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The Specs on Toyota's Plug-in Prius

Here's the skinny on Toyota's plug-in version of the groundbreaking hybrid, its answer to GM's development of the electric Volt

When General Motors (GM) showed off its Chevy Volt plug-in hybrid concept car at the North American International Auto Show in January, it achieved a rare public relations coup over Toyota (TM). After all, the Japanese auto dynamo has long grown accustomed to praise for its leadership in the hybrid segment and its unrivaled green image.

But this time around, GM won plaudits for signaling its interest in developing a plug-in electric vehicle that could be charged by a conventional power source at home as well as by the car's engine. That the Volt won't appear before 2010 at the earliest and faces important technical challenges didn't dampen interest. "It is a rare occurrence when Toyota gets 'out-greened' at a major auto show, or anywhere, for that matter. But GM has done just that with its Volt," the blog noted at the time (see, 1/19/07, "In the Green Push, GM Still lags Japan").

At a July 25 press conference in Tokyo, Toyota showed it won't be left behind in the race to take plug-in hybrids mainstream. Toyota announced that it has won approval from the Japanese government to begin testing a new, plug-in version of its current Prius hybrid vehicle on Japanese roads. Further tests will begin in the fall in the U.S. and Europe. "[The plug-in Prius] is effective at reducing carbon dioxide and conserving oil and air quality," Masatami Takimoto, an executive vice-president at Toyota, told reporters. "After reviewing the results, we plan to accelerate our plug-in hybrid plans."

Battery Hitch

The July 25 announcement means Toyota is the first Japanese automaker to win approval to test plug-in hybrids in Japan. Takimoto declined to say, though, how long it will take Toyota to get its plug-in Prius from the test stage to commercialization. He admitted that, like GM with the Volt, Toyota faces an obstacle in battery technology. The problem is that automakers need more powerful, lighter lithium-ion cells—variations of the kind used in cell phones and laptops—but to date no one seems to have found a way to mass-produce the cells for use in cars.

Speaking in February, Toyota chief Katsuaki Watanabe told BusinessWeek that the next-generation Prius, expected in late 2008 or early 2009, would use li-ions (see, 3/5/07, "Toyota's Bid for a Better Battery"). But in recent months, Toyota appears to be having difficulties meeting that timeline.

Reports in Japan have noted that Toyota executives are concerned about safety, and that the next model upgrade of the Prius will use nickel metal hydride cells, at least initially. Executives, meanwhile, are reluctant to discuss the progress of li-ions. "This is a problem for Toyota. They still need more time to develop lithium-ion batteries," says Hirofumi Yokoi, an auto analyst at CSM Worldwide in Tokyo. "I don't know if GM will beat Toyota, but I'd guess it's pretty even right now."

No Space for a Spare Tire

All of which could explain why the test models of the plug-in Prius in Tokyo today all use nickel metal hydride cells like those used in current conventional hybrid models. From the outside, the plug-in version looks much the same as any other Prius. Indeed, only the paint job (which features a large, white plug and the words "plug-in hybrid" in large letters) makes it obvious that this isn't a conventional version of the best-selling hybrid.

Among the main differences, the plug-in Prius has twice the battery power of a conventional hybrid Prius, which adds 100kg to its weight. That also means that there's no space for a spare tire. Instead, the test models come with a puncture repair kit.

There are some key design differences between the plug-in Prius and GM's Volt. For instance, the Prius plug-in, like a conventional Prius, is powered by either its gasoline engine or its electric motor. The Volt, by contrast, is essentially an electric vehicle, powered by an electric motor, which uses an auxiliary engine and a generator to recharge its batteries.

Green Benefits Vary

Toyota reckons its system is more cost-effective and will require less space for batteries. "We concluded that Toyota would build a plug-in using the Toyota hybrid system, which has been in use since 1997, as a base," says Takimoto.

In terms of environmental performance, Toyota's plug-in Prius is cleaner than current hybrids on the market. Even with heavy nickel metal hydride batteries, the environmental benefits are impressive. In Japan, Toyota calculates that the reduction of carbon dioxide emissions, including emissions created in the production of the electricity used to recharge the batteries, will be 13% better than for a normal Prius, assuming it's driven 25km a day. That's on top of the 40%-50% less carbon dioxide a conventional Prius emits compared with an equivalent gasoline model.

However, the level of emissions reduction varies from country to country, depending on how the electricity is produced. In France, which relies heavily on nuclear power, the projected carbon dioxide reduction could be as much 45%, Toyota estimates. But in the U.S., where most energy is created by burning fossil fuels, the benefits are far smaller, at an estimated 4%. Toyota says those benefits could be boosted by the use of biofuels, which the plug-in Prius accepts.

Current Range: 13km

Operating costs are also lower. Toyota estimates that, in Japan, the plug-in Prius will cost 8% less to run if recharging is conducted during the daytime. If recharging is carried out at night, when electricity is cheaper, that savings could rise to 41%.

And what about performance? In electric mode, the maximum speed of the plug-in Prius is 100 kilometers per hour, after which the 1.5-liter gasoline engine kicks in. That's an improvement over the current Prius, where the maximum speed before the gasoline engine kicks in is 68kmh. Recharging takes 1-1.5 hours at 200 volts or 3-4 hours at 100 volts.

Still, it's the cruising range—at just 13km—in electric mode that shows just how much Toyota needs lithium-ion cells. Even in Japan, where 70% of people drive less than 30km per day, that's not a great distance. "The cruising range of 13km is purely a provisional figure," says Takimoto. "The testing will clarify the necessary requirements for the batteries." For Toyota, like GM, developing those batteries remains the key requirement for its plug-in plans.

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