Last month, electric car maker Tesla Motors took the unusual step of opening up its patents to other automakers.

Automakers usually guard their patents very closely, ensuring them as much competitive advantage as they can get away with before someone builds something better.

Open Tesla's patents may now be, but as far as America's Big Three automobile makers are concerned, Tesla might as well have released a recipe for potato salad.

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According to The Detroit News, General Motors, Ford and Chrysler have largely expressed disinterest in the Tesla patents--which range from battery control details to the workings of its Supecharger rapid-charge stations.

Assessing Tesla's patents is "not something that’s on the front burner for us to look at" said Kevin Kelly, GM’s manager of electrification communications.

Tesla CEO Elon Musk had previously remarked that he didn't want to lay "intellectual property landmines" behind Tesla's electric car progress, as it would be contrary to the company's desire to put more electric cars on the road.

But industry analysts suggest the Big Three have found Tesla's batter technology either outdated, too expensive, or incompatible with their existing programs.

In other words, Tesla has brought its potato salad recipe to a party where everyone has already filled up on their own cole slaw.

Pride may have something to do with it too, suggested Jack Nerad, executive market analyst for KBB.com.

He noted that GM, Ford and Chrysler have been working on electric vehicle technology for some time now--in one format or another--and that they may feel they don't need Tesla's assistance.

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"I think they like what they do and generally think the technology they develop is top tech," Nerad explained. It's what's sometimes known as the "Not Invented Here" syndrome.

Tesla's Supercharger technology may prove useful across the wider electric car industry, though--and Detroit's automakers have already said they're open to working with other companies in this regard.

Still, Detroit's apathy towards Tesla's patents isn't necessarily absolute. GM's Kelly told The Detroit News he thought that anything that helped to advance the adoption of electric vehicles is a positive thing.

And outside North America's automakers, German manufacturer BMW is said to have inquired about the patents.

As far as manufacturer collaborations go, Tesla has already provided powertrains to German brand Daimler, and Japanese firm Toyota--each of whch owns a portion of Tesla Motors.

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