Volt Batteries in Prototypes

After visiting the GM technical center last April, which resulted in the feature story “GM’s Volt EREV,” it was clear the next big step for the Volt would be to get the actual production design batteries into prototypes and onto the test track. That step has been taken, with an official announcement by GM Vice Chairman Bob Lutz on his post of June 5th on the GM FastLand blog entitled “At Last: Behind the Wheel of Volt Test Mule.”

With a program as fast paced as GM’s Volt project, the first major automotive development program in history that does technology development and vehicle development in parallel, it is amazing how dated a print magazine article can be, before it even goes to press. In the July/August (it isn’t even July yet!) issue of the Atlantic Monthly, a feature appears on the Volt entitled “Electro-Shock Therapy” by Jonathan Rauch. If you read this feature closely, you will see the final interviews with GM officials cited in the story were in March – for a story published in a magazine with a cover date that is still in the future! In the article, Rauch reports “the car is 10 weeks behind the original schedule.” When you have about 130 weeks to launch, that is not a trivial delay. But is this claim still accurate?

When I visited GM in April, Frank Weber (GM’s Global Vehicle Line Chief Engineer E-Flex Systems) stated “we are working with incredible speed,” and “all project plans we have now are targeting November 2010.” So where are they now? As GM spokesperson Rob Peterson put it in an email received earlier today, “The timelines for the Volt’s development remain intact – the team is still targeting a November 2010 launch,” adding “As Frank [Weber] noted in April, we did indeed install prototype li-ion E-Flex batteries into our engineering development mules in May. Testing of the battery under dynamic conditions has been very encouraging.”

Returning to Lutz’s comments of June 5th: “On the drive out to Milford, as I passed gas station after gas station with prices for regular unleaded hugging the $4 mark. This makes the importance and potential of our all-electric glide through our proving ground roads even clearer.” Clear indeed. As we have endlessly explained here, there are a host of advantages to electric drive compared to gasoline drive – great traction, a great power-to-weight ratio, a huge functional RPM range, and zero pollution. But perhaps the most dramatic advantage of the electric motor over the gasoline engine is its superior ability to convert fuel into traction. An electric motor converts electricity into traction at a 90% (or better) efficiency. A modern internal combustion engine rarely can achieve efficiencies converting gasoline energy into traction at more than about a 35% efficiency.

To illustrate what this means in practice, normalize the units of energy, by converting kilowatt-hours and gallons of gasoline into BTUs – a universal unit of energy. One kilowatt-hour contains about 3,400 BTUs of energy. One gallon of gasoline contains about 125,000 BTUs of energy. So if a car gets 25 MPG, it is consuming 5,000 BTUs of gasoline energy per mile. If a car gets 50 MPG, it is consuming 2,500 BTUs of gasoline energy per mile. The Chevy Volt, a compact (but not subcompact) vehicle that will get an impressive 50 MPG on gasoline only, will get 3.5 miles per kilowatt-hour on electricity only. Rounding slightly, this means the car can go one mile using only 1,000 BTUs of electrical energy. This astonishing 2.5x to 5.0x efficiency advantage is the reason electric cars are going to dramatically change the rate at which we consume energy.

If you examine this advantage in terms of dollars and cents, the disparity between costs using gasoline vs. costs using electricity become even more dramatic. It appears likely electricity prices, off peak, can stay around $.10 per kilowatt-hour. Even new solar thermal utility projects are projecting costs per kilowatt-hour of less than $.10/kWh. This means the Volt as a plug-in, even allowing for a 10% energy loss in the charge & discharge of the onboard battery, can be operated at a fuel cost of about 3.5 cents per mile. Gasoline, on the other hand, even with 50 MPG, at $4.00 per gallon will cost a driver 8.0 cents per mile, more than twice as much.

As Venrock’s Matt Trevithick, an expert in EV technology puts it, “With electricity, we have always had a better motor, but with gasoline, we have a better fuel. History tilted in favor of the fuel.” With production design lithium ion batteries now onboard EREVs on a test track of the world’s largest automaker, history is beginning to tilt in favor of the motor. The electric age continues to dawn.

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