Why the in-wheel motors instead of wheel-hub electric motors, as in some prototypes? Mercedes says it's all about reducing unsprung mass. The company says it's also engineered the car to have the same low center of gravity and balanced weight distribution as the gasoline-powered model. Also, a software-controlled all-wheel-drive system, dubbed AMG eDrive, micromanages torque delivery down to the individual wheel. The first prototype will get a liquid-cooled 48 kWh, 400-volt lithium-ion battery that can be charged by a plug-in system as well as regenerative braking. More details to be announced.