Tesla Motors [NSDQ:TSLA] and technology company Panasonic have been working together for several years now, and that relationship is set to expand as Tesla seeks to meet its future battery needs.

The two companies have reached an agreement for future automotive-grade lithium-ion battery supply, Panasonic now set to supply nearly 2 billion cells to Tesla over a four-year period.

Panasonic has been supplying cells since the days of the Tesla Roadster, but the electric car company's increasing sales and wider product plan mean battery supply has to meet their increasing demand.

The new agreement ensures both the Tesla Model S, and upcoming models like the Model X crossover, will receive a steady supply of cells for years to come. Tesla's press release reveals that customers have driven over 130 million miles so far, with thousands of vehicles now on the roads.

The benefits are reciprocal of course--back in 2009, Panasonic bought a $30 million stake in Tesla. That's an important cash injection in the early years of a business, and has helped Tesla Motors to get to the position it's in today--selling cars and making headlines.

Both companies will continue to work together to develop the next-generation of lithium-ion cells, improving the potential of electric vehicles and expanding the market. Tesla and Panasonic's cells already boast the highest energy density of any cells on the market, contributing to the class-leading 265-mile EPA-rated range of the 85 kWh Model S.

"We look forward to strengthening our relationship with Panasonic," said Tesla Motors CEO Elon Musk of the new deal, adding, "I’m confident that this partnership will continue to be an integral part of Tesla’s success for years to come."


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