What happened

Shares of Tortoise Acquisition (NYSE:SHLL) were rising on Wednesday. The special purpose acquisition company's planned merger with electric semi-drivetrain maker Hyliion appears on track to close by the end of September. 

As of 2:00 p.m. EDT, Tortoise's shares were up about 9.3% from Tuesday's closing price.

So what

While Tortoise hasn't yet announced a date for the shareholder vote that will seal its deal to merge with Hyliion, recent filings show that the deal appears to be on track for a vote later this month.

A green and white Freightliner semi with Hyliion's hybrid powertrain installed.

Hyliion has installed its hybrid powertrain in about 20 trucks, which together have racked up over 2 million test miles. Image source: Hyliion.

Tortoise filed an updated preliminary version of its proxy statement with the Securities and Exchange Commission last Friday. From that we learn (among other things) that all existing Hyliion investors still plan to "roll over" their investments into the new company, that Tortoise will bring $235 million in cash to the deal, and that other investors still plan to invest $325 million in exchange for shares of the new company (at $10 per share). 

From an earlier filing, in mid-August, we learned that Hyliion is on track to commercialize its hybrid heavy-truck powertrain, that it has already installed the powertrain in about 20 trucks that have accumulated over 2 million test miles, and that the funding provided by this deal will be enough for Hyliion to get its planned natural-gas-hybrid Hypertruck ERX system to market, without additional cash infusions.

Now what

I think Tortoise's recent stock gains are simply a function of auto investors learning more about Hyliion and the merger deal. While there's always risk involved in a start-up with very little revenue, at least on paper there's a lot to like here.

Hyliion is an intriguing company with a strong management team, a well-developed set of products, and the right partnerships in the existing heavy-truck ecosystem that's going to market at a moment when truck-fleet operators are looking for greener options that work with their existing infrastructure.