Tesla battery pack capacity confusion

Post date: 2022-08-10 04:16:12

I'm confused about the Tesla battery pack specifications. My understanding is that when you add cells in series their overall capacity stays the same - it's only when you add them in parallel that you add the capacities. But the spec seems to be as if the modules that make up the pack are both in series and in parallel! Maths below the fold.

A Tesla module contains 6 series x 74 parallel 18650 cells. This gives 6 x 3.7V = 22.2V total, and 74 x 3.4Ah x 22.2V = 5.6 (rounded)kWh capacity. So far, so good! My calculations match the specs.

16 modules are wired in series to create the battery pack. I'm confused because the total capacity is given as 89-90kWh. This is 16 x 5.6 (89.6) but that would only work if the modules were connected in parallel! If they are in series then isn't it still 5.6kWh?

What am I missing here? I'm guessing it's to do with the configuration within the modules? Or just some weirdness in how the specs are given?

(This is to satisfy my curiosity, no actual battery use is intended. I don't even own a Tesla.)

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