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A look at the new Tesla cells

11950 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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Any reliable updates on the 21700 Tesla cell specs?
As others have pointed out, things don't pencil out for the new Semi and R2 to be using today's battery technology. It seems like the batteries in these vehicles must have energy densities improved by a factor of ~ 2.
While the Semi's battery size and packaging are mysteries at this point (it could have five tons of battery), that's a good point about the Roadster - it's hard to see that body with double the battery volume (or mass) of a Model S.
The Tesla Semi main designer, Jerome Guillen, said in a recent presentation in Europe that the Tesla truck weighs no more than a diesel truck. If you take a modern diesel semi (also designed by a team lead by Jerome Guillen when he worked for Daimler/ Freightliner) and pull the engine: ; transmission: say ~1000# of tanks, radiators, non-fuel fluids, and other ICE related equipment; and 200gal(~1400#) of fuel. You save ~6000# (if I haven't left any thing out). So how much energy will ~6000#(~2700kg) of batteries give us?
This could also mean that the claim of matching diesel weight is just bunk. :rolleyes: To be fair, this claim was likely for a shorter-range version, not the 500-miler.
It could be. Although in the presentation, I believe he only talks about the longer range Semi. To clarify, he does parse the weight discussion by saying the Semi has the same cargo capacity as a diesel semi. Hear for yourself at ~ 4:30:
On the other hand, Guillen refers to only a single GVW limit (the US federal value) and says that they are aiming to have the same payload... so nothing has actually been achieved, and we're still talking about aspirations. Even the 800 kilometre (500 mile) range is expressed as a target, not an actual specification. By the time these numbers get from the Truck VP to the Supreme Leader (Musk), of course they become absolutes.
The trucking industry is a careful, conservative lot. Tesla is not going to be able to fool them for long, if they can't deliver the goods. I suspect the better cheaper batteries that we speculate must be in the Semi and R2 are here, with full production coming sometime later. I also suspect Tesla isn't bragging about it so as to not tick off the people buying the Model 3, that has the older batteries.
Here's some quick(some might say frantic!) info on the better batteries that could be in the Semi and R2 starting at ~1:20:
So if we eliminate the possibility of two 2-speed gearboxes, then in order to have two rear motors, the following architectures remain:

a) Different reduction ratios + rear (and front) differential. The Model 3 reduction ratio is close to 10. So for the R2, it would be 14 on one motor and 7 on the other motor. A further twist here is that if the 14 motor could be disengaged by a clutch, then the ratios could be wider such as 16 and 6. The front ratio would remain at 10.

b) Another possibility is just one 2-speed gearbox in the rear for one of the motors. One motor runs at ratio 14 the other at 7 but also has the benefit of the 2-speed gearbox and then can also run at 14, for low-speed high acceleration. I don't think this would be a good design.
If I'm not mistaken, the R2 has motor based torque vectoring. This implies symmetry, side to side, for the two motors and gear reduction boxes in the back. Another thing: somebody said that when the Semi was accelerating at the event in Hawthorne, they thought they heard a shift(electronic shift?). Maybe something like a shift from a Delta to a Wye stator configuration? Is this a possibility? Or, something else electronic?
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