Plug-and-Play Prius Runs on Electricity
By Todd Kaho
The irony was impossible to ignore: There we were behind the wheel of a prototype Toyota Plug-In Prius Hybrid tooling around the legendary streets of the Motor City … on clean, quiet, electric power. Woodward Avenue, after all, is home turf of the American muscle car, where cubic inches and high octane gasoline have ruled for decades. The car we were driving is an early variant of a high efficiency hybrid that EV aficionados want in the worst way...with little or no gasoline required.
The plug-in hybrid vehicle (PHEV) designation is what sets this Prius apart from the current showroom model. Essentially, Toyota doubled the battery capacity of the current model, recalibrated the electronics, and provided an onboard charger to make this Prius unique. The extra nickel-metal-hydride (NiMH) cells take up the space formerly occupied by the spare tire and raise total capacity to 13 ampere-hours, from 6.5 Ah in stock form. Secreting batteries in the spare tire well allows the rear cargo floor to remain flat without intruding on cargo capacity.
A quick walk around shows that the gasoline filler neck is still on the driver’s side of the Prius, but now there’s a matching filler door on the passenger’s side as well. Pop this second filler door and you’re greeted with an electrical outlet that accepts Toyota’s plug-in cord. The cord is small and lightweight with an inline black box at the plug end. It easily stows in the rear of the car for charging top-offs if you have an outlet at your destination. To charge, simply plug the car connector -- which has a handle somewhat like a gas nozzle -- into the Prius and the other end into a household outlet. Toyota says a full charge will take 3-4 hours when plugged into a 110 volt outlet or 1-1 ½ hours from a 220 volt outlet.
That charge enables the PHEV Prius to travel seven miles solely on electricity. New programming in the Prius’ hybrid controls also allows the PHEV to be driven more aggressively as an electric vehicle before the gasoline kicks in to assist. An EV button to the left of the steering column controls this function. From behind the wheel, the only other clue that the PHEV Prius is unique is a new energy monitor screen on the center display, which offers a green/red bar as a visual aid for maximizing EV operation.
Another major revision a recalibration of top speed cut-off in electric mode. The prototype will accelerate all the way up to 62 mph on electric and hold that speed until the battery is depleted, but only if you treat the accelerator gingerly. We found it very easy to maintain electric only propulsion both in town and up to moderate highway speeds.
As a commuter car, that seven mile range is enough to make the trek to and from work much less expensive. Even if you travel longer than the maximum all-electric range, the PHEV Prius will offer exceptional economy. If you have a round-trip commute of 14 miles or less with an outlet at the other end, then it may be possible to travel on electric power for the entire trip. Around town errands are ideal applications for a PHEV.
Toyota has produced a number of the plug-in prototypes as research platforms to gauge the market and potential customer expectations. Toyota Division group vice president and general manager Bob Carter explains: “Our goal with these early prototype vehicles is to begin the process of understanding customer wants and needs in order to help determine the optimal balance between electric vehicle miles, charge time, battery size, and cost.”
Additional battery-power-to-cost ratio is a major issue, since even NiMH batteries are quite expensive and lithium-ion – the favored technology for most developmental plug-in hybrids -- are more costly yet. When you consider that the aftermarket plug-in conversions for the Prius run well over $10,000, it’s easy to see why Toyota has concerns about the economics. With so many unknowns, Toyota obviously isn’t ready to discuss pricing. If the PHEV Prius does make it to market, we can only wonder if the world is ready for a $30,000-$35,000 Prius. Economies of scale will obviously bring prices more in line over time and hopefully more powerful and economical battery technology is just around the corner.
In addition to the test units Toyota is allowing media to drive, a Clean Mobility Partnership program with the University of California Irvine and Berkeley campuses is providing additional opportunity for market research. Two PHEV models were presented to these universities last November, with UC Berkeley using the prototypes in its Institute of Transportation Studies Program and UC Irvine operating its plug-in Prius through the university’s Advanced Power and Energy Program.
Berkeley’s program will consider if, when, and where people will want to plug-in their vehicles and also study the trade-offs between range, charging time, battery size, and battery cost. Irvine will look at how best to measure and test PHEV fuel economy and emissions, and also how to account for upstream emissions from the powerplant that provides electrical power, and what emissions benefits might be gained in regions with a higher-carbon grid mix.
Our drive through downtown Detroit with a brief freeway blast was enlightening. We tipped into the throttle several times to experience the electric/gas transition, but the entire 15 minute loop could easily have been covered solely on electric drive. Even in this very early stage of development, the PHEV Prius is a very impressive and alluring green car.
Want to know more about plug-in hybrids? Be sure to check out these articles on GreenCar.com:
Making Plug-In Hybrid Batteries Affordable
Why We Want to Plug In Our Cars
Electric Cars Revived: Behold the Plug-In Hybrid
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