At the Frankfurt auto show last fall, the 2010 Toyota Prius Plug-In Hybrid was revealed, sending the message that Toyota had taken the next step toward the electric future. Now Toyota has brought 150 examples of the car to the U.S. as part of a demonstration program, putting them into the hands of assorted government and educational institutions in order to collect data about real-world use, establish warranty standards and promote the establishment of charging stations in urban areas.
We had a chance to drive a couple of these demonstration units before the program got into full swing. The cars are not mules or concept vehicles, but perfectly finished units. And it turns out that the Prius PHV (Plug-in Hybrid Vehicle, in Toyota techspeak), drives and feels just like a regular Prius. Which is a good thing, really.
Just like a standard 2010 Toyota Prius, the Prius PHV combines a 98-horsepower 1.8-liter gasoline engine with an electric motor that produces the equivalent of 80 hp. The difference is that the PHV can operate in electric-only mode, powering itself on batteries alone for as far as 13 miles or as fast as 100 km/h (62 mph).
So fuel mileage improves, and the car is quieter and cleaner than ever. It's Prius heaven.
The Battery of the Future Is Small and Cheap
Unlike the standard 2010 Toyota Prius, the PHV has lithium-ion battery packs instead of the usual nickel-metal hydride batteries. The three battery banks are under the rear seat, and a primary central pack is flanked by a sub-pack on either side. The main pack is reserved for normal hybrid operation; the two sub-packs power electric-only driving. Each of the three packs contains 96 battery cells, and the system is rated at 345 volts. (The configuration of this battery pack is still evolving, the Toyota engineers tell us, and this is unlikely to be the final form.)
Lithium-ion batteries are even more susceptible to temperature swings than nickel-metal hydride batteries, so the PVH Prius has no fewer than 42 temperature sensors to monitor the batteries, not to mention a separate cooling system for the battery area. The only signs of these measures within the passenger cabin are small vents under the backseat, but hidden inside are three fans that circulate air around the batteries just like the fan in your personal computer.
The battery packs can be recharged from an ordinary 110-volt electrical outlet in about three hours. A charge cable is included with the vehicle, and its round plug fits into a socket under the driver-side mirror. Mary Nickerson, Toyota's cross-vehicle marketing manager, tells us that the company is also working with a supplier to develop a charge cable for 220-volt outlets, which would make complete recharging possible in about an hour and a half.
Toyota is betting that smaller, cheaper batteries with the ability to sustain themselves with frequent, quick recharges will prove to be more compatible with real-world driving habits than a single large battery that recharges once overnight. It's a strategy calculated to allow Toyota to hit a lower price point with its car than a vehicle with a large long-charge battery like the forthcoming Chevy Volt.
You'll Never Notice
While it's clearly a Prius, the PHV looks just a little different. There is the lid that covers the battery charger port that has a unique emblem. There are high-intensity silver accents on the mirrors, door handles and rear hatch. And on the demonstration vehicles, there is a none-too-subtle body stripe plus graphics that announce the car's identity as a plug-in hybrid.
Not available is the solar-panel roof that is an option for the standard 2010 Toyota Prius, but the plug-in can still cool itself while the vehicle is parked. The air-conditioning system can be activated with the key fob to either cool or heat the vehicle while it's being charged. (The recharging process is all about thermal management, which becomes a major consideration when li-ion batteries are involved.)
Another necessary trade-off is the elimination of a full-size spare tire from the Prius package. At least for these demonstration vehicles, the substitute is a can of flat-fixer goop and a small air compressor that's located in a compartment in the rear.
You will notice that the PHV's instrumentation is significantly different from a standard Prius. The PHV has a unique dash display with multiple graphic indicators. The display seems cluttered at first, because speed, fuel and transmission indicators are crowded by information that most of us don't normally use. There are graphic indicators that display the ratio of EV driving vs. hybrid driving, EV distance remaining, battery condition and more. A series of screens can be called up using a mode button on the steering wheel.
Once you sort through the instrumentation options, you realize that this stuff is for hybrid and EV enthusiasts, who like to pay attention to their own sort of performance parameters. After a while, it makes sense. Now that electricity is a type of fuel and three operating modes are possible, there is more to keep track of.
The Power-to-Weight Conundrum
The 2010 Toyota Prius PHV is about 300 pounds heavier than a standard Prius, which would put its curb weight at about 3,360 pounds. It turns out that the PHV's heavier battery packs are an advantage on short trips, where they make possible extended EV motoring, but become a disadvantage on the highway. When you jump on the freeway quickly, the acceleration drains the battery packs of juice, forcing the Prius to run on engine power alone. At this point, the PHV system offers no advantage, only dead weight. It's as if you were driving a regular Prius, but with two people in the backseat.
