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# Juiced UpPUBLIC ACCESS

The Next Stage in the Development of the Hybrid Car May Involve an Electrical Outlet.

[+] Author Notes

Associate Editor

Mechanical Engineering 128(07), 34-37 (Jul 01, 2006) (4 pages) doi:10.1115/1.2006-Jul-2

## Abstract

This article describes evolution of the hybrid cars involving an electrical outlet. The modifications made to the Prius at the Maker Faire take the hybrid concept to the next level. With an added battery back, new electronics, and a socket, the car becomes what is known as a plug-in hybrid electric vehicle. The conversions performed by CalCars have involved installing either lead-acid or nickel-metal hydride battery packs in the rear compartments of stock Priuses. The engineering for these conversions has followed an open-source model, with the design being discussed and improved through collaboration with volunteers on an Internet message board. EDrive Systems, an automotive company based in southern California, and Hymotion, a Toronto-based automotive supply company, have unveiled full conversion kits, including auxiliary battery packs, electronics, and control systems. According to experts, with a Hymotion plug-in pack, a Prius can run as much as 30 miles on electricity alone.

## Article

The interior of a Toyota Prius converted to a plug-in hybrid is not so much different from stock models. An auxiliary monitor (seen above) displays the charge left in the bank of batteries that have been added to the car’s storage compartment (shown below with the safety cover removed).

When automobile technology changes, it usually occurs behind the scenes: A new regulation is written, a new material is developed in a research lab, some new feature is introduced on high-end vehicles. In time, the changes percolate down to the Chevys and Hondas that most people buy.

But in April, the potential future direction of automobiles unfolded in public, on display. A team of automobile enthusiasts at the Maker Faire, a two-day technology exhibition in San Mateo, Calif., set upon a stock Toyota Prius, pulling out a storage compartment, cutting Plexiglas, splicing wires. The goal was simple and revolutionary: Before the end of the event, convert the standard Toyota Prius into a semi-electric vehicle.

Hybrid electric vehicles such as the Prius or the Honda Insight, have been touted by some as the silver bullet in handling tighter fuel supplies. Thanks to their ability to recover energy that would otherwise be lost during braking and use that to supplement power from a conventional gasoline engine, hybrids have been able to post high fuel efficiency numbers. Whether this fuel efficiency was worth the price differential between hybrids and conventional cars has been a subject of debate, however.

The modifications made to the Prius at the Maker Faire take the hybrid concept to the next level. With an added battery back, new electronics, and a socket, the car becomes what is known as a plug-in hybrid electric vehicle. Such vehicles have the potential to be powered substantially by grid electricity. Whether plug-in hybrids can move beyond a niche of electric vehicle enthusiasts and affluent environmentalists remains to be seen.

Electric vehicles have had a long history in the United States. Full electrics were running on the streets of New York as long ago as the 1890s and were popular as ladies’ cars, though they were soon supplanted by steamers and gasoline-powered cars. In spite of recurring attempts to bring full electrics back into large-scale production, they have proven to be a hard sell for many of the same reasons they disappeared 100 years ago. The infrastructure supporting combustion engines, from gas stations to parts distributors and garages, is infinitely more developed than what is available for electrics. The larger culture has embraced gasoline-powered cars as normal, while electric vehicles have been marginalized as eccentric and risky.

This 1915 Detroit Electric Brougham had a top speed of only 20 miles per hour. It was marketed to women motorists as being reliable and easy to start.

Most importantly, however, the technology underpinning electric vehicles just hasn’t been as robust as that of cars with gas engines. Battery packs have been massive and bulky, and their power densities have been so low that the range ofEVs has been limited to a few dozen miles. Whatever other virtues they may have had, electrics haven’t been able to perform what Americans have asked of their cars.

That history has informed the way hybrid electric vehicles have been sold in the United States. European models of the Prius have a button that enables electric-only operation. With the energy stored in the hybrid’s battery pack, the car could run about one mile without assistance from the gasoline engine. Models of the Prius sold in North America are missing that button, although the cars are capable of running in full electric mode all the same.

