TLDR: At low speeds, such a car is basically an EV with a petrol power generator and some power control circuitry which chooses to alternate between charging th

TLDR: At low speeds, such a car is basically an EV with a petrol power generator and some power control circuitry which chooses to alternate between charging the battery or powering the electric motor directly. Under heavy acceleration and after a certain speed threshold (enough for the petrol engine to utilise the fixed final drive ratio), a clutch is engaged and then mechanical power is sent directly to the motor, then to the wheels.