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Tour of the Sun by Plug-In Hybrid

Mike Biachi reports on 125 mpg plug-in hybrid prototype

June 05, 2005
By Michael Bianchi

There are some of us who never understood the `complaint' that you had to plug a battery-electric car in. Like I really would miss the trip to the gas station? They haven't given me a free cup or a scratch-to-win card in decades! So when I heard that a plug-in Prius was not only coming to the Tour de Sol, but was participating in the Monte Carlo Rally, I was really excited.

Greg Hanssen, Vice President of Energy Control Systems Engineering (EnergyCS) was explaining the plug-in Prius that his company and Valence Technology have created.

The idea of a plug-in hybrid is to charge the batteries by plugging in every night and then drive as much as you can on 2 cents per mile house current and only then use the 4 cents per mile gasoline. Clearly quoting just the gasoline mileage is not a true measure, but saying "I'm getting 100 miles per gallon" will get people's attention.

"People understand what a gallon of gas costs, but they don't understand what kiloWatt-hour of electricity costs, or even what a kiloWatt-hour of electricity IS! So we've been focusing more on the national security side of the story; the petroleum reduction is really the hot topic right now."

Maybe that's true most places, but the Tour de Sol is not most places. Lots of people who visited the car at the Tour displays wanted to understand the technology and what its benefits are.

"Aside from the battery system in the back of the car and the little display and control module up on the dashboard, this is a stock Toyota Prius. We've taken out the 80 pound, 1.3 kiloWatt-hour nickel metal hydride battery that came with the car, as well as the battery controller, and replaced them with a 250 pound, 9 kiloWatt-hour Valence Saphion lithium ion battery system, with our own EnergyCS control system on top of it.

EnergyCS is working with a company in Los Angles called Clean Tech to start a new company called EDrive Systems which will commercialize this system. We expect that by early 2006 we will have a upgrade option for sale, between $10,000 to $12,000. Right now the batteries alone cost more than that. But we are working on ways to integrate it and repackage it, and Valence is working on new chemistries and packaging methods for the battery cells and modules, to bring it down to that price point.

"We supply a 1 kiloWatt, 110 Volts AC battery charger. If the 9 kiloWatt hour battery we provide were totally empty it would take 9 hours to charge it to full.

"With the battery fully charged, we trick the Toyota hybrid system, without modifying it. We turn on the Electric Vehicle mode where the car drives strictly on battery below 34 miles per hour. Above 34 mhp we convince the Toyota hybrid controller that the battery needs to be discharged by telling it that the battery is full." The car tries to bring it back down again, to the 80% state-of-charge it likes.

"But we keep saying `you are full'. So, even with the engine running, it's putting 6 to 8 kiloWatts from the battery into the electric motors, which lowers the gasoline consumption." The result is that even on the freeway, you're still getting 80, 90 miles per gallon with the electric assist. At low speeds you're getting infinite miles per gallon, because you are not using the gas at all."

Instead, you're using the energy from last night's charge. "So combined, we get about 100-to-150 mpg for the first 50-to-60 miles of the day.

The Prius still has the full regenerative braking capability, like normal.

How long will the batteries last? "The Valence guys say 8 to 10 years."

The idea of a plug-in Prius has been around for a while. How does this compare with the California Cars Initiative?

"About a year and a half ago, Felix Kramer started CalCars to press for the idea of plug-in hybrids, to push the concept. He put together an internet group, which the New York Times called `garage tinkerers', to find a way to make the Prius a plug-in hybrid. But we could tell that the methods they were trying weren't destined to go anywhere. We sold them our electronics to do the battery monitoring and the control, because we had already figured some of this stuff out. They put lead acid scooter batteries in a Prius with our control system. Even though those batteries were not a really good match to the car, they could see some respectable performance gain. We then moved along to a more advanced battery. My company has been working with Valence on a number of other projects, and it became clear that the Valence module was a perfect fit."

How does Toyota view this with respect to the warranty?

"Toyota says you are voiding your warranty, of course. When EDrive commercializes the system we will have some sort of warranty on the battery, the installation and the controller. We are still working some of these details out. Technically, when there is a problem, an Original Equipment Manufacturer (OEM) is responsible to demonstrate that what an after-market installer caused it. If the engine conks out, or the emissions control system conks out, we'll say `we didn't touch any of that.' And they'll say, `yeah, but your manipulating the car to run in a way that is not normal.' Then the finger pointing could start. We'll have to work all that out. Fortunately, since we are working with Toyota and one of the best built cars in the world we are not as worried about things falling apart."

Will this be available on the east coast? "When we launch in early 2006, it will be in California. As we add other hybrids into the EDrive system, like the Escape, Lexus and Highlander (which are completely different systems and their own challenges), we will be looking to get certified installers in other areas."

"One of the things we are trying to figure out is how to label the car so people know it's a 125 mile per gallon vehicle. Maybe we'll put a display in the rear window displaying the miles per gallon."

[I wondered how the charge management of the battery was handled. Would every _cell_ get individual attention?] "Yes. Every parallel block of cells, 3.2 Volts, has its own voltage measurement and balancing circuit." [Yippee! Right Answer! Thank you. (I do have some prejudices when it comes to battery management of advanced chemistries.)]

How did they do in the Rally? "By the time we ended our plug-in boost range, where we pulled as much as we could out of the batteries (which were charged the night before), we had driven 90 miles averaging 123 miles per gallon. By the time we drove 120 miles, we were just at 100 miles per gallon. According to our computers, we drove the required 150 miles averaging 90 miles per gallon."

Speaking of the on-board computers, the normal Prius energy usage display doesn't know it's being fooled, so all the little markers start out pegged at 99.9 and the whole screen is bright green. "After 60 miles, when you've used the plug-in energy, it goes down. When it gets to 50 the display looks like a normal Prius."