Plug in your Prius

What does it take to retrofit your Toyota Prius so it never sips a drop of gasoline again? Twenty batteries the size of a carton of milk, some aluminium strips, a charger, a spool of electrical wire and electrical components. Oh, and knowledge of automotive electronics.

The onboard computer in the Prius calculates the most efficient collaboration between the electric- and the gas-powered engine. In practise, the Prius only uses electricity at low speeds. A group of California-based engineers, electric-car fans and environmental activists have been tinkering to create a plug-in hybrid that can be charged at any outlet and can drive farther on electricity.

“Not only is it cleaner,” says Felix Kramer, “it’s also cheaper, partly because you can charge your car at night when rates are lower.” Kramer is the founder of the California Cars Initiative, or CalCars, a group that is trying to persuade car manufacturers to mass produce plug-in hybrids.

The first step is to activate the “electric-only” function, an option that has been disabled on the U.S. market, though in Europe and Japan you only need to push a button. The problem can be remedied using wire, a switch and a soldering iron. Then things get tougher. The battery that powers the Prius’ electric engine only makes it 1.5 kilometres, a mile, before needing a charge from the combustion engine. But the “Prius hackers” have drastically expanded the car’s electrical capacity by putting 20 lead-acid batteries in the trunk and installing the necessary software and electronics, as well as a charger that can be plugged into the electricity grid.

There are limitations. Even 20 batteries only last 16 kilometres (10 miles) and the Prius can’t go faster than 55 kilometres per hour (33 mph) on electricity. “An acceptable speed or city commuting,” says Kramer.

Unfortunately, only the technical DIY crowd can follow the painstaking instructions on the CalCars website. But Kramer claims the most important goal has been achieved. “Car manufacturers are testing the prototypes. By 2010 at the latest, you’ll be able to buy an affordable plug-in hybrid from your dealer.”

Find out more: calcars.org