Fisker Automotive, designer and builder of boutique hybrid and electric vehicles, came to enemy territory yesterday to debut its Fisker Karma at Santana Row, and to announce the opening of a Silicon Valley retail outlet. But the news was eclipsed by the announcement today that Fisker’s rival, the Silicon Valley-based Tesla Automotive, inked a big-money deal with Daimler Motors.

Wired magazine’s Autopia blog gave the Tesla/Daimler deal top-story treatment: “One of the oldest automakers joined one of the newest Tuesday as Daimler took an equity stake of ‘nearly 10 percent’ in Tesla Motors.”

“The deal provides Daimler with batteries and the know-how needed to bring an electric car to market “at the highest possible speed,” company officials said. In exchange, Tesla gets a big pile of cash and, perhaps more importantly, the parts and engineering expertise it needs to build the Model S sedan.”

The Model S—which for a time was set to be built in San Jose—is slated to be an affordable, practical version of the Tesla Roadster, a $100,000 two-seater that single handedly turned the world on to the viability of electric cars. (See a cool video from the front seat of a Tesla here). Despite a quick start, the company has recently hit some roadbloacks.

A few months back, Dan Neil of the Los Angeles Times test drove a mockup of the Model S, and called it “just barely ambulatory — more like a glorified golf cart than a harbinger of tomorrow tech.”

The Daimler deal could get Tesla back on track.

According to Autopia, neither company provided specific details of the deal, but Daimler officials said its investment is “a double-digit million sum.”

Jalopnik, another popular auto-phile website, pointed out that today’s agreement is the culmination of a partnership that began several montns ago.

“It’s not the first time these two companies have partnered. This year at the Detroit Auto Show the two automakers agreed to a minor partnership for Tesla to provide the powertrains for a test run of electric smart cars. Now, with Daimler scooping up 10% of the new company, both automakers are now claiming the alliance will “make electro mobility a reality.”

For its part, Fisker also sees a bright future for electric cars. According to a press release regarding Monday’s unveiling: “Fisker Silicon Valley will be among the first group of U.S. retailers to market and service the Fisker Automotive luxury plug-in hybrid vehicles, beginning with the $87,900, 100mpg Karma.”

Despite (or because of) the car companies’ similar philosophies and designs, Tesla and Fisker are bitter rivals. Three years ago, Tesla CEO Elon Musk hired Henrik Fisker, former design director at Aston Martin. Last year, Tesla sued Fisker, claiming he stole confidential design information and trade secrets.

San Jose Mayor Chuck Reed, who worked hard to lure Tesla to build a plant here, attended to Fisker ribbon-cutting yesterday.

“I am delighted to welcome Fisker to Silicon Valley,” Reed said. “As a leader in clean-tech innovation, we are working regionally to make the Bay Area the electric vehicle capital of the world. Having a variety of options like Fisker vehicles available to our residents will help put San Jose on the road to improving air quality, decreasing greenhouse gas emissions, and reducing our dependence on foreign oil.”