That isn't quite how it works.
there isn't enough power to charge the battery fully while driving. that is why with the hybrids out today, you can drive up to like 40 - 60 miles on a single charge. but if you drive to fast like 60+ mph or to far, you use some gasoline while driving. which is why they get like 60 MPG because it isn't much gas to help recharge the batteries to use them to power the car

