Kurt Kelty, director of battery technology at Tesla, has stepped down from his post just days after the company’s lavish party to celebrate the delivery of the first Model 3s, Bloomberg reports. Kelty, who has worked at Tesla since 2006, led Tesla in forging partnerships and battery cell material sourcing at the company’s Gigafactory near Reno, Nevada. He was also responsible for the overall performance of Tesla’s batteries.

“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 company spokesperson told The Verge by email. “Kurt’s responsibilities will be distributed among Tesla’s existing teams."

Prior to joining Tesla, Kelty worked at Panasonic for nearly 15 years. At Tesla, Kelty served as lead negotiator with Panasonic for that facility, according to LinkedIn. Earlier this year, he accepted the award for “Battery Innovator of the Year” presented by the 34-year-old International Battery Seminar.

Kelty’s departure couldn’t come at a worse time for Tesla, which is finally entering what CEO Elon Musk calls “production hell” for the Model 3. Musk has promised that Tesla will produce 100 cars in August, more than 1,500 by September, and then 20,000 per month by December. If the company fails to hit these marks or runs into manufacturing issues that happen at higher scales, or demand for the Model 3 drops, analysts argue it would be a setback not just for Tesla, but perhaps the entire electric vehicle movement.

Here’s a video of Kelty talking about battery production at the Gigafactory back in March 2017:

Update August 1st 5:00PM: The original article has been updated to include Tesla’s statement on Kelty’s departure.