Their system is still not economic compared with running the Prius on gasoline. One will save 180 gallons of gas a year with the lead acid system or about $540 a year in gasoline savings. The lead acid battery charge discharge efficiency is 60% so it will cost about $1.20 per day to purchase the 12 kilowatt hours of electricity from the grid to yield the 7.5 kilowatt hors of power delivered to the wheels. Net savings are therefore approximately $100 a year and guess what the lead acid batteries need replacement in 3 or four year so there is no payout for their system. It is not as big a rip off as A 123 but you still will get overcharged with the lower cost system.
Well just how dumb or smart is it to convert the Prius to a plug in with lead acid batteries other than being economically stupid.? To travel 50 miles in a Prius one needs one US gallon of gasoline. To travel 50 miles in the overweight plug in Prius using battery power one needs 15 kwh delivered to the wheels or 25 kilowatt hours from the grid given the low charge discharge efficiency. The generation of electricity even in the most modern generation station is 50% efficient so one needs 50 kilowatt hours of natural gas to generate the electricty. A gallon of gasoline has approximately 34 kilowatt hours of chemical energy and even if the refining and transportation of oil entails the loss of 10% of energy, the straight up Prius is 25% more energy efficient that the lead acid plug in conversion. Simply adding 500 pounds of added mass to the Prius in the form of lead acid batteries is dumb and not smart. This just goes to show how dumb the folks in a city with a famous university are. Here is article from CNN Money on these fuel fools from the nuclear free city of Bezerkley. Perhaps the CNN Money reporters are even dumber for reporting the dumass story. Of course readers of the Green Machine are thermodynamic Einsteins, and none of us will get over charged and super excited by this Rube Goldberg contraption.
The Prius hackers
Daniel Sherwood, left, and Paul Guzyk in a Pruis that they modified to run on battery power alone.
Paul Guzyk and Daniel Sherwood are computer geeks who co-founded 3Prong Power, a Berkeley business that transforms standard Toyota Priuses into all-electric green machines.
In 1999, Guzyk moved to California and rediscovered an old passion for cars after tinkering with a Prius. He found that in many ways the Toyota hybrid was more like a computer than an automobile. Notably, it ran on recognizable computer standards similar to those found in an office network.
"I found that modifying the Prius is like getting your computer to do what you want it to do," says Guzyk.
In 2006, he met fellow Prius tinkerer Sherwood. Together they gave a 2004 model an all-electric makeover.
First, they installed a bank of Prius batteries they had salvaged from a junkyard. That didn't work well, so they tried traditional lead-acid batteries, used in electric wheelchairs, which did the trick.
Next, they developed software that programmed the Prius to run only on its newly enlarged battery pack. Unlike the one in an unmodified Prius, the car's internal-combustion engine doesn't fire up -- and burn gas. Presto: instant electric car, albeit one with a range of only about 25 miles.
In 2007, they launched their startup in a former Cadillac dealership with less than $100,000 of their own money. Since then they've added six employees and now expect to do 500 conversions, or some 40 a month, through 2010; at $4,500 per job, that works out to about $2.2 million in annual sales.
By Jonathan Blum