We estimate the battery pack at 7 feet long and 4 feet wide. Tesla Chief Engineer Peter Rawlinson explained to us that the battery pack also serves to help the Model S' torsional rigidity and safety. Cross members keep it from flexing much, and he anticipates that the Model S will lead its segment in rigidity, contributing to the car's handling. The pack also serves as a brace, helping to limit cabin intrusion during a side impact. Although the battery pack is a large slab that makes up a key component of the car's structure as well as powertrain, Tesla is designing it to be swappable in one minute. Tesla boasted during our tour that its battery packs have the highest energy density amongst all electric vehicle competitors, and the company is constantly working to improve that density. Even though competitors have designed batteries in different form factors, the Tesla battery pack, relying on what are essentially laptop batteries, still gives its cars greater range because of this higher density. A liquid cooling system helps maximize the life of the battery packs, which Tesla sets out 7 years/100,000 miles, although its warranty for the Roadster is only 3 years/36,000 miles. No word yet on the Model S warranty. The Model S will also use a liquid cooling system for its drive motor to help performance. Tesla will discontinue production of the Roadster in 2011, when its contract with Lotus ends, but should still have Roadsters for sale into 2012. The Model S begins production in mid-2012 with sales coming soon after. Your guide