Investors want to believe in Tesla (TSLA), the upstart maker of electric cars, and its gravity-defying CEO, Elon Musk. How else can you explain a six-fold increase in the company's stock price over the past year when it sold fewer than 23,000 vehicles? General Motors (GM) sold a whopping 2.8 million vehicles, yet saw its stock price gain just 35%. Ford (F) sold nearly 2.5 million and its stock rose a mere 22%.

Investors are "betting on Elon Musk and new technology," says The Daily Ticker's Aaron Task. "You can't value that."

Related: Tesla Is on Fire! Consumers Give Model S Highest Rating in Years

More specifically, investors are bullish on Musk's latest plan to build a $5 billion "gigafactory" to manufacture cheaper batteries for electric cars on a massive scale. It's scouting sites in the Southwest but hasn't chosen one yet.

"Tesla is thinking around the bend," says Rick Newman, columnist at Yahoo Finance. "If you can make these batteries more affordable you can transform many things about the auto industry and the energy industry...They're not trying to be only an automaker. They're trying to be a power company or an energy company."

Musk, who co-founded PayPal before Tesla, may be just the guy to achieve that. He's also the chairman and the largest shareholder of SolarCity (SCTY), the single largest solar power provider in the United States, and the CEO of SpaceX, which has successfully launched satellites into space and aims to enable people to live on other planets.

Related: Tesla's Elon Musk's Next Big Thing

But Newman says Tesla still has "some growing pains [that investors] are not thinking about" but should be considering.

Chief among those pains are battery fires that have been reported in at least four Tesla cars including one that was reportedly in a garage and not connected to any charging source. The government is investigating.

"We just don't know what's going to happen here," says Newman about those investigations.

Meanwhile The National Highway Traffic Safety Administration (NHTSA), which is conducting the investigation, has reaffirmed a 5-star safety rating of the Tesla Model S overall, and Consumer Reports ranks Tesla's Model S as the best overall vehicle. 

But famed investor and Mad Money co-host Jim Cramer warns Tesla investors they're playing with fire.

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