Toyota Chairman Takeshi Uchiyamada rode his pioneering work on the Prius hybrid to the top of the world's biggest car company.
But that doesn't mean he is a zealot when it comes to the growing expectations for electric vehicle technology. The technical barriers to better battery life and performance are real, he said, and are not on the verge of disappearing.
"We don't have an answer yet. We might not have an answer," Uchiyamada said after an address at the Economic Club of Washington. There will need to be "two breakthroughs to see the age of electric vehicles" -- one to increase the distance that cars can drive on a charge and one to reduce that charging time, he told the group.
The day when an affordable vehicle that could supplant, in a widespread way, the existing internal combustion fleet may be a long way off.
Uchiyamada said Toyota plans to introduce a car powered by a hydrogen fuel cell as early as 2015. But its range will be limited to perhaps 300 miles and its initial sales restricted to a handful of markets -- think California -- where charging stations could be available.
The company is also working on a next-generation battery, aimed for completion in 2020, that could make hybrids even more efficient or extend the range of fully electric vehicles beyond their typical few dozen miles on a charge.
But even that will require a trade-off. For fully electric use, for example, the automaker has to balance the more potent battery with the longer length of time it takes to charge, and choose whether to funnel the benefits of better technology into improved performance or cost savings.
Until the basic constraints are broken -- and technology offers a cheaper way to deliver more power and a fast charge -- upcoming improvements may mark more of an evolution than a revolution.
That doesn't mean they won't be substantial.
Uchiyamada, a physicist who worked with the team that developed the Prius in the 1990s, said the group underestimated what it could achieve. It looked to boost fuel economy by 50 percent. Instead, the team more than doubled it.
Prius and other hybrids are now staples in the Toyota line, and Uchiyamada said that over the next five years he expects they could account for more than half of the company's U.S. sales.
He said he does not see a business challenge coming from companies such as Tesla, which makes high-end, all-electric cars, because its price is far too high for the vehicle to become a widespread replacement for gas.
Nor is he convinced that driverless cars and networked highways will take over anytime soon. Toyota is using things such as radar systems and object recognition to add new safety features to its vehicles, he said, but the technology that will allow cars to talk to each other and coordinate their motions is far from proven.
While it's tempting to hope "that we can drink champagne and have fun," Uchiyamada said, "a human at the end will need to control."