While in Tokyo to pitch his $78,000 car, Tesla Motors Inc.'s Elon Musk enjoyed an "awesome" bowl of $7 ramen.

The chief executive of the upstart electric-car maker went for Sunday dinner at a cult ramen shop in the Shinjuku area called Jiro--no relation to Sukiyabashi Jiro, the $300-a-person sushi sanctum where President Barack Obama dined in April.

Mr. Musk is known for his unpredictable comments, such as when he said last week that his own company's share price was "kind of high." But he stuck to polite praise for Japan at a Monday news conference, where he celebrated the arrival of Tesla's Model S vehicle in the country.

"An important point that I should emphasize about the Model S is that the batteries are all made in Japan," said the 43-year-old entrepreneur. Because the battery is the "heart" of an electric car, he said, "the heart of Model S is Japanese. I think that's a pretty cool thing."

Though he hasn't generated as much buzz in Japan as in the U.S., more Japanese lately have been paying attention to Mr. Musk. That's partly because of his tie-up with Panasonic Corp., which makes Model S batteries, for a $5 billion battery factory in Nevada.

While there hasn't been any official word from Panasonic on its investment size, Mr. Musk reiterated Monday that he expected the Japanese company to contribute between 30% and 40% of the so-called gigafactory, while his own company would pay for the half.

One of the first nine Model S vehicles delivered to Japanese owners Monday went to Yoshi Yamada, executive vice president of Panasonic, who was present at the handover ceremony. Mr. Yamada said the vehicle was for company use.

As in the U.S., the Japanese electric-car market has been growing but not as quickly as some auto makers hoped because of the cars' high price and lack of charging stations. Some Japanese auto executives believe hybrid cars and fuel-cell vehicles have a better chance of capturing the interest of environmentally conscious car owners.

Tesla's Model S is priced from ¥8.23 million (about $78,000). Mr. Musk said Model S owners would be able to charge their cars free at Tesla-built power stations "forever." The first "supercharger" station was built in Roppongi.

As for his visit to the noodle shop, Mr. Musk said it wasn't something he or his staff planned.

"I was just waking around the street with my friend, and said, 'Hey, this place looks so cool, let's eat here,' " Mr. Musk said. "They gave me a huge bowl, and it was awesome."

Noodles in Shinjuku pic.twitter.com/MWztTqByuA

— Elon Musk (@elonmusk) September 7, 2014