Toyota’s Prius Hybrid Gets Even Greener as a Plug-In

December 4, 2010/Steve Tackett


Back when Toyota launched the Prius in the U.S. in 2001 consumers didn’t know what “hybrid” meant and fretted over where they would “plug in” an electric car like the Prius and how far it would go on a charge. That left Toyota in the position of having to invest in educating consumers about the basics of its hybrid battery operation.
Now it is time for the company to undo all that work, as it has just launched a test fleet of plug-in Prius models that will pave the way for full production plug-in hybrids from the company in 2012. To this point, Toyota has insisted that the nickel-metal-hydride batteries used in the Prius are a more cost-effective solution to the cars’ electrical storage requirements than the costly and finicky lithium-ion cells.
But lithium-ion batteries pack a lot more energy in a given volume of space and weight and are really the only solution for plug-in hybrids and battery electric vehicles. While the current 2010 Prius carries a single 110-pound nickel-metal-hydride battery pack, the upcoming 2012 plug-in Prius is designed with three lithium-ion battery packs totaling 330 pounds and storing 5.2 kilowatt hours of juice.
The plug-in Prius uses the first two battery packs, first one, and then the other, to propel the car in conjunction with the third pack. Once the first two packs are depleted, the Prius operates as a regular hybrid, using the third battery pack.
The plug-in Prius has a big advantage in performance over the regular Prius Hybrid. The regular Prius Hybrid can travel about a mile with a top speed of 25 mph while running on electric power, while the plug-in Prius prototype can travel 13 miles at speeds up to 60 mph without using the gas engine.
By comparison, the regular Prius battery holds a paltry 1.3 kWh, while the lithium-ion batteries in the Chevrolet Volt and Nissan Leaf store 16kWh and 24 kWh respectively.

After many test miles on regular Prius cars over the years the expectation is that when pressed for a little bit of speed that we’ll hear the familiar sound of the gas engine starting to contribute its thrust to the project, but in the plug-in model the engine stays blissfully off-line as long as there are enough electrons in the battery and the speed is below 60 mph. In test fleet we did experience engine start-up occasionally under other circumstances, maybe to provide cabin heat on cold days.
While the plug-in does enjoy a souped-up battery it still has the same 80-hp electric motor, so when relying on that alone to propel the Prius, acceleration is unenthusiastic. The car isn’t an obstacle on the road, but it will remind the driver that they are saving the planet every time they tip in to the “gas” pedal.
We still don’t know the specifics of Toyota’s plan to sell the plug-in Prius, other than that it will arrive in the U.S. in 2012. The price will be critical to its appeal in a market that will by then have seen full availability of the Volt and the Leaf.
At a low enough price the Prius could garner a market for itself. The plug-in car would work well for commuters who have access to a 110-volt electric outlet at work and live within its 13-mile driving range (10 miles or less to allow for heat, air conditioning and headlights).
The car’s 110-volt charger recharges the battery pack in about three hours, so if drivers can recharge at work they can not only drive to work on electric power, but home as well. And the relatively short recharge time means that they can run errands at lunch on a freshly recharged battery and still have another full charge before it is time to go home.
Realistically, a portion of the commuting population could drive to work strictly on electric power using the plug-in Prius, and then have a conventional fuel-efficient hybrid for after-hours and weekend use. Toyota just needs to reeducate consumers about the Prius, so they know that now it does have a plug. — Dan Carney, Motor Matters

Copyright, Motor Matters, 2010

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