In CS mode (aka battery depleted or hold mode) accelerating from a stop will first use an electric motor, then power up the ICE to take over and charge the depleted battery as acceleration tapers off. Under hard acceleration (e.g., passing on a highway), the Volt will continue to use both an electric motor and the ICE to provide necessary power. How long will it continue to draw on the depleted battery to do this? Does the answer change whether you have a depleted battery or are in hold mode?
All theoretical, of course. Just curious if anyone has done this.
Keep in mind that when the Gen 1 Volt is driving in Extended Range (CS) mode under one-motor operation, the gas engine isn’t providing any propulsion torque at all. It’s clutched to the second motor, transforming it into a generator that supplies the primary motor with electricity and, when needed, recharges the battery (according to Wikipedia’s Chevrolet Volt article, the electrical power from the generator is sent primarily to the electric motor, with the excess going to the batteries, depending on the state of charge of the battery pack). Switching the primary motor’s fuel source from battery to generator output (and utilizing the battery as a buffer) would be more efficient than just draining and recharging the battery.
Under certain speed and torque demand conditions, two-motor operation is more efficient, and for the Gen 1, that means the ICE, which is turning the generator (the second motor), is now also helping to turn the wheels. My understanding is that under hard acceleration such as passing on the highway, the Gen 1 Volt switches from two-motor operation back to one-motor operation, in which case the ICE again is not providing any propulsion torque at all.
The Gen 2 Extended Range operation is far more complex.