Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Horsepower

This site may earn commission on affiliate links.
Where did 7800 cells in the 300 mile pack come from? AFAIK there are 7104.

Where did you hear the 7104 number? No one I spoke with at the factory would confirm nor deny any particular number of cells.
The 7800 number was from a number of articles a long while back when Model S was first announced.
For instance, in wired:
First Look at Teslas Stunning Model S | Autopia | Wired.com
...Power comes from a lithium-ion battery pack with either 5,500 or 7,800 cells...
I recall that there may have been a company press release that had those numbers too.

But that was in 2009, and a lot could have changed since then.
Perhaps the original intention was 7800 3100mAh, but now they have 7104 3400mAh?
3100*3.75*7800=90kWh
3400*3.75*7104=90kWh

Also, for Roadster, 2200*3.75*6831=56kWh, which was the original pack spec, which later got revised down to 53kWh. So maybe Model S has a similar 90kWh max->85kWh published capacity.
 
ehh... you can work it out from the math. 16 modules/sub-packs in the Model S battery pack. We've seen the same modules in the RAV4 EV and the Merc A-class battery packs (strapped underneath), so guess based on that pack size. The number of cells has to be an integer, after all... so that limits the solution space. Cells per module can't be prime, etc...
 
ehh... you can work it out from the math. 16 modules/sub-packs in the Model S battery pack. We've seen the same modules in the RAV4 EV and the Merc A-class battery packs (strapped underneath), so guess based on that pack size. The number of cells has to be an integer, after all... so that limits the solution space. Cells per module can't be prime, etc...

You're making it sound like Nikola's Last Theorem...
 
At the S event in Boston (end of June 2011) the Tesla tech said the 160 and 230 mi batteries would use the same type and capacity of cells. The 160 would just have less of them. He said the 300 mi battery would have the newer higher density cells and weigh about the same as the 230 mi battery. He expected the replacement Roadster batteries that will be available in a couple years to have a reduced number of cells at higher capacity to get 53kwh. When I started asking more detailed questions he said "I can't say." I asked "You don't know or you can't say?" He smiled and said "Some of both."
 
At the S event in Boston (end of June 2011) the Tesla tech said the 160 and 230 mi batteries would use the same type and capacity of cells. The 160 would just have less of them. He said the 300 mi battery would have the newer higher density cells and weigh about the same as the 230 mi battery...

This is the same thing I have heard multiple times. The only thing that has really changed is that they are starting with the 300 mile pack.
A couple years back they were suggesting that the 300 might come later, but I gather they got it all sorted in time for it to come out with the launch.