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Following up on earlier tweets indicating several new battery vehicles were under development, Tesla CEO Elon Musk tweeted that the company was planning to introduce a new semi-truck in September, with an electric pickup truck to follow in about 18 to 24 months.

The big truck was first hinted at last July, when Musk unveiled his “Master Plan, Part Deux.” He had previously expressed interest in a pickup several years ago, about the same time Tesla began searching for a site for its Gigafactory battery plant.

“Tesla Semi truck unveil set for September,” Musk said on Thursday, the tweet adding, “Team has done an amazing job. Seriously next level.”

Tesla Semi truck unveil set for September. Team has done an amazing job. Seriously next level. — Elon Musk (@elonmusk) April 13, 2017

Exactly how big the truck will be is unclear. A Tesla spokesperson confirmed there would be no additional information beyond what was in the Musk tweets.

But the Tesla Master Plan released in July 2016 noted that, “We believe the Tesla Semi will deliver a substantial reduction in the cost of cargo transport, while increasing safety and making it really fun to operate.”

Tesla isn’t the only company looking at ways to electrify commercial vehicles. There are already hybrid buses in widespread use and some limited-application all-electric products. The big challenges, however, are range and charging time. In fact, those pose potential more seriously limits for trucks than for passenger vehicles.

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Trucks: Literally the Next Big Thing

And Tesla isn’t the only one looking at zero-emissions trucks. Salt Lake City-based start-up Nikola Motor Co. recently unveiled a hydrogen fuel-cell semi, and Toyota is working on a similar concept. Daimler AG, the parent of both Mercedes-Benz and Freightliner, showed off a prototype battery truck last November. But it would allow a maximum 124 miles per charge, limiting its use to local deliveries.

The man who led the Daimler effort, Jerome Huillen, left the German maker to join Tesla in 2012.

As for the pickup truck, another Musk tweet said it will be unveiled in 18 to 24 months.

Related: Will Trump Unplug the Electric Vehicle Market?

Tesla first began dropping hints about a pickup when it went looking for a Gigafactory site. Some observers, at the time, thought it was more publicity stunt than reality, as one of the finalists for the plant was the State of Texas, the country’s largest pickup market. Ultimately, the battery plant went into a site in Reno, Nevada.

As with the semi, range and charging times could prove a challenge for a pickup. It is likely that Tesla will use a platform similar to what is underneath its current Models S and X passenger cars, a skateboard-style design with the battery pack in its floorboards.

However, Musk has expressed interest in the possibility of using swappable batteries, something that would eliminate the need for motorists to wait while the vehicle is recharged. That approach might make sense in a vehicle like a pickup, or even a semi.

More to Come

In a series of Thursday tweets, Musk confirmed the company’s planned Roadster would be a convertible.

He also confirmed the final, production-ready version of the Tesla Model 3 sedan will be unveiled in July, about the same time it is set to go into production.

That compact, mainstream-priced sedan will be the critical lynchpin for Tesla, analysts have stressed, as it is expected to help boost Tesla production from around 100,000 in 2016 to 500,000 in 2018, Musk has promised.

Skeptics note that Tesla has yet to deliver a product on time, and the company has been faulted repeatedly for quality issues, especially with the Model X battery-SUV. So, getting the Model 3 to market on-time and without quality problems could be essential.

On the other hand, proponents look at the potential of the Model 3 as a primary justification for Tesla’s latest run-up on the stock market, the maker gaining another $7.16, or 2.41 percent, on Thursday, to close at $304.00 a share. Earlier in the week, the company surpassed the market capitalization of General Motors, to become the most highly valued automaker in the U.S.

CEO Musk has hinted that still other products are in the pipeline, including a sport-utility vehicle based on the same platform as the Model 3. It will be known as the Model Y, something Musk recently admitted was part of a “bad joke.” It will result in a line-up that runs Models S-3-X-Y. The original goal was to call the mainstream sedan the Model E, but Tesla couldn’t get the rights for that from Ford.