The Hymotion High Mileage Prius Plug-In Conversion Module


Battery maker A123 Systems (A123) just started selling its L5 Hymotion Plug-in Conversion Modules, which can transform the Toyota Prius into a plug-in vehicle capable of getting up to 100 mpg for the first 30-40 miles of driving.  The L5’s high energy capacity lithium ion batteries supplement the vehicle’s battery and allow the Prius to use its electric drive more often and for longer distances.  More frequent periods of all electric driving translate into better fuel efficiency. (read the Ecogeek piece and green tech gazette article on the L5)

A123 calls the Hymotion technology Nanophosphate, which means the batteries use lithium iron phosphate as cathode material.  Several of A123’s patents and applications cover lithium iron phosphate batteries, including U.S. Patent No. 7,348,101, U.S. Patent No. 7,261,979 and U.S. Application Pub. No. 2007/0166617. 

A123’s patented battery technology reduces the amount of time necessary for charging and loses relatively little capacity and power over numerous charge/discharge cycles, an important advantage for applications that need high power for long periods of time, such as motor vehicles.  Specifically, one problem with rechargeable batteries is that relatively high charge rates (i.e., less than half an hour) typically cause growth in impedance (resistance and voltage drop). 

Impedance can lead to lithium plating, a film formation on the surface of the negative electrode materials which consumes some of the active lithium from the battery and results in a loss of capacity.  The materials used by A123, including lithium iron phosphate, achieve low impedance growth.  The resulting batteries don’t have the problem of lithium plating and therefore maintain higher power capacities over time, enabling the highly efficient Prius to be even more efficient.

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Eric Lane

Eric Lane, the founder and principal of Green Patent Law, is an intellectual property lawyer and registered U.S. patent attorney in New York and is a member of the bar in New York and California. Eric has more than two decades of experience working with wind, solar PV, CSP, biofuels, and geothermal, energy storage technologies, carbon capture and sequestration, medical devices, data communications, mechanical, chemical, internet and software.