Tesla shares fall as Musk dampens Battery Day expectations

Key Points
  • Tesla stock closed down 5.6% Tuesday.
  • Tesla is expected to announce details later in the day about a new type of battery cell it has developed.
  • But CEO Elon Musk cautioned about hurdles to reaching mass production.
Here's what to expect from Tesla's Battery Day

Tesla shares closed down 5.6% Tuesday after CEO Elon Musk sought to manage expectations ahead of the electric carmaker's Battery Day presentation.

Musk's company is expected to announce on Tuesday afternoon details about a new type of battery cell it has developed. Analysts had hoped the technology could help Tesla maintain its edge over rivals in the electric vehicle space, but Musk dampened such hopes Monday when he cautioned about hurdles to reaching mass production.

"Important note about Tesla Battery Day unveil tomorrow," Musk tweeted, often his go-to for communications about the company. "This affects long-term production, especially Semi, Cybertruck & Roadster, but what we announce will not reach serious high-volume production until 2022."

Musk said Tesla would increase battery cell purchases from suppliers Panasonic, LG and CATL but warned "we still foresee significant shortages in 2022 & beyond unless we also take action ourselves." Tesla has built a prototype manufacturing line for battery cells at a lab in Fremont, California, near the company's U.S. car plant.

Tesla shares fell over 6% in after-hours trading as a result Monday, after closing almost 2% higher at $449.39. Still, share prices are up over 400% year to date on the back of a stock split and optimism around the possibility of Tesla's entry into the S&P 500.

- CNBC's Lora Kolodny and Jessica Bursztynsky contributed to this report.