General Motors says it's nailed the lithium-ion battery technology at the heart of the Chevrolet Volt and is consistently achieving a range of 40 miles in road tests, thereby clearing a big hurdle to getting the car built by 2010.

Company Vice Chairman Bob Lutz says GM is road-testing the gas-electric hybrid drivetrain at its Milford Proving Grounds and "it is reliably meeting its objectives." That's a key milestone because sorting out the batteries has long been considered the biggest obstacle to meeting GM's aggressive time line for producing the car.

Maximum Bob is so confident with the status of the battery development that he told Auto Observer, "I can almost say the battery is the least of our problems."

So it's clear sailing from here, right?

Not quite.

Lutz says the next challenge is smoothly integrating the battery drivetrain and the gasoline engine. Unlike a conventional hybrid like the Toyota Prius, which uses a gasoline engine to drive the wheels, the Volt will be driven entirely by electricity. The engine will drive a generator that will charge the batteries.

According to Auto Observer, GM's engineers are answering such questions as: "When does the engine cut in? How long does it stay on? How will it deal with extreme cold, when the engine will have to warm up the battery? Lutz says answering these questions requires "reams and reams of software" and is key to reaching GM's goal of building an electric vehicle with a range of 640 miles.

With the batteries performing as expected and the drivetrain being sorted out in a test vehicle – a 2003 Chevrolet Malibu – Lutz says General Motors is increasingly confident it'll have the Volt in showrooms by the end of 2010.

"November 2010 looks good," he says.

Photo by Dr. Lyle Dennis, editor of GM-Volt.com, which has been covering the Volt in almost microscopic detail.