The PHV's disadvantage on the highway is proportional to time you spend at cruising speeds. Once the stored battery power is used up, the PHV's average mileage will begin to decline. On a very long trip — say, a cross-country route largely on the interstate — the Prius PHV's fuel mileage could even be worse than the 48-mpg highway rating of the standard Prius. In short, the more you do long trips on the highway, the less appropriate the Prius PHV would be.
At the same time, the Prius PHV can easily achieve over 70 mpg during around-town driving. During our brief experience with the car, we averaged 67 mpg during heavy-footed driving on a loop of 9.9 miles, a route that combined city and highway driving. We operated in pure EV mode some 56 percent of the time (the instrumentation told us), drawing on the batteries and recharging them by braking. Our colleague John O'Dell from Edmunds.com's Green Car Advisor achieved 99.9 mpg on the same loop in 80 percent EV mode and did 59 mpg on the highway loop.
Clearly, for those who make lots of short trips, the PHV can offer significantly higher mileage, especially if they have access to a plug here and there. Taken to extremes, if you regularly take trips of less than 13 miles and then recharge, there is a possibility that the Prius PHV will use no gas at all.
Toyota will even happily tell you all about the way the system works with an online video.
The Dynamic Challenge
Lithium-ion batteries are more densely packed with energy than the nickel-metal hydride batteries you see in current hybrid vehicles. In the Prius PHV, the primary benefit of lithium-ion technology is the ability to provide an expanded electric-only driving range, not greater performance. So it's probably no surprise that while there are two modes for speed — Eco and Power — we did not discern much difference.
Driving in Eco mode, we found the Prius PHV does readily accelerate onto freeways and respond to the throttle well enough for easy maneuvering in traffic. But like the standard Prius, the PHV is not built for speed. The 2010 Toyota Prius accelerates to 60 mph from a standstill in 10.1 seconds (9.7 seconds with 1 foot of rollout like on a drag strip). The Prius PHV's additional 300 pounds are bound to make it slower than this, not to mention less responsive overall.
For all that, the Prius PHV still rides, steers and corners like a normal five-passenger family car. The brakes will seem progressive and confidence-inspiring to those coming from earlier-generation hybrid cars. Of course, you still notice a transition between light braking (which invokes battery regeneration) and harder braking (which actually slows the car).
During our test-drive, the PHV seamlessly shifted among pure battery power, pure engine power and blended battery-engine propulsion. The computer makes these decisions based on what the driver does with the throttle, the brakes and the driving mode selected. It's always working to achieve the best possible use of gas and electricity, considering the demands of the driver. As a result, the final fuel-efficiency numbers will be highly variable. Ask for speeds over 60 mph and engine power is substituted for pure-EV mode and mileage goes down. Around town, you might get 13 miles of pure EV driving or you might not, depending on the traffic, your behavior at stoplights, or even the temperature.
Where to From Here?
It's easy to get the impression that this very quiet, very normal car is bland and uninspired, but nothing could be farther from the truth. For a vehicle designed to provide a nerdy transportation solution, the 2010 Toyota Prius Plug-In Hybrid is unusually engaging and even highly entertaining in its own unique way.
Getting into the 2010 Toyota Prius PHV is kind of like opening the box on a glossy new laptop. There are unique qualities to be discovered, customizing choices to be made, and the whole process is interactive. There is much information to compile, process and study. And Toyota has enhanced the experience with a lot of clever design and packaging details that make operating this car a curiously satisfying experience.
It's interesting to note that the data from the demonstration project for the 2010 Toyota Plug-In Hybrid is being made available by Toyota online. At this stage, Toyota is offering no information about the cost of the PHV, but our sources suggest that once the car goes into full-scale production for 2012, its price will begin at about $27,000, moving up to $34,000 with options. Within this range, Toyota seems likely to hit its target of 24,000 sales annually.
Even so, the 2010 Toyota Prius PHV is not for everyone. It will appeal to customers who want something advanced, efficient, versatile and exceptionally clean. It will work best in geographical areas that are not too hot or cold, since lithium-ion batteries don't like extremes of temperature. It will work best for people who have driving patterns that match the strengths of the PHV drivetrain. Throw in access to charging, make the price right, and Toyota might have a winner.
Edmunds attended a manufacturer-sponsored event, to which selected members of the press were invited, to facilitate this report.
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