Unlike full electrics, hybrids have an internal combustion engine running in tandem with the electric drive. Indeed, in many models on the market, the gasoline engine is the primary drive, with the electric system providing only supplemental power. In any event, the source of electricity for the battery pack in a hybrid is gasoline combustion, drawn either from recapturing energy from the brake system or from the motor spinning a generator. In that sense, hybrids are not so much different from standard ICE-powered cars; they are just more efficient—and complicated.

To occupy the true middle ground between battery-electric vehicles and internal combustion-powered autos, one would need a car that could draw power either from gasoline or from externally supplied electricity. That is, a car that can be fueled or juiced. Such a vehicle, called a plug-in hybrid, would run as a full electric during its first few miles of a journey, powered only by batteries. After the batteries were substantially depleted, the gasoline motor would kick on and the car would operate pretty much like a familiar hybrid. When parked, the car could be plugged into a standard outlet and the batteries would be recharged.

To advocates of plug-in hybrids, these cars would offer the best of both gasoline and electric cars. Such cars would have the long range and ease of refueling of conventional cars. But they could also operate using a variety of energy sources. At current prices, for instance, the cost of driving per mile running on electricity is about one-third that of using gasoline. What’s more, overall emissions could be lower, as energy for driving is derived from clean-burning natural gas power plants or emissions-free hydroelectric plants rather than burning petroleum.

The Electric Power Research Institute, an industry group based in Palo Alto, Calif., has become a big booster of plug-in hybrids. The institute’s interest stems from research and advocacy for battery electric vehicles in the 1990s. “We had a large research effort supported by major utilities looking at bringing electric vehicles to the market,” said Mark Duvall, manager of technology development for EPRI’s electric transportation program. “When the OEM programs began faltering, we moved those resources into plug-in hybrids.

“If the car companies weren’t going to build electric vehicles, maybe we could interest them in plug-ins,” Duvall said.

## Electric Range

EPRI has sponsored several studies of plug-in vehicles. One key finding is that half of American cars are driven 25 miles or less per day. If the electric-running range of a plug-in hybrid could be extended past that mark, a typical driver might go most of a week without burning any gas.

As part of its promotion strategy, EPRI is trying to partner with large automakers and with fleet owners to develop plug-in hybrids that can be introduced to the market before the end of the decade. EPRI and Daimler Chrysler have collaborated on a plug-in delivery van that can be recharged from a standard 240-volt outlet in five hours. Duvall said that DaimlerChrysler would begin touring the United States with some demonstration vans by early next year, with hopes of introducing them to the American fleet market shortly thereafter.

The lithium-ion battery pack (top), which is at the heart Of the Hymotion plug-in hybrid kit, can hold 5 kWh of electric charge. That can supply the energy for as much as 30 miles of gasoline-free driving.

Back at the Maker Faire, another strategy was being tried out. The dozen or so volunteers assembled by the California Cars Initiative, a nonprofit organization based in Palo Alto, was working in the middle of the exhibition space— not as lobbyists, but as mechanics. The plan was to convert a normal Prius into a plug-in hybrid as visitors to the exhibition stood around and watched. With a dozen volunteers assembled, team members took turns fielding questions from curious onlookers and the press.

One of the volunteers, Amanda Kovattana, wrote in her online Web log, “With no access code, we were having to spoof the computer, fool it into accepting the new battery pack without shutting off the electric mode and turning on the gas engine. When I told people that Toyota didn’t think the public would understand the concept or accept a plug-in option, they rolled their eyes.”

And the media was quite interested. One reporter confided to Kovattana that he wanted to report on the group’s progress because it was doing something actually useful.

