The Toyota Mirai doesn't look like much of a threat to Tesla's sleek and powerful Model S. But it's a sign that the world's largest green-car maker isn't buying Tesla's vision. Source: Toyota.

Who could crush Tesla Motors (TSLA -3.55%)? Probably nobody could at this point -- except Tesla itself.

But there's one company that could make a very serious run at the Silicon Valley upstart. This company has a huge war chest, massive global scale, unparalleled car-manufacturing prowess, a deep and well-funded research and development team, and years of experience with battery-electric car technologies.

If you know the auto business, you've probably figured out that I'm talking about Toyota (TM -0.91%). Toyota is already far and away the world's leading producer of battery-hybrid vehicles. It's not much of a stretch to say that Toyota could create a pure battery-electric car with great range and performance -- and build it at a price that Tesla, and most others, would struggle to match.

But instead, Toyota threw that R&D team -- and a lot of cash -- into a quixotic-seeming effort to develop the Mirai, a car powered by a hydrogen fuel cell. Why? 

The insurmountable problem, as Toyota sees it, with battery-electric cars
Here's why: After a great deal of research and pondering, Toyota's electric-car experts came to the conclusion that recharging time would prove to be an insurmountable obstacle in the mass adoption of battery-electric cars. Even with Tesla's vaunted "Superchargers," it takes a long time to fully charge a battery-electric car with reasonable range. Everyone seems to assume that recharging times will fall as the technology advances, and perhaps it will. 

But Toyota's scientists have concluded that recharging time can't be brought down enough without building massively inefficient chargers that squander the technology's efficiency advantages. That means, they say, that electric cars will remain niche products.

Toyota thinks that mass-market consumers will stick with cars that can be refueled at a gas station -- like conventional hybrids -- until electric cars that can be recharged just as quickly hit the mass market. That's why they developed the Mirai. 

Toyota says fuel cells are "a better battery"
Toyota's U.S. CEO, Jim Lentz, told me earlier this year that the company sees the hydrogen fuel cell as a "better battery." The Mirai is an electric car, but it runs on the electricity that its fuel cell chemically converts from hydrogen gas. "Recharging" the Mirai takes about five minutes: One simply refuels the hydrogen tank.

The Mirai doesn't look like a car that could threaten Tesla. It's kind of strange looking, it's not particularly fast, and at almost $60,000, it's still very expensive for what it offers. And right now, there are very few hydrogen refueling stations in the U.S. For most consumers, it doesn't make any sense.

But Toyota -- the world's largest car company, and arguably the greenest -- has made a very big bet on what the Mirai represents. It says that the costs of the fuel cell will come down sharply during the next several years. And Toyota (and others) are investing in networks of hydrogen-refueling stations, just as Tesla has invested in its charging network.

Toyota's standing makes it hard to dismiss
It may well turn out that Toyota has made a bad bet here. If it were almost any other automaker -- almost any other company -- it would be tempting to just laugh and dismiss the idea.

But this isn't any other company. It's Toyota. Betting against Toyota when it comes to green-car technology should give any thoughtful investor pause. I think that anyone investing in battery-electric automotive technology needs to ponder the Mirai -- and the thinking that led to it -- very carefully.