# Elon's comment about a battery box in a box



## bwilson4web (Mar 4, 2019)

During the "Third Row" row interview, Elon made a comment about building battery modules, a pack assembly, and then the pack in a box. Thinking about it, there is a reasonable approach:









Eliminate individual cells by starting with a battery block.
Either cylindrical or prismatic recesses, which ever is easiest to stuff.
cylindrical is traditional for a 'jelly roll'
prismatic uses a sandwich (aka., the Toyota style)

Bottom has base buss bars for assembling cells into groups.
Top has the fuse wires and top buss bars.
Coolant channels run through the battery block.
The battery block replaces individual cell walls. This approach makes a single battery assembly with the cells and interconnects. Dimensions are optimized for efficiency and thermal management.

In this sketch, the cooling channels are shown between top and bottom surfaces. However, the cooling channels could go side-to-side so the bottom remains flat. The coolant manifolds would be on the edges.

Bob Wilson


----------



## gary in NY (Dec 2, 2018)

I'm curious about which cell types are easier to thermally manage. Tesla's method with the cylinders seems pretty good, but there is a lot of surface area on the prismatic cells. Interesting that dividing the battery into modules is not necessary, but just a holdover from the early days.


----------



## bwilson4web (Mar 4, 2019)

Turns out, 'Hyper Change' found the Tesla patent:





Toyota prismatic batteries have six cells, ~"D" volume, in a plastic module. Buss bars connect adjacent modules to make a pack. Cylindrical cell or prismatic makes no difference. Which ever gives the greatest efficiency works.

Bob Wilson


----------



## TrevP (Oct 20, 2015)

Makes total sense to drop the traditional modules they’ve been doing. Elon said that doing modules was their way of ensuring easy replacement if any of them failed but they ended up not doing that in favour of total battery pack replacements. They packs are so tightly sealed it just wasn’t feasible to repair them. As for Model 3 that thinking carried over but only to 4 modules. 

Going forward I don’t think they will be doing modules at all, just a box with cells and cooking and even no box cover since the packs will seal with the body. Makes it easier and cheaper to manufacture and increases the cell count and density. 

Watch as they keep iterating while the other car makers keep making packs the old fashioned way.


----------



## bwilson4web (Mar 4, 2019)

TrevP said:


> Going forward I don't think they will be doing modules at all, just a box with cells and cooking and even no box cover since the packs will seal with the body. Makes it easier and cheaper to manufacture and increases the cell count and density.
> 
> Watch as they keep iterating while the other car makers keep making packs the old fashioned way.


Here is where economies of scale and vertical integration pays big dividends. The LG Chem is not going to have enough volume with the 'honorable competition' to scale a 'box of cells' for each manufacturer at an affordable price. So they will be stuck with individual cells to assemble into a traditional pack. In contrast, Tesla is already making as many Model 3 as all of the honorable competition.

Bob Wilson


----------

