Kurt Kelty, Tesla’s battery tech director, has left the company as the company enters “production hell” for the Model 3.

The news was first reported by Bloomberg’s Dana Hull. A Tesla spokesperson confirmed Kelty’s departure to Business Insider, adding that his responsibilities will be distributed among existing teams.

Kelty has served as Tesla’s battery tech director since 2006, before Elon Musk became CEO of the company, according to Kelty’s LinkedIn page. Before joining Tesla over a decade ago, Kelty was director of Panasonic’s Energy Lab.

Panasonic manufactures and supplies lithium-ion cells to Tesla for its battery packs and plans to invest a total of $1.6 billion in Tesla’s Gigafactory, a massive battery plant in Sparks, Nevada.

Kelty’s departure comes a few days after Tesla delivered its Model 3 sedan to its first 30 customers at handover party in Fremont, California. Musk said the company will enter six months of “production hell” for the Model 3, the company’s first mass-market sedan.