Mercedes-Benz has announced its first hybrid passenger car, the S400 BlueHYBRID. Based on the S350 platform, this mild hybrid pairs an electric motor/generator and the first lithium-ion battery in a production car with a specially tuned version of the company’s 3.5L V6 driving the wheels through a 7-speed automatic transmission. The V6 produces 279 horsepower and can be aided by the electric motor during acceleration with an additional 20 horsepower and 88 lb-ft of torque, giving the drivetrain a combined torque output of 285 lb-ft and what MB calls an electric “boost” effect. Like most hybrids, the S400 features a start-stop function and regenerative braking, but since Mercedes didn’t want any interior or trunk space sacrificed for batteries, the S400’s special li-ion battery was made small enough to be placed under the hood with the engine. The net result of all this technology is a very large car that would get around 29 mpg in the U.S. The M-B S400 BlueHYBRID will be next summer.