Engineering the plug-in hybrid - Embedded.com

Engineering the plug-in hybrid

Big news at the Embedded Systems Conference in Boston was a teardown presentation on a Toyota Prius hybrid equipped with an extra pair of battery packs. These energy devices allow the vehicle to run in an electric-only propulsion mode for 14 miles before requiring a power boost from the car's internal combustion engine. The developers say the overall result is an effective mileage of over 100 mpg, depending on driving profile.

The conversion was designed by the California Cars Initiative using advanced NiMH batteries developed by Nilar. According to Nilar founder Neil Puester, the battery consists of thin layers of electrodes (about 4 x 10 inches in area), so the current path between cells is on the order of 0.050 inch, as opposed to roughly 4 inches in conventional NiMH batteries. Simply put, the result is a battery pack equal in power and energy, Puester says, to that of an original Prius battery, but in a package 11 inches long rather than 29 inches.

Kim Adelman of Plug-In Conversions Corp. (Poway, CA), a distributor for the system, noted, based on previous court rulings, the conversion should only impact the Prius battery warrantee rather than that of the entire car. There are also liability issues that need resolution because the batteries are below the trunk floor in a safety crumple zone.

Adelman adds the cost of the 2-pack conversion needed for the 14-mile electric-only operation is $10-12 thousand. Is plug-in performance worth that cost? Right now, early adopters are the ones opting for the cars, according to Adelman¬óbut in light of the “planetary emergency” of global warming and foreign oil dependence, he's looking for more widespread interest, because he says, over a 10-year life of the car, that's about $1k per year, which is much less than the cost of the gas that would be saved annually by a typical driver.

Rick DeMeis is the site editor for the Read Rick DeMeis’s blog.

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