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Discussion in 'Model S' started by TEG, Oct 7, 2010.
So you guys think that is one or two cells stacked on top of each other? Do you still think Tesla has the blade concept where you can extract a limited number of batteries in case of a failure and not have to scrap the whole pack?
If you work out the dimensions of 8000 * 18650 cells, it's got to be 3, possibly 4 layers of them. [EDIT] With CNET guessing 7 feet by 4 feet, it has to be 4 layers deep. That's still compatible with 4 inches deep.
Also, from here, and overview of the factory.
That story also claims that Panasonic are not the exclusive suppliers...
That shape was to be expected. I think for the sake of simplicity and rigidity, they went for a single block. Not a blade design. But I think the pack it smaller than CNET suggests. At most 10cm high (4 inches). Although it's hard to judge from the pics.
I would really love to know how it gets filled with cells. I mean, by hand (and using just two seconds per cell) it will take more than four hours to fill the biggest 8000 cells pack.
Also, the coolant dock would perfectly fit under the rear seats. But on a second thought, it would be much better for it be in front (where the coolers will certainly be) and the power connectors to be below the rear seats, to keep the distance to PEM and motor low. No?
I bet it is a single layer with cells standing upright. 18650 cells are 6,5cm long, add 2 cm for the bottom plate and 2 cm for top plate and you get 10 cm height. Cells are circular with 18 mm diameter, when stacked together in triangular pattern there is space for vertical connections and coolant pipes between them.
Yep, got to that conclusion myself. Packed together they need 2.6 m^2, which is almost the 7ft by 4ft they saw.
I wonder what cells will end up in each pack.
They will have a lot of choices in cells and I think it all comes down to how much those cells cost because I think the cost increases non-linearly with energy density.
Lets say the 160 mile pack is 42 kWh
That would be ~5300 2200mAh cells ~4500 2600mAh cells ~4000 2900mAh cells or ~3600 3200mAh cells.
If the 230 mile pack is 60kWh
That would be ~7500 2200mAh cells ~6400 2600 mAh cells ~5700 2900mAh cells or ~5200 3200mAh cells
If the 300 mile pack is 85kWh
That would be ~8000 2900mAh cells ~7300 3200mAh cells or ~5900 4000mAh cells
Here are my wild guesses:
The 160 mile pack will use 2600mAh cells.
The 230 mile pack will use cells between 2600mAh and 2900mAh
The 300 mile pack will use cells between 2900mAh and 3600mAh
IIRC it was already mentioned that high-milage pack will use bigger format cells and will thus be non-proportionally more expensive. Mid and low-milage pack are supposed to use different number of same cells.
Another variable in this equation is DOD. Car never uses full cell capacity, even if you charge in range mode, only about 90-95%. Exactly how much is technical secret.
Quite a press Junket. More here:
Did they say "bigger format" somewhere? My assumption was that the 300 mile pack was still to use 18650s, just higher capacity per cell.
Sorry, I've meant higher capacity.
On a side note, is it just me or are those Model S motor assemblies with an S on the case in that last pic? They look different that the roadster motor(h2o cooled).
I think they might just be Roadster motors. Perhaps the "S" is for "Sport" variant?
What a significant developement.... it leads me to thinks that TM is ahead of scheduling on the development of the Model S.
Is that battery pack the only available?
How long did it take Tesla to produce that battery pack and how long will it take to make a production Model S battery pack when the time comes?
Is the battery pack in the photo just for show or will it be used in testing? I did not notice any mounting hardware or a protective shell so I taking it may be a test pack.
How will the pack add structural integrity to the Model S chassis?
All very good questions / points.
Where did you hear that the battery pack is suppose to add structural integrity to the car? My thinking at this point is that what we are seeing is obviously the pack itself. When it does get installed into Model S it will probably be fitted into a bracket / housing / box, with all of the necessary connecting points to the chassis.
I myself am quite astonished by how thin this pack is. I was expecting at least double in thickness ~8" to 10".
If the cells are indeed oriented vertically and this is the ~8000 cell (230 or 300 mile) pack, I'm currious about the arrangement and weight distribution of the 160 mile pack. You'd think they should want the same form factor.
I'm sure the individual cells are still connected in blades. Or rather that instead of thin layers or blades they are arranged in boxes with a certain number of cells. So for the the 160 packs they either 2/3 fill each individual blade/box or they leave 2/3 of the blade/boxes empty. That way the outer shell of battery pack is the same and does the same for the structural integrity of the car. The car industry has a long tradition for boxes with lots of empty space, just look at the engine compartment for my old eighties Mazda
Here's the promised battery specs based on original March 26, 2009 press release:
160 mile - 5500 cells - ~600lbs - 42kWh
230 mile - 8000 cells - ~900lbs - 70+? kWh
300 mile - 8000 cells - ~900lbs - 70+? kWh
Hopefully more details on the pack will be available soon.
I know the press release quoted a bunch of numbers for cells, but I doubt that was a final decision on which cells and how many.
I think in the end it is going to come down to $/Ah and they still have time for the prices to change before 2012.
If the 2600s are less than 18% more expensive than the 2200s then it is a no-brainer to use 2600s.
You'll end up with a lighter pack and slightly more range for the same kWh. Fewer cells is also less interconnects and less monitoring hardware.
( Depending on the costs of that extra per cell overhead, it might still be cheaper to use 2600s if they are a little more than 18% more than 2200s )
The same equation applies to all the different capacity cells.
I also think they will build the same box for all packs and just fill them with different numbers of cells, leaving more or less empty space.
I realize none of these specs are final, but I just wanted to post them so there is some direction in guessing the specs.
Of course if $/Ah is lower going higher capacity, it makes more sense to use higher capacity. However, I think the trend is lower capacity tends to yield better $/Ah simply because lower capacity cells are made in higher volume. I think that is part of the reason why they planned to have 8000 cells for both the 230/300 mile packs (since this will minimize $/Ah for the 230 pack). It also probably makes manufacturing easier to have the same number of cells and similar weight.
The number of cells for the standard pack doesn't matter as much since it will have to be different anyways (having 8000 cells will need 1450/1500mah cells which are not in production anymore).