That sort of response was music to the ears of CalCars’ founder, Felix Kramer. Begun in 2002 as a public advocacy group promoting efficient vehicles, CalCars has emerged as the grassroots counterpart to EPRI. Much like EPRI, CalCars has been visible in Washington, D.C., meeting with lawmakers and auto company representatives, and trying to get them interested in supporting a move to plug-in hybrids.

But part of their strategy has involved doing more than simply talking up the possibilities. The organization has sponsored conversions of conventional hybrids to plugins. “Conversions for us is completely a strategy,” Kramer said. “Their only goal is to increase awareness of plug-in hybrids and motivate carmakers—for example, by pressure, whatever it is.”

## Open-Source Conversions

The conversions performed by CalCars have involved installing either lead-acid or nickel-metal hydride battery packs in the rear compartments of stock Priuses. The engineering for these conversions has followed a so-called open-source model, with the design being discussed and improved through collaboration with volunteers on an Internet message board.

As Kramer and his colleagues complete more conversions, they aim to have the technique so standardized that they can write up a manual. Armed with that and the right parts, Kramer said, a couple of mechanically inclined people could convert a Prius over the course of a week. The total cost of such a conversion would run under $3,000, Kramer said. Kramer is careful to stress that the goal of these do-it-yourself plug-ins is to pave the way for factory-built models. CalCars is an advocacy group, not an automotive company. “It’s not a business model,” Kramer said. “Our goal is to have carmakers put us out of business.” Fortunately, a hybrid owner who wants to drive a plug-in this year need not hand his car over to a merry band of volunteers. With a bit of cash, he can convert his car himself. In fact, two companies have begun to service this do-it-yourself market, supplying conversion kits to owners of Priuses and other makes of hybrids. EDrive Systems, an automotive company based in southern California, and Hymotion, a Toronto-based automotive supply company, have unveiled full conversion kits, including auxiliary battery packs, electronics, and control systems. EDrive will be offering its kits to the public before year’s end, while the Hymotion system won’t be available to consumers until 2007. Hymotion founder Ricardo Bazzarella said his interest was natural. “We were thinking about hybrids and how hybrids were becoming popular,” Bazzarella said. “We started shooting around different ideas on how we could make that kind of vehicle better, and the next thing you know we thought about adding batteries to the back of the vehicle.” With a Hymotion plug-in pack, a Prius can run as much as 30 miles on electricity alone, Bazzarella said. That’s enough for a typical round-trip commute. For now, however, the packs will be offered only to fleet buyers. Bazarella said the kits will run in the neighborhood of$6,000, installation included.

Bazzarella said that while he hoped that the kits would lead to plug-ins being offered directly by automakers, he thought there would be a continuing call for aftermarket conversions. “Because we are small and nimble, we will always be able to stay a step ahead of the OEMs,” he said.

But what of the major carmakers? For all their publicity, hybrids make up only a small fraction of auto sales, and companies such as General Motors have seemed lukewarm at best to the technology. With conventional cars still swamping car dealers’ lots, might talk of plugins be premature?

Perhaps not. Already, DaimlerChryslers Sprinter fleet van is in development. And it is rumored that Toyota will introduce a plug-in hybrid version of its Prius before the end of the decade.

That might seem appropriate to the pace of international corporations, but to the advocates at CalCars and elsewhere, the future can’t wait that long. Even so, obstacles keep popping up. For instance, the team at the Maker Faire couldn’t meet the deadline of converting their Prius before the end of the weekend. They needed another day. But for the benefit of the reporters who had been following their progress, the team pre-enacted their triumph for the television cameras.

The engineering for the plug-in hybird conversions has followed a so-called open-source model, with the design being discussed and improved throught collaboration with volunteers on an internet message board

“To wrap up our demo, we did a mock installation of the battery pack for our camera crew, followed by a group photo and cheer,” Kovattana wrote. “We were happy to act out this triumph, for now it was documented and would serve to show that we had tried. We had defied the powers that be and shown that ordinary citizens could bring forth real solutions to real-world problems.”

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