> but I think they use different battery chemistries but use the same cell size (18650) I also read something like that. I suspect it is more of a tweak than a

> but I think they use different battery chemistries but use the same cell size (18650) I also read something like that. I suspect it is more of a tweak than anything major. No doubt it is the same basic chemistry but perhaps with minor tweaks to the various ratios and material thicknesses and so on. The Tesla batteries are a single-application cell, so you know exactly the maximum discharge current, the maximum charge current, the temperature parameters, and so on, whereas a generic 18650 has to balance those for a "typical application" or whatever. See for example the Samsung high-discharge INR18650 cells which trade off capacity for higher max discharge current. OTOH the other hand I also heard the early Teslas were using exactly the Panasonic 18650B cell. They could both be true: maybe it was a stock cell in the early days and they tweaked the formula later in concert with Panasonic as their volumes rose. There was no big evident spike in capacity vs weight though...