A 170-mpg Prius Conversion? Don't Bet on It, Says Toyota

Last Updated Jun 11, 2009 3:30 PM EDT

There are a range of plug-in hybrid conversion kits on the market, all making extravagant claims of 100 miles per gallon equivalent, seamless operation and zero impact on the warranty of the Toyota Prius donor car. Well, forget 100 mpg. Plug-In Conversions Corporation (PICC), founded in 2007, claims 170+ mpg, with 25 miles of all-electric range, and it's installing kits from Hong Kong to Australia.

An Achilles heel for plug-in conversions is the 2004 to 2009 Prius' onboard computer, which wants to start the gas engine at 34 mph. PICC CEO Kim Adelman says that, with the aid of Chicago-based Ewert Energy Systems, he's finally cracked the code to defeat that provision--his conversion can cruise at 70 mph on the highway in all-electric mode, and it has 25 miles of range in that mode. But Adelman says you shouldn't call his computer massage a "hack." Instead, he says, "We've augmented some of the systems; it's mostly a software modification."

Toyota has never been supportive of conversion companies modifying its cars. And although the company is fielding a fleet of 500 plug-in versions of the Prius, it has been saying lately that it has mixed feelings about the entire concept. But Irv Miller, Toyota's group vice president of environmental and public affairs, says the company just wants clarity and realism. "We are investing billions of R&D dollars in battery development--We own a battery company and manufacture batteries for profit and are looking well beyond current technology for the next-generation battery!"

Toyota's goal, Miller said, is "to offset some of the hyperbole being published about 100-mpg vehicles being the norm. Some may experience 100 mpg, many will not--.Our efforts are to bring some element of real-world results into the debate, not to pour water on the fire."

That being said, Miller added that the PICC conversion would likely result in "less-efficient range in electric mode at highway speeds," with the range very dependent on the driver's habits and style. He also said that, when compared to a 50-mpg third-generation Prius, "25 miles of pure electric would yield a savings of about a half gallon a day or about $1.50, and around $500 annually." PICC has done 30 conversions so far, but its business is picking up since it added the software upgrade to the package. Ten of the 30 were within the last month, Adelman said. He added PICC is working with China Light and Power and with the Australian equivalent of the National Science Foundation.

In another departure from standard conversions, PICC takes out Toyota's standard 1.3-kilowatt-hour nickel-metal-hydride battery pack, replacing it with a much-bigger 6.1 kilowatt-hour NiMH pack from its partner, Gold Peak Batteries Industries, North America. Gold Peak bought an undisclosed equity stake in Plug-In Conversions late last year.

PICC's conversion kit (adding 225 pounds) sells for $12,500, including one-day installation. Miller called that "a chunk of change." The battery pack is warranted for three years. Adelman says the kit "allows a Prius to perform much like the Chevy Volt, but for a much lower cost." Those are fighting words for General Motors, of course. A Chicago test ride in a PICC conversion is forthcoming, but the company says it has Argonne National Laboratory treadmill data that proves that, under certain specific drive cycles, it can achieve 170.27 mpg.

But PICC says real-world achievement will depend on how you drive the car. "If you drive just 40 miles, you'll double your mileage in our car," Adelman says. "If you go, say, 100 miles, you'll have 75 miles as a standard Prius and the results won't be as dramatic."