Today Tesla Motors along with Panasonic Corporation announced from Japan that they would expand a supply agreement to allow Tesla to increase production of the Model S and pending Model X due for launch by the end of next year.

The update to a 2011 supply deal calls for 2 billion cells over the next four years and builds on a collaboration between the two companies going back to the Roadster.

“This expanded agreement with Panasonic is important to Tesla as we continue to increase the pace of production,” said Tesla Co-Founder and CEO Elon Musk. “We look forward to strengthening our relationship with Panasonic, and I’m confident that this partnership will continue to be an integral part of Tesla’s success for years to come.”

Tesla says miles driven by Model S and Roadster buyers now exceeds 130 million and “together, Panasonic and Tesla have developed a next-generation battery cell technology that provides the highest energy density and best performance cells in the market.”

Panasonic’s cylindrical cells are often called by observers “laptop batteries,” but they are actually a prodict of an internal company of Panasonic called the Automotive & Industrial Systems Company.

From Osaka, Japan, the subcompany’s President Yoshihiko Yamada affirmed the relationship will continue to grow enabling Tesla to grow.

“We are extremely proud to be a strategic partner of Tesla,” said Yamada, “Panasonic will increase its production capacity of lithium-ion battery cells to supply Tesla’s growing needs as it expands its production of EVs.”

The cells used in Teslas are based on existing technology, but are customized to deliver improved quality and longevity of electric vehicles, Tesla says.