For a few months now, Tesla has been rumored to be working on making its own battery cells for its electric vehicles.

It started with the acquisition of Maxwell, a supercapacitor manufacturer with some battery cell technology, and later at its annual shareholder's meeting, Tesla all but confirmed that it's going to manufacture its own battery cells.

Later, we reported that Tesla referred to battery cells as a new "product line" for the company in some job listings for cell manufacturing.

Now we've learned that Tesla is building a battery cell pilot production line in Fremont, according to a new 'Pilot Line Production Engineer, Cell Engineering' job listing.

In some of the listings, Tesla describes responsibilities to "drive design, commissioning ramp of a complex manufacturing tool that is the first of its kind at Tesla" to manufacture battery cells: