Man rigs car to get 100 mpg

DENVER – Most people would be happy with the 50 miles per gallon drivers get behind the wheel of a Toyota Prius. Clarence Robinson wasn't.

"This is not the neatest in the world and it's not a professional job, but it works," he said.

Robinson says he now gets 100 miles to the gallon in his Toyota Prius after making some improvements.

He says he worked for months using plans he got off the Internet to hook up a series of extra batteries to his original Prius battery.

"These turn on these batteries to this battery whenever the original battery starts to wind down and brings it back up to the proper level. It's that simple," said Robinson, pointing to a matrix of wires and battries under his hood.

He plugs his car into an outlet to charge the batteries.

He spent just under $3,000 for the improvements to his hybrid, but it is tricky work.

"It's very challenging to get it right," said Carl Lawrence, the owner of Boulder-based Hybrid plus.

Lawrence's company builds plug-in conversion kits for the Prius and the hybrid Ford Escape.

"The basic system is a 4.5 kilowatt hour battery pack and that is about $21,000," he said.

The difference between Lawrence's company and Robinson's home-made battery pack is technology: Robinson uses lead acid batteries and Hybrid Plus uses lithium ion cells.

"We replace the original battery system with the 4.5 kilowatt hour system so it has four times as much energy storage in ours compared to the original Panasonic," said Lawrence.

It all depends on if you have the motivation to do it yourself.

"This is not something that was a kit, I had to order the parts, had to figure out how it's going to fit and then I just went ahead and did it," said Robinson.

Toyota plans to bring out its own version of a Prius plug in 2010 and more plug-ins are expected to follow soon after that.