Elon Musk described the current state of Model 3 production ramp-up as "hell." Hell is about to get a bit warmer for Tesla, as the company just lost a long-time executive in a critical part of its business.

Kurt Kelty, Tesla's director of battery technology, left the company after 11 years. Prior to that, he worked for 14 years at Panasonic, the company that partnered with Tesla to build its Gigafactory battery plant in Nevada. Bloomberg reports that Kelty was the one who led those negotiations.

"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 said in a statement. "Kurt's responsibilities will be distributed among Tesla's existing teams."

If there was a good time to leave Tesla, this probably wasn't it. Tesla finally handed off the first 30 Model 3 sedans to their owners last week, and production is now underway to clear out the backlog of hundreds of thousands of reservations. Production will start slow and ramp up in the coming months, ideally growing to over 20,000 units per month by the end of the year. That's nearly as many vehicles as Tesla delivered in Q2 2017 -- in a single month.

Tesla should send out its second-quarter financial report later on Wednesday, after the markets close.