electruck
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- Oct 6, 2019
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- Dallas, TX
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- 2023 Rivian R1S
Lots of misnfo there, not going to try to address it all. As for cold-plate vs tesla's cooling ribbons, even tesla has admitted that axial cooling is more effective than radial (to the extent that they are moving from radial to axial cooling in newer designs). Heat conduction between the cells and cold plate is not a function of gravity so no difference between top/bottom cells. Rivian has stated that cell temps are extremely consistent across all cells in their packs (RJ has quoted the variance somewhere, don't have that reference handy).With Rivian's inaugural pack, they are using a sandwiched cooling plate to warm/cool the pack. This is of course going to have nowhere near the ability to wick away heat that Tesla's in-pack cooling has, so heat throttling is going to happen. The reason cold weather does not help this much is the fact that the center of the packs (they are stacked) are well insulated from the outside temperature, so the main way for the heat to escape remains that single sandwiched cold plate. This is a physical thermal bottle-neck that is designed into the system and cannot be helped.
Why did they not put cooling ribbons between the cylinders the way Tesla does? Cost, and manufacturing difficulty. I expect Rivian's packs to evolve and get better at thermal management, but this is a good way to get decent cooling without breaking the bank as they try to ramp up. It is similar to how Ford & GM are doing it, except Rivian is using Tesla style cylindrical cells.
For those watching the pack tech closely as I am, I will add that the sandwiched cold plate design has another characteristic that could easily cause problems down the road. Because there are vertical banks of 2170s both above and below the cold plate, both cooling and heating will potentially be quite different between the upper and lower packs. When attempting to cool the pack during DCFC, the pack under the cold plate will get the bulk of the cooling due to thermal dynamics. Keeping the _whole_ pack at an ideal temperature becomes impossible, the pack on top of the plate will always be much hotter.
Heating the pack will have the reverse problem, but since heating is not as critical as cooling, that should have less of an impact on the life of the packs. Just based on common sense, one would expect the packs sitting on top of the cooling plate to fail before the lower ones.
Time will tell, and I am certain that the design will evolve.
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