Tesla is preparing to build a battery development and production facility in California under a project called Roadrunner.

Tesla plans to build a battery plant for development and production in Fremont, California, according to a local government document cited by Reuters. While tesla already has a small battery manufacturing plant, the new facility is larger and plans to operate 24/7. The paper also provides a timetable for the plant, which is expected to be completed within three months.

If approved, the move would make California both a manufacturing base and a battery base for Tesla.

The news follows unofficial reports that Tesla will hold a "Battery Day" on September 15 this year. According to Elon Musk's own twitter feed, the date will be the date of this year's annual shareholder meeting, when Tesla will unveil details of a "million-mile" battery life.

Currently, tesla cars carry batteries from three main sources. Some are made at its Stuxnet factory in Nevada in collaboration with Japan's Panasonic, some from South Korea's LG Chem and some from the Ningde Era.

Shortly after the Tesla factory in Shanghai went into production in 2019, there were reports that Panasonic would enter the factory to make battery equipment for tesla, but Panasonic President Kazuhiro Tsuga said there were no plans to build a new battery factory in China.

Panasonic has long supplied batteries for Tesla's Model S and Model X. Panasonic began supplying the 18650 battery in 2009. When the Gigafactory opened in Nevada in 2014, Panasonic joined as a partner and became Tesla's sole battery supplier, covering Model S and Model X models. At its No. 1 plant in Nevada, Panasonic also supplies battery equipment for Model 3 models. Last April Mr Musk said panasonic's gigafactyl battery production had been hampering production of the Model 3.

LG Chem reached a deal with Tesla last August to supply batteries for the company's first gigafacfactory outside the US, before Mr Musk hinted that production was running into a battery bottleneck. Initially, LG's batteries will be used in the Model 3 at its Chinese factory, and later in the Model Y, its compact crossover sedan. LG Chem, the world's second-largest maker of lithium-ion batteries, has supply deals with major manufacturers such as Volvo, Renault and General Motors.

In November of that year, Ningde Times and Tesla reached a preliminary supply agreement, and in February they finally struck a partnership to supply the Chinese-made Model 3.

The Expansion of the California business, the Fremont Battery plant, also hinted at the demise of Mr Musk's plans to move the business. The conflict between fremont's city government and Musk over returning to work due to the covid-19 outbreak led Musk to file a lawsuit against the local government and threaten to move Tesla's headquarters, also in California, to Nevada or Texas "immediately."