I understand that Toyota is planning to sell a plug-in Prius that will greatly improve the car’s already impressive fuel efficiency. Will I be able to convert my older (2006) Prius to make it a plug-in hybrid vehicle?
—Albert D. Rich, Kamuela, HI
Toyota is readying a limited run of a plug-in Prius, which can average 100 miles per gallon, for use in government and commercial fleets starting in 2009. Toyota will monitor how these cars, which will have high efficiency lithium ion batteries that haven’t been fully tested yet, will hold up under everyday use.
Essentially, a plug-in version of the Prius reverses the roles of the two motors under the hood. The regular Prius relies more on its gas engine, switching to (or combining) use of the electric motor in slow traffic, to maintain cruising speed, and when idling or backing up. The car doesn’t need to plug in because its battery stays charged by the gas motor and by the motion of the wheels and brakes. The plug-in will primarily use its electric motor, allowing commuters to go to and from work every day fully on the electric charge, saving the gas engine for longer trips that exceed the distance the car can go on electricity alone.
Toyota has made no announcement yet as to when consumers will be able to buy a plug-in; that depends largely on the results of the field test of the fleet version. But owners of a current or past model don’t need to wait. Those with automotive mechanical skills can convert their Priuses to plug-ins themselves.