@RexRed,
You need to get a basic physic book.
First you have the energy needed to change the velocity of a car to a certain speed and then you have a steady state energy requirement to keep it at that speed against friction both rolling wheel friction and wind friction.
Any repeat any likely solar cell array the size of one that would fit on a roof is not going to be able to provide the energy to fight friction and therefore the battery will be drain and almost at the same rate as if the array was not there at all.
As I had posted the energy that such an array could give is less then one horse power and even a very small tiny car have engines in the order of 40 plus horse power.
Hell
the leaf had a 107 horse power electric motor for example so if you are running your leaf at 30 percent full power
your solar array can only provide three percent of the energy the car is using driving down the highway.
Let put it another way for every hour you would wish to drive your leaf you would need to let it sit in sunlight for 30 plus hours and more likely 45 hours as batteries are far less then a 100 percent efficient.
Or let put it another way if your battery would allow you to travel a 100 miles the solar array under ideal conditions would allow you to drive 103 miles.
