Tesla Is Now Buying Enough Batteries To Quadruple Production By 2017

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Tesla has greatly expanded the number of lithium-ion battery cells it's buying from Panasonic, the electric car maker announced today, hinting at a major increase in production of the Model S sedan and upcoming Model X SUV.

Under the new agreement, Panasonic will supply nearly 2 billion cells over the next four years.

The number of cells used in a Tesla Model S battery varies, but the biggest one uses about 7,000 cells, according to The New York Times.

That means the new deal will provide Tesla enough juice to power more than 285,000 top-of-the-line sedans.

Right now, Tesla is building more than 400 cars per week. In July, CEO Elon Musk said he plans to crank that up to 800 per week in late 2014. That's about 41,000 per year.

To use all of the Panasonic battery cells within four years, Tesla will need to roughly double that production rate again.

The new deal expands on a 2011 agreement, under which Panasonic provided enough battery cells to build 80,000 cars, according to Forbes.