I was wondering why can't we embed permanent magnets on the road and coils underneath a car. This way, the car can generate its own energy as one drives over the magnets.
I think in case of a car provided with a combustion motor having an electric generator on board electric energy is always offered to the batteries when the motor is running. This should be more 'comfortable' to the batteries compared to your proposed restricted case when the car is really driving. But I am not a specialist in batteries. Maybe someone from the RG community will comment on this aspect.
For the case of a solely electric driven car your proposal is a waste of energy to my opinion and has no benefits.