Tesla suffered a major personnel setback just as it entered “production hell,” or crunch time for pumping out CEO Elon Musk’s much-hyped, mass-produced Model 3.

On Tuesday, Tesla confirmed that Kurt Kelty, the company’s battery technology director, had left the company. Kelty and CTO JB Straubel led Tesla’s efforts to refine batteries, not only for the company’s electric cars, but for its plan to create long-term sustainable energy storage in massive battery farms. Recently, however, the company’s focus was on the Tesla Model 3, the company’s first semi-affordable vehicle, which launched to great fanfare on July 28. Musk described the company’s next few months as “production hell” during the car’s debut, as the automaker struggles to meet the massive demand for the vehicle.

Kelty first joined Tesla in 2006. The company confirmed his departure in an email to Inverse today, after Bloomberg first reported the news.

“We can confirm that Kurt Kelty has left the company to explore new opportunities and we want to thank him for everything he’s done for Tesla,” a Tesla spokesperson told Inverse. “Kurt’s responsibilities will be distributed among Tesla’s existing teams.”

Before Tesla, Kelty spent 14 years at Panasonic, and even helped orchestrate the partnership between the two companies at Tesla’s Nevada Gigafactory. Panasonic has agreed to produce 1.8 billion battery cells for the latter company’s Model S and Model X cars, and collaborated with Tesla on a new design for the Model 3’s batteries.

Tesla’s goal is to make 20,000 Model 3 vehicles a month by December. The demands of scaling production will likely affect every part of the company, including Kelty’s former division, although the design for the car and its batteries is finalized. Regardless, after 11 years at the company, Kelty’s loss is a major development.

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