tidmutt
Well-known member
- First Name
- Daniel
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- Feb 25, 2020
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- Model Y Performance, Model X P100D
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- Software Architect
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- #1
Hi All,
Something I have been wondering for a while and I'm hoping someone here can help me understand relates to pack level energy density versus cell level.
I keep seeing this interesting numbers for the growth in cell level specific energy for the cells Tesla use. Numbers for cell level energy density in the Model S are close 270 Wh/kg. This has grown significantly and there is discussion about the 4680 cells being 300 or more.
However, when you look at pack level energy density it seems to have hardly moved since the original Model S. Some sources say the model 3 improved between 2019 and now somewhat, growing from 150 Wh/kg (at the pack level) to 166 Wh/kg. However, this isn't really much of an improvement over the Model S. I haven't found good numbers for pack level 4680 energy density but some sources say it won't be much different.
I believe I understand why pack level specific energy is lower than cell level. When you combine the batteries into a pack it takes structure and wiring and insulation and other things which means the overall energy stored in the mass of the pack is lower. Plus perhaps loses to heat when energy is conducted out of the cells and out of the pack etc. But why has the pack level energy density stayed relatively flat where as cell level as improved so much?
Thanks in advance!
Something I have been wondering for a while and I'm hoping someone here can help me understand relates to pack level energy density versus cell level.
I keep seeing this interesting numbers for the growth in cell level specific energy for the cells Tesla use. Numbers for cell level energy density in the Model S are close 270 Wh/kg. This has grown significantly and there is discussion about the 4680 cells being 300 or more.
However, when you look at pack level energy density it seems to have hardly moved since the original Model S. Some sources say the model 3 improved between 2019 and now somewhat, growing from 150 Wh/kg (at the pack level) to 166 Wh/kg. However, this isn't really much of an improvement over the Model S. I haven't found good numbers for pack level 4680 energy density but some sources say it won't be much different.
I believe I understand why pack level specific energy is lower than cell level. When you combine the batteries into a pack it takes structure and wiring and insulation and other things which means the overall energy stored in the mass of the pack is lower. Plus perhaps loses to heat when energy is conducted out of the cells and out of the pack etc. But why has the pack level energy density stayed relatively flat where as cell level as improved so much?
Thanks in advance!
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