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They aren't really COTS. They were for the Roadster, but for the Model S they use a specialized chemistry as well as removing the protection circuit.

[Source](https://www.youtube.com/watch?feature=player_detailpage&v=9c...)

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That's standard for NCR18650A cells though - they ship with no protection circuit and I believe the same chemistry that the Model S is using. The protection circuits are added by companies that buy raw cells from Panasonic.

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