Bignate603
Lifer
I thought the Volt had a series drivetrain, with no capability for direct gas power
For the most part, yes the car uses a series drive train where no torque from the motor is used to drive the wheels of the car. For most situations the wheels of the car are driven solely by the electric motors in the car. However under certain conditions after the battery is depleted GM found they could get better efficiency if some of the power produced by the gas engine was applied to the wheels in addition to the power coming from the electric motor. Even in this condition the gas motor is still producing some electricity that is being used to run the electric motor, only part of the gas motor's power is being used to drive the wheels.
It's actually a pretty slick idea and the car will switch between all-electric, series hybrid, and the electric motor working in conjunction with the gas motor seamlessly. Which mode it picks depends on how much power you have in the batteries, your speed, and how much power you're asking the car to give you. The system itself is quite impressive, but what's more impressive is the fact that the driver doesn't need to worry about which mode is better for their condition, they just drive the car normally.