Investors shouldn’t expect much mileage out of Tesla’s latest capital increase.

The electric car company raised a total of $2.7 billion in convertible debt and stock earlier this month, its first trip to the capital markets since August 2017. That nearly two-year stretch was the company’s longest between raises since it went public in 2010. It would be a big surprise, however, if Tesla can wait that long next time.

Elon...