or charge conditions. It will be interesting to see what this functionally means when higher-rate Superchargers are eventually announced.
Generally, obtaining higher C-rating in a cell requires lower energy density, as the cell designer has to provide more area for conductivity at the expense of reactive material. I was suggesting that Tesla/Panasonic may have gone with a lower impedance, higher C-rating cell at the expense of some energy capacity. Low impedance also has advantages in avoiding pack heating under high-draw or charge conditions. It will be interesting to see what this functionally means when higher-rate Superchargers are eventually announced.
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