Samsung SDI is providing BMW with Battery. GM is getting it from LGChem. The whole myth of Tesla being the Apple of Car Battery supplies is just that myth.
It doesn't seem like a myth at all - tesla could be the Apple in that its vertically integrated w/ a tightly controlled supply chain and an ecosystem producing lock-in (superchargers), capturing the high end of the market and most of the profit in the industry.
GM and BWM would be the android device manufacturers - assembling 3rd party components, poorly differentiated, initially not competitive on quality but eventually catching up, while competition w/ each other prevents any of them from achieving profits comparable to Tesla.
