What happened

Shares of Lightning eMotors (ZEV) were trading lower on Wednesday, a day after the company's stock price surged on news of a deal with a shuttle-bus maker owned by Berkshire Hathaway (BRK.A -1.39%) (BRK.B -1.07%).

As of 10:45 a.m. EDT, Lightning eMotors' shares were down about 8.5% from Tuesday's closing price -- but still up almost 70% since the end of last week. 

So what

Lightning eMotors' stock closed up a whopping 81% on Tuesday on some big news: The company, which makes electric drivetrains for commercial vehicles like pickups and vans, signed a deal to provide powertrains for up to 7,500 shuttle buses to be built by Berkshire-owned Forest River. 

Lightning eMotors will also provide charging products and services under the deal, which runs for the next 4 1/2 years. All in, it could be worth as much as $850 million in revenue, making it a big deal for the small company.

A Ford Transit commercial van with a Lightning eMotors electric drivetrain.

Lightning eMotors installs electric drivetrains in commercial vehicles, many of which are built by Ford Motor Company. Image source: Lightning eMotors.

But it's more than that. For much of its existence, Lightning eMotors has focused on fitting electric drivetrains to a variety of commercial vehicles based on underpinnings supplied by Ford Motor Company (F -3.30%), including Transit commercial vans and various medium-duty vehicles built on Ford Super Duty chassis. 

But with Ford moving to launch its own battery-electric version of the huge-selling Transit commercial van this fall, Lightning eMotors needed a Plan B -- and the deal with Forest River seems to have provided one.

That's why auto investors bid the stock up in a huge way on Tuesday. Why was it down on Wednesday? Because a bit of settling is to be expected after an 81% one-day gain. 

Now what

Investors holding those suddenly more valuable shares won't have to wait long for an update. Lightning eMotors will report its second-quarter results after the U.S. markets close next Monday, Aug. 16.